Final Report on the Risk Assessment of the Mercury Spill in Northern

Transcripción

FINAL
Final Report on the Risk Assessment
of the Mercury Spill in
Northern Peru
Prepared for:
Minera Yanacocha S.R.L.
Av. Camino Real 348
Torre El Pilar, Piso 10
Lima 27, Peru
Prepared by:
Shepherd Miller
3801 Automation Way, Suite 100
Fort Collins, Colorado 80525
November 2002
FINAL
FINAL REPORT ON THE RISK ASSESSMENT OF THE MERCURY
SPILL IN NORTHERN PERU
TABLE OF CONTENTS
EXECUTIVE SUMMARY……………………………………………………………….. ES-1
1 INTRODUCTION .........................................................................................................................1
1.1 Project Background..........................................................................................................1
1.2 Mercury ..........................................................................................................................2
1.2.1 Introduction.......................................................................................................2
1.2.2 Environmental Cycling .......................................................................................4
1.2.3 Typical Background...........................................................................................8
2.0
RISK ASSESSMENT PROBLEM FORMULATION............................................................ 12
2.1 Identification of Contaminants of Potential Concern (COPCs)........................................... 12
2.2 Site Description and Ecological Resources ....................................................................... 13
2.3 Conceptual Site Model: Fate, Transport, and Potential Exposure ........................................ 16
2.4 Assessment and Measurement Endpoints......................................................................... 20
3.0
EFFECTS CHARACTERIZATION AND BENCHMARK SELECTION.............................. 22
3.1 Mercury Toxicity to Humans and Benchmark Determination............................................. 22
3.2 Mercury Toxicity to Other Terrestrial Animals and Benchmark Determination ................... 26
3.2.1 Birds and Mammals ......................................................................................... 26
3.2.2 Plants ............................................................................................................. 33
3.3 Mercury Toxicity to Aquatic Biota and Benchmark Determination..................................... 37
3.4 Benchmark Summary..................................................................................................... 41
4.0
EXPOSURE ASSESSMENT................................................................................................ 43
4.1 Sampling Associated with Remediation and Monitoring ..................................................... 44
4.2 Phase I (Year 2000) Sampling Conducted In Support of the Risk Assessment.................... 49
4.2.1 Terrestrial Sampling and Tissue Analysis........................................................... 49
4.2.2 Sampling and Tissue Analysis of Aquatic Biota.................................................. 61
4.3 November 2000 Sampling (Shepherd Miller, SENASA, MYSRL)...................................... 74
4.4 Phase II Sampling Conducted In Support of the Risk Assessment...................................... 76
4.4.1 Terrestrial Sampling and Tissue Analysis........................................................... 77
4.4.2 Sampling and Tissue Analysis of Aquatic Biota.................................................. 88
4.5 Mercury Transfer to Terrestrial Biota .............................................................................. 99
5.0
RISK CHARACTERIZATION .......................................................................................... 102
5.1 Aquatic Resources ....................................................................................................... 102
5.2 Human Health.............................................................................................................. 105
P:\100673\Risk\PDF files\English\Final Risk Report\PDF_Final Report_english.doc
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5.3 Terrestrial Resources ................................................................................................... 107
5.3.1 Plants ........................................................................................................... 107
5.3.2 Animals ........................................................................................................ 108
6.0
SUMMARY AND CONCLUSIONS.................................................................................. 111
6.1 Summary..................................................................................................................... 111
6.2 Human Health.............................................................................................................. 111
6.3 Agricultural and Native Plants....................................................................................... 113
6.4 Terrestrial Animals ....................................................................................................... 114
6.5 Aquatic Resources ....................................................................................................... 115
6.6 Uncertainty.................................................................................................................. 116
7.0
REFERENCES .................................................................................................................. 119
LIST OF TABLES
Table ES-1
Table ES-2
Table ES-3
Summary of the RA Conclusions for each Assessment Endpoint.............................ES-4
Mercury Concentrations in Aquatic Biota from Exposed and Reference Locations...ES-5
Mercury Concentrations in Soil and Vegetation and Terrestrial Insect Tissue ...........ES-5
Table 1.2.1
Table 1.2.2
Table 1.2.3
Example Solubility of Some Forms of Mercury............................................................ 5
Typical Units and Conversions ................................................................................... 8
Ranges of Mercury Concentrations in Diets in the U.S.A., Canada, Scotland, Italy, and
Spain...................................................................................................................... 10
Evaluation of Trace Constituents in MYSRL Mercury............................................... 13
Mammal Orders and Likely Occurrence Near the Spill Area ..................................... 15
Fish Species in the Jequetepeque River and Gallito Ciego Reservoir ........................... 16
Summary of Assessment Endpoints and Measures of Effect and Exposure................. 21
Representative Human Health Drinking Water Criteria ............................................. 24
Listing of Values Reported as Safe Hg Limits by Various Countries and Regulatory
Agencies for Fish.................................................................................................... 25
NOAEL and Effect Levels of Dietary Mercury for Mammals and Birds .................... 28
NOAEL and Effect Levels of Mercury in Drinking Water for Mammals and Birds ..... 30
Reported NOAEL and Effects Levels of Mercury in Animal Tissue .......................... 31
NOAEL and Effect Levels of Mercury in Plant Tissue ............................................. 34
NOAEL and Effect Levels of Mercury in Soil to Plants ............................................ 36
NOAEL and Effect Levels of Mercury in Water to Aquatic Biota ............................. 38
NOAEL and Effect Levels of Mercury in Aquatic Biota Tissue................................. 41
Summary of Benchmark Mercury Concentrations ..................................................... 42
Water and Sediment Sampling Locations .................................................................. 45
Results of the Phase I Soil Samples.......................................................................... 51
Results of the Phase I Vegetation Analyses.............................................................. 53
Table 2.1.1
Table 2.2.1
Table 2.2.2
Table 2.4.1
Table 3.1.1
Table 3.1.2
Table 3.2.1
Table 3.2.2
Table 3.2.3
Table 3.2.4
Table 3.2.5
Table 3.3.1
Table 3.3.2
Table 3.4.1
Table 4.1.1
Table 4.2.1
Table 4.2.2
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Table 4.2.3
Table 4.2.4
Table 4.2.5
Table 4.2.6
Table 4.2.7
Table 4.2.8
Table 4.2.9
Table 4.2.10
Table 4.2.11
Table 4.2.12
Table 4.2.13
Table 4.3.1.
Table 4.3.2
Table 4.3.3
Table 4.4.1
Table 4.4.2
Table 4.4.3
Table 4.4.4
Table 4.4.5
Table 4.4.6
Table 4.4.7
Table 4.4.8
Table 4.4.9
Table 4.4.10
Table 4.4.11
Table 4.4.12
Table 4.4.13
Table 4.5.1
Table 5.1.1
Table 5.2.1
Table 5.3.1
Table 5.3.2
Table 5.3.3
Table 6.1.1
Summary Statistics for the Phase I Vegetation Sampling ........................................... 58
Results of the Phase I Insect Tissue Sampling .......................................................... 59
Summary Statistics for the Phase I Insect Sampling .................................................. 60
Comparison of Soil and Insect Tissue Concentrations (Phase I) ................................. 60
Mercury Concentration in Phase I Aquatic Macroinvertebrate Samples...................... 63
Summary Statistics for the Phase I Macroinvertebrate Sampling ................................ 64
Results of the Phase I Fish Analyses........................................................................ 67
Summary Statistics for the Phase I Fish Sampling ..................................................... 72
Mercury Concentration in Fish at Each Location (Phase I) ........................................ 72
Mercury Concentrations for Each Fish Tissue Type (Phase I) ................................... 72
Mean Total Hg Concentrations for Each Fish Species and Tissue Type (Phase I) ....... 74
Results from the November 15, 2000 Plant and Soil Sampling .................................... 75
Summary Statistics for the November 15, 2000 Soil and Vegetation Samples .............. 75
Results from the November 15, 2000 Animal Tissue Sampling ................................... 76
Results of the Phase II Soil Samples ........................................................................ 78
Results of Vegetation Analyses from the Phase II Sampling ...................................... 80
Summary Statistics for the Phase II Vegetation Sampling .......................................... 85
Results of the Phase II Terrestrial Insect Samples Collected in 2002 .......................... 86
Summary Statistics for the Phase II Insect Sampling ................................................. 88
Mercury Concentration in Phase II Aquatic Macroinvertebrate Samples .................... 89
Comparison of Mercury Tissue Concentrations (Phase II) in Macroinvertebrates at
Different Sample Locations ..................................................................................... 89
Results of Fish Analyses from the Phase II Sampling ................................................ 92
Re-analyzed Fish Tissue Samples from the Phase II Sampling ................................... 96
Summary Statistics for the Phase II Fish Sampling .................................................... 96
Mercury Concentration in Fish at Each Location (Phase II)....................................... 96
Mercury Concentrations for Each Fish Tissue Type (Phase II) .................................. 98
Mean Mercury Concentrations for Each Fish Species and Tissue Type (Phase II) ...... 99
Mercury BAFs for Birds and Mammals ..................................................................101
Calculated Hazard Quotients (HQs) for Aquatic Resources......................................103
Calculated Hazard Quotients (HQs) for Humans .....................................................106
Calculated Hazard Quotients (HQs) for Plants.........................................................107
Calculated Hazard Quotients (HQs) for Terrestrial Animal Diets ..............................109
Calculated Hazard Quotients (HQs) for Terrestrial Animal Tissues...........................110
Conclusions From Assessment Endpoints, Measures of Effect, and Exposure ............112
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LIST OF FIGURES
Figure 1.2.1
Figure 1.2.2
Figure 2.3.1
Figure 2.3.2
Figure 4.1.1
Figure 4.1.2
Figure 4.2.1
Figure 4.2.2
Figure 4.2.3
Figure 4.2.4
Figure 4.2.5
Figure 4.2.6
Figure 4.4.1
Figure 4.4.2
Figure 4.4.3
Figure 4.4.4
Figure 4.4.5
Figure 4.4.6
Global cycling and fluxes of mercury.......................................................................... 4
Local cycling of the spilt mercury............................................................................... 6
Conceptual site model of mercury transport and potential receptors in the terrestrial
ecosystems............................................................................................................. 18
Conceptual site model of mercury transport and potential receptors in the aquatic
ecosystems............................................................................................................. 19
Dissolved mercury concentration in water samples at each sampling location.............. 47
Average mercury concentration of sediment samples ................................................ 48
Scatterplot of Phase I soil Hg concentrations (dw) versus location ............................. 52
Total Hg tissue concentrations in the Phase I vegetation tissues collected at reference and
exposed locations.................................................................................................... 57
Scatterplot of mercury concentrations in insects versus location (Phase I). . ............... 61
Mercury concentration in macroinvertebrates versus sampling location (Phase I).. ...... 65
Mercury concentration in fish at all sampling locations (Phase I).. .............................. 71
Mercury concentrations (ww) in each fish tissue type plotted versus fish length (Phase I).
.............................................................................................................................. 73
Scatterplot of Phase II soil Hg concentrations (dw) versus location ............................ 79
Total Hg tissue concentrations (ww) in Phase II vegetation collected at reference and
exposed locations.................................................................................................... 84
Scatterplot of mercury concentrations in insects versus location (Phase II). ................ 87
Mercury concentration in macroinvertebrates versus sampling location (Phase II)....... 90
Mercury concentration (ww) in fish at all sampling locations (Phase II)...................... 97
Mercury concentrations (ww) in each fish tissue type plotted versus fish length (Phase
II).......................................................................................................................... 98
LIST OF MAPS
Map 1.
Map 2.
Map 3.
Map 4.
Mercury Spill Locations
Water and Sediment Sampling Locations
Ecological Sampling Locations
Sampling Locations for the November 2000 Sampling
LIST OF APPENDICES
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Appendix G
Appendix H
Oak Ridge National Laboratory RfD Derivation
SENASA and CONSULCONT Data
Water Data (Remediation Sampling)
Sediment Data (Remediation Sampling)
Homero Bazan Sampling Report- Phase I
ENKON Sampling Report
Frontier letter discussing methyl versus total in fish tissue
Homero Bazan Sampling Report- Phase II
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EXECUTIVE SUMMARY
This report comprises the Final Risk Assessment (FRA) for the mercury spill that occurred in the
Jequetepeque watershed of Northern Peru on June 2, 2000. The methodology utilized in assessing potential
risk from this spill is consistent with the approach that was presented to the Ministry of Energy and Mines
(MEM) by Shepherd Miller on January 24, 2001, and as established with the independent reviewer, Dr.
Peter M. Chapman of EVS Environment Consultants, North Vancouver, Canada. The original timetable
for Risk Assessment (RA) activities included the presentation of a Preliminary Risk Assessment (PRA)
after analysis of sampling conducted in 2000. This preliminary report was to be updated and revised based
on the results of additional sampling conducted in 2001 after the first wet season. The revised report was
then to be issued as the final risk sssessment report. However, due to delays in obtaining permission to
send the samples collected in 2000 to the United States for analysis, the issuance of the PRA was deemed
impractical. Instead of presenting a PRA, the decision was made to issue a Draft version of the FRA that
includes analysis and discussion of all of the sampling conducted at the site. The Draft Final Risk
Assessment (DFRA) was provided to the MEM on September 30, 2002. No comments were received on
the DFRA. This report is therefore issued as the Final Risk Assessment Report.
The primary conclusion of the RA is that there are no unacceptable risks, as based on the comparison of
measured mercury concentrations to protective concentrations, associated with the mercury spill, to human
health or to terrestrial or aquatic ecological resources. There may have been some short-term risk to
terrestrial insects, as based on sampling conducted in 2000, but subsequent sampling indicated that any risk
to insects was no longer present by 2002. The finding of minimal risk (i.e., mercury concentrations below
protective values) to humans and the ecology of the Jequetepeque watershed is not unexpected given the
extensive and comprehensive response and spill cleanup activities conducted by MYSRL (MYSRL 2001).
The best estimate of the amount of the 151 kg of mercury spilt that is not accounted for, is six to nine
kilograms. This amount of mercury has a volume of 0.67 L. This volume is either widely dispersed over
the 40 Km spill area, or partially in the possession of individuals.
Risk assessment (RA) is a procedure for making environmental decisions based on the evaluation of
possible effects of an activity, in this case the spill of mercury, to the environment and to human health.
The risk assessment process can determine if a chemical release, such as a spill, has contaminated or
polluted an area. Contamination is defined as the presence of a chemical in excess of natural conditions
but below biologically available concentrations that result in risk, whereas pollution is defined as
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contamination causing adverse biological or health effects. The United States Environmental Protection
Agency (USEPA 1998) outlines three primary steps in conducting a risk assessment: 1) Problem
Formulation, 2) Risk Analysis, and 3) Risk Characterization. Essentially, the RA conducted for the
mercury spill used data collected at the site that measured the concentrations of mercury in different
environmental media (e.g., water and soil) and biological tissues (e.g., vegetation and fish) along with a
review and synthesis of the scientific literature on the effects, fate and transfer of mercury in the
environment, to assess the potential risk to humans, aquatic biota, and terrestrial plants and animals.
In the Problem Formulation step of the RA, mercury was confirmed as the only chemical constituent that
needed to be evaluated as a result of the spill. A conceptual site model (CSM) was developed that
outlined the fate and transport of mercury in the environment and identified the exposure pathways and
receptors that needed to be included in the RA. Receptors are species or biotic groups (e.g., plants) that
need to be considered in the evaluation of risk. From the CSM, four assessment endpoints were
established in order to evaluate the overall management goal of protecting the terrestrial and aquatic
resources of the Jequetepeque watershed that may have been exposed to the spilt mercury. The
assessment endpoints, which are listed in Table ES-1, are explicit expressions of the environmental values
that require protection.
A primary initial focus of the Risk Analysis step of the RA was to collect, analyze, and review data on
mercury concentrations in the environment following the spill. This process is called the Exposure
Assessment. Five sets of field data were collected between June 2000 and April 2002. The first set of
data is composed of water and sediment concentrations collected from June 2000 to April 2002. These
samples were collected by MYSRL in support of the spill remediation effort. The second set of data was
collected by Ministry of Agriculture- Servicio Nacional de Sanidad Agraria (SENASA) personnel and their
consultant, Consulcont SAC.
These samples included vegetation, animals, fish, soil, and water.
Unfortunately, due to uncertainties associated with the sampling and analytical methodologies used, the
results of this sampling were deemed unreliable for use in the RA. However, the third set of data, which
was collected at three locations in or near Choropampa where SENASA had previously reported elevated
mercury concentrations in vegetation, was utilized. This dataset was collected in November 2000 by
MYSRL, SENASA, and Shepherd Miller personnel. The final sets of data were collected specifically to
support the RA. For this final effort, co-located soil, vegetation, and terrestrial insect samples were
collected from several locations that could have potentially been impacted by the spill (Exposed Locations),
and from several locations that were outside of the spill influence (Reference Locations). Samples of fish
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and macroinvertebrate tissues were also collected from several Exposed Locations and Reference
Locations within the Jequetepeque watershed. The first set of samples (Phase I) was collected in 2000
before the start of the first wet season after the spill. Phase II samples were collected in 2001 and 2002,
after the end of the first wet season following the spill. Because these data sets were the most extensive
and best-controlled sampling of mercury concentrations for the site, they are the primary source of data
used in the RA. In order to provide a high level of conservatism, and thus a high level of environmental
protection, the 95% Upper Confidence Level of the mean concentrations was used as the Exposure
Concentrations (ECs) in the RA.
The second aspect of the Risk Analysis step is called Effects Characterization. For this portion of the RA,
safe and toxic mercury concentrations reported in the scientific literature and from governmental and other
organizations (e.g., the World Health Organization) were reviewed and synthesized. The end result of the
Effects Characterization was the establishment of mercury concentrations that are protective of 1)
environmental media, such as water and soil, 2) the tissues of plants and animals, and 3) the diet of animals
that consume plants or other animals. These established protective concentrations are termed Benchmark
concentrations.
The final step of the RA is called Risk Characterization. In this stage, the EC values outlined in the
Exposure Assessment were compared to the Benchmark concentrations to evaluate risk potential. Risk
was evaluated through the use of Hazard Quotients (HQs). HQs are calculated by dividing the Exposure
Concentration (EC) by Benchmark Values (USEPA 1998). An HQ less than 1 indicates minimal risk.
HQs greater than 1 indicate that there may be the possibility of risk.
The results of the Risk
Characterization are summarized in Table ES-1.
With only a single exception, the calculated HQ values for each of the assessment endpoints is less than
one, indicating minimal risk from the spilt mercury. The single exception is for mercury concentrations
measured in terrestrial insect tissues (HQ=1.68) during the September 2000 sampling. The follow-up
sampling conducted in 2002, however, found that the mercury concentrations in insect tissues had returned
to protective levels and that there was no longer any potential risk to this group.
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Table ES-1
Summary of the RA Conclusions for each Assessment Endpoint
Assessment Endpoint
Measures of Effect and Exposure
Conclusions
Health of individual humans Measures of effect: regulatory benchmarks for Risk from ingestion of fish, crabs,
who may consume water and concentrations of mercury in water and food
plants and drinking water is minimal;
food that may be influenced Direct measures of exposure: concentrations of HQs<1.
by the mercury spill
mercury in fish, macroinvertebrates (crabs),
vegetation, and water
Indirect measures of exposure: modeled
concentrations of mercury in terrestrial animal
tissue using literature transfer factors
Survival, growth, and
Measures of effect: established benchmark
reproduction of populations concentrations of mercury in soil and plant
of agricultural and native
tissues from a review of the scientific literature
terrestrial plants within the Direct measures of exposure: concentrations of
spill area
mercury in soil and vegetation tissue collected
at the spill locations
reproduction of populations concentrations of mercury in water and food
of terrestrial animals that
from a review of the scientific literature and
may be exposed to mercury regulatory benchmarks
from drinking water,
Direct measures of exposure: concentrations of
consumption of plants, or
mercury in water and food items (vegetation
consumption of other
and insects) collected at the spill locations
animals
reproduction of populations
of aquatic biota (macroinvertebrates and fish) that
may be exposed to mercury
from the spill
concentrations of mercury in water and animal
tissue from a review of regulatory guidelines
and the scientific literature
mercury in water and aquatic animal tissue
Risk from ingestion of terrestrial
mammals and birds is minimal; HQs<1.
Risk to plants from mercury in soil or
in tissues is minimal; HQs<1.
Risk to mammals and birds from water
and dietary consumption is minimal;
HQs<1.
Risk to mammals and birds from
mercury tissue concentrations is
minimal; HQs<1. Potential risk to
insects in 2000 (HQ=1.68), risk in 2002
is minimal; HQ<1.
Risk to aquatic biota from water and
tissue concentrations of mercury is
minimal; HQs<1.
HQ= Hazard Quotient (discussed in Section 5, indicates minimal risk if HQ<1)
Other conclusions from the RA are that there has not been any detectable movement of mercury from the
spill sites into waterways. This conclusion is supported by water sampling conducted between June 2000
and April 2002 and by sampling of aquatic biota in 2000 and 2001. The 2000 sampling was conducted
before the onset of the first wet season after the spill and the 2001 sampling was conducted after the end
of the first wet season. The mean concentration of mercury in water at both Reference and Exposed
Locations was 0.017 ppb. Mercury concentrations in aquatic biota tissue at Exposed locations and at
Reference locations were similar for both sampling dates (Table ES-2). Overall, mercury concentrations
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in water and aquatic biota tissue at both Exposed and Reference locations are indicative of typical
background concentrations of mercury in the environment.
Table ES-2
Mercury Concentrations in Aquatic Biota from Exposed and Reference
Locations
FISH
ppb (ww)*
MACROINVERTEBRATES
ppb (ww)*
YEAR
LOCATION
2000
Upstream (Reference)
Downstream (Reference)
All non-spill (Reference)
Spill locations (Exposed)
61.3
177.5
167.0
90.6
151.3
78.9
67.8
25.1
2001
Downstream (Exposed)
All non-spill (Upstream+Downstream)
40.9
234.4
228.1
94.1
453.1
98.9
96.8
26.7
* Values listed are 95% UCL of the mean from samples collected at the different location types.
While the sampling conducted in 2000 found that mercury concentrations in vegetation and insects
collected at the Exposed locations tended to be higher than those at Reference locations (Table ES-3), the
95% UCL of the mean concentrations were below protective levels for 1) plants and 2) animals that
consume vegetation or insects (Table ES-1). The soil samples that were co-located with the plants and
insects at the Exposed locations were not elevated relative to those at Reference locations. Furthermore,
concentrations in plant and insect tissue at both the Exposed and Reference locations significantly
decreased in the 2002 sampling, relative to the 2000 sampling. The 2000 sampling was conducted during
the dry season, whereas the 2002 sampling was conducted during the wet season. Based on these results,
it is believed that dry deposition of mercury on plant surfaces explains the seasonal differences in mercury
levels. The elevated concentrations of mercury in tissues collected in 2000 were likely a result of the air
deposition of mercury that was mobilized by spill remediation activities.
Table ES-3
Mercury Concentrations in Soil and Vegetation and Terrestrial Insect Tissue
SOIL
ppb (dw)*
YEAR
LOCATION
2000
Reference Locations
Exposed Locations
432.9**
105.6
2002
Reference Locations
Exposed Locations
62.8
60.3
VEGETATION
ppb (ww)*
INSECTS
ppb (ww)*
29.4
156.6
63.8
252.0
7.9
9.8
20.5
13.2
* Values shown are the 95% UCL of the mean.
**The concentration listed is influenced by a single value of 1130 ppb, 95% UCL of the mean excluding that value equals 53.9
ppb (dw)
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1.0
INTRODUCTION
This document is the Final Risk Assessment (FRA) report on the evaluation of ecological and human
health risks associated with the mercury spill that occurred on June 2, 2000 near the towns of San Juan,
Choropampa, and Magdalena, in Northern Peru. The methodology utilized in assessing the potential risk is
consistent with the approach that was presented to the Ministry on January 24, 2001, and as established
with the independent reviewer, Dr. Peter M. Chapman of EVS Environment Consultants, North
Vancouver, Canada.
1.1
Project Background
The purpose of this report is to provide an assessment of the potential risks to humans and the
environment from the spill of elemental mercury (Hg) that occurred on June 2, 2000 in Northern Peru.
The spill occurred as the mercury, a minor product of mining at the MYRSL facility, was being
transported on a truck owned by the transport company RANSA (contract carrier for MYSRL) from the
mining operations to Lima. An extensive account of the spill can be found in the Mercury Spill Incident
Report (MYSRL 2001). For the purpose of this report, only a brief summary of the spill response is
provided.
The spill occurred during transport of the mercury from the mine to Lima along the road between
Cajamarca and the Pan American highway (Map 1). At approximately Km 155, a chlorine gas cylinder
became dislodged from the trailer and disrupted the mercury containers such that they were knocked loose
from their original positions, and several were inverted. Elemental mercury began to spill in the area of
Km 155 and subsequently along the route of travel until the truck parked in Magdalena later in the evening
of June 2. MYSRL first received word of the spill on the morning of June 3rd and immediately started to
respond. Initial response efforts included identifying the spill locations and working with local agencies to
inform the public about the potential hazards of possessing and handling the spilt mercury. Subsequent
efforts focused on addressing the potential health risks associated with the collection of the spilt mercury
by local citizens, as well as further identifying spill locations and cleaning-up the spilt mercury.
The initial response efforts detailed 16 distinct spill locations (Map 1) where visible mercury was identified.
Upon identification of spill areas, clean-up was initiated at these locations, with all visibly contaminated
material (roadside soil and asphalt) removed and transported to the heap leach pile at the Maqui Maqui
Mine. Unfortunately, prior to identification and clean up of all locations, some of the mercury was
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collected by residents, primarily in Choropampa, and taken to homes. Upon learning of the residential
collection of mercury, MYSRL undertook a program to recover mercury from the local citizens and
initiated public education regarding the health risks associated with mercury. These programs were
conducted in cooperation and coordination with local and regional governmental and health care agencies.
Later surveys identified additional areas where visible mercury was not present, but where elevated
mercury levels required remediation.
Determining the success of the recovery of mercury during the remediation effort was evaluated using a
mass balance approach. Upon completion of the recovery activities, final mass balance calculations were
performed by MYSRL and by an independent auditor (MYSRL 2001).
Using two very separate
approaches, both of the calculations determined that only six to nine Kg of mercury likely remained in the
environment or in the possession of local citizens after the completion of clean-up activities. This indicates
that greater than 94% of the mercury was successfully removed from the immediate environment around
the spill. The remaining mercury is likely widely dispersed in the environment or in the possession of local
citizens.
1.2
Mercury
1.2.1
Introduction
Mercury is the seventh metal of antiquity and has been known and used by mankind for over 3500 years,
including gold mining by the Romans (Meech et al. 1998). Uses of mercury throughout time have included
both industrial and ‘medicinal’ applications. Mercury has been used as a fungicide, as a slime control
agent, and in various manufacturing processes, including the production of chlorine (chloralkali plants) and
sodium hydroxide (Eisler 2000, Meech et al. 1998). The inorganic form of mercury has historically, but not
presently, been used as an antiseptic, a disinfectant, a purgative, a counterirritant, and when dissolved in oil
of vitriol (sulphuric acid) and distilled with alcohol, as a cure for syphilis (Veiga and Meech 1995). The
potential for mercury toxicity was first reported in 1533 by the famous Swiss physician Paracelsus, in a
book on occupational diseases, in which he discussed Hg poisoning of miners (Veiga and Meech 1995).
Mercury naturally occurs in the environment and cycles through the Earth’s atmospheric, water, and
terrestrial components (Figure 1.2.1). The total global annual input of mercury to the atmosphere is
estimated to range from 900 to 6200 metric tons (0.9-6.2 million Kg). This includes input from both natural
and anthropogenic (i.e., human caused) sources (Chu and Porcella 1995, USEPA 1997a).
Natural
releases of mercury to the environment occur as gases (vapor emission from natural ores), as solutions
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(e.g., in lava), or as particulates (e.g., dust). The global cycling of mercury involves atmospheric transport
(primarily as elemental mercury vapor) of mercury that has degassed from the earth’s crust and from
evasion (evaporation) of mercury from water bodies. Some of the elemental mercury vapor is oxidized to
form ionic mercury (Hg+2), which is then re-deposited onto land and water surfaces, primarily as a
particulate. The estimated residence time, or the average time that an evaporated mercury particle is redeposited from the atmosphere to the earth’s surface, is one year (Eisler 2000, Porcella 1994).
Human activity has caused large increases in the concentration of mercury in different environmental
media (Hylander 2001, USEPA 1997a). It is estimated that atmospheric depositional rates have increased
by a factor of 3.7 since 1850. River sediment concentrations are reported to have increased fourfold, and
lake and estuarine sediments two to fivefold, since pre-cultural times. Currently, it is estimated that in the
United States alone, 100 to 158 metric tons of mercury (100,000-158,000 Kg) are released to the
atmosphere each year, primarily from the burning of fossil fuel (e.g., coal) and from industrial factories
(Chu and Porcella 1995, USEPA 1997a). A single medium to large-sized coal power plant emits 114 Kg of
Hg per year via the smokestack and another 23 Kg from cleaning of the coal (NWF 2000). Overall, fuel
combustion (primarily coal) results in 54% of the annual global Hg emissions (Hylander 2001).
Humans also release mercury to the environment through industrial processes and from artisanal
(rudimentary) precious metal mining. Mercury is utilized in more than 2000 manufacturing industries and
products (Jones and Slotton 1996). Operation of chloralkali plants, to produce chlorine and caustic soda, is
one of the largest industrial emitters of mercury. Chloralkali plant emissions are thought to produce 90%
of the anthropogenic releases of mercury in Europe (Hylander 2001). In Latin America, artisanal mining
with mercury amalgamation is a major source of mercury to the environment, with an estimated 200
tonnes (200,000 Kg) of Hg released annually as a result of these activities (Veiga et al. 1999). While
there is current artisanal mining in Peru, there is no known artisanal mining ongoing in the Jequetepeque
watershed.
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Figure 1.2.1
Global cycling and fluxes of mercury (from USEPA 1997a)
Mercury is mined as a primary product, or as a byproduct of other metal mining. Mine production in 1999
was 2100 tonnes, with Algeria, Kyrgyzstan, and Spain as the largest producing countries (USGS 2000). A
single mine, the Almaden mine in Spain, produced 860 tonnes in 1997. This mine has been in nearly
continual production for the last 2000 years, and is the largest known deposit of mercury (Lindberg et al.
1979). As a single source of emissions to the atmosphere, the Almaden mine emits 0.5 to 1 Kg of
mercury per hour.
Humans and other biota are exposed to mercury from both naturally-occurring levels in the environment
and from releases due to the burning of fossil fuels and industrial releases. Humans are also directly
exposed to mercury from the use of mercury in dental fillings. Exposure from dental work is more
common in the industrial world due to wider availability of dentistry. As an example, it has been estimated
that an average citizen of Sweden has 10 g of mercury in their body as a result of dental work (Hylander
2001).
1.2.2
Environmental Cycling
The cycling of mercury in the environment is complex, with toxicity and movement of environmental
mercury highly dependent on the chemical form present. The primary chemical forms of mercury in the
environment are: elemental (Hg0), ionic mercury (Hg+2 and Hg+1), and organometallic, primarily in the
form of methylmercury (HgCH3).
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Global Cycling
Elemental mercury is the most common form in the atmosphere (Figure 1.2.1). Over time, a small amount
of this mercury is oxidized to become the ionic Hg+2 form, which is subsequently deposited into surface
soils and waters.
Ultimately, this deposited mercury is converted to the essentially insoluble HgS
(cinnabar) form (Jones and Slotton 1996). Estimated residence times for mercury are up to one year in
the atmosphere and 1000 years in soils (Eisler 2000). The predominant form of mercury in aquatic
environments is mercuric ion (Hg+2), which can bind firmly to sediments, or under appropriate conditions
can be reduced to elemental mercury and lost to the environment via vapors, or microbially converted to
methylated mercury (Lorey and Driscoll 1999).
Except for volatilization of the elemental form, both elemental and ionic mercury are largely immobile in
the environment (Battelle and Exponent 2000, Kabata-Pendias and Pendias 1992). In general, elemental
mercury is very insoluble and ionic forms are only slightly more soluble (Table 1.2.1), which limits the
movement of mercury in the environment.
Table 1.2.1
Example Solubility of Some Forms of Mercury
Chemical Form
Elemental
HgCl2
HgO
HgS
Hg 2Cl2
Hg Species
Solubility (ug Hg/ml water*)
0
Hg
Hg +2
Hg +2
Hg +2
Hg +1
0.056
74,000
51.6
insoluble-0.013
2
* Data from Davis et al. 1997
As an example of the limited mobility of mercury, at a site where sewage sludge was applied for twenty
years, the mercury contained in the sludge did not move past the top 15 cm of the soil profile (Granato et
al. 1995). Since mercury will not readily migrate through the soil column, the degree to which plant roots
will be exposed to increases in mercury concentrations at the soil surface is limited. Furthermore, plants
have a low affinity (i.e., uptake) for mercury. This is largely a result of low solubility, as well as strong
affinity of the dissolved forms of mercury (i.e., Hg+2) binding strongly to soil organic matter and clays, thus
further limiting the availability to plants (Hempel et al. 1995). Researchers have found that large increases
in soil mercury concentrations result in only slight increases in plant tissue mercury concentrations (Patra
and Sharma 2000). The limited amount of mercury that is absorbed by plants is largely retained in the
roots, and is not transferred to stems and leaves that could then be eaten by herbivores (i.e.,
livestock)(Granato et al. 1995). The greatest concern with mercury in the environment is typically
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reserved for methylmercury, due to its greater toxicity and its ability to build-up to high levels in aquatic
food-chains (Clarkson 1994). Methylmercury is uncommon in terrestrial soils and ecosystems since the
conditions amenable to methylation are not present in these systems (Davis et al. 1997).
Local Cycling
Over time, the elemental mercury that was spilled in Northern Peru will be transformed into ionic forms
(likely HgO and HgS) in the environment. Solubility and transport may increase, especially for the
mercury-oxide complexes (Figure 1.2.2). The uptake rates of ionic mercury into plants will be higher, as
will the absorption of mercury into animals that eat the plants or soil. Even after elemental mercury has
been converted into ionic forms, however, soil microorganisms can re-convert Hg+2 (e.g., HgO) back to
elemental mercury, which can then evaporate from the soil to the atmosphere (Kim et al. 1997).
Figure 1.2.2
Local cycling of the spilt mercury
Due to the generally steep terrain in the Jequetepeque watershed and movement of surface particles
through erosion, the ultimate fate of mercury remaining from the spill (i.e., not removed by clean-up
activities), and that does not evaporate to the atmosphere, will likely be the Gallito Ciego reservoir, via the
Jequetepeque River. Once transported to surface water, some of the mercury bound to soil particles may
dissolve. The dissolved mercury, primarily in the Hg+2 form, should be fairly evenly distributed in the
water column. Mercury associated with soil particles that have eroded and been transported in the water
column to the reservoir will likely preferentially drop out at the river-reservoir interface, as evidenced by
the extensive depositional zone at the mouth of the reservoir. Overall, in order for the spilt elemental
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mercury to be accumulated in food-chains, it must first be rendered soluble (i.e., oxidized into ionic
mercury) and then converted into methylmercury (Meech et al. 1998).
Methylation and Aquatic Systems
Mercury in aquatic environments is typically dissolved mercuric ion (Hg+2). Over time, the dissolved ionic
mercury can be bound up in sediments, can be reduced to elemental mercury and lost to the atmosphere,
or can be converted to organic mercury (i.e., methylated) in the sediment. Methylmercury in lakes can
also come from precipitation in heavily contaminated industrial areas (Rudd 1995). Phytoplankton (algae)
can reduce ionic Hg to elemental Hg at the rate of 0.5%-10% per day, increasing the loss of mercury to
the atmosphere and reducing the amount of mercury in aquatic systems available for potential methylation
(Mason et al. 1995).
The uptake of mercury into aquatic biota is strongly influenced by water chemistry. Ionic mercury (Hg+2)
in the water column can interact with S-2 (sulfide) if present, forming an essentially insoluble HgS
precipitate, which is unavailable to biota. Sulfide levels are influenced by pH and redox conditions in the
water. As such, aquatic systems with higher pH (>7.0) or lower redox potentials tend to have less
potential for mercury accumulation in aquatic biota. High calcium, zinc, and selenium concentrations in
water also can reduce mercury uptake into aquatic biota (Bjornberg et al. 1988). Selenium has also been
shown to be protective, or reduce the effects of mercury, to aquatic biota (Eisler 2000). Generally, ionic
mercury (Hg+2) does not bioaccumulate to a significant degree in aquatic systems (Jackson 2001, Laporte
et al. 2002). Because of this, the amount of methylation that occurs is important for determining the risk to
aquatic systems.
The mercury associated with sediments can undergo methylation if appropriate conditions exist. Elemental
mercury cannot be directly transformed into methylmercury, but must first be oxidized (Meech et al. 1998,
Veiga 1997). Production of methylmercury is controlled by the mercury complexing characteristics, the
microbial metabolic activity, and the total inorganic concentration in the sediment (Hintelmann et al. 2000,
Rudd 1995). Methylation of mercury is favored where there are humus or peat sediments (i.e., high
organic matter) and anoxic conditions. This explains why fish tissue levels of methylmercury increase in
newly created lakes since soils with organic matter (i.e., humus) are placed under saturated (i.e., anoxic)
conditions (Morrison and Thierien 1995, Porvari and Verta 1995). Essentially no methylation occurs under
aerated conditions (Porvari and Verta 1995).
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In general, lower pH waters tend to liberate more methylmercury from sediments into water than higher
pH waters. Methylmercury released to the water column can be incorporated into aquatic biota. High
fulvic acid waters will also result in more methylmercury being released from the sediment to the water
column, primarily by increasing mercury solubility (Veiga 1997). Darkwater rivers (i.e., the Amazon)
result in higher methylmercury levels in fish than corresponding Hg in whitewater rivers due to the
presence of fulvic acids (Meech et al. 1998). In lakes, seasonal stratification of the water can create an
anoxic hypolimnion (i.e., oxygen-free zone), which can induce spikes in methylmercury production
(Slotton et al. 1995).
1.2.3
Typical Background
Mercury is widely distributed in the environment, with concentrations present in all waters, soils, and in
every living organism (Clarkson 1994). Due to industrialization, mercury levels in the environment have
increased over the past 40 years, though atmospheric concentrations appear to be stable, if not declining,
due to recognition of the problem and implementation of controls for limiting mercury dispersal (Hylander
2001). Typical conversion factors and units for mercury in the environment are provided in Table 1.2.2
Table 1.2.2
Typical Units and Conversions
Media
water
soil
vegetation
animal tissue
Typical
Units
ug/L
mg/kg
ug/kg
u g/kg
Equivalent
Units
ppb
ppm
ppb
ppb
1 ppm
1 ppb
1000 ppb
0.001 ppm
Conversions
ppm to ppb
ppb to ppm
Mercury naturally occurs in all components of the environment. On average, mercury is present in the
earth’s crust at 500 ppb on a dry weight (dw) basis. The mercury concentration in rainwater ranges from
0.001 ppb in remote non-urban areas up to 3.5 ppb in urban areas. Forest fires and rain are responsible
for the majority of mercury deposition onto the world’s surface waters and soils (Fergusson 1990, Hall
1995, Jones and Slotton 1996). The Geological Survey of Canada collected 1684 soil samples throughout
Canada and measured mercury concentrations. The reported mercury concentrations in these samples
ranged from 2 to 1530 ppb (dw), with a geometric mean of 60 ppb (Richardson et al. 1995). KabataMinera Yanacocha S.R.L.
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Pendias and Pendias (1992) report that the concentrations of mercury in uncontaminated soils from around
the world range from 4 ppb (Sweden) to 5800 ppb (Russia), with typical mean soil values for different
countries of approximately 200 ppb (dw). Shales typically contain up to 3200 ppb (dw) and coal up to
8500 ppb (dw) mercury, with mercury sulfide being the most commonly occurring form in coal (Adria no
1986). Surface water concentrations of mercury vary greatly, but reported values are usually less than 0.5
ppb (Bjornberg et al. 1988, Irwin 1997a).
Mercury also naturally occurs in food items. Typically reported mercury concentrations in terrestria l
plants range from 30-700 ppb (dw). The reported average concentration of mercury in wheat from the
United States is 290 ppb (dw) (Adriano 1986).
The highest concentrations of mercury in food are
generally reported for fish and shellfish. Concentrations in food items from different countries are shown
in Table 1.2.3. There is a large degree of variability in observed tissue concentrations of mercury, even
for the same type of food.
As estimated by Richardson et al. (1995), the total human intake of mercury in Canada is 7.7 ug/day, or
0.11 u g of Hg per Kg of body weight per day (ug/Kg-day). The absorbed dose was estimated to be 5.3
ug/day, or 0.076 ug/Kg-day. Only the absorbed dose can cause toxicity in humans or animals. The nonabsorbed dose is excreted, primarily in the feces. It was determined that fish consumption accounted for
27% of the mercury intake and 40% of the absorbed dose. Dental work accounted for 36% of intake and
42% of absorbed dose. The dose from food, other than fish, is primarily from intake of Hg+2, which has
much lower absorption in the gastrointestinal tract. The dose from the rest of the diet (i.e., non-fish) was
estimated at be 1.82 ug/day with the absorbed dose only 0.18 ug/day. In a study of the Swedish diet, the
estimated mercury exposure from the diet ranged from 1 to 30.6 ug/day (Underwood 1977).
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Table 1.2.3
Ranges of Mercury Concentrations in Diets in the U.S.A., Canada, Scotland,
Italy, and Spain
Food Type and Item
Range* (ppb)
Meat
Beef liver
Meat and poultry
Viscera
Other meats (lamb, pork, hare)
Wild fowl (muscle)
Can. goose (muscle)
Ducks (muscle)
Ducks (liver)
2-30
<2-7
<2-80
2-3
<126-242
<30-135
<23-704
16-3800
Fish and shellfish
Canned fish
Frozen Fish
Shrimp
Various fresh fish
Shellfish
135-612
6-736
28
30.5-1082
6-490
Vegetables
Various
1-18
Grains
Bread/pasta/cereal
4-33.4
Various- citrus/berries
1.3-5.6
Fruit
Eggs
Chicken/domestic
Waterfowl eggs
<2-5
<60-500
Other
Sugar/condiments
Dairy- milk,cheese
Nuts
Beverages
<2-6
<2-22.6
<2-19
<2
*data sources: USFDA (1999), MAFF (1997), MAFF (1994), Environment Canada (1999),
Ristori and Barghigiani (1994) and Urieta et al. (1996); values listed are for food as consumed in the
diet
Mercury concentrations in fish are of great interest to health professionals since fish contribute much of
the mercury dose to humans. There is a high degree of variability in typical concentrations of mercury in
fish. Some of the factors influencing fish tissue mercury concentrations include: fish type and age, water
chemistry, and concentration of mercury in water and sediment. Sweet and Zelikoff (2001) reported that
fish from uncontaminated areas had mercury concentrations that ranged from 18 to 600 ppb (ww). Shilts
and Coker (1995) reported that fish collected in a remote Arctic area of Canada, that is not influenced by
any nearby mercury emissions, had mercury tissue levels of 570-2200 ppb (ww). These seemingly
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elevated levels were determined to be related to high natural backgrounds of mercury associated with the
presence of sulphide mineralizations in the area. As humans have decreased concentrations of mercury
released to the environment in some locations, the measured concentrations of mercury in fish have also
decreased. (Winstanley 1999).
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2.0
RISK ASSESSMENT PROBLEM FORMULATION
Risk assessment (RA) is a procedure for making environmental decisions based on the evaluation of
possible effects of an activity (i.e., spill) to the environment and to human health. The risk assessment
process can determine if a chemical release, in this case a mercury spill, has contaminated or polluted an
area. Contamination is defined as the presence of a chemical in excess of natural conditions but below
biologically available concentrations that result in risk, whereas pollution is defined as contamination
causing adverse biological or health effects.
The USEPA (1998) outlines three primary steps in
conducting a risk assessment: 1) Problem Formulation, 2) Risk Analysis, and 3) Risk Characterization.
Problem Formulation is the planning phase of a RA, in which the goals, scope, focus, and analysis plan are
formulated. The plan developed in the Problem Formulation is implemented in the Risk Analysis phase.
The Risk Characterization phase then documents the analysis and integrates the results to describe overall
risk. In brief, the risk assessment process utilized involved a process of gathering information, through
sampling, on the concentrations of mercury in the environment and comparing these measured
concentrations to benchmark effect concentrations for both humans and applicable biota. The exposure
pathways and receptors are outlined in the conceptual model of the site (Section 2.3), which is based on
the fate and transport of mercury in the environment and characterization of the ecosystems in the spill
area. Benchmark values are discussed in Section 3 and the measured exposures are discussed in Section
4 of this report.
2.1
Identification of Contaminants of Potential Concern (COPCs)
The mercury spilt was essentially pure elemental mercury that is recovered as a by-product of the milling
process at the MYSRL facilities. While only mercury was spilled, the collected mercury was analyzed to
confirm that there were no other chemical constituents in the mercury that might pose risk to the
environment. The analysis found that the mercury was essentially pure, with only trace amounts of other
inorganic chemicals present. In order to verify that none of these trace inorganic constituents in the
mercury would need to be evaluated in the risk assessment, the results of the chemical analysis were
compared to guidance values. Additional inorganic constituent concentrations in the mercury were
verified to be less than U.S. Environmental Protection Agency (USEPA) soil screening levels (SSLs) and
risk based screening levels for residential soils (Table 2.1.1; USEPA 1996, 2001d). While there are no
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guidance values for four of the inorganic constituents (bismuth, gallium, gold, and strontium), the
concentrations of these constituents are low and none of them are generally considered to be an
environmental or human health concern (Amdur et al. 1991, Irwin 1997b).
Table 2.1.1
Evaluation of Trace Constituents in MYSRL Mercury
Trace
Constituent
Aluminum
Antimony
Arsenic
Barium
Beryllium
Bismuth
Boron
Cadmium
Chromium
Cobalt
Copper
Gallium
Gold
Iron
Lead
Lithium
Manganese
Molybdenum
Nickel
Selenium
Silver
Strontium
Thallium
Tin
Titanium
Vanadium
Zinc
Mercury
Sample 1
Sample 2
(mg/Kg)
(mg/Kg)
2.24
<0.057
<0.29
0.078
<0.005
<0.005
<4.15
0.009
<0.05
0.004
0.33
0.041
1.62
15.7
0.322
<0.003
0.11
<0.04
0.03
22
102
0.084
2.01
0.12
0.1
<0.62
0.09
S S L1
(mg/Kg)
2.08
<0.057
<0.29
0.067
<0.005
0.061
4.5
<0.005
<0.05
0.004
0.19
0.057
1.69
14.7
0.275
<0.003
0.05
<0.04
0.02
7.9
35.8
0.068
1.99
0.08
<0.05
<0.62
0.15
31
0.4
5500
0.1
78
390
Benchmark Values
Residential 2
Exceed safe
(mg/Kg)
values
78000
31
0.43
5500
160
7000
78
230
4700
31000
23000
400
1600
390
390
1600
1600
390
1600
390
390
550
23000
5.5
47000
310000
550
23000
N
N
N
N
N
NA
N
N
N
N
N
NA
NA
N
N
N
N
N
N
N
N
NA
N
N
N
N
N
NA= no applicable guidance values
1
USEPA (1996); values listed are safe levels for human consumption of soil
2
USEPA (2001d); values listed are safe levels for residential soils
2.2
Site Description and Ecological Resources
This report assesses potential risk from mercury to human and ecological receptors in the upper portion of
the Jequetepeque watershed, located in the District of Magdalena, Province and Department of
Cajamarca. The overall watershed is large, covering a distance of 160 Km and a total area of 623,220 ha
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(Cabanillas 1998), with the headwaters in the Central Cordilleras, and the terminus at the Pacific Ocean.
This report, however, only focuses on a portion of the upper watershed, specifically, the area between Km
155 and the Gallito Ciego Reservoir (approximately Km 52; see Map 1).
The ecology of the area is summarized by Cabanillas (1998) and Bazan et al. (2000). The specific area of
interest for this assessment ranges from approximately 2500 m above mean sea level (amsl) at Km 155 to
450 m amsl at the Gallito Ciego Reservoir. A wide variety of vegetation communities occur within this
area, including Montane Tropical Humid Forest, Lower Montane Tropical Dry Forest, Pre-montane
Tropical Dry Forest, Pre-montane Tropical Thorny Slopes, and Tropical Desert Shrub (Cabanillas 1998).
The overall assessed area, however, is largely limited to the Lower Montane Tropical Dry Forest and
Tropical Desert Shrub communities.
The climate of the region varies significantly with elevation. As an example, San Juan, at an elevation of
2300 m (amsl) recorded 876 mm of rainfall during 1982-83, whereas Tembladera, at 450 m (amsl), only
received 100 mm over the same time period. Yearly variability in rainfall is substantial, and is reflected in
the flow of the Jequetepeque River. Over the time period 1977 to 1993, the recorded annual flow at the
Yonan recording station ranged from 105 million cubic meters in 1980 to 1947 million cubic meters in 1984.
The annual average flow over this time period was 698 million cubic meters (Cabanillas 1998).
Except at the highest elevations in the watershed, the land has been extensively modified by the human
inhabitants. At higher elevations, wheat and corn are the primary cultivated species, with non-cultivated
land utilized as grazing areas for cattle, goats, and sheep. Further down-valley, sugarcane and rice are
more common, though corn, banana plantations, and mixed-vegetable gardens are also prevalent.
Furthermore, many varieties of fruit (e.g., mango and lemon) are grown, especially near houses for
personal consumption. An extensive network of irrigation canals, that primarily utilize seeps and tributaries
of the Jequetepeque, are employed to irrigate the cultivated crops.
Due to the long history of human inhabitation of the watershed, larger wildlife are not common in the spill
area. Smaller mammals and birds, however, are observed and are likely to occur in much greater densities
than larger animals. From reviews by Eisenberg and Redford (1999) and Bazan et al. (2000), mammals
that have been observed in areas near the spill, or are native to the broader region, are shown in Table
2.2.1. Mammal families are listed, along with an estimate of the likelihood of occurrence near the spill
area. The likelihood of occurrence is based on 1) distribution maps provided by Eisenberg and Redford
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(1999), 2) observations on habitat made during the field investigations, and 3) conversations with MYSRL
personnel and the local population. Where possible, if members of a particular mammal order are likely to
occur, or may possibly occur, representative genus and common names of the mammals are listed as well.
Table 2.2.1
Mammal Orders and Likely Occurrence Near the Spill Area
Order
Marsupialia
Edentata
Common name
Insectivora
Chiroptera
Marsupials
Anteaters
Armadillos
Insectivores
Bats
Primates
Carnivora
Monkeys, apes, humans
Carnivores
Perissodactyla Odd-toed ungulates
Artiodactyla Even-toed ungulates
Rodentia
Rodents
Lagomorpha
Rabbits
In area?
Genus represented
possible
unlikely
unlikely
unknown
likely
likely
likely
likely
likely
likely
likely
yes
possible
possible
possible
possible
possible
unlikely
possible
likely
likely
likely
yes (domestic)
likely
yes (domestic)
Common names
Didelphis spp.
opossum
Glossophaga spp
Pteronotus spp
Tonatia spp
Myostis spp
Chiroderma spp
Sturnina spp
Vampyressa spp
Homo sapiens
Pseudolopex culpaeus
Mustela frenata
Felis colocolo
Felis concolor
Conepatus semistriatus
long-tongued bats
mustached bats
round-eared bats
little brown bats
large-eyed bats
yellow-shouldered bats
yellow-eared bats
humans
South American fox
long-tailed weasel
gato de pajonal
mountain lion
hog-nosed skunk
Odocoileus virginianus
Thomasomys spp
Microryzomys spp
Oligoryzomys spp
Cavia tschudii
Lagidium peruanum
Oryctolagus spp
white-tailed deer
rat
rat
rat
cuy (guinea pig)
big chinchilla
domestic rabbit
Bazan et al. (2000) lists species of raptors, dabbling ducks, grebes, and shorebirds that are known to
inhabit areas near the spill. Bird species that were observed in the area during site visits were: wild
canaries (Sicalis spp.), vermilion flycatcher (Pyrocephalus rubinus), groove-billed ani (Crotophaga
sulcirostris), and other unidentified small songbirds (Order Passiformes) and herons.
Table 2.2.2 shows the species of fish known to occur in the Jequetepeque River and the Gallito Ciego
Reservoir. The occurrence of these species was determined by sampling work conducted to support the
risk assessment and from interviews with local fishermen. All of the species listed in Table 2.2.3, except
paco and tilapia, occur in both the reservoir and the river. Paco and tilapia were only collected in the
reservoir and did not occur in the river. Overall, the life history of the native fish species in the watershed
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(i.e., all species except tilapia) are not well characterized in the scientific literature. As an example, some
individual fish collected during sampling are larger than what the literature indicates as the maximum
length for that species.
Table 2.2.2
Peru vian
Name
Fish Species in the Jequetepeque River and Gallito Ciego Reservoir
Common
Name
Cachuela
Carachita
Cascafe
(Sabalo)
Charcoca
Twospot
lebiasina
catfish
Life
Scientific Name
Bryconamericus
peruanus
Brycon
atrocaudatus
Lebiasina
bimaculata
Trichomycterus
dispar
Family
Characins
Omnivorous
Characidae
Characins
Plants and
zooplankton
Insects
benthopelagic,
freshwater
pelagic, freshwater
Lit.
Site
Max length
Length range
(cm)
(cm)
2-10
3.7-33
pelagic, freshwater;
6.2 <pH< 7.5
benthopelagic,
freshwater
10
3.513.5
8-17.8
benthopelagic,
fresh-water;
6.5<pH< 8.0
Astroblepida Climbing
Insects and
demersal,
e
catfishes
algae
freshwater
Characidae Characins
Insects and
pelagic, freshwater;
decaying plants 4.8<pH< 6.8. An
important foodfish
Atherinidae Silversides
Plankton
pelagic, freshwater,
and insects
brackish, marine
Pimelodidae Long-whiskered Algae
demersal,
catfishes
freshwater
Cichildae
Cichlids
Plankton
Inhabits warm
ponds and
impoundments as
well as lakes and
streams. demersal,
freshwater, brackish
20
3.1-21
Lebiasinidae Characins
T richomycteridae
Aequidens rivulatus Cichlidae
Nato life
catfish
Astroblepus rosei
Paco
Pirapatinga Piaractus
brachypomus
Pejerrey
Pejerrey
Tilapia
Habitat
40
Green
terror
Picalon
Diet
Characidae
Mojarra
Odontesthes
bonariensis/regia
catfishes
Pimelodella
yuncensis
Blue Tilapia Oreochromis
(Introduced aureus
)
Family
common name
Pencil/
parasitic
catfishes
Cichlids
Detritus
Plants and
invertebrates
3.1-14
45
7-8
23.4
4.5-20
4.8-10
37
13-30
All of the fish species that occur in the watershed (Table 2.2.2) are either herbivorous (plant eaters) or
omnivorous (eat both plant and animal matter). There are no identified higher-trophic order piscivorous
fish (fish that eat fish) in the river or reservoir. Piscivores are known to have the greatest potential for
accumulating mercury (Uryo et al. 2001).
2.3
Conceptual Site Model: Fate, Transport, and Potential Exposure
Five systems are at potential risk from the spilt mercury: agricultural, native terrestrial, residential, riverine,
and the reservoir ecosystems. Residential is included as a system type since some of the mercury spill
sites (Map 1) occur within towns. Biota in these towns, including domestic animals and garden plants,
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were potentially exposed to mercury. Other general receptor types within the terrestrial systems are
humans, wildlife, and plants (agricultural and native). The conceptual exposure pathways and fate and
transport of mercury in the terrestrial ecosystems are shown in Figure 2.3.1. Possible receptors within the
aquatic ecosystems include fish and aquatic macroinvertebrates. The conceptual exposure pathways and
fate and transport of mercury in the aquatic ecosystems are shown in Figure 2.3.2.
Conceptually, mercury is initially in the form of elemental mercury. Elemental mercury can volatilize, be
mobilized via wind or water transport, or be oxidized to form Hg+2. Over time, much of the elemental
mercury will be oxidized, thus converting the mercury to ionic forms. For ionic mercury, the volatilization
rate substantially decreases, while the water solubility increases slightly. Ionic mercury does bind strongly
to soil particles, but over longer time periods, it may be transported into streams through erosion of surface
soils or by limited dissolution. If appropriate reducing conditions exist (see Section 1.2.2), mercury that
enters the surface water may be methylated. Methylmercury has much higher availability to organisms,
thus increasing the potential for mercury bioaccumulation in biological tissues.
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Figure 2.3.1
Conceptual site model of mercury transport and potential receptors in the terrestrial ecosystems
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Figure 2.3.2
Conceptual site model of mercury transport and potential receptors in the aquatic ecosystems
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2.4
Assessment and Measurement Endpoints
The overall management goal for the spill area is:
Protecting the terrestrial and aquatic resources of the Jequetepeque watershed that were
potentially exposed to mercury contamination from the spill.
Assessment endpoints are explicit expressions of the actual environmental values that are to be protected
within the overall management goal (USEPA 1998). The assessment endpoints for the risk assessment
are:
1. Health of individual humans who may consume water and food that may be influenced
by the mercury spill.
2. Survival, growth, and reproduction of populations of agricultural and native terrestrial
plants that are within the spill area.
3. Survival, growth, and reproduction of populations of terrestrial animals that may be
exposed to mercury from drinking water, consumption of plants, or consumption of
other animals.
4. Survival, growth, and reproduction of populations of aquatic biota (macroinvertebrates and fish) that may be exposed to mercury from the spill.
The USEPA (1998) identifies three types of measures that are used to evaluate the assessment endpoints
and to assess the risk potential:
n
n
n
Measures of Effect – Direct measures of changes in an attribute of the assessment
endpoint that can be attributed to exposure to the chemical in question.
Measures of Exposure – Measures of chemical concentrations and movement in the
environment.
Measures of Ecosystem and Receptor Characteristics – Measures of ecosystem and
receptor characteristics that influence the potential for contact between the receptors and
chemicals.
No direct site-specific measures of effect were made.
The measures of effects used in the risk
assessment are benchmark effect concentrations issued by various regulatory groups or values derived
from the scientific literature. These benchmark values are discussed in Section 3. Extensive direct
measures of exposure were collected through sampling of terrestrial and aquatic media and biota.
Sampling included water, sediment, soil, vegetation, terrestrial insects, aquatic macroinvertebrates and fish.
For the exposure assessment of the consumption of terrestrial animal tissue, which was not directly
sampled, mercury transfer from the measured vegetation tissue to herbivore tissue was modeled using
20
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literature transfer factors. The various measures of exposure are discussed in Section 4. There were no
direct measures of ecosystem and receptor characteristics. The assessment endpoints and associated
measurement of effects and measures of exposure are summarized in Table 2.4.1.
Table 2.4.1
Summary of Assessment Endpoints and Measures of Effect and Exposure
Assessment Endpoint
Health of individual humans who may
consume water and food that may be
influenced by the mercury spill
Measures of effect: regulatory benchmarks for concentrations of
mercury in water and food
Direct measures of exposure: concentrations of mercury in fish,
macroinvertebrates (crabs), vegetation, and water
Indirect measures of exposure: modeled concentrations of mercury
in terrestrial animal tissue using literature transfer factors
Survival, growth, and reproduction of
populations of agricultural and native
terrestrial plants within the spill area
Measures of effect: established benchmark concentrations of
mercury in soil and plant tissues from a review of the scientific
literature
Direct measures of exposure: concentrations of mercury in soil and
vegetation tissue collected at the spill locations
populations of terrestrial animals that may mercury in water and food from a review of the scientific literature
be exposed to mercury from drinking
and regulatory benchmarks
water, consumption of plants, or
Direct measures of exposure: concentrations of mercury in water
consumption of other animals
and food items (vegetation and insects) collected at the spill
locations
Indirect measures of exposure: modeled concentrations of mercury
in terrestrial animal tissue using literature transfer factors
populations of aquatic biota (macroinvertebrates and fish) that may be
exposed to mercury from the spill
mercury in water and animal tissue from a review of regulatory
guidelines and the scientific literature
Direct measures of exposure: concentrations of mercury in water
and aquatic animal tissue
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3.0
EFFECTS CHARACTERIZATION AND BENCHMARK SELECTION
Regulatory guidance values and the scientific literature were reviewed and summarized for measures of
effects. As outlined in Section 2.3, terrestrial receptors are plants (agricultural and native), livestock,
rodents, birds, humans, and other secondary consumers (e.g., fox). Receptors at potential risk from
pathways that start with water exposure are: aquatic macroinvertebrates and fish, as well as secondary
consumers of aquatic biota, including humans and birds. Terrestrial animals and birds may also utilize
surface water as a source of drinking water.
The literature was surveyed for concentrations of mercury that were reported as 1) resulting in no adverse
effects or 2) resulting in an adverse effect. The no adverse effect concentrations are termed NOAELs,
short for no observed adverse effect levels. Concentrations that result in an effect are called Effect
Levels.
NOAEL concentrations are sometimes reported as safe levels, no effect levels, threshold
concentrations (i.e., the threshold before effects are observed), or normal levels. Commonly reported
Effect Levels are 1) the lowest observed adverse effect level (LOAEL), 2) specific effects on growth or
reproduction, or 3) lethal concentration (LC). While both NOAEL and Effect Levels are summarized in
this section, the RA relies on the more conservative NOAEL values to assess the risk potential. The
literature survey focused on finding information on species relevant to the receptors identified in Section
2.3. Additionally, effort was made to locate and summarize papers that discussed long-term exposures
and reported non-lethal effects from relevant exposure routes (e.g., ingestion rather than injection).
Reports that provide information on the effect, or lack of effect, of mercury on growth and reproduction of
receptors are more desirable than studies that provide lethal concentrations.
3.1
Mercury Toxicity to Humans and Benchmark Determination
Possible effects and manifestations of mercury intoxication to humans, and other animals, are varied.
Effects depend on the chemical form of the mercury, the exposure route (inhalation or ingestion), and the
exposure dose, including the length of exposure and concentration of mercury involved (Amdur et al.
1991). For residents around the spill, the primary possible exposure routes are 1) the inhalation and
ingestion of the spilt ele mental mercury, and 2) the ingestion of ionic mercury after oxidation of the spilt
elemental mercury has occurred. Additionally, if the spilt mercury enters waterways around the spill areas
over time, humans may be exposed to methylmercury through consumption of aquatic organisms that
might be influenced by the increased mercury concentrations in surface water and sediment.
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Methylmercury exposure from consumption of terrestrial plants and animals is unlikely because
methylmercury is uncommon in soils, due to the lack of reducing conditions required to methylate mercury
in soils (Davis et al. 1997).
Inhaled elemental mercury vapor is distributed to the entire body (systemic), whereas ingested mercury is
first cycled through the liver, which is an important detoxification site, prior to systemic distribution.
Ingestion of elemental mercury is generally not considered a health risk since it is largely passed directly
through the gastrointestinal tract, with little absorption, and is excreted in feces, therefore limiting the
amount of mercury that enters the body. Inhaled elemental mercury, conversely, readily crosses the
alveolar membrane of the lung since it is lipid soluble, and is therefore absorbed to a much greater degree.
Mercury absorbed in the body, via ingestion or inhalation, is excreted with a half-life (i.e., time required to
reduce the concentration in the body by 50%) of 35 to 70 days (Amdur et al. 1991, WHO 1991).
Elemental mercury is not listed as a known carcinogen by the U.S. EPA (USEPA 2001b).
As discussed in Section 2.4, the spilt elemental mercury will be transformed to ionic forms over time.
Effects from acute ingestion of ionic mercury include ulcers and other gastrointestinal effects. Chronic
exposure can result in kidney damage, which can be manifested as changes in urine production or in a
build-up of urea in the blood (Amdur et al. 1991, USEPA 2001b). There is also limited evidence that
chronic exposure may effect fertility, likely through effects on sperm production. These effects, however,
were only evidenced after large acute exposures in mice, and fertility returned to normal levels within
about two months (USEPA 2001b, WHO 1991). Ionic mercury is not listed as a known carcinogen
(USEPA 2001b, WHO 1991).
Due to the rapid remediation response and strong sorption of mercury to soils, it is unlikely that any
significant amount of the spilt mercury has entered or will enter the waterways in the future. Any
mercury, however, that enters the water may be transformed to methylmercury, as discussed in Section
1.2.2. Methylmercury is essentially a nervous system toxicant and is generally considered as the most
toxic form of mercury (USEPA 2001c). Because methylmercury effects different organs within the
human body, the possible risks from exposure are treated separately from exposure to other forms of
mercury (i.e., ionic and elemental). Note that potential impacts from methylmercury and other forms are
not considered to be additive.
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Benchmark Determination
The RA only addresses the oral ingestion of mercury. Inhalation exposure to the spilt mercury has been
assessed in earlier documents (Consulcont SAC 2000, SMI 2002).
Drinking Water Exposure
Table 3.1.1 lists some representative safe levels for mercury in drinking water. The lowest level of 1.0
ppb listed in Table 3.1.1 is utilized as the drinking water benchmark for humans. The Peruvian Ministry of
Health (Peru MH 1983) has issued a criterion value of 2.0 ppb for domestic water use.
Table 3.1.1
Representative Human Health Drinking Water Criteria
Country/Organization
USA
Peru
European Union (EU)
Canada
World Health Organization
Mercury
(ppb)
2.0
2.0
1.0
1.0
1.0
References
USEPA (1997b)
Peru MH (1983)
EU (1992)
Health Canada (1998)
WHO (1996)
Dietary-methylmercury
As discussed in Section 1.2.3, fish and seafood consumption typically accounts for the large majority of
mercury ingestion by humans.
Additionally, mercury concentration in fish is almost all in the
methylmercury form and has greater absorption into humans than ionic or elemental forms (Richardson et
al. 1995). Humans essentially only consume methylmercury by eating fish or shellfish (WHO 1991). A
compilation of safe consumption levels for mercury in fish is shown in Table 3.1.2.
No Peruvian
regulations for mercury concentrations in fish are available. The lowest value listed in Table 3.1.2 of 300
ppb (ww) is utilized as the benchmark for consumption of methylmercury in the RA. This value is for the
average dietary concentration of methylmercury, and not for any individual dietary item.
Dietary-elemental/ionic
In general, for oral ingestion, the USEPA approach for evaluating risk to humans utilizes a Reference
Dose, denoted RfD, to establish safe levels for chronic ingestion of a chemical. The USEPA defines a
RfD as “an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the
human population (including sensitive subgroups) that is likely to be without an appreciable risk of
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deleterious effects during a lifetime” (USEPA 1999b). However, the USEPA does not issue a RfD for
elemental mercury (USEPA 2001a).
Table 3.1.2
Listing of Values Reported as Safe Hg Limits by Various Countries and
Regulatory Agencies for Fish
Country/Organization
USA
USA
Brazil
Canada
Denmark
Ecuador
Finland
France
Germany
Greece
India
Italy
Japan
Japan
Netherlands
Philippines
Spain
Sweden
Switzerland
Thailand
Venezuela
Zambia
Australia/ New Zealand
World Health Organization
Type
FDA- fish
EPA- fish MeHg
Fish Std.
Fish Std.
Fish Std.
Fish Std.
Fish Std.
Seafood
Fish Std.
Fish Std.
Fish Std.
Fish Std.
Fish-MeHg
Fish- Total Hg
Seafood
Fish- MeHg
Fish Std.
Fish Std.
Fish Std.
Fish Std.
Seafood
Fish Std.
Fish/seafood standard
Non-predatory /predatory fish
Hg (ppb, ww)
1000
300
500
500
500
1000
1000
500-700
1000
700
500
700
300
400
1000
500
500
1000
500
500
500
300
500-1000
500/1000
References
1
2
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
4
5
1
FDA (U.S. Food and Drug Administration). 1998. Action levels for poisonous or deleterious substances in human food
and animal feed. March 1998.
2
USEPA (U.S. Environmental Protection Agency). 2001. Water Quality Criterion for the Protection of Human Health:
Methylmercury. EPA-823-R-01-001.
3
Nauen, C. 1983. Compilation of Legal Limits for Hazardous Substances in Fish and Fishery Products. Food and
Agriculture Organization of the United Nations, Rome.
4
ANZFA (Australia New Zealand Food Authority). 1987. Food Standards Code: Standards A11- Specifications for Identity
and Purity of Food Additives, Processing Aids, Vitamins, Minerals and Other Added Nutrients (as amended and current
as of December 2001)
5
CODEX. 1991. Guideline Level for Methylmercury in Fish. Food Safety Programme. Codex Commission on Food
Additives and Contaminants. WHO, Geneva.
For the non-fish portion of the diet (i.e., non methylmercury), an RfD derived for mercuric sulfide by the
U.S. Department of Energy (DOE)- Oak Ridge National Laboratory (ORNL 2002) of 0.04 mg of Hg per
Kg of bodyweight per day (mg/kg-day) is used. Additional information on the derivation of this value is
included as Appendix A. Due to similar solubility (Table 1.2.1) and bioavailability between elemental
mercury and mercuric sulfide, ORNL states that this RfD value is also applicable to ele mental mercury.
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As discussed with SENASA personnel in November 2000, the RfD of 0.04 mg/Kg-day can be used to
arrive at safe concentrations of mercury in non-fish food items. By multiplying the RfD by the average
bodyweight of a person, which in this case is assumed to be 60 Kg, the average safe daily intake of
mercury would be 2.4 mg of mercury per day (0.04 mg/Kg-day * 60 Kg). The USEPA (1997c) assumes
that an average person in the U.S. consumes 1.5 kg of food per day. Assuming the same food ingestion
for residents near the spill, 2.4 mg of mercury could be contained in 1.5 kg of food. The allowable
average concentration of mercury in non-fish food, therefore, is equal to 1600 ppb (2.4 mg Hg/ 1.5 Kg
food = 1.6 mg /kg or 1600 ppb). If only 1 Kg of food is consumed, the average safe level is equal to 2400
ppb. In general, the population living near the spill are smaller (height and weight) than the average person
in the USA, upon which the USEPA bases their calculations. It is therefore reasonable to assume that the
average diet for residents near the spill is less than the 1.5 Kg of food per day assumed by the USEPA
(1997c). However, to be conservative, the RA assumes a diet of 1.5 Kg per day, which results in an
average safe mercury concentration in the diet of 1600 ppb. It is important to note, however, that the 1600
ppb safe level is the average for all of the diet. Consumption of occasional individual food items exceeding
this value is not problematic, unless the overall average concentration of mercury in the diet exceeds 1600
ppb.
Summary
In summary, the benchmark values for humans are 1.0 ppb for drinking water, 300 ppb (ww) for
methylmercury consumption in fish and shellfish, and 1600 ppb (ww) for non-fish dietary consumption. All
of these values are based on regulatory guidance values.
3.2
Mercury Toxicity to Other Terrestrial Animals and Benchmark Determination
3.2.1
Birds and Mammals
Overall, the reported toxic symptoms of mercury poisoning in both animals and plants are non-specific.
Essentially, this means that the same symptoms could be explained by a wide variety of causes, and
cannot be easily associated with mercury exposure. Puls (1992) reviewed the literature on symptoms
reportedly associated with mercury toxicity in various domestic animals. The symptoms reported, and the
animals affected by the different symptoms are shown below:
n
n
n
ataxia (incoordination):
muscle weakness:
tremors:
cats, cattle, pigs
cats, pigs
cats
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n
n
n
n
n
changes in urine production/chemistry:
stomach irritation/damage:
diarrhea:
loss of appetite/weight:
decreased fertility:
cats, cattle, horses
horses
horses
horses, pigs, poultry
poultry
These symptoms are similar to effects that are observed in animals afflicted with a variety of diseases, or
other conditions (e.g., poor nutrition or parasites).
The kidney is the primary concentrating organ for inorganic mercury in mammals and fish. For mammals,
the kidney typically contains 50-80% of all of the mercury in the body (WHO 1991). The level of the
glutathione enzyme, in the kidney, is the likely primary determinant of the ultimate concentration of
mercury in kidneys. Other known sites of mercury deposition in animals are fat reserves, brain, and liver.
In fish-eating birds, mercury builds up to a greater extent in the liver than in the kidney (Scheuhammer et
al. 1998). As with humans, methylmercury effects in animals are typically manifested in the central
nervous system, with effected animals become anorexic and lethargic (Amdur et al. 1991). Because
methylmercury targets different organ systems than other mercury forms, it is considered separately from
the other forms, and methylmercury effects are not considered to be additive to effects from other
mercury forms.
Overall, methylmercury is more mobile in the body than ionic (e.g., HgO and HgS) or elemental mercury
(Sweet and Zelikoff 2001). One example of this is that methylmercury crosses the placenta and can effect
fetuses of pregnant animals, whereas inorganic mercury is essentially unable to cross the placenta (Amdur
et al. 1991, WHO 1991). Up to 95% of ingested methylated forms of mercury are absorbed in the
gastrointestinal tract of mammals, whereas only 7-15% of ingested inorganic salt forms (e.g., mercuric
chloride, HgCl2) are absorbed, and approximately 0.01% of ingested elemental mercury is absorbed
(Amdur et al. 1991, WHO 1991). Excretion of inorganic mercury in mammals is through urine, bile, feces,
and sweat (Sweet and Zelikoff 2001). Birds also excrete mercury by molting feathers. Mercury is
incorporated into the disulfide bonds in the keratin protein of feathers, and is lost when the feathers are
molted by the birds (Eisler 2000).
Dietary and drinking water benchmarks
Table 3.2.1 lists NOAEL and Effect Levels of mercury in the diet of birds and mammals. NOAEL values
are listed first and are unshaded. The Effect Levels in Table 3.2.1 are shaded and listed from lowest to
highest effect concentrations. All of the dietary values are listed in dry weight unless noted otherwise. If
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the report did not state if the concentration was based on wet or dry weight, dry weight was assumed to
be conservative.
Table 3.2.1
NOAEL and Effect Levels of Dietary Mercury for Mammals and Birds
Species
ppb,dw
Chemical Form/Notes
Effect
Reference
Rat
Rat
Animal (general)
Mink
Animal (general)
Mink (ww*)
Mouse
500
800
1000
1100
2000
7930
69500
MAMMALS- NOAEL
Methyl Hg chloride - chronic
NOAEL
Total, 90 day physiology
NOAEL
Hg2+, growth effects
NOAEL
Methyl Hg chloride
NOAEL
Total Hg
Safe limit
HgCl; chronic, reproduction
NOAEL
Mercuric sulfide-chronic
NOAEL
American mink
Northern river
otter
Rat
Mouse
Mouse
1800
2000
MAMMALS- EFFECT LEVELS
Methyl Hg chloride
Lethal
Methyl Hg
Lethal
Wobeser and Swift 1976
O’Connor and Nielsen 1981
2500
8000
10000
Methyl Hg chloride
Hg(NO3 ) 2
Methyl Hg
Sample et al. 1996
Von Burg and Greenwood 1991
15000
29000
210000
357000
388000
1429000
Methyl Hg chloride
HgCl2
HgCl
HgI 2
HgNO3
Elemental Hg
Reduced pup viability
LD50
Impaired immune
response
Renal tumors
LD10
LD50
LD10
LD50
LD10
BIRDSMethyl, 77 day exposure
HgCl2 - chronic exposure
Inorganic
NOAEL
LD0
No effect
LD0
Rat
Human
Rat
Human
Mouse
Human
Zebra finch
Japanese quail
Japanese quail
2500
4000
32000
Mallard
Mallard
Zebra finch
Poultry
Japanese quail
Japanese quail
Japanese quail
Japanese quail
500
3000
5000
5000
8000
8000
18000
32000
Japanese quail
Japanese quail
Pheasant
Mallard
Japanese quail
42000
47000
3790000
5000000
5086000
Sample et al. 1996
Dellinger et al. 1995
NAS 1980; Underwood 1977
Hapke 1991a
Aulerich et al. 1974
Sample et al. 1996
Mitsumori et al. 1984
Wolfe et al. 1998
Sample et al. 1996
Eisler 2000
BIRDS- EFFECT LEVELS
MeHg dicyandiamide
Decreased reproduction
Methylmercury
Methyl, 77 day exposure
LD25
Total Hg
HgCl2
LOAEL- chronic
Methyl Hg
Poisoning occurs
Methyl Hg chloride
Acute LD50
HgCl2
No effect on growth rate;
decrea decreased fertilization
Heinz 1974
Eisler 2000
Wolfe et al. 1998
Hapke 1987
Sample et al. 1996
Aagdal et al. 1978
WHO 1989
WHO 1989
HgCl2
Methyl Hg chloride
HgCl2
HgCl2
HgCl2
WHO
WHO
WHO
WHO
WHO
Acute LD50
5-day LC50
5-day LC50
5-day LC50
5-day LC50
1989
1989
1989
1989
1989
Unshaded cells are NOAELs and shaded cells are Effect Levels
*ww= wet weight diet
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Methylmercury is reported to be lethal to mink and otters at a dietary concentration of 1800 ppb and 2000
ppb, respectively (Table 3.2.1). Both of these mammals are members of the Carnivore family and are
primarily fish-eaters. Rodents are less sensitive, with non-lethal effects reported for rats at a dietary
methylmercury concentration of 2500 ppb (Table 3.2.1). Reported lethal concentrations of ionic forms of
mercury range from an LD50 (lethal dose for 50% of the test population) of 8000 ppb for mice exposed to
Hg(NO3)2 to an LD50 of 388,000 ppb for mice exposed to HgNO3.
Reported dietary NOAELs for methylmercury are 500 ppb for rats and 1100 ppb for mink. NOAELs for
ionic mercury forms range from 1000 ppb for animals in general up to 69,500 ppb for mice (Table 3.2.1).
The most relevant NOAEL for elemental mercury exposure is the value of 69,500 ppb value for mice
exposed to chronic levels of mercuric sulfide (HgS). Mercuric sulfide is similar to elemental mercury in
terms of having a low solubility (Table 1.2.1) and bioavailability (ORNL 2002). However, to be
conservative, the general animal NOAEL of 2000 ppb (dw) from Hapke (1991a) is set as the dietary
benchmark value for most mammals in this risk assessment. As a comparison to this value, the U.S.
Department of Energy (DOE; Sample et al. 1996) has issued benchmark values for mercuric sulfide and
mercuric chloride. All of the benchmark values for the exposure of different species to mercuric sulfide
exceed 26,000 ppb (ww). The benchmark values for mercuric chloride range from 3400 ppb (ww) for
bats to 11840 ppb (ww) for deer.
An additional benchmark value of 1100 ppb (dw) is set for mammals that essentially only consume fish.
This second value is equal to the NOAEL reported for mink, which is the species that had the lowest
reported toxic concentration of 1800 ppb (Table 3.2.1). There are, however, no known species of fisheating (piscivorous) mammals that occur in the area (Table 2.3.1).
The lowest reported Effect Level of 500 ppb (reproduction in mallard ducks) is for methylmercury
dicyandiamide. This form of methylmercury was developed as a pesticide, and is therefore less relevant
to understanding the toxicity of naturally-occurring chemical forms of mercury. The next lowest Effect
Level is 3000 ppb methylmercury for mallards. Other reported Effect Levels (Table 3.2.1) are an LD25
of 5000 ppb for zebra finches (methylmercury), decreased reproduction in poultry at 5000 ppb (total
mercury), and a chronic LOAEL for Japanese quail of 8000 ppb (HgCl2). As shown in Table 1.2.1,
mercuric chloride is a much more soluble ionic form of mercury than either the mercuric oxide or mercuric
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sulfide forms that naturally occur in the environment. Based on the values listed in Table 3.2.1, the
concentrations of methylmercury and mercuric chloride that are toxic to birds are similar.
Reported dry weight NOAELs are 2500 ppb methylmercury for zebra finches, 4000 ppb mercuric chloride
and 32,000 ppb inorganic mercury for Japanese quail (Table 3.2.1). Based on these NOAEL values, a
benchmark concentration of 4000 ppb (dw) is selected to be protective of birds from ionic mercury
exposure. This value is equal to the lower of the two NOAEL values listed for Japanese quail. For
piscivorous birds, a second safe dietary benchmark is set at 2500 ppb (dw) based on the NOAEL for
methylmercury exposure of zebra finches.
Both mammals and birds are relatively insensitive to mercury exposure from drinking water (Table 3.2.2).
The lowest reported toxic values are 5000 ppb for mammals and 250,000 ppb for birds. However, to be
conservative, the benchmark value for human drinking water of 1 ppb mercury is utilized as the
benchmark for all animals.
Table 3.2.2
NOAEL and Effect Levels of Mercury in Drinking Water for Mammals and Birds
Species
ppb
Chemical Form/Notes
Effect
MAMMALS- NOAEL
No effect
No effect
Mouse
Mouse
1000
5000
Methylmercury
HgCl2
Mouse
5000
MAMMALS- EFFECT LEVELS
Methylmercury
Decreased growth
Chicken
Chicken
Chicken
Chicken
BIRDS- NOAEL
300000 HgCl2 in drinking water; chicks No effect
Reference
Schroeder and Michener 1975
WHO 1989
BIRDS- EFFECT LEVELS
250000 HgCl2 in drinking water; 8Slight decrease in body WHO 1989
month old hens
weight, smaller eggs
300000 HgCl2 in drinking water;
Decreased growth
WHO 1989
juveniles
500000 HgCl2 in drinking water; 4-week Decreased growth rate, WHO 1989
males
higher mortality
30
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November 2002
FINAL
Tissue benchmarks
In addition to NOAELs and Effect Levels of mercury in animal diets, the scientific literature was
reviewed to determine NOAELs and Effect Levels of mercury in the tissues of animals. Literature values
for tissue concentrations are shown in Table 3.2.3. As before, NOAELs are listed first, followed by
shaded Effect Levels.
Table 3.2.3
Reported NOAEL and Effects Levels of Mercury in Animal Tissue
Species
ppb, dw
Notes
Tissue Type Effect
Reference
MAMMAL- NOAEL
Liver
No effect
Heart
No effect
Kidney
No effect
Liver
No effect
Liver
Normal
Muscle
Normal tissue concentration
Lung
No effect
Muscle
Hapke 1991a
Kostic et al. 1977
Kostic et al. 1977
Kostic et al. 1977
Fimreite et al. 1970
Falandysz et al. 1994
Kostic et al. 1977
Pig
Rat
Rat
Rat
Rodents
Rabbit
Rat
Sheep
100
120
780
800
900
1200
1260
3700
Total
Total
Total
Total
Total
Total
Total
Total
Hg
Hg
Hg
Hg
Hg
Hg
Hg
Hg
American mink
Northern river otter
76000
80000
Total Hg
Total Hg
MAMMAL- EFFECT LEVELS
Muscle
Lethal
Muscle
Lethal (chronic)
American mink
160000
165000
Total Hg
Total Hg
Kidney
Liver
Lethal
Lethal (chronic)
195000
Total Hg
Kidney
Lethal (chronic)
American mink
291000
Total Hg
Liver
Lethal
31
O’Connor and Nielson
1981
1981
1981
Shepherd Miller
November 2002
FINAL
Table 3.2.3
Reported NOAEL and Effects Levels of Mercury in Animal Tissue (continued)
Poultry
Songbirds
Upland game birds
Chicken
Common tern
Duck/geese sp.
Duck/geese sp.
Turkey
Common tern
Common tern
40
150
1750
1800
3930
4300
5000
6000
33600
76700
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
BIRD- NOAEL
General tissue Normal background
Liver
Normal background
Liver
Normal background
Muscle
Liver
No effect
Muscle
Muscle
Muscle
Liver
Nesting success
Liver
Hatching success
Hapke 1991b
Wolfe et al. 1998
Wolfe et al. 1998
Wolfe et al. 1998
Common loon
Chicken
Pheasant
Water birds
Am. Black Duck
Great white heron
Great white heron
Common loon
Zebra finch
Common tern
Common tern
Common loon
Birds-general
Osprey
Japanese quail
Common grackle
Common loon
Common grackle
Red-winged blackbird
European starling
Gannet
European starling
Red-winged blackbird
7400
15000
15000
18500
18500
22200
26700
30900
74100
82200
102000
110000
111000
130000
135000
150000
192000
202000
275000
320000
362000
384000
469000
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Methyl Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
BIRD- EFFECT LEVELS
Brain
Reduced reproduction
Hen liver
Decreased hatchability
Liver
Liver
Toxic threshold- reproduction
Brain
Failure to hatch
Correlated mortality from chronic disease
Liver
Liver
Increased disease and emaciation
Liver
Brain
25% mortality
Liver
Abnormal feather loss in juveniles
Liver
Decreased fledge success
Liver
Reduced nesting success
Liver
Neurological effects
Liver
lethal
Liver
Poisoning occurs
Kidney
LD33
Liver
Reduced hatching success
Liver
LD33
Kidney
LD33
Kidney
LD33
Liver
Lethality
Liver
LD33
Liver
LD33
Wolfe et al. 1998
Fimreite 1970
Borg et al. 1969
Zillioux et al. 1993
Wolfe et al. 1998
Wolfe et al. 1998
Wolfe et al. 1998
Wolfe et al. 1998
Scheuhammer 1988
Wolfe et al. 1998
Wolfe et al. 1998
Wolfe et al. 1998
Heinz 1974
Wolfe et al. 1998
Aagdal et al. 1978
Wolfe et al. 1998
Wolfe et al. 1998
Wolfe et al. 1998
Wolfe et al. 1998
Wolfe et al. 1998
Wolfe et al. 1998
Wolfe et al. 1998
Wolfe et al. 1998
Earthworm
Earthworm
Earthworm(ww)
2
20
27000
Methyl Hg Whole
Total Hg Whole
Total Hg Whole
TERRESTRIAL INVERTEB RATE- NOAEL
Normal
Normal
NOAEL-reproduction
Vonburg and Greenwood 1991
Vonburg and Greenwood 1991
Beyer et al. 1985
TERRESTRIAL INVERTEB RATE- EFFECT LEVELS
Aphid
Green lacewing
Earthworm (ww)
25000
31000
85000
Methyl Hg Whole
Methyl Hg Whole
Total Hg Whole
LD50
Lethal
70% decrease in reproduction
Haney and Lipsey 1973
Haney and Lipsey 1973
Beyer et al. 1985
* unless noted otherwise, values are for dry weight tissues; ww= wet weight tissue concentration
The highest NOAEL level for mammals in Table 2.3.2 is 3700 ppb (dw) in sheep muscle. Assuming 80%
moisture in muscle, this is equivalent to 740 ppb on a wet weight basis. Higher NOAELs, up to 76700 ppb
(dw) are listed for birds. The lowest Effect Level for birds is 7400 ppb (dw) in loon brain tissue. The
highest muscle NOAEL for birds is 6000 ppb (dw) for turkeys. Again, assuming 80% moisture, this is
32
Shepherd Miller
November 2002
FINAL
equivalent to 1200 ppb on a wet weight basis. The 740 ppb (ww) value from sheep muscle and the 1200
ppb (ww) value for turkey muscle are utilized as the benchmark tissue concentrations in the RA.
NOAEL concentrations of mercury in terrestrial invertebrate tissue range from 2 ppb (dw) to 27,000 ppb
(ww). Reported Effect Levels are equal to or higher than 25000 ppb (dw). The lowest Effect Level of
25000 ppb (dw) was divided by an uncertainty factor (UF) of 50, as recommended by Calabrese and
Baldwin (1993), to go from a lethal endpoint to a chronic NOAEL. The resulting benchmark value is 500
ppb (dw). Assuming 80% moisture, the corresponding wet weight benchmark value is 150 ppb.
3.2.2
Plants
The World Health Organization (WHO 1989, 1991) states that plants are generally insensitive to the
inorganic forms of mercury (i.e., elemental and ionic), likely because of the strong sorption of mercury to
soil particles, which largely prevents plant uptake and toxicity. Evidence of the lack of mercury uptake by
plants comes from greenhouse studies, as well as reports from sites with plants growing on mine spoils or
near mercury smelters (Lindberg et al. 1979). Patra and Sharma (2000), in a review of mercury toxicity to
plants, also state that mercury availability to plants is low, and that large increases in soil mercury
concentrations do not result in large increases in mercury uptake into plant tissues. Organic forms of
mercury (i.e., methylmercury) are more available to plants than inorganic forms, though methylmercury is
uncommon in soils since the reducing conditions required to methylate mercury rarely occur in soils (Davis
et al. 1997).
NOAEL and Effect Levels of mercury in plant tissues are listed in Table 3.2.4. Mercury concentrations
in vegetables, or other herbaceous plants, need to exceed 4600 ppb (dw) before there is a possibility of
mercury toxicity. The most sensitive grasses are affected by tissue concentrations as low as 3333 ppb in
grain, 4000 ppb in stems, and 59,000 ppb in roots (dw; Table 3.2.4). NOAEL values for tree and shrub
tissue are as high as 3500 ppb (dw). No toxic levels for trees and shrubs were located in the literature.
Based on the review of the literature, plant toxicity would likely be manifested by a reduction in the rate of
growth, not the overall survival or viability of plants (i.e., mercury will not kill the plant). A benchmark
value of 3000 ppb (dw) for plant tissue is established for plant tissue in the RA. This value was chosen
since it is within the reported NOAEL levels and is less than the lowest Effect Concentration of 3333 ppb
(dw) for plants.
33
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November 2002
FINAL
Table 3.2.4
NOAEL and Effect Levels of Mercury in Plant Tissue
Species
ppb (dw)
Corn (maize)
Corn (maize)
Rye
Oats
Oats
Wheat
Wheat
Oats
Barley
Barley
Barley
Oats
Wheat
Rice
Barley
Oats
Wheat
Grass (mixed)
Barley
Sheep fescue
Rice
Kentucky bluegrass
Bermuda grass
Velvet bentgrass
Barley
3
4.6
9
9
9
11
12
12
12
12
12
14
14
15
19
33
36
70
80
300
500
750
1000
1680
2000
Grass (mixed)
Kentucky bluegrass
Bermuda grass
Sheep fescue
Barley
Rice
2200
2500
2900
3250
3000
1000000
Corn (maize)
Oats
Bermuda grass
Hg form
Effect
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
T otal Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
MeHg
hydroxide
Total Hg
Total
Total
Total
Hg2+
Total
Root
Leaves
Root
Leaves
Roots
Hg
Hg
Hg
Hg
3333
4000
59000
Total Hg
Total Hg
Total Hg
1.4
1.5
3
3.7
5.7
6.5
8.3
11
19
24
39
40
51
58
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Jewel flower
Tall whitetop
Beans
Woodland strawberry
Carrot
Cabbage/broccoli
Lettuce
Beans
Flax
Oilseed rape
Alfalfa (lucerne)
Oilseed rape
Oilseed rape
Lima bean
Tissue Type
GRASS- NOAEL
Grain
NOAEL
Grain
NOAEL
Grain
NOAEL
Grain
NOAEL
Grain
Normal
Grain
NOAEL
Grain
Normal
Grain
Normal
Grain
Normal
Grain
NOAEL
Grain
Normal
Grain
Normal
Grain
Normal
Grain
NOAEL
Grain
Normal
Straw
NOAEL
Straw
NOAEL
Leaf
NOAEL-growth
Straw
NOAEL
Shoot
NOAEL-growth
Stem
Critical level*
Shoot
NOAEL-growth
Stems
NOAEL growth
Shoot
NOAEL-growth
Leaves
Upper critical
level
Root
NOAEL-growth
NOAEL-growth
NOAEL growth
NOAEL-growth
Upper critical
Critical level
GRASS- EFFECT LEVELS
Grain
Decreased growth
Straw
Decreased growth
Roots
Decreased growth
VEGETABLES - NOAEL
Whole plant
NOAEL
Whole plant
NOAEL
Pods
NOAEL
Whole plant
NOAEL
Roots
NOAEL
Leaves
NOAEL
Leaves
NOAEL
Pods
NOAEL
Straw
NOAEL
Straw
NOAEL
Foliage
NOAEL
Tubers
NOAEL
Tops
NOAEL
Bean
Normal
background
34
Reference
Kabata-Pendias and Pendias 1992
Shacklette 1980
Fergusson 1990
Gracey and Stewart 1974
Fergusson 1990
Saha et al. 1970
Kabata-Pendias and Pendias 1992
Fergusson 1990
Saha et al. 1970
Fergusson 1990
Kabata-Pendias and Pendias1992
VonBurg and Greenwood 1991
Cocking et al. 1995
Cocking et al. 1995
Adriano 1986
Cocking et al. 1995
Weaver et al. 1984
Estes et al. 1973
Lipsey 1975
Cocking et al. 1995
Cocking et al. 1995
Weaver et al. 1984
Cocking et al. 1995
Davis et al. 1978
Adriano 1986
Lipsey 1975
Sorteburg 1978
Weaver et al. 1984
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Shacklette 1980
Shacklette 1980
Haller et al. 1968
Shepherd Miller
November 2002
FINAL
Table 3.2.4
NOAEL and Effects Concentrations of Mercury in Plant Tissue (continued)
Tissue
ppb (dw)
Species
Mercury
Form
Tissue Type
Effect
VEGETABLES - NOAEL (cont.)
Stem
NOAEL- growth
Roots
NOAEL
Pea
Normal background
Aboveground Normal background
Stem
NOAEL- growth
Leaves
NOAEL- growth
Stem
NOAEL- growth
Leaves
NOAEL- growth
Root
NOAEL- growth
Leaf
NOAEL- growth
Root
NOAEL- growth
Stem
NOAEL- growth
Root
NOAEL- growth
Whole plant
NOAEL- growth
Whole
NOAEL- growth
Root
NOAEL- growth
Whole
NOAEL- growth
Root
NOAEL- growth
Whole plant
NOAEL- growth
Broadleaved pepperweed
Carrot
Pea
Cabbage/broccoli
Douglas' sagewort
Douglas' sagewort
Woodland strawberry
Common milkweed
Common milkweed
Jewel flower
Jewel flower
Jewel flower
Woodland strawberry
Woodland strawberry
Douglas' sagewort
Douglas' sagewort
70
86
128
166
200
200
300
300
350
470
500
800
1200
1390
1500
3300
3700
4200
4600
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Cabbage/broccoli
Cabbage/broccoli
6000
8000
Hg +1
Hg +2
Outer leaves
Outer leaves
Composite 1
Poplar
Composite 1
Spruce
Composite 1
Eucalyptus
Douglas sage
Composite 1
Poplar
Composite 1
Spruce
Tasmanian bluegum
Tasmanian bluegum
Tasmanian bluegum
Tasmanian bluegum
Tea
0.08
0.1
0.21
0.5
0.58
3.2
4.6
14.4
20
51.8
70
80
100
2900
3200
3500
Total Hg
Methylated
Total Hg
MeHg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
TREE/SHRUBShoot
Leaves
Shoot
Needles
Shoot
Whole plant
Whole plant
Shoot
Leaves
Shoot
Needles
Leaves
Stem
Root
Whole plant
Stems
Reference
Leonard et al. 1998
Haller et al. 1968
Bowen 1974
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Cocking et al. 1995
Cocking et al. 1995
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
VEGETABLES - EFFECT LEVELS
Decreased growth
Decreased growt h
NOAEL
NOAEL
NOAEL
NOAEL
NOAEL
NOAEL
NOAEL- growth
NOAEL- growth
NOAEL
NOAEL
NOAEL
NOAEL
NOAEL –growth
NOAEL- growth
NOAEL
NOAEL- growth
NOAEL- growth
Hara and Sonoda 1979
Hara and Sonoda 1979
Gnamus et al. 2000
May et al. 1985
Gnamus et al. 2000
May et al. 1985
Gnamus et al. 2000
Leonard et al. 1998
Leonard et al. 1998
Gnamus et al. 2000
May et al. 1985
Gnamus et al. 2000
May et al. 1985
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Shacklette 1970
1
Composite of 42 plant species MeHg= methylmercury
*
The critical value is the upper limit of mercury in tissue for which no effects to the plant are observed.
NOAEL and Effect Levels of mercury in soil are listed in Table 3.2.5. The lowest concentration of
mercury in soil that resulted in an effect (decreased growth) is 25000 ppb (dw). Reported effects tend to
be related to plant growth, rather than germination or survival. As an example, Panda et al. (1992) did not
find significant effects on barley germination at soil mercury concentrations up to 103,000 ppb, whereas
35
Shepherd Miller
November 2002
FINAL
growth of the seedlings was decreased at mercury soil concentrations of 64,000 ppb or greater. A
benchmark concentration of 10,000 ppb (dw) is selected on the basis that it is within the reported range of
NOAEL values, and is only 40% of the lowest Effect Level. This value is also equal to the lowest Soil
Screening Level for mercury listed by the USEPA (2001e). This value, however, is driven by human
health concerns, rather than ecological effects.
Table 3.2.5
NOAEL and Effect Levels of Mercury in Soil to Plants
Species
ppb (dw)
Comment
Effect
Reference
GRASS-SOIL NOAEL
Grass
Bermuda grass
Bermuda grass
Barley
Bermuda grass
Sheep fescue
Kentucky bluegrass
Velvet bentgrass
11000-31000
20000-62000
23000-40000
34900
40000
50000-70000
50000-70000
450000
Total Hg
Total Hg -Clay soil
Total Hg -Sandy soil
Total Hg
Total Hg- Sandy loam soil
Total Hg
Total Hg
Total Hg
Bermuda grass
Bermuda grass
Barley
25000-67000 Total Hg -Loamy soil
50000
HgCl2
64000
Total Hg
NOAEL
NOAEL
NOAEL
No effect on growth
NOAEL
NOAEL
NOAEL
No effect
Cocking et al. 1995
Weaver et al. 1984
Weaver et al. 1984
Panda et al. 1992
Weaver et al. 1984
Cocking et al. 1995
Cocking et al. 1995
Estes et al. 1973
GRASS- EFFECT LEVELS
Bermuda grass
Barley
65000
103300
Total Hg -Sandy soil
Total Hg
Decreased growth
Reduced growth
19% growth inhibitionheight
Decreased growth
44% growth inhibitionheight
Weaver et al. 1984
Weaver et al. 1984
Panda et al. 1992
Weaver et al. 1984
Panda et al. 1992
VEGETABLE(FORB)- NOAEL
Flax
23
Total Hg; Avg. of ~2000 soil
samples
Common milkweed
11000-31000 Total Hg
Jewel flower
23800
Total Hg
31800
Total Hg
Woodland strawberry
33700
Total Hg
Douglas’ sagewort
53500
Total Hg
Garden onion
100000
Total Hg
Normal
NOAEL
NOAEL
NOAEL
NOAEL
NOAEL
No effect on emergence
Gracey and Stewart
1974
Cocking et al. 1995
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Leonard et al. 1998
Adriano 1986
VEGETABLE(FORB)- EFFECT LEVELS
Lettuce/carrot
50000
Total Hg
Severe loss of biomass
Adriano 1986
NOAEL
NOAEL
NOAEL
Gnamus et al. 2000
Leonard et al. 1998
Gnamus et al. 2000
TREE- NOAEL
Composite woody plants1
Tasmanian bluegum
Composite woody plants1
651
25800
2456000
Methyl Hg
Total Hg
Total Hg
1
Composite of 42 plant species
36
Shepherd Miller
November 2002
FINAL
3.3
Mercury Toxicity to Aquatic Biota and Benchmark Determination
Several factors influence the toxicity of mercury to aquatic biota, including the form of mercury,
developmental stage of exposed organisms, and the chemistry of the water. Changes in the temperature,
salinity, and hardness of the water can alter the toxicity of mercury to biota (WHO 1989). Generally,
organic forms are more toxic to aquatic biota than inorganic forms of mercury. Early (larval) lifestages are
typically more sensitive to impacts than are adults. Sublethal effects include physiological and biochemical
alterations, as well as impacts to reproductive abilities (WHO 1991).
NOAEL and Effect Levels of mercury in water to aquatic biota are listed in Table 3.3.1. Effects are
broken-out separately for fish and aquatic macroinvertebrates. NOAELs are listed first from lowest to
highest, followed by Effect Levels (shaded) from lowest to highest concentrations. There are relatively
few NOAELs in comparison to reported Effect Levels. The lowest reported toxic value for fish is 3.7 ppb
methylmercuric chloride for fingerling rainbow trout (Table 3.3.1). The lowest reported toxic value for
aquatic macroinvertebrates is an LD50 of 2 ppb inorganic mercury for crayfish. The highest reported
NOAELs are 0.29 ppb for fish and 30 ppb for macroinvertebrates. USEPA (1999c) regulations for
protection of aquatic life are 1.4 ppb for acute exposures (i.e., short-term) and 0.77 ppb for chronic, or
continual, exposures (USEPA 1999c). The Peruvian Ministry of Health lists a value of 0.2 ppb for
protection of aquatic life (Peru MH 1983). The 0.2 ppb criterion value is used as the benchmark value for
water exposure for all aquatic biota.
37
Shepherd Miller
November 2002
FINAL
Table 3.3.1
NOAEL and Effect Levels of Mercury in Water to Aquatic Biota
Species
Pike
Brook trout - larvae
ppb
Notes
Effect
FRESHWATER FISH- NOAEL
0.036 Methyl Hg
Not poisoned
0.29 Mercuric chloride
NOEC
Rainbow trout-fingerlings
Mosquitofish
3.7
10
Rainbow trout-fingerlings
Guppy
Rainbow trout, Steelhead
Rainbow trout, Steelhead
Colorado pikeminnow-larva
Bonytail-larva
Brook trout
Catfish
Brook trout
Striped bass
Razorback sucker-juvenile
Bonytail-juvenile
Banded killifish
Razorback sucker-larva
Catfish
American eel
Striped bass
Largemouth bass
Banded killifish
Colorado pikeminnowjuvenile
Fathead minnow- 30 day olds
Fathead minnow- 30 day olds
Common Carp
American eel
Common Carp
White perch
24
30
33
42
57
61
65
75
75
90
90
108
110
128
131
140
140
140
160
168
FRESHWATER FISH- EFFECTS LEVELS
Methylmercuric chloride Toxic - 70d
Hg +2
Impaired escape
behavior
Organic Hg
96-hr LC50
Hg+2
Acute toxicity
Mercurous nitrate (Hg+1) 96-hr LC50
Organic Hg
96-hr LC50
Hg+2
96-hr LC50
Hg+2
96-hr LC50
Organic
96-hr LC50
Inorganic
96-hr LC50
Organic
96-hr LC50
Inorganic
96-hr LC50
Hg+2
96-hr LC50
Hg+2
96-hr LC50
Inorganic
96-hr LC50
Hg+2
96-hr LC50
Inorganic
240-hr LC50
Inorganic
96-hr LC50
Inorganic
48-hr LC50
Mercuric chloride
LC50 - 8d
Inorganic
48-hr LC50
Hg+2
96-hr LC50
168
172
180
190
210
220
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
96-hr LC50
96-hr LC50
96-hr LC50
48-hr LC50
48-hr LC50
96-hr LC50
38
Reference
Lockhart et al. 1972
McKim et al. 1976
Matida et al. 1971
Kania and O’Hara 1974
Wobeser 1975
USEPA 1986
Hale 1977
Wobeser 1975
Buhl 1997
Buhl 1997
USEPA 1980
WHO 1989
McKim et al. 1976
Rehwoldt et al. 1972
Buhl 1997
Buhl 1997
Buhl 1997
WHO 1989
Birge et al. 1978
Buhl 1997
Snarsky and Olson 1982
Spehar and Fiandt 1986
Shepherd Miller
November 2002
FINAL
Table 3.3.1
NOAEL and Effect Levels of Mercury in Water to Aquatic Biota (continued)
Species
ppb
Notes
Effect
Reference
FRESHWATER FISH- EFFECTS LEVELS (cont.)
Striped bass
Rainbow trout
American eel
Banded killifish
Rainbow trout
Rainbow trout
Pumpkinseed
Catfish
Common Carp
White perch
Catfish
Pumpkinseed
Rainbow trout
Pumpkinseed
White perch
Salmonids (trout)
Rainbow trout
White sucker
African mouthbrooders
Catfish
Rainbow trout
Brook trout- larva
Freshwater tilapia
Catfish
Catfish
Catfish
Flounder
220
220
250
270
280
300
300
314
330
340
350
390
400
410
420
420
450
687
739
860
903
930
1000
1000
1000
1256
1500
1700
3300
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Mercuric chloride
Inorganic
Inorganic
Inorganic
Mercuric chloride
Inorganic
Hg +2
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
24-hr LC50
96-hr LC50
24-hr LC50
24-hr LC50
96-hr LC50
48-hr LC50
96-hr LC50
96-hr LC50
24-hr LC50
48-hr LC50
96-hr LC50
48-hr LC50
96-hr LC50
24-hr LC50
24-hr LC50
96-hr LC50
48-hr LC50
96-hr LC50
72-hr LC50
24-hr LC50
24-hr LC50
Death - chronic
48-hr LC50
Acute toxicity
72-hr LC50
24-hr LC50
48-hr LC50
24-hr LC50
48-hr LC50
WHO 1989
WHO 1989
WHO 1989
WHO 1989
WHO 1989
WHO 1989
USEPA 1985
WHO 1989
Duncan and Klaverkamp 1983
WHO 1989
WHO 1989
Wobeser 1975
McKim et al. 1976
WHO 1989
US EPA 1986
WHO 1989
WHO 1989
WHO 1989
WHO 1989
WHO 1989
FRESHWATER INVERTEBRATES- NOAEL
Hg +2
Hg +2
Total Hg
Daphnia magna
Daphnia magna
Daphnia magna
0.0001
1.1
30
Crayfish
Daphnia magna
Daphnia pulex
Water flea
Daphnia magna
2
2.2
3
3.2
3.4
Inorganic
Hg +2
Inorganic
Inorganic
Hg +2- 3 weeks
Daphnia magna
Daphnia magna
Crayfish
Daphnia magna
Midge
Crayfish
Midge
Snail-adult
Midge- larvae
Snail
Snail
Snail
Midge- larvae
Snail
5
5
7
13
20
20
60
80
100
135
188
296
316
369
Hg +2
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Inorganic
Normal
Chronic safe level
Toxic threshold
Lithner 1989
USEPA 1986
Bringman and Kuhn 1959
FRESHWATER INVERTEBRATES- EFFECTS LEVELS
30-day LC50
LC50
48-hr LC50
48-hr LC50
16% decrease in
reproduction
LC50
48-hr LC50
96-hr LC50
21-day LC50
96-hr LC50
96-hr LC50
24-hr LC50
96-hr LC50
96-hr LC50
96-hr LC50
48-hr LC50
72-hr LC50
48-hr LC50
48-hr LC50
39
WHO 1989
WHO 1989
WHO 1989
WHO 1989
Biesinger and Christensen 1972
USEPA 1985
Wren et al. 1995
WHO 1989
WHO 1989
WHO 1989
WHO 1989
WHO 1989
WHO 1989
WHO 1989
Shepherd Miller
November 2002
FINAL
Table 3.3.1
NOAEL and Effect Levels of Mercury in Water to Aquatic Biota (continued)
Species
Crab
Midge- larvae
Crab
Crab
Midge- larvae
Copepod
Nais sp.
Midge- larvae
Snail-adult
Snail
Caddisfly
Damselfly
Nais sp.
Mayfly
Stonefly
Caddisfly
Snail-egg/embryo
Copepod
Damselfly
Daphnia magna
Mussels
Daphnia magna
Daphnia magna
Caddisfly
Mussels
Snail-egg
Mussels
ppb
Notes
Effect
Reference
FRESHWATER INVERTEBRATES- EFFECTS LEVELS (cont.)
443 Inorganic
72-hr LC50
WHO 1989
547 Inorganic
96-hr LC50
WHO 1989
591 Inorganic
48-hr LC50
WHO 1989
739 Inorganic
24-hr LC50
WHO 1989
750 Inorganic
48-hr LC50
WHO 1989
850 Inorganic
48-hr LC50
WHO 1989
1000 Inorganic
96-hr LC50
1028 Inorganic
24-hr LC50
WHO 1989
1100 Inorganic
24-hr LC50
1108 Inorganic
24-hr LC50
WHO 1989
1200 Inorganic
96-hr LC50
1200 Inorganic
96-hr LC50
1900 Inorganic
24-hr LC50
2000 Total Hg
96hr LC50
Warnick and Bell 1969
2000 Total Hg
96hr LC50
2000 Inorganic
96-hr LC50
2100 Inorganic
96-hr LC50
2200 Inorganic
48-hr LC50
WHO 1989
3200 Inorganic
24-hr LC50
3610 Inorganic
48-hr LC50
WHO 1989
3690 Inorganic
LC50 - 96hr
Wren et al. 1995
4300 Inorganic
48-hr LC50
WHO 1989
4890 Inorganic
24-hr LC50
WHO 1989
5600 Inorganic
24-hr LC50
5910 Inorganic
48-hr LC50
WHO 1989
6300 Inorganic
24-hr LC50
7390 Inorganic
24-hr LC50
WHO 1989
NOAEL and Effect Levels of mercury in the tissues of aquatic macroinvertebrates and fish are shown in
Table 3.3.2. Tissue mercury concentrations of 2680 ppb (ww) impaired the escape behavior of fish.
Reported NOAEL values range from 67 to 8000 ppb (ww) for fish tissue.
NOAEL values for
macroinvertebrate tissue range from 10 to 5500 ppb (ww). No Effect Levels for macroinvertebrates
were located. A benchmark tissue concentration of 2000 ppb (ww) was selected for both fish and
macroinvertebrates based on these values. This concentration is within the reported NOAEL range for
fish and macroinvertebrates and is less than the Effect Levels for fish of 2680 ppb (ww).
40
Shepherd Miller
November 2002
FINAL
Table 3.3.2
NOAEL and Effect Levels of Mercury in Aquatic Biota Tissue
Species
ppb (ww)
Notes
Common Carp
Common Carp
Fish
Lake whitefish
Northern pike
Northern pike
Brook trout
Fish
Pike
Northern pike
67
70
200
280
440
1000
2700
4000
8000
8000
Methyl Hg
Total Hg
Total Hg
Total Hg
Total Hg
Methyl Hg
Total Hg
Total Hg
Methyl Hg
Methyl Hg
Mosquitofish
Pike
Walleye
Fathead minnow
2680
5000
5000
5440
Total
Total
Total
Total
Brook trout
Rainbow trout
Trout
Fish
Trout
Trout
Crayfish
Crayfish
Mayfly
Crayfish
Dragonfly
Shredder stonefly
Freshwater shellfish
Mayfly nymph
15000
26000
76000
100000
112000
272000
10
15
18
30
45
48
2800
5500
Hg
Hg
Hg
Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Total Hg
Tissue Type
Effect
FISH- NOAEL
Not specified
Normal background
Not specified
Normal background
Muscle
Normal background
Whole(less head) Normal background
Whole(less head) Normal background
Muscle
Normal
Whole body
No effect
Whole body
Normal background
Whole body
Not poisoned
Whole body
Not poisoned
FISH- EFFECT LEVELS
Whole body
Impaired escape behavior
Muscle
Chronic lethal
Muscle
Chronic lethal
Whole body
Reduced growth and
deformities
Whole body
Lethal
Liver
Toxic
Whole
Equilibrium loss
Whole body
Toxic
Muscle
Equilibrium loss
Liver
Equilibrium loss
MACROINVERTEBRATES - NOAEL
Total Hg
Gill
NOAEL
Total Hg
Muscle
NOAEL
Methyl Hg whole
NOAEL
Total Hg
Hepatopancreas NOAEL
Methyl Hg whole
NOAEL
Methyl Hg whole
NOAEL
Total Hg
Whole
No effect
Total Hg
Whole
NOAEL
Reference
Fimreite and Reynolds 1973
Uthe and Bligh 1971
Uthe and Bligh 1971
Spry and Wiener 1991
Ewers 1991
Kania and O’Hara 1974
Snarski and Olson 1982
Matida et al. 1971
Matida et al. 1971
Matida et al. 1971
Matida et al. 1971
Wright et al. 1991
Wright et al. 1991
Mason et al. 2000
Wright et al. 1991
Mason et al. 2000
Mason et al. 2000
Ewers 1991
Saouter et al. 1991
3.4
Benchmark Summary
The benchmark values established from the literature review are summarized in Table 3.4.1.
41
Shepherd Miller
November 2002
FINAL
Table 3.4.1
Summary of Benchmark Mercury Concentrations
Receptor type
Human
Benchmark type
Drinking water
Non-methyl dietary
Methyl dietary
Terrestrial mammals
Drinking water
Non-methyl dietary
Methyl dietary
Tissue concentration
Birds
Drinking water
Non-methyl dietary
Methyl dietary
Terrestrial insects
Terrestrial plants
Soil concentration
Fish
Water concentration
Aquatic macroinvertebrates
Water concentration
42
ppb
ww/dw
1
1600
300
ww
ww
ww
1
2000
1100
3700
ww
dw
dw
dw
1
4000
2500
6000
ww
dw
dw
dw
150
ww
10000
3000
dw
dw
0.2
2000
ww
ww
0.2
2000
ww
ww
Shepherd Miller
November 2002
FINAL
4.0
EXPOSURE ASSESSMENT
Site-specific sampling was the primary component of the exposure assessment portion of the RA. There
are several sources of data on mercury concentrations in abiotic (soil and water) and tissue samples from
the spill area. Some of the data utilized were collected as part of the spill response and remediation
activities, whereas other data were collected specifically to support the risk assessment. The different
sampling efforts that were utilized to evaluate exposure are discussed in greater detail below.
In addition to the discussed sampling efforts, additional sampling was conducted by Peruvian governmental
agencies or their consultants as part of the Governments’ response to the spill. These data are provided in
Appendix B. Due to several concerns with the validity of this sampling, the data are not utilized in the
Exposure Assessment of the RA. Primary concerns with the data are: 1) a lack of information on
sampling locations and methodologies, 2) inconsistent and insufficient reporting of analytical results, 3)
concerns with the analytical methods and detection sensitivity. As examples of these concerns, for many
of the samples only very general information is provided on sampling location (e.g., fish collected in the
Jequetepeque); additionally, a large number of samples are reported at a concentration of 0.0000 ppb. It is
unclear if these samples were below the detection limit, which is undefined, or if they are misreported.
Additionally, there is no information on the quality assurance and quality control (QA/QC) procedures
utilized in the analytical work. Finally, it is not stated if the results listed in the reports are reported on a
dry weight or wet weight basis.
Efforts were made to resolve concerns with this dataset, including extensive conversations with Dra.
Anaya, the Director of the Centro De Informacion Control Toxicologica (CICOTOX) laboratory. These
efforts, however, failed to resolve the primary concerns with the validity of the collected data. Though it
was determined that the dataset could not be used for the RA, in order to utilize the information gathered
by the SENASA sampling, a subsequent round of sampling was conducted jointly by SENASA, MYSRL,
and Shepherd Miller personnel in November 2000 at the locations where the earlier SENASA sampling
had reported elevated concentrations of mercury in plant tissue. The results of this sampling are discussed
in Section 4.3.
43
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November 2002
FINAL
4.1
Sampling Associated with Remediation and Monitoring
The water and sediment sampling program supporting the remediation and clean-up activities was
designed such that samples would be collected weekly for the first month following the spill or after
significant rainfall events. Sampling frequency was less intense during subsequent months, with at least
monthly water and sediment sampling for the first year following the spill to assess mercury mobility in the
natural waterways. Additional discussion of this sampling can be found in MYSRL (2001).
Water and sediment sample collection was initiated on June 15, 2000, from most of the locations listed in
Table 4.1.1. Sampling was also conducted the following week (June 22). Sampling locations are shown on
Map 2. As indicated in Table 4.1.1 and on Map 2, the locations labeled as ‘Reference’ were collected
from sites that were outside of the potential exposure areas, and are therefore reflective of background
conditions in the area. Samples from the June 15 and June 22 sampling events were sent to a local
Peruvian laboratory (Envirolab-Peru S.A.C.) for analysis. The analytical results of the sediments from
Envirolab were acceptable, but all of the reported mercury concentrations in water samples were below
Envirolab’s detection limit of 400 ng/L (0.4 ppb). In order to quantify the mercury concentrations,
subsequent water and sediment analyses were completed by Frontier Geosciences in Seattle, Washington,
USA, utilizing Cold Vapor-Atomic Fluorescence Spectrometry (CV-AFS) because of its increased
analytical sensitivity and the resulting lower detection limits.
Water and sediment samples were collected weekly for the first month following the spill (samples were
collected on June 15, June 22, June 28, and July 3) to determine if mercury was being transported down
the drainages immediately following the spill. Water and sediment samples were collected every two
weeks for the subsequent month (July 12 and August 2). Monthly sampling occurred again in September
(on September 2). Late in the dry season (e.g., August and September) many of the sampling locations
were dry and no samples were collected.
44
Shepherd Miller
November 2002
FINAL
Table 4.1.1
Water and Sediment Sampling Locations
Sampling Code
RHUAC
MCNG
QCHO-0
DITCH-155
QCHO-1
QCHO-2
WKM144.7
RSJ
RLT
RLTC
RCHO-1
WKM-133.1
RCHO-2
RJEQUE-0
WKM130.9 Ditch
WKM130.9 Irr
RCUM-1
RCUM-2
RJEQUE-1
Stream Name
Rio Huacraruco
Q. Gavilan
Q. Choten
Km 155 Road Ditch Discharge
Q. Choten
Q. Choten
Surface drainage crossing
Rio San Juan
Rio La Tranca
Rio La Tranca
Rio Choten
Km 133.1drainage
Rio Choten
Rio Jequetepeque
Irrigation water
Irrigation water
Rio Cumbe
Rio Cumbe
Rio Jequetepeque
S10-11-ID-1
S10-11-ID-2
TIN-1
TIN-2
QJOR-1
QJOR-2
AMP
AP-ET -CHOROP
AP-ST-CHOROP
CHOPOS
CHOCOL
LZAR
RJEQUE-2
RSUC-1
RSUC-2
QTALLAL-1
QTALLAL-2
RJEQ-AHUA
DITCH-114
RCHI-1
RCHI-2
QTRI
RAM-1
RAM-2
RMAG113
RJEQUE-3
RJEQUE-PUNETE
Irrigation water
Irrigation water
Spring
Spring
Q. Jordan
Q. Jordan
Potable Water at Residence
Potable Water
Potable Water
Potable Water at Posta Medica
Potable Water at School
Potable Water at Residence
Rio Jequetepeque
Q. Succha
Q. Succha
Q. Tallal
Q. Tallal
Rio Jequetepeque
Magdalena
Rio Chilango
Rio Chilango
Q. Trinchera
Rio Amelia
Rio Amelia
Rio Jequetepeque
Rio Jequetepeque
Rio Jequetepeque at Bridge near
Reservior
Rio Jequetepeque at Gallito Ciego
Reservoir
RJEQUE-RES
Sampling Description
Upstream San Juan
Upgradient Road, km 162
Downgradient from km 155 loss area
Downgradient Road, km 155
Downgradient from highway crossing
Downgradient of Road at km 144.7
Downgradient from San Juan
Downgradient from road
Upgradient from road
Downgradient from km 133.1
Downgradient from Rio Choten confluence
Irrigation Culvert drainage beside Site 8
Irrigation Ditch (off culvert) beside Site 8
Upgradient of Road
Downgradient of Road
Downgradient of the Rio Cumbe/
Rio Jequetepeque confluence
Irrigation ditch above Sites 10 and 11
Irrigation ditch below Sites 10 and 11
Upgradient Road, km 126.5
Downgradient Road, km 126.5
Choropampa Residence
Upgradient Choropampa water supply
Choropampa water supply
Choropampa Posta Medica
Choropampa School
Choropampa Residence
Downgradient from Choropampa
Downgradient from Q. Tallal confluence
Street Drainage
Downsgradient Road, km 114
Upgradient Road, km 112.5
Downgradient Road, km 112.5
Downgradient of Magdalena
Downgradient from Magdalena
40 kilometers Downgradient of Magdalena
Road Km
NA
162
155.5
155
155
154.5
144.7
140.5
140
140
133.5
133.1
133
132.5
130.9
130.9
130
130
128.5
Site type
Reference
Reference
Reference
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Reference
Reference
Exposed
Exposed
Exposed
Exposed
Exposed
Reference
Exposed
Exposed
128.5
128..5
127
127
126.5
126.5
126
126
126
126
126
126
126
125
125
121.5
121.5
121.5
114.5
114
114
113
112.5
112.5
110
109
80
Reference
Exposed
Reference
Exposed
Reference
Exposed
Exposed
Reference
Reference
Exposed
Exposed
Exposed
Exposed
Reference
Exposed
Reference
Exposed
Exposed
Exposed
Reference
Exposed
Exposed
Reference
Exposed
Exposed
Exposed
Reference
45 kilometers Downgradient of Magdalena
75
Reference
45
Shepherd Miller
November 2002
FINAL
Several weeks of early season rains occurred between the middle of September and the beginning of
October. Weekly sampling was resumed on September 18 to determine if these early season rains were
mobilizing mercury. Early wet season samples were also collected on September 25 and October 2 before
the rains stopped. After the October 2 sampling it did not rain again for over a month, therefore,
scheduled wet season sampling was postponed. Sampling returned to the monthly dry season schedule
until the wet season resumed. Samples were collected during the week of November 13. The rains
resumed at the end of November and three weeks of wet season sampling resumed on December 1.
Additional samples were collected weekly for three weeks (December 7, 14, and 21), and then once every
two weeks through January of 2001 (January 8 and 20). Subsequent samples were collected in 2001
starting on the following dates: March 1, May 1, May 25, July 4, August 1, August 25, October 25,
November 6, and December 6. These dates covered the end of the 1st wet season and the start of the 2nd
wet season after the spill. There have been two sampling efforts in 2002, conducted during the week of
January 6 and April 15.
Figure 4.1.1 shows each sampling location with the mean concentration of mercury in water, the number
of samples used to calculate the mean, and the maximum recorded concentration. Also shown are the
benchmark values established in Section 3 for drinking water (human, mammal, and bird) and for the
protection of aquatic biota. The supporting data for this figure are provided as Appendix C. For many
locations, the mean concentration is greater than the maximum concentration because for samples that
were below the detection limit (i.e., < 400 ng/L), the detection limit was used in calculating the mean. The
mean concentration across all of the Exposed locations, over all sampling dates, is 0.017 ppb. The mean
concentration across all of the Reference locations, over all sampling dates, is 0.017 ppb. The mean
sediment mercury concentrations from the locations listed in Table 4.1.1, are shown in Figure 4.1.2, along
with the number of samples used to calculate the mean. The supporting data for this figure are provided
as Appendix D. The mean sediment mercury concentration across all of the Exposed sample locations,
over all of the sampling dates, is 112.4 ppb (dw). The corresponding mean for the Reference locations is
177.9 ppb (dw).
46
Shepherd Miller
November 2002
2.5
US EPA and Peru Drinking Water Standard = 2.0
ppb
1.5
Average (including non-detects as MDL)
Maximum Value (excluding non-detects)
Drinking Water Benchmark for all terrestrial animals= 1.0 ppb
1.0
0.5
21
23
2
20
22
25
20
20
20
DITCH-114
**RCHI-1
RCHI-2
QTRI
**RAM-1
RAM-2
RCUM-2
WKM-133.1
19
25
19
18
**RJEQUE-RES
22
RJEQUE-3
20
**RJEQUE-PUENTE
25
-
RMAG-113
13
QTALLAL-2
21
RJEQ-AHUA
22
**QTALLAL-1
25
RSUC-2
23
**RSUC-1
22
CHOPOS
22
RJEQUE-2
9
**AP-ST-CHOROP
7
QJOR-2
23
**AP-ET-CHOROP
20
TIN-2
20
**QJOR-1
1
**TIN-1
2
S10-11-ID-2
18
**S10-11-ID-1
22
RJEQUE-1
22
**RCUM-1
22
WKM-130.9 IRR
8
WKM-130.9 Ditch
QCHO-2
WKM-144.7
6
RCHO-2
QCHO-1
17
RJEQUE-0
7
**RCHO-1
24
**RLTC
23
RSJ
17
RLT
24
**QCHO-0
24
DITCH-155
21
**MCNG
Aquatic Biota Water Benchmark = 0.2 ppb
**RHUAC
Hg (dissolved) ppb
2.0
Note: Maximum values are measured values excluding non-detects.
Averages include all non-detects values of <0.4 as the value 0.4.
The number above each bar is the number of results that went into the average calculation.
**Denotes Reference Sites.
Site
FIGURE 4.1.1
DISSOLVED MERCURY CONCENTRATION IN
WATER SAMPLES AT EACH SAMPLING
LOCATION
Date:
NOVEMBER 2002
Project: 100673
File:
MERC-CHARTS.dwg
1,600
1,400
23
Reference Sites
Exposed Sites
1,200
Number above the mean value equals the
number of samples in the average calculation
M.Y.S.R.L Remediation Goal 1,000 ppb
800
19
600
9
17
400
18
18
19
17
22
RJEQUE-RES
RSUC-1
RJEQUE-2
AP-ST-CHOROP
QJOR-2
QJOR-1
TIN-2
TIN-1
RJEQUE-1
RCUM-2
RCHO-2
WKM-133.1
RCHO-1
RLTC
RLT
RSJ
WKM-144.7
QCHO-2
QCHO-1
DITCH-155
QCHO-0
MCNG
26
RJEQUE-3
22
18
18
20
RJEQUE-PUENTE
20
17
RMAG-113
20
-
3
RAM-2
23
RAM-1
24
QTRI
21
25
RCHI-2
20
RCHI-1
19
DITCH-114
6
6
QTALLAL-2
RCUM-1
22
RJEQ-AHUA
20
QTALLAL-1
9
WKM-130.9 IRR
22
20
9
WKM-130.9 Ditch
21
25
19
S10-11-ID-2
8
22
RSUC-2
23
22
RJEQUE-0
200
9
22
S10-11-ID-1
21
RHUAC
Hg ppb
1,000
Site
FIGURE 4.1.2
AVERAGE MERCURY CONCENTRATION OF
SEDIMENT SAMPLES
Date:
NOVEMBER 2002
Project: 100673
File:
MERC-CHARTS.dwg
FINAL
4.2
Phase I (Year 2000) Sampling Conducted In Support of the Risk Assessment
A sampling program was designed to specifically support the RA. The sampling design and protocols to
be utilized in conducting the sampling were presented to Dr. Peter M. Chapman, an independent third
party reviewer, prior to the collection of samples.
Dr. Chapman was identified early in the risk
assessment process as a qualified individual who could provide an independent review of the RA and its
findings.
Soil, vegetation, terrestrial insects, fish, and aquatic macroinvertebrates were collected at
reference locations outside of the influence of the spilt mercury, and at locations that were potentially
exposed to mercury. There are two phases to this sampling. Phase I collected samples in 2000, prior to
the occurrence of a wet season, which could mobilize the mercury. Phase II sampling was conducted in
2001-2002 after the end of the first post-spill wet season. Results of the Phase II sampling are discussed
in Section 4.4. All of the samples that were collected to specifically support the risk assessment were
analyzed by Frontier Geosciences (Seattle, WA, USA). Original laboratory reports have been previously
supplied to the Ministry of Energy and Mines (MEM).
4.2.1
Terrestrial Sampling and Tissue Analysis
Sampling locations were selected to allow for the analysis of mercury movement, as well as to establish
relative baseline conditions around the spill locations. It was assumed that movement of mercury from the
points of spill along the roadway to adjacent terrestrial systems, if it occurred, would be by either or both
of two vectors: water and road dust. Therefore, at each location, sampling was performed within the
migration route starting near the spill location to areas more distant, but still within the identified potential
migration route. Additionally, at several locations, sampling was performed upgradient of the spill location,
in areas that could not be impacted by the spill (i.e., Reference Sites).
At each terrestrial sampling location (Map 3), soil, aboveground portions of plants, and insects were
collected. All samples were co-located to allow for the analysis of mercury transport in the system. For
agricultural crops, the sampled plant material was divided into different tissue types, with particular
emphasis placed on collection of edible plant tissue (e.g., tomato fruit and corn kernels). Additionally,
tubers were collected, when available, at the specific sampling locations. Each collected species (and
species tissue in some cases) was bagged separately. Soil samples were collected using a stainless steel
trowel to a depth of 20 cm. Soil was composited over the entire 20 cm depth. A depth of 20 cm was
selected as representative of the shallow root system, which would most likely be impacted by surficial
mercury contamination. Insects were collected using insect sweeps at each sampling location. Target
49
Shepherd Miller
November 2002
FINAL
collection amounts were 20+ grams for plants, 50 grams for soil, and 2+ grams for insects. Sampling
equipment was cleaned between samples by scrubbing with detergent water, followed by two de-ionized
water rinses. Samples were placed in Ziploc bags, labeled with Site number, sample number, sample type
(scientific name for plants), tissue type (total, leaves, fruit, etc.), and date collected and then wrapped in
aluminum foil. Samples were kept in coolers for less than 12 hours, until they could be frozen in dedicated
freezers.
The terrestrial sampling was conducted by Homero Bazan of the Cole gio de Biologos del Peru and
Manual Cabanillos and Alfonso Miranda of the Universidad Nacional de Cajamarca. Overall, 154 plant
samples, 45 insect samples, and 48 soil samples were collected in September 2000. Descriptions of
sampling locations, samples collected at each location, and pictures of sampling sites provided by Professor
Bazan are included as Appendix E.
The U.S. Environmental Protection Agency (USEPA 1992) recommends using the 95 percent upper
confidence limit (95% UCL) of the mean for estimating exposure. The 95% UCL is calculated by the
following equation:
95% UCL= x + t (s/q n); where x is the mean value, t is the one -sided t statistic, s is the
standard deviation and n is the number of samples used to calculate
the mean
For the results of all of the sampling conducted in support of the risk assessment, the 95% UCL of the
mean is utilized as a conservative estimate of the true mean.
Soil Analyses
Results of the soil sampling are shown in Table 4.2.1. The results are broken-out by location and by site
type (Reference Site or Exposed Site samples). Site names reflect Identified Spill Locations (i.e., Spill
Locations 1-15, Map 1) or in the case of A, B, and C, locations where visible mercury was not observed,
but surveys identified elevated mercury levels (MYSRL 2001). Reference Sites listed in Table 4.2.1 are
from locations near the actual spill locations, but up-gradient of potential mercury migration routes.
50
Shepherd Miller
November 2002
FINAL
Table 4.2.1
Results of the Phase I Soil Samples
15-2
15-3
14-4
13-6
6-3
6-4
5-4
1-3
Road
Km
119.73
119.73
123.89
124.77
135.39
135.39
139.81
155
Location
Type
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Sample
ID
15-2-SOIL
15-3-SOIL
14-4-SOIL
13-6-SOIL
6-3-SOIL
6-4-SOIL
5-4-SOIL
1-3-SOIL
Total Hg
(ppb, dw)
9.70
27.3
39.8
82.8
39.3
39.1
21.0
1130
15-1
14-1
14-2
14-3
13-1
13-2
13-3
13-4
13-5
10-1
10-2
10-3
8-1
8-2
8-3
8-4
8-5
8-6
8-7
8-8
8-9
7-1
7-2
7-3
7-4
6-1
6-2
5-1
5-2
4-1
4-2
B-1
B-2
C-1
C-2
A-1
A-2
1-1
1-2
119.73
123.89
123.89
123.89
124.77
124.77
124.77
124.77
124.77
128.94
128.94
128.94
130
130
130
130
130
130
130
130
130
134.45
134.45
134.45
134.45
135.39
135.39
139.81
139.81
140.18
140.18
145.433
145.433
145.455
145.455
147.423
147.423
155
155
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
15-1-SOIL
14-1-SOIL
14-2-SOIL
14-3-SOIL
13-1-SOIL
13-2-SOIL
13-3-SOIL
13-4-SOIL
13-5-SOIL
10-1-SOIL
10-2-SOIL
10-3-SOIL
8-1-SOIL
8-2-SOIL
8-3-SOIL
8-4-SOIL
8-5-SOIL
8-6-SOIL
8-7-SOIL
8-8-SOIL
8-9-SOIL
7-1-SOIL
7-2-SOIL
7-3-SOIL
7-4-SOIL
6-1-SOIL
6-2-SOIL
5-1-SOIL
5-2-SOIL
4-1-SOIL
4-2-SOIL
B-1-SOIL
B-2-SOIL
C-1-SOIL
C-2-SOIL
A-1-SOIL
A-2-SOIL
1-1-SOIL
1-2-SOIL
16.5
27.1
48.6
34.9
58.7
21.4
59.4
68.5
33.0
25.9
18.7
794
33.4
47.7
57.4
20.1
112
7.68
26.2
75.9
57.9
30.1
12.9
34.0
98.1
91.9
53.4
58.8
45.7
49.2
74.1
40.7
29.3
51.4
33.7
66.5
40.6
197
156
Site
51
Shepherd Miller
November 2002
FINAL
All of the collected soil samples (Figure 4.2.1) had reported mercury concentrations significantly below the
United States Environmental Protection Agency (USEPA) soil remediation standard for mercury of 10,000
ppb in residential soils (USEPA 1996), which is also equal to the benchmark established for soil that is
protective of plants (Section 3.2.2).
The mean and 95% UCL of the mean dry weight mercury
concentration from the eight Reference Site samples were 173.6 and 432.9 ppb, with values ranging from
9.70 to 1130 ppb. The 1130 ppb value was from Sample 1-3, which was upgradient of Identified Spill
Location 1, and is much higher than the other concentrations at the Reference locations. The mean soil
concentration at the Reference Sites excluding this value was 37.0 ppb (dw) and the 95% UCL was 53.9
ppb (dw). The mean and 95 % UCL of the mean dry weight mercury concentration from the 39 Exposed
Sites were 72.0 and 105.6 ppb. Concentrations ranged from 7.68 to 794 ppb (dw). Only one of the 46
samples, from a Reference Site, exceeds (1130 ppb) the MYSRL remediation goal of 1000 ppb mercury in
soil. Overall, all of the measured soil concentrations were within concentrations representative of
background conditions for the region.
12000
Soil Hg (ppb)
10000
USEPA soil limit=10000 ppb
Soil Benchmark= 10000 ppb
Reference Sites
8000
Exposed Sites
6000
4000
MYSRL Remediation Goal=1000 ppb
2000
0
160
150
140
130
120
110
Spill Area
To Cajamarca
Figure 4.2.1
Road (Km)
To Trujillo
Scatterplot of Phase I soil Hg concentrations (dw) versus location
Vegetation Analyses
Results of the vegetation sampling are shown in Table 4.2.2. Results are first listed for Reference Sites
and then for Exposed Sites, on both a wet weight and dry weight basis. Approximate location along the
road (i.e., Road Km) is also indicated. The results are plotted in Figure 4.2.2, and summary statistics are
shown in Table 4.2.3.
52
Shepherd Miller
November 2002
FINAL
Table 4.2.2
Results of the Phase I Vegetation Analyses
Sample
ID
Road
Km
Site
type
1-3-Baclat
1-3-Bacsp
1-3-Indhoro
5-4-Passp
5-4-Polsp
6-3-Zeamay-fruit
6-3-Zeamay-kernels
6-3-Zeamay-leaves
6-3-Zeamay-stalk
6-4-Acamac
6-4-Altpor
6-4-Crosp
6-4-Schmol
13-6-Bid
13-6-Plamaj
13-6-Trirep
13-6-Verlit
14-4-Eusp
14-4-Schmol
14-4-Solnig
15-2-Cheamb
15-2-Sonole
15-3-Alltub
15-3-Arrxan
15-3-Capfru
15-3-Corsat
155
155
155
139.81
139.81
135.39
135.39
135.39
135.39
135.39
135.39
135.39
135.39
124.77
124.77
124.77
124.77
123.89
123.89
123.89
119.73
119.73
119.73
119.73
119.73
119.73
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Sci. Name
Baccharis latifolia
Baccharis sp.
Indigofora humilis
Paspalum sp.
Polypogon sp.
Zea mays
Zea mays
Zea mays
Zea mays
Acacia macracantha
Alternanthera poirigens
Croton sp.
Schinus molle
Bidens pilosa
Plantago major
Trifolium repens
Verbena littoralis
Euphorbia sp.
Schinus molle
Solanum nigrum
Chenopadium ambrosioides
Sonchus oleraceaus
Allium tuberosum
Arracacia xanthorrihiga
Capsicum frutescens
Conandrum sativum
1-1-Pencla
1-1-Plasp
1-1-Verpar
1-2-Gasven
1-2-Junbuf
1-2-Trirep
A-1-Metind
A-1-Oeosp
A-1-Trirep
A-2-Dalsp
A-2-Medlup
A-2-Phyper
155
155
155
155
155
155
147.42
147.42
147.42
147.42
147.42
147.42
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Pennisetum claudestinum
Plantago sp.
Verbena parvula "verbena"
Gastridium ventricosum
Juncus buffonius
Trifolium repens
Melilotus indica
Oeonothera sp.
Trifolium repens
Dalea sp.
Medicago lupulina
Physalis peruviana
English
Common name
Groundsel
Groundsel
Indigo
Paspalum
Beard grass
Corn
Corn
Corn
Corn
Porknut
Joyweed
Croton
California pepper tree
Beggar's tick
Common plantain
White clover
Verbena
Spurge
Black nightshade
Mexican tea
Sow thistle
Onion
Peruvian carrot
Cayenne pepper
Coriander
Kikuyu grass
Plantain
Verbena
Nitgrass
Toad rush
White clover
Clover
Evening primrose
White clover
Dalea
Black medic
Peruvian groundcherry
53
Spanish
Common name
Tissue1
Chilca negra
Chilca negra
Nudillo
Maiz
Maiz
Maiz
Maiz
Huarango, Espino
Moradilla
Cadillo
Llanten macho
Trebol
Verbena
Lecherita
Molle
Heirba mora
Paico
Cerraja
Cebolla china
Arracacha
Aji verde
Culantro
Kikuyu
Llanten macho
Verbena
Junco
Trebol blanco
Trebol
Flor de cavo
Trebol blanco
Dalea
Tomate de bolsa
cob
kernels
leaves
stalk
fruit
Veg.
Type
Dry
Fraction
Total Hg (ng/g)
wet wt
dry wt
Forb
Forb
Forb
Grass
Grass
Grass
Grass
Grass
Grass
Tree
Forb
Shrub
Tree
Forb
Forb
Forb
Forb
Forb
Tree
Forb
Forb
Forb
Forb
Forb
Forb
Forb
0.337
0.342
0.283
0.269
0.472
0.878
0.912
0.846
0.585
0.455
0.367
0.252
0.304
0.321
0.223
0.218
0.429
0.196
0.381
0.220
0.232
0.217
0.309
0.168
0.163
0.224
12.3
20.8
13.0
5.23
8.97
1.27
65.1
58.1
2.42
34.8
32.5
20.6
9.95
55.6
15.2
21.4
85.5
12.8
38.9
20.2
8.95
5.49
6.84
6.47
4.23
5.41
36.6
60.9
46.1
19.5
19.0
1.45
71.3
68.7
4.14
76.4
88.4
81.7
32.7
173
68.2
98.0
199
65.2
102
92.0
38.6
25.3
22.1
38.5
25.9
24.1
Grass
Forb
Forb
Grass
Forb
Forb
Forb
Forb
Forb
Shrub
Forb
Forb
0.640
0.198
0.244
0.856
0.305
0.326
0.222
0.259
0.333
0.410
0.320
0.222
159
30.4
85.6
52.7
25.6
62.8
14.8
62.4
63.4
11.4
10.0
12.7
248
153
351
61.5
84.1
193
66.7
241
190
27.8
31.3
57.3
Shepherd Miller
November 2002
FINAL
Table 4.2.2
Results of the Phase I Vegetation Analyses (continued)
Sample
ID
C-1-Calsp
C-1-Escpen
C-1-Stesp
C-2-Hypsp
C-2-Minsp
C-2-Salopp
B-1-Escpen
B-1-Phesp
B-1-Rhysp
B-2-Baclat
B-2-Calsp
B-2-Pencla
4-1-Medlup
4-1-Trisp
4-2-Polavi
4-2-Rumsp
5-1-Penela
5-1-Tareff
5-2-Apilep
5-2-Cyndac
5-2-Oxacor
5-3-Cheamb
5-3-Phesp
6-1-Brosp
6-1-Caespi
6-1-Pencla
6-2-Lycsp
6-2-Oxyvis
6-2-Penweb
7-1-Corsp
7-1-Phycan
7-2-Ammvis
7-2-Ophchi
7-2-Rhysp
7-3-Cheamb
7-3-Plamaj
7-3-Rumsp
7-3-Sacoff
Road
Km
145.46
145.46
145.46
145.46
145.46
145.46
145.43
145.43
145.43
145.43
145.43
145.43
140.18
140.18
140.18
140.18
139.81
139.81
139.81
139.81
139.81
139.81
139.81
135.39
135.39
135.39
135.39
135.39
135.39
134.45
134.45
134.45
134.45
134.45
134.45
134.45
134.45
134.45
Site
type
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Sci. Name
Calceolaria "globito"
Escallonia pendula
Stevia sp.
Hyptis sp.
Minthostachys sp.
Salvia oppositiflora
Escallonia pendula
Phenax sp.
Rhynchosia sp.
Baccharis latifolia
Calceolaria "globito"
Pennisetum claundestinum
Medicago lupulina
Trifolium sp.
Polygonum aviculare
Rumex sp.
Pennisetum clandestinum
Taraxarum officinalis
Apium leptophyllum "rulantillo"
Cyndon dactylon
Oxalis corniculata
Chenapodium ambrosioides
Phenax sp.
Browallia sp.
Caesalpinia espinosa
Lycopersicum sp.
Oxybaphus viscosus
Pennisetum weberbaueri
Cortaderia sp.
Phyla canescens
Ammi visnaga
Ophryosporus sp.
Rhynchosia sp.
Chenopodium ambrosioides
Plantago major
Rumex sp.
Saccarum officinasum
English
Common name
Pocket book plant
Escallonia
Stevia
Mint weed
Mint
Peruvian salmon sage
Escallonia
Phenax
Snoutbean
Groundsel
Pocket book plant
Kikuyu grass
Black medic
Clover
Knotweed
Dock
Kikuyu grass
Dandelion
Wild celery
Bermuda grass
Creeping oxalis
Mexican tea
Phenax
Bush violet
Spiny holdback
Kikuyu grass
Tomato
Umbrella wort
Kikuyu grass
Pampas grass
Lippia
Tothpick plant
Snoutbean
Mexican tea
Common plantain
Dock root
Sugar cane
54
Spanish
Common name
Tissue1
Globito
Pauco
Chancua
Salvia
Pauco
Chilca negra
Globito
Kikuyo
Trebol
Kikuyu
Diente de leon
Culantrillo
Grama dulce
Vinagrillo
Paico
Taya
fruit
Rabo de zorro
Turre hembra
Visnaga
Pilhuish
Paico
Lengua de vaca
Cana de azucar
leaves
Veg.
Type
Dry
Fraction
Forb
Tree
Forb
Forb
Shrub
Forb
Tree
Shrub
Shrub
Forb
Forb
Grass
Forb
Forb
Forb
Forb
Grass
Forb
Forb
Grass
Forb
Forb
Shrub
Forb
Tree
Grass
Forb
Forb
Grass
Grass
Forb
Forb
Forb
Forb
Forb
Forb
Forb
Grass
0.149
0.309
0.287
0.389
0.481
0.331
0.315
0.298
0.409
0.353
0.286
0.384
0.326
0.307
0.392
0.267
0.285
0.292
0.216
0.417
0.229
0.230
0.234
0.341
0.516
0.251
0.270
0.213
0.505
0.433
0.645
0.326
0.494
0.434
0.183
0.232
0.213
0.192
Total Hg (ng/g)
wet wt
dry wt
139
254
276
27.2
107
114
156
9.55
41.4
19.9
38.3
16.6
246
263
44.9
81.6
41.4
77.2
12.3
28.3
38.8
7.22
6.89
1930
422
159
46.7
158
122
210
275
46.8
146
115
4.82
7.92
6.07
2.71
931
824
962
69.9
223
345
496
32.1
101
56.2
134
43.1
753
858
115
306
145
265
56.8
68.0
170
31.4
29.5
5660
817
634
173
744
243
485
426
144
296
265
26.3
34.1
28.5
14.1
Shepherd Miller
November 2002
FINAL
Table 4.2.2
Sample
ID
7-4-Apilep
7-4-Setsp
7-4-Sposp
8-1-Annche
8-1-Phycan
8-1-Viglut
8-2-Adisp
8-2-Alltub
8-2-Cheamb
8-2-Taroff
8-2-Vitvin
8-3-Amicel
8-3-Crosp
8-3-Ophchi
8-4-Annche
8-4-Aruclon
8-4-Leonep
8-5-Altper
8-5-Pencla
8-5-Plasp
8-6-Pencla
8-6-Solnig
8-6-Sonole
8-7-Brosp
8-7-Cesaur
8-7-Salopp
8-8-Cyndac
8-8-Phycan
8-9-Annche
8-9-Budsp
8-9-Cessp
10-1-Echsp
10-1-Oxyvis
10-1-Rhyrep
10-2-Asccur
10-2-Bid
10-2-Lansp
10-3-Minsp
10-3-Oeosp
10-3-Plasp
Road
Km
134.45
134.45
134.45
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
128.94
128.94
128.94
128.94
128.94
128.94
128.94
128.94
128.94
Site
type
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Sci. Name
Apium leptophyllum
Setaria sp.
Sporobulus sp.
Annona cherimola
Phyla canescens
Vigna luteola
Adiantum sp.
Allium tuberosum
Chenopodium ambrosioides
Taraxicum officinalis
Vitis vinifera
Amaranthus celosioides
Croton sp.
Ophryosporus chilca
Annona cherimola
Arundo donax
Leonitis nepentaefolia
Alternanthera porrigens
Plantago sp.
Solanum nigrum
Sonchus oleraceaus
Browallia sp.
Cestrum auriculatum
Salvia oppositiflora
Cyndon dactylon
Phyla canescens
Annona cherimola
Bauddleia sp.
Cestrum sp.
Echinochloa sp.
Oxybaphus viscosus
Rhynchelitium repens
Asclepias curassavica
Bidens pilosa
Lantana sp.
Minthostachys sp.
Oeonothera sp.
Plantago sp.
English
Common name
Wild celery
Foxtail
Dropseed
Custard apple
Lippia
Dalrymple vigna
Maidenhair fern
Onion
Mexican tea
Dandelion
Grape
Amaranth
Croton
Custard apple
Giant reed
Lion's ear
Joyweed
Kikuyu grass
Plantain
Kikuyu grass
Black nightshade
Sow thistle
Bush violet
Jasmine
Peruvian salmon sage
Bermuda grass
Lippia
Custard apple
Butterfly bush
Jasmine
Cockspur
Umbrella wort
Natal redtop
Scarlet milkweed
Beggar's tick
Lantana
Mint
Evening primrose
Plantain
55
Spanish
Common name
Pasto negro
Cherimoya
Turre hembra
Porotillo
Culatrillo
Cebolla china
Paico
Diente de leon
Uva
Yuyo
Pilhuish
Chirimoya
Carrizo
Pochequiro
Moradilla
Llanten macho
Kikuyo
Huerba mora
Cerraja
Hierba santa
Grama dulce
Turre hembra
Chirimoya
Hierba santa
Flor de seda
Cadillo
Lantana
Muña
Flor de clavo
Llanten macho
Tissue1
fruit
Veg.
Type
Dry
Fraction
Forb
Grass
Grass
Tree
Forb
Forb
Forb
Forb
Forb
Forb
Tree
Forb
Forb
Forb
Tree
Grass
Forb
Shrub
Grass
Forb
Grass
Forb
Forb
Forb
Shrub
Forb
Grass
Forb
Tree
Tree
Shrub
Grass
Forb
Grass
Forb
Forb
Shrub
Shrub
Forb
Forb
0.311
0.412
0.486
0.292
0.227
0.470
0.424
0.177
0.285
0.239
0.218
0.361
0.341
0.435
0.200
0.179
0.250
0.320
0.262
0.216
0.218
0.280
0.183
0.343
0.291
0.355
0.534
0.407
0.303
0.276
0.192
0.249
0.259
0.352
0.212
0.200
0.260
0.332
0.339
0.168
Total Hg (ng/g)
wet wt
dry wt
47.1
117
89.0
48.2
412
214
85.3
8.80
31.9
45.8
61.9
48.8
426
103
15.2
0.44
53.0
91.8
13.8
16.8
19.0
33.4
8.00
80.8
107
46.8
82.3
680
22.1
1640
5.87
30.3
26.4
10.0
6.85
7.96
19.4
51.2
65.9
83.1
152
284
183
165
1820
455
201
49.7
112
192
284
135
1250
237
76.1
2.47
212
287
52.7
77.8
87.0
119
43.7
235
368
132
154
1670
73.1
5940
30.5
122
102
28.4
32.3
39.8
74.7
154
194
494
Shepherd Miller
November 2002
FINAL
Table 4.2.2
Sample
ID
10-3-Polsp
13-1-Asccur
13-1-Cyndoc
13-1-Leanep
13-1-Monsp
13-2-Acamac
13-2-Altpor
13-2-Cesaur
13-2-Crosp
13-3-Annche
13-3-Citlim-f
13-3-Citlim-l
13-3-Helsp
13-3-Leonep
13-4-Ammvis
13-4-Argsub
13-4-Asccur
13-4-Cucdip
13-5-Zeamay
13-5-Zeamay-fruit
13-5-Zeamay-kernels
13-5-Zeamay-leaves
14-1-Ammvis
14-1-Medhyp
14-1-Phycan
14-1-Riccon
14-2-Bid
14-2-Densp
14-2-Melalb
14-3-Ammvis
14-3-Asccur
14-3-Cyndac
14-3-Datstr
14-3-Galcil
14-3-Phavul
14-3-Rornas
14-3-Staarv
15-1-Althal
15-1-Rueflo
1
Road
Km
128.94
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
119.73
119.73
Site
type
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Sci. Name
Polypogon sp.
Cyndon dactylon
Monnina sp.
Acacia macracantha
Cestrum auriculatum
Croton sp.
Annona cherimola
Citrus limon
Citrus limon
Heliotropium sp.
Ammi visnaga
Argemone subfusiformis
Cucumis dipsaceus
Zea mays
Zea mays
Zea mays
Zea mays
Ammi visnaga
Medicago hyspide
Phyla canescens
Ricinus Communis
Bidens pilosa
Denothera sp.
Melilotus alba
Ammi visnaga
Asclepias curassivaca
Cyndon dactylon
Datura stoamonium
Galinsoga ciliata
Phaseolus vulgaris
Rorripa nastartium aquaticum
Stachys arrensis
Alternanthera halimifolia
Rueilla floribunda
English
Common name
Beard grass
Scarlet milkweed
Bermuda grass
Lion's ear
Monnina
Porknut
Joyweed
Jasmine
Croton
Custard apple
Lemon
Lemon
Heliotroope
Lion's ear
Tothpick plant
Mexican poppy
Scarlet milkweed
Hedgehog
Corn
Corn
Corn
Corn
Tothpick plant
Bur clover
Lippia
Castor bean
Beggar's tick
Primrose
Clover
Tothpick plant
Scarlet milkweed
Bermuda grass
Jimson weed
Hairy galinsoga
Beans
Watercress
Field woundwort
Joyweed
Mexican Petunia
Spanish
Common name
Tissue1
Flor de seda
Grama dulce
Ponchequiro
Palomilla
Huarango
Moradilla
Hierba santa
Chirimoya
Limon
Limon
Ponchequiro
Visnaga
Cardo santo
Flor de seda
Jaboncillo de campo
Maiz
Maiz
Maiz
Maiz
Visnaga
Carretilla
Turre hembra
Higuerilla
Cadillo
Alfaltilla
Flor de clavo
Visnaga
Flor de seda
Grama dulce
Chamico
Galinsoga
Frejol
Berro
Supiquehua
Yerba blanca
fruit
leaves
fruit
kernels
leaves
fruit
Veg.
Type
Dry
Fraction
Grass
Forb
Grass
Shrub
Forb
Tree
Shrub
Shrub
Shrub
Tree
Tree
Tree
Forb
Forb
Forb
Forb
Forb
Forb
Grass
Grass
Grass
Grass
Forb
Forb
Forb
Tree
Forb
Forb
Forb
Forb
Forb
Grass
Forb
Forb
Forb
Forb
Forb
Forb
Shrub
0.324
0.237
0.280
0.252
0.232
0.393
0.521
0.344
0.325
0.412
0.443
0.196
0.316
0.292
0.227
0.176
0.185
0.178
0.892
0.895
0.953
0.952
0.246
0.314
0.254
0.234
0.189
0.354
0.404
0.160
0.302
0.319
0.160
0.261
0.260
0.110
0.215
0.290
0.319
Total Hg (ng/g)
wet wt
dry wt
71.3
68.5
18.2
47.2
60.8
31.2
1120
161
984
485
220
2.47
39.8
26.0
7.75
3.87
8.63
28.6
3.46
3.29
61.1
57.7
34.5
34.0
67.9
29.6
19.4
44.2
28.4
4.78
13.5
6.67
3.15
11.9
4.26
4.15
11.4
73.8
57.5
220
289
65.0
187
262
79.4
2150
469
3030
1178
496
12.6
126
89.1
34.2
22.0
46.6
161
3.88
3.67
64.2
60.6
140
108
267
126
102
125
70.4
29.9
44.7
20.9
19.7
45.7
16.4
37.7
53.1
255
180
aboveground tissue collected, unless specific tissue type noted
56
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November 2002
FINAL
2500
total Hg (ppb, ww)
Reference samples
2000
1500
Exposed samples
Human Dietary Benchmark=1600 ppb
1000
500
0
155
145
135
125
115
Spill Area
To Cajamarca
Location (Road Km)
To Trujillo
7000
Reference samples
total Hg (ppb, dw)
6000
Exposed samples
5000
Bird Dietary Benchmark= 4000 ppb
4000
3000
2000
Mammal Dietary Benchmark= 2000 ppb
1000
0
155
145
135
125
115
Spill Area
To Cajamarca
Figure 4.2.2
Location (Road Km)
To Trujillo
Total Hg tissue concentrations in the Phase I vegetation tissues collected at
reference and exposed locations. Wet weight and dry weight values are plotted
separately. The two values exceeding the human dietary benchmark are nonedible bush-violet and butterfly plants.
57
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November 2002
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Table 4.2.3
Summary Statistics for the Phase I Vegetation Sampling
Reference
wet weight
dry weight
Exposed
wet weight
dry weight
mean
(ppb)
95%UCL
(ppb)
range
(ppb)
22.0
60.7
29.4
76.5
1.3-85.5
1.45-199
118.0
354.4
156.6
472.2
0.44-1930
2.47-5940
Terrestrial Insect Analyses
Results of the insect tissue sampling are listed in Table 4.2.4. Results are listed by location along the road
and by the type of sample (Reference or Exposed).
Summary statistics are provided in Table 4.2.5. The dry weight tissue concentrations were calculated
based on the average dry fraction of the 14 samples analyzed for percent moisture. Insufficient sample
size prevented the analysis of all samples for percent moisture. A scatterplot of the measured insect
tissue mercury concentrations versus location along the road is shown in Figure 4.2.3. The insect tissue
benchmark of 150 ppb (ww) and the bird dietary benchmark of 4000 ppb (dw) are indicated on Figure
4.2.3.
58
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Table 4.2.4
Results of the Phase I Insect Tissue Sampling
Sample
ID
Road Km
1-3 Insects
5-4 Insects
6-3 Insects
6-4 Insects
13-6 Insects
14-4 Insects
15-2 Insects
15-3 Insects
155
139.81
135.39
135.39
124.77
123.89
119.73
119.73
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
NA
0.41
NA
NA
NA
NA
0.39
NA
13.7
21.1
49.9
35.0
53.6
118
9.51
19.9
51.8
24.3
-
1-1 Insects
1-2 Insects
A-1 Insects
A-2 Insects
C-1 Insects
C-2 Insects
B-1 Insects
B-2 Insects
4-1 Insects
4-2 Insects
5-1 Insects
5-2 Insects
5-3 Insects
6-1 Insects
6-2 Insects
7-1,2 Insects
7-3 Insects
7-4 Insects
8-1 Insects
8-2 Insects
8-3 Insects
8-4,5,6 Insects
8-7 Insects
8-8 Insects
8-9 Insects
10-1 Insects
10-2 Insects
10-3 Insects
13-1 Insects
13-2 Insects
13-3 Insects
13-4 Insects
13-5 Insects
14-1 Insects
14-2 Insects
14-3 Insects
15-1 Insects
155
155
147.423
147.423
145.455
145.455
145.433
145.433
140.18
140.18
139.81
139.81
139.81
135.39
135.39
134.45
134.45
134.45
130
130
130
130
130
130
130
128.94
128.94
128.94
124.77
124.77
124.77
124.77
124.77
123.89
123.89
123.89
119.73
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
NA
NA
0.37
0.32
NA
NA
0.39
0.41
0.29
NA
NA
0.35
0.40
0.40
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
0.33
NA
0.57
NA
NA
NA
0.31
NA
NA
NA
NA
0.38
19.8
22.6
34.7
40.4
35.9
42.8
54.8
46.0
24.1
33.1
531
39.6
7.10
2240
736
63.2
27.7
61.1
47.1
28.2
56.6
34.6
447
105
105
25.1
20.5
21.3
77.2
133
35.7
23.0
22.0
44.6
50.6
29.9
13.7
95
126
140
113
83.8
112
18.0
5550
75.4
37.5
73.8
36.4
Site type
Dry
Fraction
Total Hg, ppb
wet wt basis dry wt basis
NA= not analyzed due to insufficient sample mass
59
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November 2002
FINAL
Table 4.2.5
Summary Statistics for the Phase I Insect Sampling
mean
(ppb, ww)
95%UCL
(ppb, ww)
range
(ppb, ww)
40.1
105.5
63.8
167.9
9.5-118
25-311
145.4
382.6
252.0
663.2
7.1-2240
18.7-5895
Reference
wet weight
dry weight*
Exposed
wet weight
dry weight*
* calculated by dividing ww by 0.38
Table 4.2.6 lists the soil, vegetation, and insect tissue concentrations measured at the four sites with the
tissue mercury concentrations that exceed the terrestrial insect tissue benchmark of 150 ppb (ww; Section
3.2.1). Also shown in Table 4.2.6 are the mean soil, vegetation, and insect tissue concentrations across all
of the Reference and Exposed sites. The soil concentrations of mercury, at the four sites with high insect
mercury concentrations, are all relatively low. Additionally, with the exception of Site 6-1, the vegetation
concentrations of mercury at these sites are also equivalent to the average mercury concentration in
vegetation samples at the Exposed locations, but elevated relative to the Exposed Site concentrations.
Table 4.2.6
Comparison of Soil and Insect Tissue Concentrations (Phase I)
Site
8-7
6-1
6-2
5-1
Average for all Reference Sites
Average for all Exposed Sites
1
Soil Hg
(ppb, dw)
26.2
91.9
53.4
58.8
173.6
72.0
Vegetation1
Hg (ppb, ww)
78.2
837.0
108.9
59.3
22
118
Insect Hg
(ppb, ww)
447
2240
736
531
40.1
145.4
value listed is the mean concentration for all plant samples at that location
dw= dry weight ww= wet weight
60
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November 2002
FINAL
Insect Hg (ppb, ww)
2500
Reference samples
Exposed samples
2000
1500
1000
Insect Tissue Benchmark=150 ppb
500
0
160
150
140
Spill Area
130
120
110
Location(Road Km)
To Trujillo
Insect Hg (ppb, dw)
To Cajamarca
6000
5000
Reference samples
Exposed samples
4000
3000
2000
1000
0
160
150
140
130
120
110
Spill Area
Location (Road Km)
To Trujillo
To Cajamarca
Figure 4.2.3
4.2.2
Scatterplot of mercury concentrations in insects versus location (Phase I). Wet
weight and dry weight values are plotted separately.
Sampling and Tissue Analysis of Aquatic Biota
Fish and aquatic macroinvertebrate (i.e., aquatic insects) samples were collected by Duke Engineering
(Bellingham, Washington) and ENKON Environmental (Surrey, British Columbia). Fish and
macroinvertebrates were selected for sampling since they are integrators of mercury levels in lower
61
Shepherd Miller
November 2002
FINAL
trophic levels, as well as in the water column and sediments (Figure 2.3.2). Stated goals of the aquatic
sampling were to:
n
n
n
n
determine background concentrations of mercury in aquatic macroinvertebrates and fish in the
surrounding waters (to be used as Reference Sites);
determine concentrations of mercury in aquatic organisms within the impact zone (i.e.,
Exposed Sites);
evaluate if there is a significant difference in mercury concentrations between the reference
and exposed populations;
evaluate if there a difference in accumulated concentrations of mercury in aquatic organisms
when comparing 2000 baseline information with 2001 post-rainy season data (Phase II).
Sampling locations were established above, within, and below the impact area. In some cases the sites are
at the same locations where water quality and sediment were sampled. The seven zones delineated for
the study were as follows:
Zone 7:
Rio San Juan, upstream of spill influence (Reference): 1 site
Zone 6:
Upstream of the initial spill site (Km 155) on tributary to Rio Choten (Reference):
1 site
Zone 5:
Upstream of Rio San Juan and below the initial spill site on Rio Choten (Km 155)
(Exposed): 3 sites
Zone 4:
From the lower end of Zone 7 on Rio San Juan downstream to its intersection
with Rio Choten (Exposed): 1 site
Zone 3:
From below the confluence of Rio Choten and Rio San Juan downstream to
Magdalena (Exposed): 3 sites
Zone 2:
Downstream from Magdalena to upstream end of the Gallito Ciego reservoir
(Reference): 3 sites
Zone 1:
Upper portion of the Gallito Ciego reservoir (Reference): 1 site and the Reservoir
itself.
Sampling locations and zones are shown on Map 3. The first five sample locations (Zones 1 and 2) are
Reference locations (i.e., non-impacted) that are several kilometers downstream of any of the spill sites,
all of which occur between Km 155 and Km 114 (Magdalena). While these sites are downstream of the
spill, they are considered as Reference sites since sampling was conducted prior to any rainstorms that
could have mobilized the spilt mercury into the waterways. Locations 6-1 and 7-1 are above any of the
spill locations and are therefore Reference locations. The remaining sample locations are all within the
general area of the spill, and are considered to be Exposed Sites. Due to sampling conducted prior to any
rainfall events, these areas, however, are also unlikely to have been influenced by the spilt mercury during
initial sampling.
62
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November 2002
Fish were collected using electroshockers.
FINAL
At each site, the collected fish were measured, placed
separately into Ziploc bags (as whole fish), labeled and placed in coolers. At the end of each day, the
Ziploc bags were wrapped in aluminum foil and then placed in dedicated freezers. Fish from the
Reservoir were collected by hook and line and bottle traps by a commercial fisherman. Macroinvertebrate
samples were collected by scrubbing rocks with brushes, and straining water through a collection net and
sieve, and then placed into Nalgene bottles or plastic Ziploc bags and frozen. Additional discussion of the
sampling methodology, along with photographs and information on habitat conditions at each site, are
included in Appendix F.
Aquatic Macroinvertebrate Tissue Analysis
Tissue concentrations for the composite macroinvertebrate samples (i.e., all species together) and
individual freshwater crabs are shown in Table 4.2.7. Both total and methylmercury concentrations are
shown on a dry weight and wet weight basis, as available. The higher of the methyl or total mercury
values are plotted in Figure 4.2.4. As shown in Table 4.2.7, the percent of the total mercury present in the
form of methylmercury in the macroinvertebrate samples ranged from 40 to 100%. Values greater than
100% reflect differences in the analytical methodology utilized to analyze for total versus methylmercury
(Appendix G).
Table 4.2.7
Mercury Concentration in Phase I Aquatic Macroinvertebrate Samples
Sample
Sample ID
Z1S1-B
CRAB-1
CRAB-2
CRAB-3
Z2S1-B
Z2S2-B
Z2S3-B
Z3S1-B
Z3S2-B
Z3S3-B
Z4S1-B
Z5S1-B
Z5S2-B
Z6S1-B
Z7S1-B
Type 1
Composite
Crab-whole
Crab-whole
Crab-whole
Composite
Composite
Composite
Composite
Composite
Composite
Composite
Composite
Composite
Composite
Composite
Road
Zone Sit Km
e
1
1
1
1
2
2
2
3
3
3
4
5
5
6
7
1
1
1
1
1
2
3
1
2
3
1
1
2
1
1
Location
Dry
type**
Fraction
50
Reservoir
50
Reservoir
50
Reservoir
50
Reservoir
61 Downstream
76 Downstream
94 Downstream
115
Exposed
126
Exposed
132
Exposed
134
Exposed
133
Exposed
153
Exposed
157
Upstream
165* Upstream
0.174
NA
NA
NA
0.203
0.239
0.167
0.436
0.201
0.285
0.322
0.161
0.197
0.141
NA
methyl Hg
(ppb)
ww
dw
102
69.3
40.9
23.6
93.7
21.4
2.74
16.4
18.5
-
587
462
89.7
16.4
57.5
57.3
-
Total Hg
(ppb)
methyl/
ww
dw
total
87.9
69.4
35.3
21.2
85
26.1
6.62
11.6
16.4
26.2
15.6
26.1
23.1
44.6
4.43
505
419
109
39.7
26.6
81.6
91.9
48.3
162
117
316
-
1.16
1.00
1.16
1.11
1.10
0.82
0.41
0.63
1.19
-
1
Composite= the analyzed sample is a composite of all of the macroinvertebrates collected at that site
* Zone 7 Site 1 is located in an upstream tributary (Rio Huacraruca) of the Jequetepeque
** Sites listed as Reservoir, Downstream, and Upstream are Reference locations
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November 2002
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All of the macroinvertebrate samples had low mercury concentrations, as expected from natural mercury
levels in the environment. The highest values were from Site 1-1 (Gallito Ciego Reservoir) and Site 2-1,
both of which are several kilometers below the spill locations and could not have been influenced by the
spill at the time of collection, since no significant rainfall had occurred between the spill and the sample
collection. Summary statistics are provided in Table 4.2.8. To be conservative, for both the Reference
and Exposed locations, the higher of the total or methylmercury value for each sample was used to
calculate the mean values. For samples that had insufficient material to measure the percent moisture, the
average dry fraction of 0.23 from the other samples was used to derive a dry weight concentration.
Table 4.2.8
Summary Statistics for the Phase I Macroinvertebrate Sampling
Area
Spill Area
Upstream
Downstream
All samples
No.
samples
6
2
7
9
15
Mean
ww
20.3
24.5
51.8
45.7
35.6
(ppb)
dw
172.4
54.1
215.6
179.7
176.8
64
95% UCL (ppb)
ww
dw
25.1
268.9
151.3
299.7
78.9
375.4
67.8
304.9
49.3
253.2
Range (ppb)
ww
dw
11.6-26.2
19.3-316
4.43-44.6
26.6-81.6
6.62-102
39.7-587
4.43-102
26.6-587
4.43-102
19.3-587
Shepherd Miller
November 2002
FINAL
Human Dietary (MeHg) Benchmark= 300
Macroinvertebrate Tissue Benchmark= 2000
120
Composite samples
Hg (ppb, ww)
100
Individual crab samples
80
60
40
20
0
165
145
125
105
85
65
45
Spill Area
To Cajamarca
Location (Road Km) To Trujillo
Bird Methylmercury Dietary Benchmark= 2500 ppb
700
Composite samples
Hg (ppb, dw)
600
Individual crab samples
500
400
300
200
100
0
165
145
125
Spill Area
105
85
65
45
Location (Road Km)
To Trujillo
To Cajamarca
Figure 4.2.4
Mercury concentration in macroinvertebrates versus sampling location (Phase
I). The Spill Area is indicated by the marked line. Wet weight and dry weight
values are plotted separately.
65
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November 2002
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Fish Tissue Analysis
All of the collected fish tissue data are shown in Table 4.2.9. Sampling was conducted at the same
locations as the macroinvertebrates were collected (see Map 3). However, fish were not present at some
of the locations where macroinvertebrates were collected. Fish were collected at five Exposed Sites
(Zones 3, 4, and 5) and five Reference Sites. Four of the Reference Sites where fish were collected are
downstream of the spill area (Zones 1 and 2), and one Reference Site (Zone 7) was upstream of the spill
in the Rio Huacraruca tributary of the Rio Jequetepeque. Some of the samples were collected in August
2000, with the remainder collected in December 2000. All of the samples were analyzed for total
mercury, and a portion of the samples was also analyzed for methylmercury, as shown in Table 4.2.9.
The analytical techniques used for the analysis of total and methylmercury differed significantly. This
difference in methods is likely responsible for the apparent discrepancy in many of the methylmercury
concentrations exceeding the measured total mercury concentrations in the analyzed samples. This
apparent discrepancy (i.e., methyl exceeding total mercury) is further discussed in Appendix G. For the
purpose of the RA, we have assumed that all of the mercury in fish is present as the methyl form and
have utilized the highest recorded mercury level (either the total or the methyl) for each sample in the risk
calculations and evaluations. The maximum mercury value for each sample, on a wet weight and dry
weight basis, is plotted versus location in Figure 4.2.5. If a sample did not have an associated percent
moisture value to calculate the dry weight basis, the mean of the other percent moisture values (0.24) was
used to calculate the dry weight concentration. The benchmark values established in Section 3 are also
shown on Figure 4.2.5.
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Table 4.2.9
Results of the Phase I Fish Analyses
Sample
Identification
Species
Cachuela#1
Cachuela#1
Cachuela#4
Cascafe-1
Cascafe-2
Cascafe-3
Cascafe-6
Cascafe-6
Charcoca#1
Charcoca-A
Charcoca-B
Charcoca-D
Charcoca-F
Charcoca-H
Nato-B
Nato-C
Nato-E
Nato-G
Nato-H
Nato-J
Life-6
Life-7
Life-9
Life-10
Mojarra-2
Mojarra-3
Mojarra-5
Mojarra-8
Mojarra-8
Pejerry-1
Pejerry-3
Pejerry-3
Pejerry-6
Pejerry-8
Picalon-4
Cachuela
Cachuela
Cachuela
Cascafe
Cascafe
Cascafe
Cascafe
Cascafe
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Nato
Nato
Nato
Nato
Nato
Nato
Life
Life
Life
Life
Mojarra
Mojarra
Mojarra
Mojarra
Mojarra
Pejerry
Pejerry
Pejerry
Pejerry
Pejerry
Picalon
Length Tissue
(cm)
Type
10
10
10
33
23
25
13
13
7.9
11
9
11
9
8
10
8
8
10
9.5
9.7
12
17
12
17
13
13
15
16
16
19
20
20
15
17
10
muscle
head
muscle
muscle
muscle
muscle
muscle
head
whole
muscle
whole
muscle
whole
whole
muscle
whole
whole
muscle
whole
whole
muscle
muscle
muscle
muscle
muscle
muscle
muscle
muscle
head
muscle
muscle
head
muscle
muscle
muscle
Sample
Zone Site
Date
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
67
Dry
Fraction
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0.177
N/A
0.189
N/A
N/A
N/A
0.225
0.306
0.253
0.239
0.25
0.238
0.248
N/A
0.244
N/A
N/A
N/A
0.29
N/A
0.212
N/A
N/A
0.19
N/A
0.194
methyl Hg, ppb
wet wt dry wt
NR
NR
NR
NR
N/A
N/A
N/A
N/A
62.7
N/A
118
N/A
114
94.9
N/A
159
49.6
N/A
185
199
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
707
162
N/A
774
796
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Total Hg, ppb
wet wt dry wt
229
69
279
605
185
293
114
40.9
64
233
116
91.1
104
92
387
146
56.8
317
155
182
95.5
185
112
265
146
250
121
120
95.6
75.8
70
53.1
47.4
57.2
114
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
1316
N/A
482
N/A
N/A
N/A
649
186
1253
649
728
401
746
N/A
1086
N/A
N/A
121
414
N/A
358
N/A
N/A
249
N/A
588
methyl/
total
0.98
1.02
1.10
1.03
1.09
0.87
1.19
1.09
Road
Km
Notes
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Shepherd Miller
November 2002
FINAL
Table 4.2.9
Results of the Phase I Fish Analyses (continued)
Sample
Identification
Species
Length
Tissue
Sample
Zone
Site
Dry
Picalon-6
Tilapia-2
Tilapia-2
Tilapia-4
Tilapia-6
Tilapia-10
Life-ZIS1 -14
Mojarra-ZIS1 -21
Mojarra-ZIS1 -21
Cascafe-ZIIS1 -10.2
Chalcoco-ZIIS1 -7.7
Chalcocoa-ZIIS1 -7.8
Chalcoca-ZIIS1 -9.3
Cascafe-ZIIS1 -18.6
Calcoca-ZIIS1 -10.0
Calcoca-ZIIS1 -10.2
Calcoca-ZIIS1 -10.8
Calcoca-ZIIS1 -10.8
Calcoca-ZIIS1 -12.2
Calcoca-ZIIS1 -12.8
Mojarra-ZIIS1 -19.2
Nato-ZIIS1 -8.5
Calcoca-ZIIS2 -7.1
Calcoca-ZIIS2 -7.8
Calcoca-ZIIS2 -9.3
Calcoca-ZIIS2 -9.8
Life-ZIIS2 -10.3
Life-ZIIS2 -10.5
Life-ZIIS2 -10.5
Life-ZIIS2 -11.9
Life-ZIIS2 -13.0
Nato-ZIIS2 -3.8
Calcoca-ZIIS3 -6.6
Calcoca-ZIIS3 -7.7
Calcoca-ZIIS3 -8.8
Picalon
Tilapia
Tilapia
Tilapia
Tilapia
Tilapia
Life
Mojarra
Mojarra
Cascafe
Charcoca
Charcoca
Charcoca
Cascafe
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Mojarra
Nato
Charcoca
Charcoca
Charcoca
Charcoca
Life
Life
Life
Life
Life
Nato
Charcoca
Charcoca
Charcoca
(cm)
10
30
30
21
13
29
14
21
21
10.2
7.7
7.8
9.3
18.6
10
10.2
10.8
10.8
12.2
12.8
19.2
8.5
7.1
7.8
9.3
9.8
10.3
10.5
10.5
11.9
13.0
3.8
6.6
7.7
8.8
Type
muscle
muscle
head
muscle
muscle
muscle
muscle
muscle
head
muscle
whole
whole
whole
muscle
whole
muscle
muscle
head
muscle
muscle
muscle
whole
whole
whole
whole
whole
muscle
muscle
head
muscle
muscle
whole
whole
whole
whole
Date
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
Fraction
0.202
0.173
0.214
N/A
N/A
N/A
0.226
0.197
0.241
0.256
N/A
N/A
N/A
0.214
N/A
0.239
0.246
0.406
0.248
0.236
0.205
N/A
N/A
N/A
N/A
N/A
0.222
0.208
0.289
0.234
0.232
N/A
N/A
N/A
N/A
68
methyl Hg, ppb
wet wt
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
59.6
105
154
N/A
108
N/A
N/A
N/A
N/A
N/A
N/A
302
114
160
148
151
N/A
N/A
N/A
N/A
N/A
245
71.4
24.0
29.9
dry wt
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Total Hg, ppb
wet wt
422
82.4
53
46.4
27.1
29.7
230
127
71.3
85.6
48.8
84.3
137
288
101
136
161
63.3
178
208
206
257
101
135
145
136
307
311
224
322
346
197
56.1
13.9
28.6
dry wt
2089
476
248
N/A
N/A
N/A
1020
646
296
334
N/A
N/A
N/A
1350
N/A
571
656
156
716
883
1000
N/A
N/A
N/A
N/A
N/A
1380
1490
776
1380
1490
N/A
N/A
N/A
N/A
Methyl/
Total
1.22
1.25
1.13
1.07
1.17
1.13
1.18
1.02
1.11
1.24
1.27
1.72
1.05
Road
Km
Notes
50
50
50
50
50
50
50
50
50
61
61
61
61
61
61
61
61
61
61
61
61
61
76
76
76
76
76
76
76
76
76
76
94
94
94
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Downstream
Shepherd Miller
November 2002
FINAL
Table 4.2.9
Sample
Species
Identification
Calcoca-ZIIS3 -9.6
Life-ZIIS3 -11.1
Life-ZIIS3 -11.2
Life-ZIIS3 -12.2
Life-ZIIS3 -17.8
Life-1
Life-1
Life-2
Life-4
Life-5
Nato-1
Nato-3
Nato-4
Nato-5
Cascafe-1
Charcoca-1
Charcoa-2
Charcoca-3
Charcoca-4
Charcoca-5
Nato-1
Nato-2
Nato-5
Nato-8
Nato-9
Nato-10
Nato-14
Nato-15
Charcoca-1
Charcoca-2
Charcoa-3
Charcoca-3
Charcoca-4
Charcoca-7
Charcoca-9
Charcoca
Life
Life
Life
Life
Life
Life
Life
Life
Life
Nato
Nato
Nato
Nato
Cascafe
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Length Tissue
Sample
(cm)
Type
Date
9.6
11.1
11.2
12.2
17.8
14
14
13
12.5
12
8.5
8.5
9.5
7.5
18
10
7.5
7.5
8
7.5
11
14
10
8.5
10
8.5
6
5.5
13.5
11.5
11
11
8.5
8
11.5
whole
muscle
muscle
muscle
muscle
muscle
head
muscle
muscle
muscle
whole
whole
whole
whole
muscle
muscle
whole
whole
whole
whole
muscle
muscle
muscle
whole
muscle
whole
whole
whole
muscle
muscle
muscle
head
whole
whole
muscle
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Zone Site
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
69
Dry
methyl Hg, ppb
Total Hg, ppb
Fraction
wet wt
dry wt
wet wt
dry wt
N/A
0.241
0.277
0.199
0.224
N/A
N/A
N/A
0.207
0.229
N/A
N/A
0.265
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0.3
0.315
N/A
53.3
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
26.8
58.5
30.1
26.4
N/A
N/A
21.7
45.2
25.2
39.6
N/A
N/A
N/A
47.3
N/A
30.2
25.5
18
N/A
N/A
N/A
N/A
44.4
49.4
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
114
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
148
157
N/A
48.9
143
44.2
78.6
132
65.3
33.1
75
84.4
120
26.6
49.8
28.1
28.1
184
81.1
21.9
35.6
19.3
29.5
124
257
99.7
36.2
113
26.2
19.4
19
236
142
181
96.3
37.9
47.7
154
N/A
593
160
395
589
N/A
N/A
N/A
408
524
N/A
N/A
106
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
126
151
N/A
Methyl/ Road
Total
Km
1.09
1.01
1.17
1.07
0.94
0.99
1.27
1.31
1.34
1.31
1.15
1.31
0.95
1.17
1.04
94
94
94
94
94
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
126
126
126
126
126
126
126
126
126
126
126
126
126
126
126
Notes
Downstream
Downstream
Downstream
Downstream
Downstream
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Shepherd Miller
November 2002
FINAL
Table 4.2.9
Sample
Identification
Species
Charcoa-9
Charcoca-10
Charcoca-11
Calcoca-ZIIIS3 -3.5
Calcoca-ZIIIS3 -3.7
Calcoca-ZIIIS3 -4.7
Calcoca-ZIIIS3 -5.1
Nato-ZIIIS3 -3.1
Nato-ZIIIS3 -3.6
Nato-ZIIIS3 -5.0
Nato-ZIIIS3 -9.7
Nato-ZIIIS3 -12.6
Pejerry-ZIIIS3 -12.2
Calcoca-ZIVS1 -4.8
Nato-ZIVS1 -3.7
Nato-ZIVS1 -12.0
Nato-1
Nato-1
Nato-2
Nato-2
Nato-3
Nato-4
Nato-6
Nato-8
Nato-9
Nato-1
Nato-7
Nato-9
Nato-13
Nato-13
Nato-17
Nato-19
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Nato
Nato
Nato
Nato
Nato
Pejerrey
Charcoca
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Length Tissue
(cm)
Type
11.5
7.5
6.5
3.5
3.7
4.7
5.1
3.1
3.6
5.0
9.7
12.6
12.2
4.8
3.7
12.0
10.5
10.5
10
10
6
10
6.5
7.5
9
10
8.4
9.4
10
10
4.2
4.4
head
whole
whole
whole
whole
whole
whole
whole
whole
whole
whole
muscle
muscle
whole
whole
muscle
muscle
head
muscle
head
whole
muscle
whole
whole
whole
muscle
whole
whole
muscle
head
whole
whole
Sample
Zone Site
Date
Aug-00
Aug-00
Aug-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Dec-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
Aug-00
3
3
3
3
3
3
3
3
3
3
3
3
3
4
4
4
5
5
5
5
5
5
5
5
5
7
7
7
7
7
7
7
2
2
2
3
3
3
3
3
3
3
3
3
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Dry
Fraction
N/A
N/A
0.315
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0.213
0.243
N/A
N/A
0.211
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0.281
N/A
N/A
N/A
N/A
methyl Hg, ppb
wet wt dry wt
N/A
43.9
112
34.3
50.0
28.8
40.2
18.1
40.2
44.5
38.6
N/A
N/A
35.0
16.0
N/A
N/A
N/A
N/A
N/A
76.6
N/A
70
48.9
95
N/A
44.4
77.5
N/A
N/A
20.9
16.9
N/A
N/A
356
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
276
N/A
N/A
N/A
N/A
Total Hg, ppb
wet wt dry wt
43.4
31.6
74.5
28.7
31.6
31.1
38.0
5.07
34.3
37.5
33.2
75.4
125
33.9
12.8
65.7
121
76.4
141
73.3
53.2
217
50.4
39.7
75.9
58.7
31.4
49.8
57.3
42.6
14.8
10.4
N/A
N/A
237
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
354
515
N/A
N/A
311
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
177
N/A
N/A
N/A
N/A
Methyl/ Road
Total
Km
1.39
1.50
1.19
1.58
0.93
1.06
3.57
1.17
1.19
1.17
1.03
1.26
1.44
1.39
1.23
1.25
1.41
1.56
1.41
1.63
126
126
126
132
132
132
132
132
132
132
132
132
132
134
134
134
133
133
133
133
133
133
133
133
133
165
165
165
165
165
165
165
Notes
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Samples listed as Reservoir, Downstream, or Upstream were collected at Reference locations
N/A= not analyze
70
Shepherd Miller
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Fish Tissue Benchmark= 2000 ppb
700
Reference Locations
Hg (ppb, ww)
600
Exposed Locations
500
400
Human Methyl Dietary Benchmark= 300 ppb
300
200
100
0
180
160
140
120
100
80
60
40
Spill Area
To Cajamarca
4000
3500
Location (Road (Km)
To Trujillo
Reference Locations
Exposed Locations
Hg (ppb, dw)
3000
2500
Bird Methyl Dietary Benchmark= 2500
2000
1500
1000
500
0
180
160
140
120
100
80
60
40
Spill Area
To Cajamarca
Figure 4.2.5
Location (Road (Km)
To
Mercury concentration in fish at all sampling locations (Phase I). The Spill Area
is indicated by the marked line. Samples shown as collected at Km 165 are from
a reference tributary upstream of the spill area. Wet weight and dry weight
71
Shepherd Miller
November 2002
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Summary statistics for Reference and Exposed samples are shown in Table 4.2.10.
Table 4.2.10
Summary Statistics for the Phase I Fish Sampling
No.
samples
55
7
75
82
137
Area
Spill Area
All samples
Mean
ww
77.6
45.5
156.5
147.0
119.0
(ppb)
dw
323.3
189.6
652.1
612.5
495.8
95% UCL (ppb)
ww
dw
90.6
377.5
61.3
255.4
177.5
739.6
167
695.8
133
554
Range (ppb)
ww
dw
16.0-257
40-1071
16.9-77.5
70.4-325
24.0-605
100-2521
16.9-605
70.4-2521
16.0-605
40-2521
Table 4.2.11 shows the results of the fish tissue analysis (ww) for each sample location.
Table 4.2.11
Mercury Concentration in Fish at Each Location (Phase I)
Site
Km
1-1
2-1
2-2
2-3
3-1
3-2
3-3
4-1
5-1
7-1
50
61
76
94
115
126
132
134
133
165(1)
Location
Reservoir
Downstream
Downstream
Downstream
Exposed
Exposed
Exposed
Exposed
Exposed
Upstream
Mean
Hg (ppb ww)
95% UCL
Hg (ppb ww)
Range
Hg (ppb ww)
155.3(44)
153.8 (13)
232.8 (10)
72.0 (8)
61.2 (15)
101.0 (18)
49.7 (10)
38.9 (3)
102.1 (9)
45.5 (7)
185.6
193.7
282.4
101.8
81.3
130.3
67.3
81.2
133.4
61.3
27.1-605
48.8-302
114.2-346
24.0-143
21.9-184
19.0-257
18.1-125
16.0-66
48.9-217
16.9-78
* values in parentheses indicate number of samples averaged
(1)
Zone 7 Site 1 (7-1) is located in an upstream tributary (Rio Huacraruca)
Samples listed as Reservoir, Downstream, or Upstream were collected at Reference locations
In order to evaluate fish as consumed by the local human population, small fish (<10 cm) were analyzed as
whole fish, whereas larger fish (>10 cm) were segregated into muscle and head samples prior to analysis.
Table 4.2.12 shows the mean, 95% UCL, and range of the wet weight mercury concentrations across all
of the samples for each of these tissue types.
Table 4.2.12
Mercury Concentrations for Each Fish Tissue Type (Phase I)
Tissue
Head
Muscle
Whole
Mean
Hg (ppb ww)
74.0 (14)
165.4 (67)
75.1 (56)
95% UCL
Hg (ppb ww)
96.4
187
89.3
Range
Hg (ppb ww)
33.1-224
27.1-605
16.0-302
Values in parentheses indicate number of samples averaged
ww= wet weight
72
Shepherd Miller
November 2002
FINAL
Muscle tissue had the highest mercury concentrations (Table 4.2.12; Figure 4.2.6). This may be due to
larger fish being selected for muscle tissue analysis versus smaller fish for whole body analysis.
Generally, larger and older fish will have higher mercury concentrations than smaller and younger fish
(USEPA 1999a). However, a regression analysis indicated that there was no significant relationship
(R2<0.10) between fish length and mercury concentrations in fish tissue of the collected samples.
700
Hg concentration in heads
Hg concentration in muscle
600
Hg concentration in whole fish
Hg (ppb)
500
400
300
200
100
0
0
Figure 4.2.6
6
12
18
24
Fish length (cm)
30
36
Mercury concentrations (ww) in each fish tissue type plotted versus fish length
(Phase I). Samples from both Reference and Exposed locations are included.
Table 4.2.13 shows the mean mercury concentrations in each tissue type (head, muscle, or whole fish) for
each of the analyzed fish species, across all sampling locations. There was significant variation between
the fish species. Much of this variation, however, may be due to the small number of samples analyzed
for each fish species. This is especially true for the head and whole body analyses. The mean mercury
concentrations in the heads of the different species ranged from 40.9 ppb (ww) to 128.6 ppb (ww).
Cascafe had the lowest mean concentration in heads and Life had the highest. In muscle tissue, Picalon
was the species with the highest mean concentration at 268 ppb (ww) and Tilapia had the lowest at 46.4
ppb (ww). Cascafe, which had the lowest mean mercury concentrations in head tissue (40.0 ppb ww), had
the third highest mean concentration in muscle tissue at 251 ppb (ww).
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Shepherd Miller
November 2002
Table 4.2.13
FINAL
Mean Total Hg Concentrations for Each Fish Species and Tissue Type (Phase I)
Species
Cachuela
Cascafe
Charcoca
Life
Mojarra
Nato
Pejerrey
Picalon
Tilapia
Head
Hg (ppb ww)
69 (1)
40.9 (1)
67.7 (3)
128.6 (2)
83.4 (2)
64.1 (3)
53.1 (1)
ND
53.0 (1)
Muscle
Hg (ppb ww)
254(2)
251 (7)
164 (11)
172 (17)
162 (6)
156 (13)
75.0 (5)
268 (2)
46.4 (4)
Whole
Hg (ppb ww)
ND
ND
75.4 (29)
ND
ND
74.8 (27)
ND
ND
ND
ND= no data ww= wet weight
Values in parenthesis indicate number of samples averaged
Smaller fish and lower trophic level species (i.e., herbivorous fish) might be expected to have the lowest
mercury concentrations. As shown in Table 2.2.2, Picalon, Tilapia, and Life are considered to only eat
plants (or detritus), whereas all of the other fish are believed to be omnivorous, eating both plants and
insects. Also shown in Table 2.2.2, is the size range (length) for each of the fish species. Overall, the
largest fish collected were Tilapia, which were only collected in the Gallito Ciego Reservoir, and Cascafe.
Cachuela, Charcoca, and Picalon tended to be the smallest fish collected. It was surprising that Picalon
had the highest mean muscle concentration, since they are small, herbivorous fish. It is important to note,
however, that only two samples were analyzed, so the results are not robust. Cascafe, which is one of the
species with larger fish analyzed, had very low head concentrations, but one of the higher mean muscle
concentrations. Tilapia, the other larger fish species analyzed, had very low head and muscle mercury
concentrations. Overall, however, the mean mercury concentration in all of the analyzed fish specie s was
low, and within ranges typical of fish in uncontaminated waters (Section 1.2.3; Sweet and Zelikoff 2001).
4.3
November 2000 Sampling (Shepherd Miller, SENASA, MYSRL)
Some limited sampling was conducted on November 15, 2000 by MYSRL, SENASA, and Shepherd Miller
personnel in and around Choropampa. The purpose of the sampling was to jointly revisit locations where
SENASA sampling (see Appendix B) had previously reported mercury concentrations above those
generally observed in the area. Specifically, samples were collected at three locations: 1) in or near Elias
Herrara’s fields between the road and the Jequetepeque River, 2) near the Juan Azanero residence in
Choropampa, and 3) on the farm of Ernesto Leon, approximately 0.5 Km to the southwest of
Choropampa. These locations are indicated on Map 4.
Results of the vegetation and soil analyses are shown in Table 4.3.1. SENASA personnel selected the
sampling locations and tissue types. For many of the sample locations, soil samples were collected directly
74
Shepherd Miller
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FINAL
beneath the sampled vegetation. However, not all of the vegetation samples have a corresponding colocated soil sample, as directed by SENASA personnel.
Table 4.3.1.
Location
Herrara
Herrara
Herrara
Herrara
Herrara
Herrara
Leon
Leon
Leon
Leon
Leon
Leon
Leon
Leon
Azanero
Azanero
Azanero
Azanero
Azanero
Azanero
Azanero
Herrara
Herrara
Herrara
Results from the November 15, 2000 Plant and Soil Sampling
Sample
No.
Road
Km
Soil
ppb (dw)
1
128
1300
2
128
NA
3
1
2
128
128
128
119
NA
NA
3
126
17.0
4
126
61.8
5
127.5
537
6
127.5
358
7
128
246
Vegetation
Type
Yuca
Yuca
Yuca
Yuca
Yuca
Potato
Alfalfa
Avocado
Avocado
Tomato
Tomato
Tomato
Grape
Grape
Orange
Orange
Orange
Lemon
Lemon
Lemon
Lemon
Taya
Taya
Taya
Tissue
root
leaf
stem
leaf
stem
stem
leaf
fruit
leaf
leaf
fruit
root
fruit
leaf
leaf
root
stem
fruit 1
fruit-washed1
leaf
root
fruit
leaf
root
Total Hg
ppb (ww)
14.2
11.2
2.65
7.59
3.39
0.69
8.75
< 0.62
12.1
5.43
0.54
3.04
2.03
12.5
476
125
176
18.2
16.0
1950
45.5
1.88
4.40
13.1
Total Hg
ppb (dw)
39.7
39.8
11.4
67.1
18.7
3.25
30.3
<2.7
39.4
29.5
4.29
14.7
13.6
43.0
1690
456
532
96.3
88.6
6090
142
4.14
11.5
24.8
dw= dry weight
ww= wet weight
NA= not analyzed
1
This lemon sample was cut into two pieces; one half was washed prior to analysis and one half was not
Summary statistics for the soil and vegetation samples are provide in Table 4.3.2. Results of the
November sampling are similar to results from the Phase I sampling discussed in Section 3.2. The mean
wet weight concentration of mercury in the Phase I vegetation samples from Exposed locations was 118
ppb, with values ranging from 0.44 to 1930 ppb (ww).
Table 4.3.2
Summary Statistics for the November 15, 2000 Soil and Vegetation Samples
Soil
Vegetation
Mean (ppb)
ww
dw
NA
377
121
396
95% UCL (ppb)
ww
dw
NA
743
264
838
Range (ppb)
ww
dw
NA
17.0-1300
0.54-1950
2.7-6090
NA= not analyzed
The highest mercury value in vegetation, 1950 ppb (ww), was from a lemon leaf collected next to Juan
Azanero Mendoza’s house in Choropampa. However, both the fruit and root samples collected from the
75
Shepherd Miller
November 2002
FINAL
same tree had low mercury concentrations (18.2 ppb and 45.5 ppb ww respectively). The soil mercury
concentration under the tree was 358 ppb (dw). Due to the low root and fruit concentrations of mercury
at this sample location, it is unlikely that the elevated mercury concentration in the lemon leaf was a result
of plant uptake from contaminated soil.
The recorded high value may have been due to surfic ial
contamination of the leaf surface. This site is across the street from the Medical Post, which is near the
single largest mercury spill location. Surficial contamination of this tree may have occurred prior to, or
during, remediation of the site and surrounding homes. The highest soil mercury concentration of 1300 ppb
(dw) was recorded at one location in Elias Herrara’s field. This value is higher than other recorded values
from the November sampling, but similar to a value of 1130 ppb measured at a Reference location in the
Phase I sampling (Section 4.2). A second sample from the same field had a mercury concentration of 128
ppb (dw), potentially indicating natural variability in soil concentrations.
Because the earlier sampling by SENASA (Appendix B) indicated that there were not significant
elevations of mercury in animal tissue near the spill locations, SENASA personnel directed the collection
of only limited animal tissue samples during the November 2000 re-sampling. Pig hair was collected from
two different animals at Juan Azanero’s house in Choropampa and the kidney and liver from a single
rabbit were sampled at Ernesto Leon’s farm. Results from the pig hair and rabbit organ sampling are
shown in Table 4.3.3. The values shown in Table 4.3.3 are indicative of expected normal background
levels (Table 1.2.3) and are below reported toxic levels in tissues (Table 3.2.3).
Table 4.3.3
Results from the November 15, 2000 Animal Tissue Sampling
Sample ID
ELT-CON-H-1-DUP
ELT-CON-R-1-DUP
JAM -POR-P-1-DUP
JAM -POR-P-2-DUP
Species*
Rabbit-1
Rabbit-1
Pig-1
Pig-2
Tissue
type
Kidney
Liver
Hair
Hair
Location
Leon
Leon
Azanero
Azanero
Dry
Fraction
0.23
0.89
0.84
Total Hg (ppb)
ww basis
dw basis
5.98
5.95
151
94.1
26.5
170
112
ww= wet weight dw=dry weight
* The liver and kidney were collected from the same rabbit, two different pigs were sampled for hair
4.4
Phase II Sampling Conducted In Support of the Risk Assessment
The results of the second phase (Phase II) of the sampling designed and conducted to specifically support
the risk assessment are presented and discussed in this section. Whereas the Phase I sampling (Section
4.2) was conducted in 2000, the Phase II sampling was conducted in 2001 and 2002, beginning after the
end of the first post-spill wet season. All of the samples that were collected in Phase II were analyzed by
Frontier Geosciences (Seattle, WA, USA). Original laboratory reports have been previously supplied to
the MEM.
76
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4.4.1
Terrestrial Sampling and Tissue Analysis
The sampling locations for the Phase II sampling were identical to those discussed in Section 4.2 for the
Phase I sampling. At each terrestrial sampling location (Map 3), co-located soil, aboveground portions of
plants, and insects were collected. The Phase II terrestrial sampling, like the Phase I sampling, was
conducted by Homero Bazan of the Colegio de Biologos del Peru and Manual Cabanillos and Alfonso
Miranda of the Universidad Nacional de Cajamarca. Overall, 130 plant samples, 47 insect samples, and 48
soil samples were collected in February 2002. This sampling was originally scheduled to occur at the end
of the second dry season in September 2001, but due to delays in receiving necessary government permits,
sampling could not occur until after the wet season had started. Descriptions of sampling locations,
samples collected at each location, and pictures of sampling sites provided by Professor Bazan are
included as Appendix H.
Soil Analysis
Results, broken-out by location and site type (Reference Site or Exposed Site samples), of the Phase II
soil sampling are shown in Table 4.4.1.
As shown in Figure 4.4.1, all of the soil samples collected in the Phase II sampling were below the soil
benchmark value of 10,000 ppb established in Section 3.3.2 and the MYSRL remediation goal of 1000 ppb
for soils. The mean and 95% UCL of the mean dry weight (dw) mercury concentration for soils at
Reference sites were 37.0 and 62.8 ppb. The corresponding values for the soils at Exposed sites were
50.4 ppb and 60.3 ppb. The range of recorded mercury concentrations was 11.5-131 ppb (dw) for
Reference soils and 8.56-149 ppb (dw) for soils at Exposed sites. All of the mercury concentrations
measured in soils during the Phase II sampling were below the remediation goal for soil clean-up and are
representative of background conditions.
77
Shepherd Miller
November 2002
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Table 4.4.1
Results of the Phase II Soil Samples
Site
Road
Km
Location
Type
Sample
ID
Total Hg
(ppb, ww)
Total Hg
(ppb, dw)
15-2
15-3
14-4
13-6
6-3
6-4
5-4
1-3
119.73
119.73
123.89
124.77
135.39
135.39
139.81
155
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
15-2-SOIL
15-3-SOIL
14-4-SOIL
13-6-SOIL
6-3-SOIL
6-4-SOIL
5-4-SOIL
1-3-SOIL
9.73
27.4
21.7
29.3
16.4
17.7
19.1
111
11.5
32.8
26.0
31.5
20.6
20.2
22.3
131
15-1
14-1
14-2
14-3
13-1
13-2
13-3
13-4
13-5
10-1
10-2
10-3
8-1
8-2
8-3
8-4
8-5
8-6
8-7
8-8
8-9
7-1
7-2
7-3
7-4
6-1
6-2
5-1
5-2
4-1
4-2
B-1
B-2
C-1
C-2
A-1
A-2
1-1
1-2
119.73
123.89
123.89
123.89
124.77
124.77
124.77
124.77
124.77
128.94
128.94
128.94
130
130
130
130
130
130
130
130
130
134.45
134.45
134.45
134.45
135.39
135.39
139.81
139.81
140.18
140.18
145.433
145.433
145.455
145.455
147.423
147.423
155
155
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exp osed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
15-1-SOIL
14-1-SOIL
14-2-SOIL
14-3-SOIL
13-1-SOIL
13-2-SOIL
13-3-SOIL
13-4-SOIL
13-5-SOIL
10-1-SOIL
10-2-SOIL
10-3-SOIL
8-1-SOIL
8-2-SOIL
8-3-SOIL
8-4-SOIL
8-5-SOIL
8-6-SOIL
8-7-SOIL
8-8-SOIL
8-9-SOIL
7-1-SOIL
7-2-SOIL
7-3-SOIL
7-4-SOIL
6-1-SOIL
6-2-SOIL
5-1-SOIL
5-2-SOIL
4-1-SOIL
4-2-SOIL
B-1-SOIL
B-2-SOIL
C-1-SOIL
C-2-SOIL
A-1-SOIL
A-2-SOIL
1-1-SOIL
1-2-SOIL
25.0
39.0
16.8
30.3
81.2
47.9
21.7
37.9
19.7
19.0
16.3
19.3
72.2
63.6
59.6
39.5
12.5
27.4
21.7
50.8
67.8
27.7
9.00
33.9
46.2
120
127
98.9
62.7
22.7
24.9
32.4
24.1
10.5
36.4
7.66
21.1
100
75.1
30.3
42.4
19.9
37.5
93.5
58.0
27.2
45.8
23.3
23.8
19.2
21.9
86.7
82.0
73.9
50.2
14.7
34.1
26.8
62.0
81.9
32.0
12.0
38.7
50.0
142
149
121
80.3
26.7
29.6
41.5
29.5
12.3
42.7
8.56
22.3
120
93.1
78
Shepherd Miller
November 2002
FINAL
12000
Reference Sites
10000
Exposed Sites
USEPA soil limit=10000ppb
Soil Benchmark for Plants= 10000 ppb
Soil Hg (ppb)
8000
6000
4000
2000
0
160
MYSRL Remediation Goal=1000ppb
150
140
130
120
110
Spill Area
To Cajamarca
Figure 4.4.1
Road (Km)
To Trujillo
Scatterplot of Phase II soil Hg concentrations (dw) versus location
Vegetation Analysis
Results of the vegetation sampling are shown in Table 4.4.2. Results are first listed for Reference Sites
and then for Exposed Sites. As with the Phase I analysis, results are listed both in terms of wet and dry
weights. Approximate location along the road (i.e., Road Km) is also indicated. Summary statistics are
provided in Table 4.4.3 and results of the mercury analysis are plotted in Figure 4.4.2. Overall, the mean
concentrations of mercury in vegetation sampled at both Reference and Exposed locations are similar to
the reported background levels of mercury in vegetation (Section 1.2.3) of 6-140 ppb ww (30-700 ppb dw)
listed by Adriano (1986).
79
Shepherd Miller
November 2002
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Table 4.4.2
Results of Vegetation Analyses from the Phase II Sampling
Sample
ID
Road
Km
Site
type
Scientific name
English
Common name
1-3 Indhum
1-3 Vigsp
1-3-Baclat
5-4 Lansp
5-4 Passp
6-3 Zeamay
6-4 Acamac
6-4 Altpor
6-4 Crosp
6-4 Schmol
14-4 Asccur
14-4 Cassp
14-4 Riccom
15-2 Baclan
15-2 Bidpil
15-2 Polsem
15-3 Capsp
15-3-Arrxan
15-3-Capfru
155.00
155.00
155.00
139.81
139.81
135.39
135.39
135.39
135.39
135.39
123.89
123.89
123.89
119.73
119.73
119.73
119.73
119.73
119.73
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Indigofera humilis
Viguiera sp.
Baccharis latifolia
Lantana sp.
Paspalum sp.
Zea mays
Acacia macracantha
Croton sp.
Schinus molle
Cassia sp.
Ricinus communis
Bacchars lanceolata
Bidens pilosa
Polypogon semiverticilatum
Capsicum sp.
Arracacia xanthorrihiga
Capsicum frutescens
Indigo
Desert sunflower
Groundsel
Lantana
Paspalum
Corn
Porknut
Joyweed
Croton
Scarlet milkweed
Cinnamon
Castor bean
Groundsel
Beggar's tick
Beard grass
Cayenne pepper
Peruvian carrot
Cayenne pepper
1-1 Pencla
1-1 Sonole
1-1 Trirep
1-2 Plasp
1-2 Polsem
A-1 Sonole
A-1 Versp
A-1-Melind
A-2 Baclat
A-2 Calsp
A-2-Dalsp
C-1 Bascp
C-1 Calsp
C-1 Escpen
C-2 Spajun
C-2-Hypsp
C-2-Minsp
155.00
155.00
155.00
155.00
155.00
147.42
147.42
147.42
147.42
147.42
147.42
145.46
145.46
145.46
145.46
145.46
145.46
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Sonchus oleraceus
Trifolium repens
Plantago sp.
Polypogon semiverticilatum
Sonchus oleraceus
Verbena sp.
Melilotus Indica
Baccharis latifolia
Calceolaria sp.
Dalea sp.
Baccharis sp.
Calceolaria sp.
Escallonia pendula
Spartium junceum
Hyptis sp.
Minthostachys sp.
Kikuyu grass
Sow thistle
White clover
Plantain
Beard grass
Sow thistle
Verbena
Clover
Groundsel
Pocket book plant
Dalea
Groundsel
Pocket book plant
Escallonia
Spanish broom
Mint weed
Mint
80
Spanish
Common
name
Tissue 1
Suncho
Chilca negra
Nudillo
Maiz
Huarango
Moradillo
Molle
Flor de seda
Cinamomo
Higuerilla
Chilca
Cadillo
Aji verde
Arracacha
Aji verde
Kikuyu
Cerraja
Trebol
Llanten macho
Cerraja
Verbena
Chilca negra
Globito
Chilca negra
Globito
Pauco
Retama
Chancua
fruit
fruit
Veg.
Type
Dry
Fraction
Total Hg (ppb)
wet wt
dry wt
Forb
Shrub
Forb
Shrub
Grass
Grass
Tree
Shrub
Shrub
Tree
Forb
Shrub
Tree
Shrub
Forb
Grass
Forb
Forb
Forb
0.292
0.258
0.352
0.404
0.374
0.129
0.487
0.377
0.305
0.418
0.230
0.453
0.280
0.323
0.198
0.285
0.254
0.154
0.237
4.41
5.24
6.35
7.92
2.96
1.14
8.47
3.88
4.98
7.39
3.57
12.6
3.45
3.84
1.65
4.39
3.58
24.0
2.23
15.1
20.3
18.0
19.6
7.91
8.82
17.4
10.3
16.3
17.7
15.5
27.8
12.3
11.9
8.33
15.4
14.1
156
9.41
Grass
Forb
Forb
Forb
Grass
Forb
Forb
Forb
Forb
Forb
Shrub
Forb
Forb
Tree
Shrub
Shrub
Shrub
0.330
0.291
0.449
0.320
0.476
0.182
0.299
0.267
0.372
0.180
0.249
0.338
0.204
0.328
0.303
0.310
0.313
31.6
28.1
49.5
56.3
54.8
3.63
9.53
4.00
4.29
2.78
3.33
3.92
3.00
3.11
1.36
5.96
4.59
95.8
96.7
110
176
115
19.6
31.9
15.0
11.5
15.5
13.4
11.6
14.7
9.49
4.49
19.2
14.7
Shepherd Miller
November 2002
FINAL
Table 4.4.2
Results of Vegetation Analyses from the Phase II Sampling (continued)
Sample
ID
Road
Km
Site
type
B-1 Escpen
B-1 Phesp
B-1-Rhysp
B-2 Lansp
B-2-Baclat
B-2-Pencla
4-1 Passp
4-2 Trirep
5-1 Pencla
5-1 Plasp
5-2 Cyndac
5-2 Pencla
5-3 Cheamb
5-3 Phesp
6-1 Brosp
6-1 Caespi
6-1 Pencla
6-2 Budsp
6-2 Oxyvis
6-2 Penweb
7-1 Corsp
7-1 Phycan
7-2 Dessp
7-2 Ophchi
7-2 Rhysp
7-3 Cheamb
7-3 Plasp
7-3 Sacoff-leaves
7-3 Sacoff-stalk
7-3 Sidsp
7-4 Setsp
7-4 Sposp
8-1 Annche
8-1 Minsp
8-1 Phycan
8-2 Altpor
8-2 Rosoff
8-2 Taroff
145.43
145.43
145.43
145.43
145.43
145.43
140.18
140.18
139.81
139.81
139.81
139.81
139.81
139.81
135.39
135.39
135.39
135.39
135.39
135.39
134.45
134.45
134.45
134.45
134.45
134.45
134.45
134.45
134.45
134.45
134.45
134.45
130.00
130.00
130.00
130.00
130.00
130.00
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Scientific name
Escallonia pendula
Phenaz sp.
Rhynchosia sp.
Lantana sp.
Baccharis latifolia
Paspalum sp.
Trifolium repens
Plantago sp.
Cynodon dactylon
Chenopodium ambrosiodes
Phenax sp.
Browalia sp.
Caesalpinia spinosa
Buddleja sp.
Oxybaphus viscosus
Pennisetum weberbaueri
Cortaderia sp.
Phyla canescens
Desmondium sp.
Ophryosporus chica
Rhynchosia sp.
Chenopodium ambrosiodes
Plantago sp.
Saccharum officinarum
Saccharum officinarum
Sida sp.
Setaria sp.
Sporobolus sp.
Annona cherimola
Minthostachy sp.
Phyla canescens
Rosmarinus officinalis
Taraxacum officinale
English
Common name
Spanish
Common name
Escallonia
Phenax
Snoutbean
Lantana
Groundsel
Kikuyu grass
Paspalum
White clover
Kikuyu grass
Plantain
Bermuda grass
Kikuyu grass
Mexican tea
Phenax
Bush violet
Spiny holdback
Kikuyu grass
White stick
Umbrella wort
Fox tail
Pampas grass
Lippia
Trefoil
Pauco
Fura parede
Chilca negra
Kikuyu
Nudillo
Trebol
Kikuyu
Llanten macho
Grama dulce
Kikuyu
Paico
Fura parede
Taya
Kikuyu
Palo blanco
Rabo de zorro
Turre hembra
Chilca
Snoutbean
Mexican tea
Plantain
Sugar cane
Sugar cane
Mallow
Foxtail
Dropseed
Custard apple
Mint
Lippia
Joyweed
Rosemary
Dandelion
Tissue1
81
Paico
Llanten macho
Cana de azucar
Cana de azucar
Yendon
Pasto negro
Cherimoya
Chancua
Turre hembra
Moradilla
Romero
Diente de leon
leaves
stalk
Veg.
Type
Dry
Fraction
Tree
Shrub
Shrub
Shrub
Forb
Grass
Grass
Forb
Grass
Forb
Grass
Grass
Forb
Shrub
Forb
Tree
Grass
Tree
Forb
Grass
Grass
Forb
Forb
Forb
Shrub
Forb
Forb
Grass
Grass
Shrub
Grass
Grass
Tree
Shrub
Forb
Forb
Shrub
Forb
0.277
0.247
0.360
0.333
0.321
0.251
0.438
0.417
0.350
0.304
0.496
0.416
0.281
0.311
0.391
0.482
0.350
0.324
0.199
0.250
0.309
0.361
0.329
0.237
0.466
0.195
0.217
0.349
0.339
0.335
0.388
0.582
0.329
0.271
0.238
0.227
0.500
0.262
Total Hg (ppb)
wet wt
dry wt
2.19
3.47
2.1 6
5.11
7.72
3.78
19.7
20.0
102
26.4
12.6
14.8
3.41
3.78
5.51
5.09
5.39
2.82
2.96
ND < 0.81
5.48
3.12
2.82
2.54
4.27
8.47
1.48
ND < 0.81
ND < 0 .81
6.87
9.09
35.3
3.09
2.21
4.07
2.72
10.9
6.03
7.90
14.1
6.00
15.3
24.1
15.1
45.0
48.0
291
86.8
25.5
35.7
12.1
12.2
14.1
10.6
15.4
8.70
14.9
ND < 3.24
17.7
8.65
8.57
10.7
9.15
43.5
6.83
ND < 2.39
ND < 2.39
20.5
23.4
60.6
9.38
8.15
17.1
12.0
21.8
23.0
Shepherd Miller
November 2002
FINAL
Table 4.4.2
Sample
ID
Road
Km
Site
type
8-3 Amacel
8-3 Crosp
8-3 Ophchi
8-4 Annche
8-4 Arudon
8-4 Phesp
8-5 Altpor
8-5 Pencla
8-5 Phyang
8-6 Cesaur
8-6 Leonep
8-6 Pencla
8-7 Brosp
8-7 Cesaur
8-7 Phesp
8-9 Annche
8-9 Cessp
8-9 Ophchi
10-1 Pencla
10-1 Phycan
10-2 Annche
10-2 Asccur
10-3 Baclan
10-3 Minsp
10-3 Ophchi
13-1 Annche
13-1 Cyndoc
13-1-Leanep
13-2 Acamac
13-2 Altpor
13-2 Cesaur
13-2 Crosp
13-3 Annche
13-3 Citlim-fruits
13-3 Citlim-leaves
13-4 Asccur
13-4 Cucdip
13-4 Leonep
130.00
130.00
130.00
130.00
130.00
130.00
130.00
130.00
130.00
130.00
130.00
130.00
130.00
130.00
130.00
130.00
130.00
130.00
128.94
128.94
128.94
128.94
128.94
128.94
128.94
124.77
124.77
124.77
124.77
124.7 7
124.77
124.77
124.77
124.77
124.77
124.77
124.77
124.77
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Scientific name
Amaranthus celosioides
Croton sp.
Ophryosporus chilca
Annona cherimola
Arundo donax
Phenax sp.
Physalis angulata
Cestrum auriculatum
Leonotis nepetifolia
Browalia sp.
Cestrum auriculatum
Phenax sp.
Annona cherimola
Cestrum sp.
Ophryosporus chilca
Phyla cannescens
Annona cherimola
Baccharis lanceolata
Minthostachys sp.
Ophryisporus chilca
Annona cherimola
Cynodon dactylon
Acacia macracantha
Cestrum auriculatum
Croton sp.
Annona cherimola
Citrus limon
Citrus limon
Cucumis dipsaceus
English
Common name
Spanish
Common name
Amaranth
Croton
Yuyo
Custard apple
Gieant reed
Phenax
Joyweed
Kikuyu grass
Wild cherry
Jasmine
Lion’s ear
Kikuyu grass
Bush violet
Jasmine
Phenax
Custard apple
Jasmine
Kikuyu grass
Lippia
Custard apple
Scarlet milkweed
Groundsel
Mint
Custard apple
Bermuda grass
Lion’s ear
Porknut
Joyweed
Jasmine
Croton
Custard apple
Lemon
Lemon
Scarlet milkweed
Hedgehog
Lion’s ear
82
Tissue1
Chilca
Cherimoya
Carrizo
Fura parede
Moradillo
Kikuyu
Capuli cimarron
Heirba santa
Ponchequiro
Kikuyu
Heirba santa
Fura parede
Cherimoya
Heirba santa
Chilca
Kikuyu
Turre hembra
Cherimoya
Flor de seda
Chilco
Chancua
Chilca
Cherimoya
Grama dulce
Ponchequiro
Huarango
Moradillo
Heirba santa
Cherimoya
Limon
Limon
Flor de seda
Jaboncillo de campo
Ponchequiro
fruit
leaves
Veg.
Type
Dry
Fraction
Forb
Shrub
Forb
Tree
Grass
Shrub
Shrub
Grass
Forb
Shrub
Shrub
Grass
Forb
Shrub
Shrub
Tree
Shrub
Forb
Grass
Forb
Tree
Forb
Shrub
Shrub
Forb
Tree
Grass
Shrub
Tree
Shrub
Shrub
Shrub
Tree
Tree
Tree
Forb
Forb
Shrub
0.181
0.389
0.376
0.303
0.564
0.199
0.310
0.333
0.130
0.291
0.261
0.279
0.269
0.292
0.197
0.317
0.227
0.231
0.338
0.302
0.395
0.203
0.418
0.270
0.307
0.336
0.446
0.252
0.453
0.381
0.283
0.427
0.350
0.167
0.447
0.203
0.242
0.213
Total Hg (ppb)
wet wt
dry wt
1.62
5.03
3.15
4.43
13.2
2.91
2.67
2.77
1.37
5.22
2.58
2.59
4.11
4.67
2.78
3.96
3.08
2.54
4.59
3.34
7.03
1.67
6.18
2.67
2.56
5.65
4.01
3.23
8.10
4.23
4.07
8.94
3.38
0.21
10.1
2.51
3.03
2.27
8.95
12.9
8.38
14.6
23.4
14.6
8.61
8.32
10.5
17.9
9.88
9.28
15.3
16.0
14.1
12.5
13.6
11.0
13.6
11.1
17.8
8.23
14.8
9.89
8.34
16.8
8.99
12.8
17.9
11.1
14.4
20.9
9.65
1.28
22.6
12.4
12.5
10.7
Shepherd Miller
November 2002
FINAL
Table 4.4.2
Sample
ID
13-5 Brasp
13-5 Helsp
14-1 Phycan
14-1 Riccom
14-1 Solnig
14-2 Amasp
14-2 Bidpil
14-2 Oensp
14-3 Ammvis
14-3 Asccur
14-3 Cyndac
14-3 Datstr
14-3 Galcil
14-3 Staarv
14-3 Zeamay-leaves
14-3 Zeamay-stalk
15-1 Crosp
15-1 Solsp
Road
Km
124.77
124.77
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
123.89
119.73
119.73
Site
type
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Scientific name
Brassica sp.
Heliotropium sp.
Phyla canescens
Ricinus communis
Solanum nigrum
Amaranthus sp.
Bidens pilosa
Oenothera sp.
Ammi visnaga
Cynodon dactylon
Datura stoamonium
Galisonga ciliata
Stachys arvensis
Zea mays
Zea mays
Croton sp.
Solanum sp.
English
Common name
Mustard
Heliotrope
Lippia
Castor bean
Black nightshade
Amaranth
Beggar's tick
Evening primrose
Toothpick plant
Scarlet milkweed
Bermuda grass
Jimson weed
Hairy galinsoga
Field Woundwort
Corn
Corn
Croton
Nightshade
Spanish
Common name Tissue 1
Turre hembra
Higuerilla
Huerba mora
Yuyo
Cadillo
Flor de cavo
Visnaga
Flor de seda
Grama dulce
Chamico
Galinsoga
Supiquehua
Maiz
Maiz
Huerba mora
leaves
stalk
Veg.
Type
Forb
Forb
Forb
Tree
Forb
Forb
Forb
Forb
Forb
Forb
Grass
Forb
Forb
Forb
Grass
Grass
Shrub
Forb
Dry
Fraction
0.242
0.255
0.350
0.220
0.249
0.313
0.200
0.430
0.149
0.181
0.536
0.163
0.192
0.284
0.242
0.166
0.401
0.268
Total Hg (ppb)
wet wt dry wt
1.75
7.23
3.61
14.2
3.78
10.8
2.04
9.29
3.23
13.0
7.32
23.4
3.01
15.1
7.39
17.2
1.30
8.72
1.72
9.50
4.90
9.14
1.85
11.3
1.97
10.3
14.0
49.3
0.60
2.47
0.11
0.69
9.08
22.6
5.28
19.7
1
aboveground tissue collected unless specific tissue-type noted
ND= non detect (below the laboratory detection limit)
83
Shepherd Miller
November 2002
FINAL
Human Dietary Benchmark= 1600 ppb
120
Reference samples
Total Hg (ppb, ww)
100
Exposed samples
80
60
40
20
0
155
145
135
125
115
Spill Area
To Cajamarca
Location (Road Km)
Bird Dietary Benchmark= 4000
To Trujillo
Mammal Dietary Benchmark= 2000
350
Total Hg (ppb, dw)
300
Reference samples
Exposed samples
250
200
150
100
50
0
155
145
135
125
115
Spill Area
To Cajamarca
Figure 4.4.2
Location (Road Km)
To Trujillo
Total Hg tissue concentrations (ww) in Phase II vegetation collected at
reference and exposed locations. Wet weight and dry weight values are plotted
separately.
84
Shepherd Miller
November 2002
FINAL
Table 4.4.3
Summary Statistics for the Phase II Vegetation Sampling
Reference
wet weight
dry weight
Exposed
wet weight
dry weight
mean
(ppb)
95%UCL
(ppb)
range
(ppb)
5.9
22.2
7.9
35.7
1.14-24.04
7.9-156
7.7
22.8
9.8
28.4
0.11-102
0.69-291
Terrestrial Insect Analysis
Results of the insect tissue sampling are shown in Table 4.4.4. Results are listed by location along the road
and by the type of sample (Reference or Exposed). A scatterplot of the measured insect concentrations
versus location along the road is shown in Figure 4.4.3. Summary statistics are provided in Table 4.4.5.
The mean and 95 % UCL of the mean insect tissue concentrations from the Exposed locations were less
than Reference locations, though overall, the measured insect tissue concentrations at all of the Exposed
and Reference Sites were low and are indicative of background levels in the environment.
85
Shepherd Miller
November 2002
FINAL
Table 4.4.4
Results of the Phase II Terrestrial Insect Samples Collected in 2002
Sample
ID
Road Km
Site type
Dry
Fraction
1-3 Insects
5-4 Insects
6-3 Insects
6-4 Insects
13-6 Insects
14-4 Insects
15-2 Insects
15-3 Insects
155
139.81
135.39
135.39
124.77
123.89
119.73
119.73
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
0.39
0.31
0.43
0.48
0.42
NA
0.39
0.41
1-1 Insects
1-2 Insects
A-1 Insects
A-2 Insects
C-1 Insects
C-2 Insects
B-1 Insects
B-2 Insects
4-1 Insects
4-2 Insects
5-1 Insects
5-2 Insects
5-3 Insects
6-1 Insectsa
6-2 Insects
7-1 Insects
7-2 Insects
7-3 Insects
7-4 Insects
8-1 Insects
8-2 Insects
8-3 Insects
8-4 Insects
8-5 Insects
8-6 Insects
8-7 Insects
8-9 Insects
10-1 Insects
10-2 Insects
10-3 Insects
13-1 Insects
13-2 Insects
13-3 Insects
13-4 Insects
13-5 Insects
14-1 Insects
14-2 Insects
14-3 Insects
15-1 Insects
155
155
147.423
147.423
145.465
145.465
145.433
145.433
140.18
140.18
139.81
139.18
139.81
135.39
135.39
134.45
134.45
134.45
134.45
130
130
130
130
130
130
130
130
128.94
128.94
128.94
124.77
124.77
124.77
124.77
124.77
123.89
123.89
123.89
119.73
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
0.36
NA
0.37
0.31
0.42
0.34
0.30
0.30
0.30
0.36
0.46
0.32
0.40
0.95
0.55
0.51
NA
0.55
0.42
0.43
0.64
0.35
0.36
0.33
0.35
0.42
0.31
0.35
0.34
0.40
0.38
0.34
0.38
0.34
0.31
0.36
0.33
0.36
0.27
Total Hg, ng/g
wet wt basis
dry wt basis
43.3
110
2.43
7.87
6.76
15.9
6.14
12.7
1.77
4.25
7.93
17.9
45.9
3.55
8.60
13.4
25.4
9.53
7.66
11.7
7.47
7.92
10.1
3.68
8.51
2.81
2.48
4.93
5.23
73.4
16.9
14.5
3.71
3.74
12.9
42.1
3.26
2.71
2.36
8.79
6.46
4.3
2.00
1.38
1.52
15.2
7.35
10.9
3.36
1.58
3.44
2.74
10.5
3.28
36.8
25.7
24.6
28.1
21.9
26.3
33.6
12.2
23.5
6.12
7.80
12.2
5.51
134
32.8
6.77
8.98
30.1
66.2
9.31
7.60
7.19
25.1
15.2
14.1
5.79
4.11
3.81
39.8
21.9
28.5
9.77
5.08
9.61
8.26
29.1
12.0
a
Sample is reported as an estimate due to laboratory error (spilt sample)
NA= not analyzed due to insufficient sample mass
86
Shepherd Miller
November 2002
FINAL
Insect Tissue Benchmark=150 ppb
80
Reference sites
Insect Hg (ppb, ww)
70
Exposed sites
60
50
40
30
20
10
0
160
150
140Spill Area 130
120
110
Location (Road Km)
To Cajamarca
To Trujillo
Insect Hg (ppb, dw)
160
Reference sites
140
Exposed sites
120
100
80
60
40
20
0
160
150
To Cajamarca
Figure 4.4.3
140Spill Area 130
Location (Road Km)
120
110
To Trujillo
Scatterplot of mercury concentrations in insects versus location (Phase II). Wet
weight and dry weight values are plotted separately.
87
Shepherd Miller
November 2002
FINAL
Table 4.4.5
Summary Statistics for the Phase II Insect Sampling
mean
(ppb, ww)
95%UCL
(ppb, ww)
range
(ppb, ww)
11.2
29.4
20.5
57.5
1.77-43.3
4.25-110
9.7
21.6
13.2
28.0
1.38-7.34
3.81-134
Reference
wet weight
dry weight
Exposed
wet weight
dry weight
4.4.2
Sampling and Tissue Analysis of Aquatic Biota
The Phase II fish and aquatic macroinvertebrate samples were collected by ENKON Environmental
(Surrey, British Columbia) in September of 2001. Sampling methodology, photographs, and information on
habitat conditions at each site are included in Appendix F. Most of the locations sampled in Phase I were
re-sampled in Phase II. The Site 2-1 and 2-2 sampling locations were not re-sampled in Phase II because
they were determined to be duplicative of the data collected at Site 2-3. Additionally, fish sampling was
not conducted at Sites 5-2, 5-3, or 6-1 since no fish were present at these locations during the Phase I
sampling. All of the Phase I and II sampling locations are shown on Map 3. While the Phase I sampling
was conducted prior to the wet season and therefore prior to possible movement of mercury into the
waterways, the Phase II sampling was conducted after the first wet season and therefore after the
potential migration of mercury into the waterways.
Aquatic Macroinvertebrate Analysis
Tissue concentrations for the composite macroinvertebrate samples (i.e., all species together) and
individual freshwater crabs are shown in Table 4.4.6. Both total and methylmercury concentrations are
shown on both a dry weight and wet weight basis, as available. The higher of the methyl or total mercury
values are plotted in Figure 4.4.4. The percent of the total mercury present in the form of methylmercury
in the macroinvertebrate samples ranged from 30 to 100% (Table 4.4.6). Values of greater than 100%
reflect differences in the analytical methodology used to analyze for total versus methylmercury (Appendix
G).
88
Shepherd Miller
November 2002
FINAL
Table 4.4.6
Mercury Concentration in Phase II Aquatic Macroinvertebrate Samples
Sample ID
Crab (4.7 cm) whole
Crab (7.7 cm) whole
Crab (8.8 cm) whole
Crab (5.7 cm) whole
Z1S1-B
Z1S1-B(split)
Z2S3-B
Crab - whole
Z3S1-B
Z3S2-B
Z3S3-B
(non-megaloptera)
Z3S3-B
(megaloptera spp.)
Z4S1-B
Z5S1-B
Z5S2-B
Z5S3-B
Z6S1-B
Z7S1-B
Sample
Type 1
Zone
Crab-whole
Crab-whole
Crab-whole
Crab-whole
Composite
Composite
Composite
Crab-whole
Composite
Composite
Composite
1
1
1
1
1
1
2
2
3
3
3
Composite
Composite
Composite
Composite
Composite
Composite
Composite
Total Hg Methyl Hg
(ppb)
(ppb)
methyl/
ww dw ww dw
total
Site
Road
Km
Location
Type
Dry
Fraction
Reservoir
Reservoir
Reservoir
Reservoir
1
1
3
3
1
2
3
50
50
50
50
52
52
94
94
115
126
132
Reservoir
Reservoir
Reservoir
Reservoir
Downstream
Downstream
Downstream
Downstream
Exposed
Exposed
Exposed
0.401
0.408
0.412
0.455
0.282
0.145
0.207
0.460
0.263
0.242
0.258
58.6
77.8
154
80.8
18.2
11.0
11.1
77.1
13.3
28.0
17.1
146
191
373
178
64.4
76.2
53.6
168
50.7
116
66.1
178
222
254
201
47.7
61.8
45.0
160
37.8
92.3
34.3
1.21
1.16
0.68
1.13
0.74
0.81
0.84
0.95
0.75
0.80
0.52
3
3
132
Exposed
0.234
15.2
65.0 8.61 36.8
0.57
4
5
5
5
6
7
1
1
2
3
1
1
134
133
153
155
157
165*
Exposed
Exposed
Exposed
Exposed
Reference
Reference
0.195
0.201
0.246
0.172
0.260
0.196
7.84
21.4
31.1
32.0
130
8.82
40.2
106
126
186
501
45.0
0.74
0.77
0.58
0.30
0.59
0.71
71.2
90.6
104
91.3
13.4
8.97
9.31
73.6
9.93
22.3
8.85
5.77
16.5
17.9
9.54
77.1
6.22
29.6
81.9
72.9
55.4
296
31.8
1
Composite= the analyzed sample is a composite of all of the macroinvertebrates collected at that site
* Zone 7 Site 1 is located in an upstream tributary (Rio Huacraruca) of the Jequetepeque
The tissue concentrations measured at locations within the spill area are compared to upstream,
downstream, and all of the non-spill sampling locations in Table 4.4.7. There is no indication that the
mercury concentration in invertebrate tissues within the spill area, or downstream of the spill area, are
elevated as a result of the spilt mercury.
Overall, mercury concentrations in the Phase II
macroinvertebrate samples generally were low and within typical background concentrations in the
environment (Table 1.2.2).
Table 4.4.7
Comparison of Mercury Tissue Concentrations (Phase II) in Macroinvertebrates
at Different Sample Locations
Area
Spill Area
Downstream
All non-spill
All samples
No.
samples
8
2
8
10
18
Mean
ww
20.7
69.6
65.5
66.4
46.1
89
(ppb)
dw
94.5
273.0
166.9
188.1
146.5
95% UCL (ppb)
ww
dw
26.7
127
453.1
1712
98.9
237.8
96.8
274.9
64.6
196.8
Range (ppb)
ww
dw
7.84-32.0
40.2-186
8.82-130
45-501
11.0-154
53.6-373
8.82-154
45-501
7.84-154
40.2-501
Shepherd Miller
November 2002
FINAL
Human Dietary (MeHg) Benchmark= 300
180
Individual crabs
Composite samples
160
140
Hg (ppb, ww)
Macroinvertebrate Tissue Benchmark= 150 ppb
120
100
80
60
40
20
0
165
145
125
105
85
65
45
Spill Area
Location (Road Km)
To Trujillo
To Cajamarca
Bird Methylmercury Dietary Benchmark= 2500 ppb
600
Individual crabs
Composite samples
500
Hg (ppb, dw)
400
300
200
100
0
165
145
125
105
85
65
45
Spill Area
To Cajamarca
Figure 4.4.4
Location (Road Km)
To Trujillo
Mercury concentration in macroinvertebrates versus sampling location (Phase
II). Wet weight and dry weight values are plotted separately.
90
Shepherd Miller
November 2002
FINAL
Fish tissue analysis
All of the Phase II fish tissue analysis data are shown in Table 4.4.8. Fish were collected at nine
locations- one upstream of the spill area, five within the spill area, and three downstream of the spill area.
The results of the Phase I analysis of fish tissue indicated that essentially all of the mercury present in the
fish tissue was in the methylated form and that the analytical methodology used for the methylmercury
analysis tended to produce slightly higher mercury values (Appendix G). Due to these factors, all of the
Phase II samples were analyzed for methylmercury, with only a percentage of the samples also analyzed
for total mercury.
A total of 114 different fish tissues were analyzed. Of the 114 analyses, 11 were of head tissue, 45 of
muscle tissue, 46 of total fish, and 12 of muscle+head tissue. The muscle+head tissue samples were a
result of an error at Frontier Geosciences, but still provide useful information and are included in
subsequent evaluations and discussions. For the samples that were analyzed for both methyl and total
mercury, the percent of mercury present in the methyl form ranged from 89% to 100%. To be
conservative, we have assumed that all of the mercury in fish is present in the methyl form and have
utilized the highest recorded mercury level (either the total or the methyl) for each sample in the risk
calculations and evaluations. Four of the samples analyzed had mercury concentrations that were higher
than the maximum value recorded in the Phase I sampling of 605 ppb (ww). These four samples are all
from the Gallito Ciego Reservoir. Frontier Geosciences was asked to re-analyze these samples. The
sample IDs and results of the two analyses are shown in Table 4.4.9. For three of the four samples, a
new digest was made prior to the re-analysis. For the fourth sample, there was insufficient material for a
re-digest, so this sample was only re-analyzed. The higher value from the two analyses is utilized in the
risk calculations and evaluations.
91
Shepherd Miller
November 2002
FINAL
Table 4.4.8
Results of Fish Analyses from the Phase II Sampling
Sample
Identification
Cachuela (10.3 cm)
Cascafe (21 cm)
Cascafe (23.2 cm)
Cascafe (26 cm)
Cascafe (26.5 cm)
Cascafe (26.5 cm)
Charcoca (10.2 cm)
Charcoca (10.5 cm)
Charcoca (10.8 cm)
Charcoca (8.2 cm)
Charcoca (8.7 cm)
Charcoca (9.5 cm)
Charcoca (9.9 cm)
Life ( 15.2 cm)
Life (12.6 cm)
Life (16.6 cm)
Life (16.8 cm)
Life (16.8 cm)
Mojarra (13 cm)
Mojarra (13.5 cm)
Mojarra (17.3 cm)
Mojarra (17.3 cm)
Mojarra (18.5 cm)
Nato (10.8 cm)
Nato (10.8 cm) *
Nato (13 cm)
Nato (9.6 cm)
Nato (9.7 cm)
Nato A (10.2 cm)
Nato A (10.2 cm) **
Nato A (9.2 cm)
Nato B (10.2 cm)
Nato B (10.2 cm) *
Nato B (9.2 cm)
Species
Cachuela
Cascafe
Cascafe
Cascafe
Cascafe
Cascafe
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Life
Life
Life
Life
Life
Mojarra
Mojarra
Mojarra
Mojarra
Mojarra
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Length
(cm)
10.3
21
23.2
26
26.5
26.5
10.2
10.5
10.8
8.2
8.7
9.5
9.9
15.2
12.6
16.6
16.8
16.8
13
13.5
17.3
17.3
18.5
10.8
10.8
13
9.6
9.7
10.2
10.2
9.2
10.2
10.2
9.2
Tissue
Type
Zone
muscle
1
muscle
1
muscle
1
muscle
1
head
1
muscle
1
muscle
1
muscle
1
muscle
1
whole
1
whole
1
whole
1
whole
1
muscle/head
1
muscle
1
muscle
1
head
1
muscle
1
muscle/head
1
muscle
1
head
1
muscle
1
muscle
1
muscle
1
muscle
1
muscle
1
whole
1
whole
1
muscle
1
muscle
1
whole
1
muscle
1
muscle
1
whole
1
Site
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
92
Dry
Fraction
0.213
0.208
0.189
0.194
0.188
0.188
0.229
0.252
0.212
0.271
0.263
0.253
0.323
0.301
0.245
0.251
0.241
0.241
0.307
0.216
0.189
0.189
0.178
0.163
0.163
0.186
0.226
0.228
NA
0.248
0.210
0.210
0.221
Total Hg (ppb)
ww
dw
159
822
154
610
232
770
88.4
497
543
-
Methyl Hg (ppb) methyl/ Road
ww
dw
total
Km Notes
242
1140
50
Reservoir
138
664
50
Reservoir
183
970
50
Reservoir
170
876
1.06641
50
Reservoir
140
745
50
Reservoir
235
1250
50
Reservoir
68.2
298
50
Reservoir
138
547
0.89636
50
Reservoir
261
1230
50
Reservoir
104
385
50
Reservoir
61.0
232
50
Reservoir
147
579
50
Reservoir
80.9
250
50
Reservoir
218
723
0.93938
50
Reservoir
16.9
69.0
50
Reservoir
159
633
50
Reservoir
148
615
50
Reservoir
362
1500
50
Reservoir
85.4
278
50
Reservoir
79.3
367
50
Reservoir
78.2
414
50
Reservoir
116
614
50
Reservoir
78.9
443
0.89212
50
Reservoir
819
5020
50
Reservoir
357
2190
50
Reservoir
535
2870
50
Reservoir
392
1730
50
Reservoir
341
1490
50
Reservoir
1410
50
Reservoir
1430
50
Reservoir
301
1220
50
Reservoir
684
3260
1.26011
50
Reservoir
722
3440
50
Reservoir
401
1810
50
Reservoir
Shepherd Miller
November 2002
FINAL
Table 4.4.8
Results of Fish Analyses from the Phase II Sampling (continued)
Sample
Identification
Pejerrey (20.6 cm)
Pejerrey (21 cm)
Pejerrey (21 cm)
Pejerrey (24.3 cm)
Pejerrey (25 cm)
Picalon (11.7 cm)
Picalon (11.7 cm) *
Tilapia (30 cm)
Tilapia (31.5 cm)
Tilapia (31.5 cm)
Cascafe (13.2 cm)
Cascafe (16.9 cm)
Cascafe (16.9 cm)
Charcoca (10.1 cm)
Charcoca (4.7 cm)
Charcoca (6.2 cm)
Charcoca (7.2 cm)
Charcoca (7.7 cm)
Life (12 cm)
Mojarra (12 cm)
Mojarra (12.8 cm)
Mojarra (13.6 cm)
Mojarra (13.6 cm)
Mojarra (14.6 cm)
Nato (6.4 cm)
Charcoca (6 cm)
Charcoca (6.6 cm)
Charcoca (8.7 cm)
Charcoca (9 cm)
Mojarra (10.7 cm)
Charcoca (11 cm)
Charcoca (11.9 cm)
Charcoca (11.9 cm)
Charcoca (9.5 cm)
Species
Pejerrey
Pejerrey
Pejerrey
Pejerrey
Pejerrey
Picalon
Picalon
Tilapia
Tilapia
Tilapia
Cascafe
Cascafe
Cascafe
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Life
Mojarra
Mojarra
Mojarra
Mojarra
Mojarra
Nato
Charcoca
Charcoca
Charcoca
Charcoca
Mojarra
Charcoca
Charcoca
Charcoca
Charcoca
Length
(cm)
20.6
21
21
24.3
25
11.7
11.7
30
31.5
31.5
13.2
16.9
16.9
10.1
4.7
6.2
7.2
7.7
12
12
12.8
13.6
13.6
14.6
6.4
6
6.6
8.7
9
10.7
11
11.9
11.9
9.5
Tissue
Type
Zone
muscle
1
head
1
muscle
1
muscle/head
1
muscle/head
1
muscle/head
1
muscle/head
1
muscle/head
1
head
1
muscle
1
muscle
1
head
1
muscle
1
muscle
1
whole
1
whole
1
whole
1
whole
1
muscle/head
1
muscle
1
muscle
1
head
1
muscle
1
muscle/head
1
whole
1
whole
2
whole
2
whole
2
whole
2
muscle/head
2
muscle
3
head
3
muscle
3
whole
3
Site
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
Reservoir
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
3
3
3
3
3
1
1
1
1
93
Dry
Fraction
0.211
0.212
0.212
0.247
0.240
0.260
0.260
0.259
0.181
0.181
0.220
0.209
0.209
0.234
0.252
0.273
0.250
0.248
0.298
0.216
0.204
0.197
0.197
0.272
0.257
0.234
0.240
0.246
0.263
0.330
0.237
0.232
0.232
0.289
Total Hg (ppb)
ww
dw
55.8
263
73.5
347
32.1
124
63.4
288
24.8
90.7
66.4
337
117
592
55.9
227
41.0
173
-
ww
dw
total
Km Notes
51.3
243
50
Reservoir
51.7
244
0.92784
50
Reservoir
68.3
322
0.92932
50
Reservoir
157
636
50
Reservoir
64.2
267
50
Reservoir
708
2720
50
Reservoir
757
2910
50
Reservoir
31.9
123
0.99376
50
Reservoir
17.4
96.3
50
Reservoir
50.5
279
50
Reservoir
76.9
350
1.21366
50
Downstream
196
940
50
Downstream
318
1520
50
Downstream
94.7
405
50
Downstream
22.4
89.0
50
Downstream
27.1
99.2
1.09426
50
Downstream
88.0
352
50
Downstream
89.1
359
50
Downstream
36.5
122
50
Downstream
113
524
50
Downstream
133
653
50
Downstream
87.1
442
1.31313
50
Downstream
109
556
0.93785
50
Downstream
128
469
50
Downstream
110
427
50
Downstream
16.4
70.0
94
Downstream
32.8
137
94
Downstream
68.9
280
1.23202
94
Downstream
22.9
87.1
94
Downstream
19.1
57.9
94
Downstream
42.5
179
1.0369 115 Exposed
60.3
260
115 Exposed
104
448
115 Exposed
34.0
118
115 Exposed
Shepherd Miller
November 2002
FINAL
Table 4.4.8
Sample
Identification
Charcoca A (10.7 cm)
Charcoca B (10.7 cm)
Life (10 cm)
Life (11.5 cm)
Life (14.5 cm)
Life (16 cm)
Nato (10.5 cm)
Nato (10.5 cm)
Nato (13.3 cm)
Nato (7 cm)
Nato (7.3 cm)
Nato (7.7 cm)
Nato (9.2 cm)
Nato (9.8 cm)
Cachuela (10.4 cm)
Cachuela (10.5 cm)
Chacoca (11.1 cm)
Chacoca (11.1 cm)
Charcoca (11 cm)
Charcoca (12.2 cm)
Charcoca (9.9 cm)
Nato (10.6 cm)
Nato (10.8 cm)
Nato (11.7 cm)
Nato (11.7 cm)
Nato (12.4 cm)
Nato (7.8 cm)
Nato (8.2 cm)
Nato A (7.9 cm)
Nato B (7.9 cm)
Charcoca (8.8 cm)
Nato (4 cm)
Nato (5.8 cm)
Nato A (7 cm)
Species
Charcoca
Charcoca
Life
Life
Life
Life
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Cachuela
Cachuela
Charcoca
Charcoca
Charcoca
Charcoca
Charcoca
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Charcoca
Nato
Nato
Nato
Length
(cm)
10.7
10.7
10
11.5
14.5
16
10.5
10.5
13.3
7
7.3
7.7
9.2
9.8
10.4
10.5
11.1
11.1
11
12.2
9.9
10.6
10.8
11.7
11.7
12.4
7.8
8.2
7.9
7.9
8.8
4
5.8
7
Tissue
Type
Zone
muscle
3
muscle
3
muscle
3
muscle
3
muscle
3
muscle
3
head
3
muscle
3
muscle/head
3
whole
3
whole
3
whole
3
whole
3
whole
3
muscle
3
muscle
3
head
3
muscle
3
muscle
3
muscle/head
3
whole
3
muscle
3
muscle
3
head
3
muscle
3
muscle
3
whole
3
whole
3
whole
3
whole
3
whole
3
whole
3
whole
3
whole
3
Site
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
3
3
3
94
Dry
Fraction
0.257
0.223
0.252
0.246
0.203
0.244
0.227
0.227
0.267
0.246
0.269
0.237
0.257
0.249
0.226
0.222
0.266
0.266
0.244
0.290
0.245
0.231
0.232
0.196
0.196
0.280
0.248
0.246
0.272
0.232
0.275
0.283
0.280
Total Hg (ppb)
ww
dw
54.3
267
65.4
254
345
1530
54.8
196
97.3
358
25.5
90.9
ww
dw
total
Km Notes
42.9
167
115 Exposed
31.2
140
115 Exposed
35.0
139
115 Exposed
27.3
111
115 Exposed
52.4
258
0.96553 115 Exposed
60.4
247
115 Exposed
89.8
396
115 Exposed
117
515
115 Exposed
103
388
115 Exposed
35.6
145
115 Exposed
23.9
88.8
115 Exposed
20.1
85.0
115 Exposed
82.0
319
1.25464 115 Exposed
38.6
155
115 Exposed
441
1950
1.2775 126 Exposed
323
1460
126 Exposed
92.0
346
126 Exposed
153
574
126 Exposed
129
530
126 Exposed
164
565
126 Exposed
103
419
126 Exposed
120
519
126 Exposed
73.6
317
126 Exposed
131
668
126 Exposed
189
967
126 Exposed
57.3
205
1.04613 126 Exposed
39.1
157
126 Exposed
38.8
158
126 Exposed
99.6
366
1.02354 126 Exposed
40.9
176
126 Exposed
27.3
99.3
132 Exposed
12.0
132 Exposed
29.1
103
132 Exposed
31.9
114
1.25372 132 Exposed
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November 2002
FINAL
Table 4.4.8
Sample
Identification
Species
Length
(cm)
Tissue
Type
Zone
Site
Dry
Fraction
Nato B (7 cm)
Pejerrey (14.8 cm)
Nato (2.4 cm)
Nato (3.2 cm)
Nato (6.5 cm)
Nato A (7.6 cm)
Nato B (7.6 cm)
Pejerrey (17 cm)
Nato (5.8 cm)
Nato (5.9 cm)
Nato (6.8 cm)
Nato (9.2 cm)
Nato (4.3 cm)
Nato (4.4 cm)
Nato (7 cm)
Nato (7.3 cm)
Nato
Pejerrey
Nato
Nato
Nato
Nato
Nato
Pejerrey
Nato
Nato
Nato
Nato
Nato
Nato
Nato
Nato
7
14.8
2.4
3.2
6.5
7.6
7.6
17
5.8
5.9
6.8
9.2
4.3
4.4
7
7.3
whole
muscle/head
whole
whole
whole
whole
whole
muscle
whole
whole
whole
whole
whole
whole
whole
whole
3
3
4
4
4
4
4
4
5
5
5
5
7
7
7
7
3
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0.277
0.276
0.288
0.255
0.260
0.253
0.250
0.291
0.304
0.229
0.237
0.226
0.284
Total Hg (ppb)
ww
dw
20.0
69.6
20.0
79.1
304
70.4
Methyl Hg (ppb) methyl/
ww
dw
total
29.5
59.7
10.5
8.35
18.2
55.9
31.2
18.1
77.6
58.7
55.4
67.2
16.1
14.5
44.4
23.7
106
216
63.2
219
120
71.6
311
202
182
293
67.9
197
83.4
0.90548
0.96522
1.18506
Road
Km Notes
132
132
134
134
134
134
134
134
133
133
133
133
165
165
165
165
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Exposed
Upstream
Upstream
Upstream
Upstream
* re-digested and re-analyzed duplicate sample
** duplicate sample only re-analyzed since insufficient material to re-digest and re-analyze
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Table 4.4.9
Re-analyzed Fish Tissue Samples from the Phase II Sampling
Sample ID
Methyl Hg (ppb, ww)
Analyses
Re-analyses
1410
1430*
819
357
708
757
684
722
Tissue
Nato A (10.2 cm)
Nato (10.8 cm)
Picalon (11.7 cm)
Nato B 10.2
muscle
muscle
muscle/head
muscle
* Sample only re-analyzed since not sufficient material to re-digest and then re-analyze
Summary statistics for the Phase II fish tissue analysis is provided in Table 4.4.10, and the maximum
mercury value for each sample is plotted versus location in Figure 4.4.5.
Table 4.4.10
Summary Statistics for the Phase II Fish Sampling
Area
Spill Area
Downstream
All non-spill
All samples
No.
samples
50
4
60
64
114
Mean
ww
75.8
24.7
189.1
178.8
133.7
(ppb)
dw
333.2
116.0
774.7
742.8
566.2
95% UCL (ppb)
ww
dw
94.1
419.1
40.9
234.5
234.4
971.6
228.1
932.5
163.3
683.5
Range (ppb)
ww
dw
8.35-441
63.2-1950
14.5-44.4
67.9-197
16.4-1430
57.9-5020
14.5-1430
57.9-5020
8.35-1430
57.9-5020
Summary statistics, on a wet weight basis, are provided in Table 4.4.11 for each sampling location.
Table 4.4.11
Mercury Concentration in Fish at Each Location (Phase II)
Site
Reservoir
Site 1-1
Site 2-3
Site 3-1
Site 3-2
Site 3-3
Site 4-1
Site 5-1
Site 7-1
(1)
Location
Downstream
Downstream
Downstream
Exposed
Exposed
Exposed
Exposed
Exposed
Upstream1
No. of
Samples
40
15
5
18
16
6
6
4
4
Mean
(ppb,ww)
238.7
109.1
32.0
55.7
137.2
32.6
24.0
65.3
24.7
95% UCL Range
(ppb,ww) (ppb,ww)
312.7
16.9-1430
142.2
22.4-318
52.5
16.4-68.9
68.2
20.1-117
184.5
38.8-441
44.3
12.0-59.7
38.5
8.35-55.9
77.3
55.4-77.6
40.9
14.5-44.4
Zone 7 Site 1 (7-1) is located in an upstream tributary (Rio Huacraruca)
96
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Fish Tissue Benchmark= 2000 ppb
1600
1400
1200
1000
800
600
Human Methyl Dietary Benchmark= 300 ppb
400
200
0
165
145
125
Spill Area
To Cajamarca
105
85
Location (Road Km)
65
45
To Trujillo
6000
5000
4000
Bird Methyl Dietary Benchmark= 2500 ppb
3000
2000
1000
0
165
145
125
Spill Area
To Cajamarca
Figure 4.4.5
105
85
Location (Road Km)
65
45
To Trujillo
Mercury concentration (ww) in fish at all sampling locations (Phase II). The Spill
Area is indicated by the marked line. Samples shown as collected at Km 165 are
from a reference tributary upstream of the spill area. Wet weight and dry weight
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In order to evaluate fish consumed by the local human population, small fish (<10 cm) were analyzed as
whole fish, whereas larger fish (>10 cm) were segregated into muscle and head samples prior to analysis.
Table 4.4.12 shows the mean, 95% UCL, and maximum mercury concentrations (ww) across all of the
samples for each of these tissue types.
Table 4.4.12
Mercury Concentrations for Each Fish Tissue Type (Phase II)
Tissue
type
Head
Muscle
Head+muscle
Whole
Mean
(ppb, ww)
99.7
196.2
153.2
75.5
95%UCL
(ppb, ww)
127.1
260.3
257.1
98.9
Range
(ppb, ww)
17.4-1096
16.9-1430
19.2-1838
8.35-401
ww= wet weight
Muscle tissue had the highest mercury concentrations and whole body analyses had the lowest mercury
concentrations. This may be due to smaller fish being selected for whole body tissue analysis versus
smaller fish for whole body analysis.
Generally, larger and older fish will have higher mercury
concentrations than smaller and younger fish (USEPA 1999a). However, a regression analysis of the data
shown in Figure 4.4.6 again indicated no significant relationship (R2=0.003) between fish length and
mercury concentrations in tissue.
1600
Hg concentration in head
1400
Hg concentration in muscle
Hg concentration in whole fish
Hg (ppb)
1200
1000
800
600
400
200
0
0
5
10
15
20
25
30
35
Fish length (cm)
Figure 4.4.6
Mercury concentrations (ww) in each fish tissue type plotted versus fish length
(Phase II). Samples from all locations are included.
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November 2002
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Table 4.4.13 shows the mean mercury concentrations in each tissue type (head, muscle, or whole fish) for
each of the analyzed fish species, across all sampling locations. There is a significant degree of variation
between the fish species. Much of this variation, however, may be due to the small number of samples
analyzed for each fish species. The mean mercury concentrations in the heads of the different species
range from 17.4 to 148 ppb (ww). Tilapia had the lowest mean concentration in heads and Life had the
highest. In muscle tissue, Nato was the species with the highest mean concentration at 451 ppb (ww) and
Pejerrey had the lowest at 48.3 ppb (ww). Whole body analyses were only conducted for Charcoca and
Nato. Additional discussion of the life history and feeding habitats of the different species is provided in
Section 2.2.
Table 4.4.13
Mean Mercury Concentrations for Each Fish Species and Tissue Type (Phase II)
Species
Cachuela
Cascafe
Charcoca
Life
Mojarra
Nato
Pejerrey
Picalon
Tilapia
Head
Hg (ppb, ww)
ND
168 (2)
76.2 (2)
148 (1)
82.7 (2)
110.4 (2)
55.8 (1)
ND
17.4 (1)
Muscle
Hg (ppb, ww)
335 (3)
187 (6)
108.1 (10)
102.1 (7)
107.9 (6)
451.4 (9)
48.3 (3)
ND
50.5 (1)
Head+Muscle
Hg (ppb, ww)
ND
ND
164 (1)
134.3 (2)
77.5 (3)
103 (1)
93.6 (3)
757 (1)
32.1 (1)
Whole
Hg (ppb, ww)
ND
ND
61.6 (15)
ND
ND
82.3 (31)
ND
ND
ND
ND= no data
ww= wet weight
Values in parentheses indicate number of samples used in calculating the mean
4.5
Mercury Transfer to Terrestrial Biota
The sampling conducted at the site provides actual mercury exposure measurements for the majority of
the exposure pathways shown in Figures 2.3.1 and 2.3.2. The exception is that there was only four
terrestrial animal tissue samples collected during the joint November 2000 sampling effort (Section 4.3).
In order to allow for the evaluation of mercury concentrations in animal tissues and to assess the risk
potential to animals that consume other animal tissue (e.g., humans), the scientific literature was revie wed
for information on the transfer of mercury from the diet to animals. Transfer factors are required to
model the expected tissue concentrations of mercury in terrestrial animals that results from mercury
concentrations in the diet. Typically, these transfer values are called bioaccumulation factors, or BAFs,
and are calculated by dividing the concentration of mercury in animal tissue by the concentration of
mercury in the diet:
BAF= mercury concentration in animal tissue (ppb)
mercury concentration in diet (ppb)
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If the BAF is less than 1, mercury does not accumulate to a greater degree in animals than it occurs in the
diet.
Values listed in the literature for transfer of mercury from dietary items to terrestrial animal tissue are
shown in Table 4.5.1. Values for transfer of non-methylmercury (e.g., ionic mercury) to mammal tissue
are shown first, followed by methylmercury BAFs. The range of values for transfer of non-methyl
mercury is 0.003 to 13.52, with a mean of 1.68 and a median value of 0.41. Fifty percent of the reported
values are greater than the median, and 50% are less. Of the 39 values reported in the literature, 24
(>60%) of the BAF values are less than 1.0. In general, the highest BAF values are associated with the
lowest dietary concentration. This suggests that the transfer of mercury from the diet to tissue is not
linear, and that as dietary concentrations increase, the relative uptake into tissues declines. The BAF
values for transfer of methylmercury from the diet to mammal tissues ranges from 0.168 to 5. The mean
of the five values listed in Table 4.5.1 for methylmercury transfer is 1.74, and the median is 0.819. The
mean value of 1.74 for methylmercury uptake is similar to the mean value of 1.68 for the nonmethylmercury BAFs. All of the BAFs found in the literature for the transfer of mercury from the diet
into bird tissue are for methylmercury forms. These values range from 0.56 to 8.6, with a mean of 2.36
and a median of 1.29. The mean value for ionic mercury transfer to mammal tissue of 1.68 and the mean
of 2.36 for transfer of mercury to bird tissue were used to model mercury transfer to mammal and bird
tissue in the RA.
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Table 4.5.1
Mercury BAFs for Birds and Mammals
Species
Notes
Tissue Type
ppm
Diet*
ppm
Tissues*
BAF
Reference
MAMMAL-DIET
Chamois (goat)
Roe Deer
Roe Deer
Chamois (goat)
Roe Deer
Roe Deer
Goat
Roe Deer
Chamois (goat)
Goat
Mouse
Roe Deer
Roe Deer
Goat
Roe Deer
Goat
Chamois (goat)
Wolf
Chamois (goat)
Goat
Goat
Goat
Goat
White-footed Mouse
Goat
Roe Deer
Roe Deer
Goat
Lynx
Lynx
Roe Deer
Lynx
Wolf
Lynx
Shorttail Shrew
Lynx
Chamois (goat)
Lynx
Roe Deer
Total Hg, dw vegetation
Hg +2 (HgCl 2)
Hg +2 (HgCl 2)
Hg +2 (HgCl 2)
Hg +2 (HgCl 2)
Hg +2 (HgCl 2)
Total Hg, deer muscle ww
Hg +2 (HgCl 2)
Hg +2 (HgCl 2)
Hg +2 (HgCl 2)
Hg +2 (HgCl 2)
Total Hg; ww
Hg +2 (HgCl 2)
Hg +2 (HgCl 2)
Total Hg
Total Hg, hare muscle ww
Total Hg, rabbit muscle ww
Total Hg
Total Hg
Muscle (ww)
Muscle (ww)
Muscle (ww)
Liver (ww)
Liver (ww)
Muscle (ww)
Omental fat (ww)
Liver (ww)
Muscle (ww)
Brain (ww)
Internal organs
Muscle (ww)
Liver (ww)
Heart (ww)
Kidney (ww)
Lung (ww)
Kidney (ww)
Muscle (ww)
Liver (ww)
Skeletal muscle (ww)
Mesenteric lymph nodes (ww)
Intestines (ww)
Spleen (ww)
Kidney (ww)
Liver (ww)
Liver (ww)
Kidney (ww)
Kidneys (ww)
Muscle (ww)
Muscle
Kidney (ww)
Muscle (ww)
Muscle (ww)
Muscle (ww)
Kidney (ww)
Liver
Kidney (ww)
Muscle (ww)
Kidney (ww)
14.4
14.4
0.58
14.4
0.58
0.08
73.9
14.4
0.21
73.9
5
0.21
0.08
73.9
0.58
73.9
14.4
0.0262
0.21
73.9
73.9
73.9
73.9
1.54
73.9
0.21
14.4
73.9
0.0262
0.15
0.08
0.13
0.0028
0.1
8.82
0.17
0.21
0.0028
0.21
0.040
0.0794
0.0034
0.192
0.0137
0.0028
3.5
0.845
0.02
7.25
0.545
0.0262
0.0142
19.5
0.155
20.5
3.35
0.00945
0.077
30.5
41.62
43.75
49.75
1.16
79.75
0.237
18.7
106
0.0424
0.37
0.204
0.37
0.00833
0.37
38.8
0.76
1.48
0.0271
2.84
0.003
0.006
0.006
0.013
0.024
0.035
0.047
0.059
0.095
0.098
0.109
0.125
0.178
0.264
0.267
0.277
0.233
0.361
0.367
0.413
0.563
0.592
0.673
0.75
1.079
1.13
1.30
1.434
1.618
2.47
2.55
2.85
2.975
3.7
4.4
4.47
7.05
9.68
13.52
Gnamus et al. 2000
Gnamus et al. 2000
Gnamus et al. 2000
Gnamus et al. 2000
Gnamus et al. 2000
Gnamus et al. 2000
Pathak and Bhowmik 1998
Gnamus et al. 2000
Gnamus et al. 2000
Schroeder and Mitchener 1975
Gnamus et al. 2000
Gnamus et al. 2000
Gnamus et al. 2000
Gnamus et al. 2000
Gnamus et al. 2000
Gnamus et al. 2000
Talmage and Walton 1993
Gnamus et al. 2000
Gnamus et al. 2000
Gnamus et al. 2000
Hernandez et al. 1985
Gnamus et al. 2000
Gnamus et al. 2000
Talmage and Walton 1993
Gnamus et al. 2000
Gnamus et al. 2000
Gnamus et al. 2000
Wolf
Lynx
Wolf
Lynx
Mouse
MethylHg, deer muscle ww
MethylHg, deer muscle ww
Methyl Hg, deer muscle ww
Methyl Hg, deer muscle ww
Methylmercury
Muscle (ww)
Muscle (ww)
Muscle (ww)
Muscle (ww)
organs
0.0371
0.0371
0.0095
0.0095
1
0.00625
0.0177
0.00782
0.0214
5
0.168
0.477
0.819
2.241
5
Gnamus et al. 2000
Gnamus et al. 2000
Gnamus et al. 2000
Gnamus et al. 2000
Schroeder and Mitchener 1975
Methylmercury dicyandiamide
Methylmercury
Crayfish ww, assumed MeHg
Perch ww, assumed MeHg
Methylmercury
Methylmercury
Liver
Liver
Liver
Liver
Breast
Breast
Liver
Egg
18
12
6
8
7.1
2.7
8
0.5
10.0
7.2
3.9
6.6
12.31
6.79
27
4.3
0.56
0.60
0.65
0.83
1.74
2.51
3.38
8.6
Fimreite and Karstad 1971
Aagdal et al. 1978
Vermeer et al. 1973
Vermeer et al. 1973
Aagdal et al. 1978
Heinz 1974
BIRD-DIET
Chicken
Chicken
Chicken
Japanese quail-female
Hooded merganser (duck)
Common merganser (duck)
Japanese quail- male
Mallard
* values listed in dry weight unless otherwise noted
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5.0
RISK CHARACTERIZATION
The Risk Characterization step of the RA takes the information gathered in the Analysis phase, which
includes both the Effects Characterization (Section 3) and the Exposure Assessment (Section 4), and
incorporates the findings with the conceptual model of the fate and transport of mercury developed in the
Problem Formulation step (Section 2), to arrive at risk estimates. Risk is evaluated through the use of
Hazard Quotients (HQs).
HQs are calculated by dividing the Exposure Concentration (EC) by
Benchmark Values (USEPA 1998). An HQ less than 1 indicates minimal risk. HQs greater than 1
indicate that there may be the possibility of risk. The ECs are the measured concentrations of mercury in
different media (water and soil) and plant and animal tissues (Section 4). In order to provide a
conservative estimate of exposure, the 95% UCL of the mean mercury concentration in samples of the
various tissues collected were used as the ECs in the calculation of the HQ values. For water, the mean
value was used because the calculated values included the detection limit for samples that were below
detection. Because of this, the mean value is actually greater than the maximum detected value at some
locations, and thus provides a conservative estimate of exposure. For terrestrial animal tissues, the ECs
were modeled using the BAF values discussed in Section 4.5 and the measured concentration of mercury
in the diet. The Benchmark Values used in the HQ calculations were established in Section 3 and are
summarized in Table 3.4.1.
5.1
Aquatic Resources
Aquatic biota can be exposed to mercury from pathways that originate from dissolved mercury in the
surface water column, or from mercury contained in sediment (Figure 2.3.2). Fish and macroinvertebrates
can uptake mercury directly from water. Macro-invertebrates can also be exposed to mercury from the
sediments, as can fish species that eat detritus on top of the sediments. Fish are the highest trophic
receptor in the aquatic systems, integrating mercury exposure from water as well as from ingestion of
plants and macroinvertebrates. Due to their position at the top of the food web in the aquatic systems, fish
are expected to have the highest mercury concentrations of the different types of aquatic biota.
Due to the rapid remediation effort and the recovery of the majority of the spilt mercury prior to the onset
of the wet season, it is unlikely that any significant amount of the spilt mercury entered the waterways.
This is supported by the data collected at the site. As discussed in Section 4.1, water and sediment
concentrations from Exposed and Reference locations are quite similar, and there is no evidence of
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increasing mercury concentrations between sampling events conducted in 2000 through 2002. The mean
concentration in water across all of the Exposed locations, over all sampling dates, is 0.017 ppb. The
mean concentration across all of the Reference locations, over all sampling dates, is also 0.017 ppb.
Because the detection limit was used in calculating both of these calculated means, these concentrations
are higher than the actual mean concentrations since some samples were below the detection limit. The
mean sediment mercury concentration across all of the Exposed sample locations, over all of the sampling
dates, is 112.4 ppb (dw). The corresponding mean for the Reference locations is 177.9 ppb (dw).
The calculated HQ values for macroinvertebrates and fish are shown in Table 5.1.1. Risk to aquatic biota
is evaluated from exposure to mercury in water and from tissue levels of mercury in fish and
macroinvertebrates.
Table 5.1.1
Calculated Hazard Quotients (HQs) for Aquatic Resources
FISH
1
MACROINVERTEBRATES
HQ
EC1
ppb (ww)
Benchmark
ppb (ww)
HQ
0.2
0.2
0.09
0.09
0.017
0.017
0.2
0.2
0.09
0.09
2000
2000
2000
2000
2000
2000
2000
2000
0.03
0.09
0.08
0.05
0.02
0.12
0.11
0.05
151.3
78.9
67.8
25.1
453.1
98.9
96.8
26.7
2000
2000
2000
2000
2000
2000
2000
2000
0.08
0.04
0.03
0.01
0.23
0.05
0.05
0.01
EC
ppb (ww)
Benchmark
ppb (ww)
0.017
0.017
WATER
Reference
Exposed
TISSUE
Phase I Upstream (Reference)
Phase II Upstream (Reference)
Downstream
All non-spill
1
61.3
177.5
167.0
90.6
40.9
234.4
228.1
94.1
EC= Exposure Concentrations, which are the measured values collected in the sampling discussed in Section 4. The water
values are means, tissue values are the 95% UCL of the mean.
All of the HQ values for the risk from exposure to mercury in water at the Reference and Exposed
locations are equal to 0.09, indicating minimal risk to aquatic biota from water. The HQ values calculated
for tissue concentrations are all less than 0.25, which also indicates minimal risk to aquatic biota from
mercury in tissue. The highest calculated HQ value of 0.23 for macroinvertebrate tissues is for samples
collected at upstream Reference locations in the Phase II sampling effort. The highest calculated HQ
values for fish tissue are 0.09 and 0.12 from the Phase I and Phase II samplings at locations downstream
of the spill area.
These values are highly influenced by the tissue concentrations in fish and
macroinvertebrates collected at the Gallito Ciego Reservoir.
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It is not surprising to find higher mercury concentrations in aquatic biota from the reservoir. There is an
extensive body of evidence in the literature that documents a trend of naturally occurring higher tissue
concentrations of mercury in biota sampled from recently impounded reservoirs. Tissue concentrations in
fish naturally spike upwards initially after the creation of a reservoir, and then decline as the reservoir
ages. Omnivorous fish species (i.e., fish that eat plants and animals) are predicted to return to background
in 15 to 20 years, whereas piscivorous fish (e.g., predatory fish) are expected to take 20 to 30 years
(Anderson et al. 1995). For a reservoir in Labrador, Canada, mercury concentrations in the omnivorous
lake whitefish (Coregonus clupeaformis) returned to background in 16 years, though concentrations in
the piscivorous pike fish (Esox lucius) were still elevated 21 years after impoundment (Anderson et al.
1995). In a second reservoir in Labrador, mercury concentrations in whitefish increased for eight years
after the creation of the reservoir, and then started to decrease. However, in the same reservoir, pike
continued to increase in concentration 14 years after the creation of the reservoir (Morrison and Therien
1995). The Gallito Ciego reservoir was created approximately 15 years ago.
There are two primary suspected mechanisms that explain the increase in mercury in fish tissue collected
from impounded reservoirs. The first is that inorganic mercury in the flooded soils is released into the
water column, and is available for uptake by fish and prey items. This initial release is followed by the
second mechanism, which is the creation of anoxic conditions due to the flooding. Anoxic conditions,
along with the presence of organic material in the soil, allow for the methylation of any mercury that was
not initially dissolved in the water. The methylated mercury is subsequently transferred into the food chain
(Povari and Verta 1995).
In summary, there are no indications that surface waters or aquatic biota have been impacted by the spill.
The surface water data cover the period from June 2000 through April 2002. The tissue concentrations
are from sampling conducted in 2000, prior to the inception of the wet season, and in 2001 after the end of
the first wet season. The concentration of mercury measured in the surface waters at Reference and
Exposed locations are essentially the same (0.017 ppb), and are significantly less than the established safe
benchmark water level of 0.2 ppb for aquatic life. Additionally, the measured mercury concentrations in
all of the fish and macroinvertebrate tissue samples are less than the established benchmark concentration
of 2000 ppb (ww).
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5.2
Human Health
The most likely mercury exposure routes to humans in the area around the spill sites are the inhalation of
elemental mercury vapor and the ingestion of water or food that have been impacted by the spill. As
discussed in Section 3.1, the potential risk to humans from inhalation has been previously addressed in
other reports (Consulcont SAC 2000, SMI 2002), and is not considered further in this RA. The primary
routes for ingestion of mercury are from drinking water or from the consumption of food, including plants,
terrestrial animals, and aquatic biota (fish and aquatic macroinvertebrates).
Table 5.2.1 summarizes the calculated HQ values for human exposure. HQ values are calculated for
exposure to mercury in drinking water and different dietary items, at both Exposed and Reference
locations, for all of the sampling efforts discussed in Section 4. The HQ for the risk from drinking water at
both Exposed and Reference locations is 0.02, indicating minimal risk from this exposure pathway.
Dietary HQ values were calculated for the consumption of fish, aquatic macroinvertebrates (crabs),
plants, and terrestrial animals. The ECs shown in Table 5.2.1 for terrestrial animal tissue were calculated
by multiplying the 95% UCL of the mean plant tissue mercury concentration by the bioaccumulation factor
(BAF) of 1.68 for mammals and 2.36 for birds (Section 4.5). Herbivores are the lost likely type of
terrestrial animal to be consumed by humans (Figure 2.3.1). For the range of values listed in Table 5.2.1,
the low end is for herbivorous mammal tissue and the upper end is for herbivorous bird tissue. All of the
dietary HQ values for all three sampling efforts are less than 1. The single highest dietary HQ of 0.76 is
for the consumption of fish tissue collected at non-spill sites during the Phase II sampling effort.
It is unlikely that carnivorous animals (i.e., animals that eat other animals) constitute a significant
proportion of the diet for humans living near the spill areas. However, assuming the highest predicted
mercury concentration of 443.5 ppb in herbivorous mammal tissue, as predicted from the November 15,
2000 plant sampling, and utilizing the same BAF of 1.68 for transfer of ionic mercury to mammal tissue,
results in a predicted mercury concentration in the tissue of carnivorous mammals of 745 ppb (ww; 443.5
ppb in tissue * 1.68). This concentration is also less than the average safe dietary level of 1600 ppb (HQ=
0.47). While there are no known piscivorous mammals, such as otters or mink, that live in the area (Table
2.2.1), there are piscivorous birds, such as herons, that might be eaten by humans. Using the highest 95%
UCL of the mean mercury concentration in fish tissue of 228.1 ppb (ww; Table 5.1.1), from fish collected
at downstream locations in the Phase II sampling, and the bird BAF of 2.36, results in a predicted mercury
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concentration in the tissue of fish-eating birds of 538 ppb (ww; 228.1 ppb in fish * 2.36). This predicted
concentration is less than the average safe dietary concentration of 1600 ppb, and results in an HQ of
0.34.
Table 5.2.1
Calculated Hazard Quotients (HQs) for Humans
EC1
ppb (ww)
Benchmark
ppb (ww)
HQ
1.0
1.0
0.02
0.02
300
300
1600
1600
0.56
0.23
0.02
0.03-0.04
90.6
25.1
156.6
263.1-621
300
300
1600
1600
0.30
0.08
0.10
0.16-0.39
264.0
443.5-623
1600
1600
0.17
0.28-0.39
228.1
96.8
7.9
13.3-16.5
300
300
1600
1600
0.76
0.32
0.00
0.01
94.1
26.7
9.8
16.5-23.1
300
300
1600
1600
0.31
0.09
0.01
0.01
WATER
Reference
Exposed
0.017
0.017
DIET
Phase I-Reference Sites
Fish
Macroinvertebrates (crabs)
Plants (ww)
Terrestrial animals*
Phase I-Exposed Sites
Fish
Plants
November 15, 2000 Sampling
Plants
Phase II-Reference Sites
Fish**
Macroinvertebrates (crabs)**
Plants
Phase II-Exposed Sites
Fish
Plants
167.0
67.8
29.4
49.4-69.4
1
EC= Exposure Concentrations, wh ich are the measured values collected in the sampling discussed in Section 4. The
water values are means, tissue values are the 95% UCL of the mean.
* Calculated using BAF of 1.68 for transfer to mammal tissue and 2.36 for transfer to bird tissue (Section 4.5)
** All non-spill locations (Upstream and Downstream)
In summary, there is no evidence that the surface waters near the spill locations have been impacted by
the spill. The ambient mercury concentrations in the water are low and do not pose risk to humans via the
drinking water pathway. Additionally, the consumption of both aquatic and terrestrial dietary items pose
minimal risk to humans. While some individual fish or plant samples exceeded the established benchmark
values, a conservative estimate of the mean dietary concentrations (95% UCL of the mean) indicates that
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there is a low risk potential from dietary mercury. Two of the 154 Phase I plant samples, both of nonedible plants, and none of the Phase II plant samples exceeded the human benchmark value of 1600 ppb
(ww). None of the Phase I nor Phase II crab samples exceeded the human dietary methylmercury
benchmark of 300 ppb (ww). Nine of the 137 Phase I and 13 of the 114 Phase II fish samples exceeded
the human dietary methylmercury benchmark of 300 ppb.
All but two of these samples occurred
downstream of the spill area, with over 60% (14 samples) of the exceedances from Gallito Ciego
Reservoir samples.
5.3
Terrestrial Resources
The two primary types of terrestrial receptors that were considered in the RA are plants and animals.
5.3.1
Plants
The potential risk to plants was assessed for mercury concentrations in both soil and plant tissue. Results
of the HQ calculations for the three sampling efforts are shown in Table 5.3.1. The highest calculated
HQ value for soil of 0.07 is from the November 15, 2000 sampling. The same is true for the tissue HQs,
with the highest calculated HQ value of 0.28, also from the November 15, 2000 sampling event. None of
the measured soil concentrations, at any date or sampling location, exceeded the benchmark value of
10,000 ppb (dw) for soil. Three plant samples out of a total of 154 samples (2%) collected in the Phase I
sampling exceeded the tissue benchmark of 3000 ppb (dw). In the November 15, 2000 sampling, one
sample out of 24 (4%) exceeded the 3000 ppb (dw) benchmark. None of the 130 plant samples collected
in the Phase II sampling effort exceeded the benchmark value for mercury in plant tissues.
Table 5.3.1
Calculated Hazard Quotients (HQs) for Plants
EC 1
ppb (dw)
SOIL
Phase I
November15, 2000 Sampling
Phase II
TISSUE
Phase I
November15, 2000 Sampling
Phase II
1
Benchmark
ppb (dw)
HQ
Reference
Exposed
Exposed
Reference
Exposed
105.6
53.9
743
62.8
60.3
10000
10000
10000
10000
10000
0.01
0.01
0.07
0.01
0.01
Reference
Exposed
Exposed
Reference
Exposed
76.5
472.2
838
35.7
28.4
3000
3000
3000
3000
3000
0.03
0.16
0.28
0.01
0.01
EC= Exposure Concentrations, which are the measured values collected in the sampling discussed in Section 4.
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5.3.2
Animals
For approximately the first month after the spill occurred, animals in the area may have been exposed to
mercury via inhalation. However, with the exception of domestic animals that were kept inside of houses
that were contaminated with the spilt mercury, animals would have had low inhalation exposure since the
evaporating mercury would be rapidly dispersed into the atmosphere, limiting the possible exposure
concentrations of mercury in the air. It is uncertain if any domestic animals were present in the homes
that were identifed as requiring remediation. If animals were present in any of these homes, however, the
potential inhalation risk would have been negated upon completion of the house remediation. More likely
exposure routes to animals (mammals and birds), especially over a longer timeframe, are from ingestion of
mercury in water and food.
Calculated drinking water and dietary HQ values for terrestrial mammals and birds are shown in Table
5.3.2. Potential dietary items for terrestrial animals are plants, insects, other terrestrial animals, fish, and
macroinvertebrates. Because there are no known mammals that eat fish or macroinvertebrates in the
area (Table 2.2.1), the modeled ECs listed in Table 5.3.2 for Other Terrestrial Animal tissue, are only for
the consumption of herbivores (plant-eaters) or insectivores (insect-eaters) by secondary consumers
(carnivores). The range of EC values listed for the Other Terrestrial Animal dietary type were calculated
by multiplying the 95% UCL of the mean concentration of mercury in the diet (plants and insects) by the
BAF factors established in Section 4.5. For the November 15, 2000 sampling, only secondary consumption
of herbivores was considered, since no insect tissue measurements were taken (Section 4.3), thus
preventing the calculation of mercury transfer to the tissues of insect-eating mammals and birds.
All of the calculated drinking water HQs (0.02) for birds and mammals were less than 1. The calculated
dietary HQs were also all less than 1, indicating a low risk potential from the diet. The highest mammal
dietary HQ of 0.84 is from the consumption of fish tissue collected in non-spill areas in the Phase II
sampling. The highest bird dietary HQ of 0.39 is for the consumption of insect-eating birds by other birds,
as based on the Phase I sampling of insect tissues at Exposed Sites.
In the Phase I sampling, a few individual samples exceeded either the mammal or bird dietary benchmark
values. However, the frequency of benchmark exceedance is low (< 3%) for all of the potential dietary
items (plants, insects, fish, and macroinvertebrates). Four of the 154 plant samples exceeded the mammal
dietary benchmark, though only two samples exceeded the bird benchmark. One insect sample, out of 45,
exceeded the bird dietary benchmark. None of the macroinvertebrate samples, and only one fish sample
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exceeded the benchmark values for birds. For the Phase II sampling, none of the plant, insect, or
macroinvertebrate samples exceeded dietary benchmarks, and only three of 114 fish samples exceeded
the benchmark for birds. All three of these fish samples were collected in the Gallito Ciego Reservoir.
Table 5.3.2
Calculated Hazard Quotients (HQs) for Terrestrial Animal Diets
MAMMALS
EC1
ppb (dw) 2
BIRDS
Benchmark
ppb (dw) 2
HQ
EC1
ppb (dw) 2
1.0
1.0
0.02
0.02
0.017
0.017
2000
2000
2000
1100
1100
0.04
0.08
0.06-0.14
0.63
0.28
2000
2000
2000
1100
1100
Benchmark
ppb (dw) 2
HQ
1.0
1.0
0.02
0.02
76.5
167.9
180.5-396.2
695.8
304.9
4000
4000
4000
2500
2500
0.02
0.04
0.05-0.10
0.28
0.12
0.24
0.33
0.40-0.56
0.34
0.24
472.2
663.2
1114-1565
377.5
268.9
4000
4000
4000
2500
2500
0.12
0.17
0.28-0.39
0.15
0.11
2000
2000
0.42
0.70
838.0
1977.7
4000
4000
0.21
0.49
2000
2000
2000
1100
1100
0.02
0.03
0.03-0.05
0.84
0.25
35.7
57.5
84.3-135.7
923.5
274.9
4000
4000
4000
2500
2500
0.01
0.01
0.02-0.03
0.37
0.11
2000
2000
2000
1100
1100
0.01
0.01
0.02
0.38
0.12
28.4
28
66.1
419.1
127.0
4000
4000
4000
2500
2500
0.01
0.01
0.02
0.17
0.05
WATER
Reference
Exposed
0.017
0.017
DIET
Phase I-Reference
Plants
76.5
Insects
167.9
Other Terrestrial Animals* 128.5-282.1
Fish
695.8
Macroinvertebrates
304.9
Phase I-Exposed
Plants
472.2
Insects
663.2
Other Terrestrial Animals* 793-1114
Fish
377.5
Macroinvertebrates
268.9
Plants
838.0
Other Terrestrial Animals* 1407.8
Phase II-Reference
Plants
35.7
Insects
57.5
Other Terrestrial Animals* 60.0-96.6
Fish**
923.5
Macroinvertebrates**
274.9
Phase II-Exposed
Plants
28.4
Insects
28.0
Other Terrestrial Animals*
47.7
Fish
419.1
Macroinvertebrates
127.0
1
EC= Exposure Concentrations, which are the measured values collected in the sampling discussed in Section 4. The water
values are means and the tissue values are the 95% UCL of the mean.
2
the dietary EC and benchmark values are in dry weight, water comparisons are on a wet weight basis
* The range of animal tissue concentrations is based on the BAF values from Section 4.5 and the plant and insect tissue
concentrations (diet)
** The Phase II fish and macroinvertebrate ECs are for all non-spill sampling locations (Upstream and Downstream)
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In addition to water and dietary benchmarks, terrestrial animal tissue benchmarks were also established in
Section 3. The calculated ECs for animal tissue in Table 5.3.2 can be compared to the established
benchmarks of 3700 ppb (dw) for mammal tissue and 6000 ppb (dw) for bird tissue (Section 3.2.1). The
calculated HQ values based on these ECs are shown in Table 5.3.2. Also shown on Table 5.3.2 are HQ
values for the measured concentrations of mercury in insect tissue.
Table 5.3.3
Calculated Hazard Quotients (HQs) for Terrestrial Animal Tissues
MAMMALS
EC 1
ppb (dw)
BIRDS
Benchmar
k
ppb (dw)
EC 1
HQ
ppb (dw)
INSECTS
EC 1
Benchmar
k
ppb (dw)
Benchmar
k
ppb (ww)
HQ
HQ
6000
6000
0.03-0.07
0.19-0.26
63.8
252
150
150
0.43
1.68
6000
0.33
NA
150
6000
6000
0.01-0.02
0.01
20.5
13.2
150
150
ppb
(ww)
Phase I
Reference
Exposed
128.5-282.1
793-1114
3700
3700
0.03-0.08 180.5-396.2
0.21-0.30 1114-1565
Exposed
1407.8
3700
60.0-96.6
47.7
3700
3700
0.38
1977.7
Phase II
Reference
Exposed
0.02-0.03 84.3-135.7
0.01
66.1
0.14
0.09
1
= Exposure Concentrations, which are the 95 % UCL of the measured or modeled values collected in the sampling discussed in
Section 4.
NA= Not analyzed
All of the calculated HQ values for the risk from mercury in mammal and bird tissues are less than 1. The
highest HQ of 0.38 for mammal tissue is based on the transfer of mercury to tissues from plant material
collected during the limited November 15, 2000 sampling. The highest HQ of 0.33 for assessing risk
associated with mercury in bird tissue also results from modeling of the transfer of mercury from plant
material that was collected during the November 15, 2000 sampling. The HQ value of 1.68 for insect
tissue collected in the Phase I sampling of Exposed Sites exceeds a value of 1, indicating that there may
have been potential risk to insects from mercury concentrations in their tissues. However, the calculated
HQ for the Phase II sampling effort, which collected insects at the same locations as Phase I, is less than
1, indicating that any risk to insects was temporary.
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6.0
SUMMARY AND CONCLUSIONS
6.1
Summary
The primary conclusion of the RA is that, with the possible exception of insects in 2000, there are no
unacceptable risks identified for aquatic biota, human health, or terrestrial ecological resources associated
with the mercury spill that occurred on June 2, 2000 along the road between Cajamarca and the Pan
American highway. This finding is not unexpected given the extensive and comprehensive response and
spill cleanup activities conducted by MYSRL (MYSRL 2001). The best estimates of the amount of the
151 kg of mercury spilt, not accounted for, is six to nine kilograms. This amount of mercury has a volume
of 0.67 L. This volume is either widely dispersed over the 40 Km spill area, or partially in the possession
of individuals.
The RA outlined four assessment endpoints, or environmental values (Section 2.4) that were to be
evaluated in the risk assessment. The conclusions associated with these assessment endpoints are
summarized in Table 6.1.1. Further discussion on each of the assessment endpoints is provided.
6.2
Human Health
The first assessment endpoint is associated with protecting the health of the human population living in and
around the spill area. The RA only addressed the risk to humans from ingestion of mercury in water and
food since previous reports have evaluated inhalation risk to residents (Consulcont SAC 2000, SMI 2002).
There was and is minimal risk to humans from the ingestion of mercury in food and drinking water.
There is no evidence that mercury from the spill was mobilized into the surface waters in the
Jequetepeque watershed. The concentration of mercury from both Reference and Exposed locations are
equivalent and low. The mean concentration of 0.017 ppb in water is less than the drinking water
benchmark for humans of 1.0 ppb, indicating that there is minimal risk to humans from the direct
consumption of mercury in drinking water (Table 5.2.1). Additionally, the sampling effort conducted from
just after the spill through the end of the second wet season demonstrated that mercury from the spill was
not mobilized into the surface waters near the spill locations.
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Table 6.1.1
Conclusions From Assessment Endpoints, Measures of Effect, and Exposure
Assessment Endpoint
Conclusions
Health of individual humans Measures of effect: regulatory benchmarks for Risk from ingestion of fish, crabs,
who may consume water and concentrations of mercury in water and food
plants and drinking water is minimal;
food that may be influenced Direct measures of exposure: concentrations of HQs<1.
by the mercury spill
mercury in fish, macroinvertebrates (crabs),
vegetation, and water
reproduction of populations concentrations of mercury in soil and plant
of agricultural and native
tissues from a review of the scientific literature
terrestrial plants within the Direct measures of exposure: concentrations of
spill area
mercury in soil and vegetation tissue collected
at the spill locations
reproduction of populations concentrations of mercury in water and food
of terrestrial animals that
from a review of the scientific literature and
may be exposed to mercury regulatory benchmarks
from drinking water,
consumption of plants, or
mercury in water and food items (vegetation
consumption of other
and insects) collected at the spill locations
animals
reproduction of populations
of aquatic biota (macroinvertebrates and fish) that
may be exposed to mercury
from the spill
concentrations of mercury in water and animal
tissue from a review of regulatory guidelines
and the scientific literature
mercury in water and aquatic animal tissue
Risk from ingestion of terrestrial
mammals and birds is minimal; HQs<1.
Risk to plants from mercury in soil or
in tissues is minimal; HQs<1.
Risk to mammals and birds from water
and dietary consumption is minimal;
HQs<1.
Risk to mammals and birds from
mercury tissue concentrations is
minimal; HQs<1. Potential risk to
insects in 2000, risk in 2001 is minimal;
HQ<1.
Risk to aquatic biota from water and
tissue concentrations of mercury is
minimal; HQs<1.
HQ= Hazard Quotient (discussed in Section 5, indicates minimal risk if HQ<1)
In most diets, fish and shellfish account for a significant proportion of mercury ingested (Section 3.1).
Because of this fact, and since essentially all of the mercury in the tissues of aquatic biota is in the more
available and toxic methylmercury form (WHO 1991), many governmental agencies and organizations
have established safe levels of mercury in fish tissue for human consumption (Table 4.1.2). The lowest of
these values, 300 ppb (ww; Table 3.1.2) was used as the benchmark to evaluate risk. The mean values
from both Exposed and Reference locations from the Phase I and Phase II sampling efforts are typical of
the mercury concentrations measured in fish and shellfish consumed in the diet of people in the USA,
Canada, Scotland, Italy, and Spain (Table 1.2.3). Additionally, the 95% UCL of the mean concentrations,
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which is a conservative estimate of exposure, indicates that mercury levels in fish and crabs pose minimal
risk to humans (Table 5.2.1). This result is in agreement with the evidence that mercury from the spill was
never mobilized into the surface waters near the spill locations.
A protective average dietary mercury concentration of 1600 ppb was established for non-fish food items in
the diet of humans (Section 3.1). The Phase I sampling found that the mercury concentrations in
vegetation collected at the Exposed locations tended to have higher mercury concentrations than samples
from Reference locations. The 95% UCL of the mean concentration of mercury in the diet at all
locations, however, were below the benchmark level and pose minimal risk to humans (Table 5.2.1). The
Phase II sampling, which was conducted during the second wet season, found much lower levels of
mercury in vegetation collected from both Reference and Exposed locations (Table 5.2.1). Soil mercury
concentrations were essentially constant between the Phase I and Phase II sampling efforts (Table 5.3.1).
This finding shows that there is a seasonal component to mercury concentrations in vegetation. The likely
explanation is that dry deposition of mercury onto plant surfaces, probably as particulates from 1) wood
and garbage burning, 2) vehicle emissions, and 3) dust from soils that naturally contain mercury causes the
seasonal variability (Hanson et al. 1995, Jones and Slotton 1996).
During the wet season, the frequent
rains reduce the levels of particulates in the air and wash deposited mercury from the surface of the
plants, reducing the measured concentrations.
Modeled mercury concentrations in animal tissue, which result from the consumption of plants, by animals
that are subsequently consumed by humans, were also below the dietary benchmark concentration for
humans (Table 5.2.1). This further indicates minimal risk to humans from the dietary consumption of
mercury.
6.3
Agricultural and Native Plants
The second assessment endpoint is for the protection of the survival, growth, and reproduction of native
and agricultural plants. Based on the literature (Section 3.2.2), plant toxicity would likely be manifested by
a reduction in the rate of growth, not the overall survival or viability of plants (i.e., mercury will not kill the
plant). There was and is minimal risk to plants as evaluated from concentrations of mercury in soil and
from the concentrations of mercury in plant tissues.
Early research on mercury levels in plants identified soil as the primary source of mercury to plants
(Warren et al. 1966). More recent work, however, has shown that foliar absorption and dry deposition are
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important contributors to mercury in plant tissue (Hanson et al. 1995, Patra and Sharma 2000). The results
of the Phase I and Phase II soil sampling efforts indicate that there is no general increase in mercury
concentrations in soils from the Exposed sites relative to Reference locations. For both of these sampling
efforts, the 95 % UCL of the mean concentration of mercury in soils from the Exposed locations was less
than the Reference locations (Table 5.3.1). Moreover, the concentrations at all locations are below the
soil benchmark value of 10,000 ppb (dw) and are typical of normal background levels of mercury in the
environment (Section 1.2.3).
As previously discussed, vegetation samples collected at Exposed locations during the Phase I sampling
tended to have higher mercury concentrations than samples from Reference locations collected at the
same time (Table 5.3.1). However, mercury concentrations in less than 2% of the collected samples
exceeded the benchmark value for mercury in plant tissue of 3000 ppb (dw). Mercury concentrations in
plant tissues collected in the Phase II sampling effort, from both Reference and Exposed locations, were
much lower than the Phase I samples (Table 5.3.1). The Phase II samples were collected during the wet
season (February 2002), whereas the Phase I samples were collected at the end of the dry season
(September 2000).
Given that the Phase I plant tissue concentrations were higher at the Exposed
locations than at the Reference locations, even though the co-located soil mercury concentrations were
lower at the Exposed locations, and that the concentrations at both Reference and Exposed locations
dropped significantly during the wet season, it is apparent that uptake from soil is not the primary exposure
route to plants. Dry deposition of mercury from a variety of sources seems to be the primary driver of
mercury levels in plants.
6.4
Terrestrial Animals
The third assessment endpoint for the RA is the protection of the survival, growth, and reproduction of
terrestrial animals. The RA evaluated the risk to terrestrial animals from exposure to mercury in drinking
water, in the diet, and in their tissues. The risk from all of these exposure pathways was and is minimal,
with the exception of terrestrial insects during the first dry season (Tables 5.3.2 and 5.3.3). The 95%
UCL of the mean concentration of mercury in insect tissue collected in the Phase I sampling exceeded the
benchmark value of 150 ppb (ww; Table 5.3.3). The Phase II sampling, however, indicated that if there
was any risk to insects based on the tissue concentrations measured in Phase I, the risk was no longer
present.
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It is generally reported that, with the exception of inhalation exposure, the toxicity of elemental mercury to
animals is low, primarily due to strong soil adsorption and low gastrointestinal absorption in animals (Amdur
et al. 1991). In addition, terrestrial pathways of mercury exposure are generally considered to be of lower
concern than aquatic pathways because: 1) terrestrial pathways generally involve inorganic mercury rather
than methylmercury, 2) uptake of inorganic mercury is limited in plants and soil invertebrates, and 3) the
mercury that is ingested by birds and mammals tends to be stored in fur and feathers which are not
consumed by higher-order consumers or are poorly digested if consumed (USEPA 1997a).
Only a few individual dietary samples from the Phase I and Phase II sampling events exceeded either the
mammal or bird dietary benchmark values. The frequency of benchmark exceedance was low (< 3%) for
all of the potential dietary items (plants, insects, fish, and macroinvertebrates). Four of the 154 Phase I
plant samples exceeded the mammal dietary benchmark of 2000 ppb (dw), though only two of these
samples exceeded the bird benchmark of 4000 ppb (dw). One Phase I insect sample, out of 45, exceeded
the bird dietary benchmark. None of the Phase I macroinvertebrate samples, and only one fish sample
exceeded benchmark values for birds.
For the Phase II sampling, none of the plant, insect, or
macroinvertebrate samples exceeded dietary benchmarks, and only three of 114 fish samples exceeded
the benchmark for birds. All three of these fish samples were collected in the Gallito Ciego Reservoir,
where mercury was present as a result of the water impoundment, prior to the spill.
6.5
Aquatic Resources
The final assessment endpoint is aimed at the protection of aquatic biota in the waterways around the spill
area. The risk from concentrations of mercury in water and in tissues of fish and aquatic
macroinvertebrates was and is minimal. The RA considered mercury concentrations measured in surface
water from the inception of water sampling, which was first conducted during the week of June 15,
through April of 2002. This time period includes sampling conducted prior to the inception of the first rainy
season after the spill (essentially November 2000), through the end of the second wet season (April 2002).
Phase I tissue sampling was conducted prior to the first season and therefore before the spilt mercury
could be mobilized. Phase II tissue sampling occurred after the end of the first wet season and served to
evaluate whether or not mercury levels in the aquatic systems had increased.
There has been no indication of any mercury mobilization from the spill sites into the waterways. The
mean mercury concentration in water collected from Reference locations is equal to the mean
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concentration of 0.017 ppb from the Exposed locations. The mean sediment mercury concentration of
112.4 ppb (ww) from the Exposed locations is lower than the mean concentration of 177.9 ppb (dw) from
the Reference locations (Section 4.1).
The tissue concentrations of mercury in fish and aquatic macroinvertebrates are similar to the water and
sediment results, with generally higher mercury concentrations observed in tissues collected from non-spill
locations (upstream and downstream) than in samples collected near the spill areas (Table 5.1.1). Some of
the highest mercury concentrations in aquatic biota were measured in samples collected from the Gallito
Ciego Reservoir. It is well documented in the scientific literature that mercury concentrations in biota
collected from recently created reservoirs, such as the Gallito Ciego, become naturally elevated (Section
5.1). Essentially, the elevated tissue concentrations are a result of the mobilization of natural
concentrations of mercury in the flooded soils.
6.6
Uncertainty
In order to minimize the impact of uncertainty associated with assumptions made in the RA, wherever
possible, conservative assumptions have been made. Examples of this conservatism include: 1) utilizing
the detection limits, for samples recorded as being less than detection, in the calculation of means, 2) using
the 95 % UCL of the mean for estimating Exposure Concentrations, and 3) assuming the higher of either
methyl or total mercury concentrations reported for fish samples in evaluating exposure and effects.
Specific sources of uncertainty are discussed in greater detail below.
There are several areas of uncertainty associated with the data utilized in the risk assessment. The
potential biggest source of uncertainty is associated with the data collected by SENASA and Consulcont
SAC (Appendix A). As discussed in Section 4, because of the high degree of uncertainty associated with
these data, they were not utilized in the RA. It is important to note, however, that the sampling that was
conducted jointly by SENASA, MYSRL, and SMI in November of 2000, at the same locations where the
earlier SENASA sampling had reported elevated mercury concentrations in plants, was utilized in the RA.
Additionally, the 95% UCL of the mean concentrations recorded by SENASA and Consulcont are all
below the benchmark concentrations. All of the recorded fish tissue concentrations are less than 50 ppb,
all of the water concentrations are reported as 0.00 ppb, and the highest soil concentration reported is 8.27
ppb (Appendix A). The mean and 95% UCL of mean mercury concentrations in animal tissue
concentrations are 17.3 ppb and 35.7 ppb, respectively. None of these concentrations exceed any of the
benchmark values (Table 3.4.1). The mean and 95% UCL of mean mercury concentrations in vegetation
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are 668.6 ppb and 1256 ppb. As previously discussed, it is unclear if the tissue values are on a wet weight
or dry weight basis. Assuming that they are reported as dry weight concentrations, none of the benchmark
values (Table 3.4.1) are exceeded. If they are on a wet weight basis, the 95% UCL of the mean plant
tissue concentration does not exceed the human dietary benchmark. Without knowing the moisture
content of the samples, it cannot be determined if they exceed the mammal and bird dietary benchmarks.
Another source of uncertainty associated with the data are the reported methylmercury concentrations in
aquatic biota that were greater than the total mercury levels reported for the same sample. Frontier
Geosciences believes that the different analyses required to measure methylmercury and total mercury
result in this apparent discrepancy (Appendix G). To overcome this uncertainty, the higher of the values
(either methyl or total) was used in calculating the Exposure Concentrations in the RA.
The last potentially significant uncertainty associated with the data is the modeled concentrations of
mercury in terrestrial animal tissues. Only limited direct measurements of mercury in terrestrial animal
tissues were made during the November 2000 sampling (Section 4.3). In order to assess the risk
associated with mercury in terrestrial animal tissues, as well as to evaluate the risk from the consumption
of terrestrial animal tissue, literature bioaccumulation factors (BAFs) were used to model the expected
tissue concentrations. While there is some uncertainty with this approach, conservative assumptions were
made including the use of the 95% UCL of the mean for the dietary concentrations for the transfer of
mercury to tissues.
There is overall a low degree of uncertainty associated with the benchmark values since conservative no
observed adverse effect levels (NOAELs) were selected as the threshold levels for evaluating risk. The
benchmark value established for mercury in insect tissue (Section 3.2.1), however, has greater uncertainty
since it was derived by dividing a lethal effect level by an uncertainty factor of 50, as recommended by
Calabrese and Baldwin (1993). While the use of a large safety factor makes it unlikely that effects would
be expected at a lower level than the benchmark established, higher concentrations may also result in no
adverse effects to insects.
The last major source of uncertainty is associated with the long term fate of any mercury that remains in
the environment. Based on the results of studies conducted at locations in the USA (e.g., Oak Ridge
National Laboratory and Carson River), spilt elemental mercury can remain in the elemental form in the
environment even decades after a spill has occurred (Campbell et al. 1998, Carroll et al. 2000, Gustin et al.
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1995). Because elemental mercury has very low solubility in water (Table 1.2.1) it is unlikely to be
dissolved and mobilized to other locations. Any mercury that is oxidized to form ionic mercury, will likely
be strongly absorbed to the soil, again limiting potential migration (WHO 1989, 1991). However, even if it
is assumed that the potentially maximum amount of mercury that remains in the environment (9 kg) is
mobilized at one time to the Gallito Ciego Reservoir, the potential risk is still minimal. Based on the volume
of the reservoir listed by Loayza (1999) of 400.4 million cubic meters, the addition of 9 kg of mercury
dissolved in this volume of water would result in an incremental increase in mercury concentrations of 0.02
ppb. This increase would not result in any significant additional risk to aquatic biota or to terrestrial
consumers of drinking water.
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Final Report on the Risk Assessment of the Mercury Spill in Northern

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