Prepared in cooperation with the Bureau of Land Management

Assessment of Mercury and Methylmercury in 

Water, Sediment, and Biota in Sulphur Creek in 

the vicinity of the Clyde Gold Mine and the Elgin 

Mercury Mine, Colusa County, California

By Roger L. Hothem, James J. Rytuba, Brianne E. Brussee, and Daniel N. Goldstein

Open-File Report 2013-1056

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

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Suggested citation: 

Hothem, R.L., Rytuba, J.J., Brussee, B.E., and Goldstein, D.N., 2013, Assessment of 

mercury and methylmercury in water, sediment, and biota in Sulphur Creek in the vicinity of 

the Clyde Gold Mine and the Elgin Mercury Mine, Colusa County, California: U.S. Geological 

Survey Open-File Report 2013-1056, 38 p. [http://pubs.usgs.gov/of/2013/1056/]

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Contents

Abstract ......................................................................................................................................................................... 1

Introduction.................................................................................................................................................................... 2

Methods......................................................................................................................................................................... 3

Sample Locations....................................................................................................................................................... 3

Clyde Mine ............................................................................................................................................................. 3

Elgin Mine............................................................................................................................................................... 3

Field Methods ............................................................................................................................................................ 3

Sediment ................................................................................................................................................................ 3

Water...................................................................................................................................................................... 4

Biota ....................................................................................................................................................................... 4

Analytical Methods..................................................................................................................................................... 5

Sediment ................................................................................................................................................................ 5

Water...................................................................................................................................................................... 5

Biota ....................................................................................................................................................................... 5

QA/QC ....................................................................................................................................................................... 6

Sediment ................................................................................................................................................................ 6

Water...................................................................................................................................................................... 7

Biota ....................................................................................................................................................................... 7

Results........................................................................................................................................................................... 8

Mercury and Monomethyl Mercury in Sediment......................................................................................................... 8

Clyde Mine ............................................................................................................................................................. 8

Elgin Mine............................................................................................................................................................... 9

Water Chemistry ...................................................................................................................................................... 10

Clyde Mine ........................................................................................................................................................... 10

Elgin Mine............................................................................................................................................................. 10

Mercury and Monomethyl Mercury in Water............................................................................................................. 10

Clyde Mine ........................................................................................................................................................... 10

Elgin Mine............................................................................................................................................................. 11

Mercury and Monomethyl Mercury in Biota.............................................................................................................. 11

Clyde Mine ........................................................................................................................................................... 11

Elgin Mine............................................................................................................................................................. 11

Conclusions ................................................................................................................................................................. 12

References Cited......................................................................................................................................................... 14
iv

Figures

Figure 1. Study sites sampled in 2010 in the Clyde Gold Mine area and the Elgin Mercury Mine area in the 

headwaters of Sulphur Creek, California ................................................................................................................. 16

Figure 2. Clyde Mine sample site 10CL1, just downstream from biota site CLUS................................................... 17

Figure 3. Clyde Mine sample site 10CL2, 130 meters upstream from biota site CLMN, below the main surface 

disruption of Clyde Mine ......................................................................................................................................... 18

Figure 4. Biota site CLDS, 380 meters upstream from water and sediment sample site 10CL3 ............................. 19

Figure 5. Biota sample site CLOK near water and sediment sample site 10CL4 .................................................... 20

Figure 6. Water and sediment sample site 10EL1 (A) and nearby biota sample site ESUS (B) on the 

West Fork of Sulphur Creek, Elgin Mine area, 2010................................................................................................ 21

Figure 7. Water and sediment sample site 10EL2 (A) and nearby biota sample site ESDS (B) on the 

West Fork of Sulphur Creek, Elgin Mine area, 2010................................................................................................ 22

Figure 8. Water and sediment sample site 10EL3 (A), located about 200 meters (m) upstream from 10EL1 and 

upstream from input from the Elgin Mine ................................................................................................................. 23

Figure 9. Biota sample site ESLT looking upstream at Salt Branch, Elgin Mine area, 2010. .................................. 24

Figure 10. Plot showing oxygen and deuterium stable isotope levels in Clyde Mine and 

Elgin Mine water samples........................................................................................................................................ 25

Figure 11. Total mercury (HgT) and monomethyl mercury (MMeHg) concentrations (μg/g ww) in invertebrate 

samples collected from Clyde Mine on April 29, 2010 ............................................................................................. 26

Figure 12. Total mercury (HgT) and monomethyl mercury (MMeHg) concentrations (μg/g ww) in invertebrate 

samples collected from Elgin Mine on May 12, 2010............................................................................................... 27

Tables

Table 1. Sample locations for water, sediment, and biota for the Clyde Gold Mine and 

Elgin Mercury Mine, 2010. ....................................................................................................................................... 28

Table 2. Physical and selected chemical parameters and total mercury (HgT), monomethyl 

mercury (MMeHg), and dissolved organic carbon (DOC) concentrations in waters and sediment from the 

Clyde and Elgin mines, 2010 ................................................................................................................................... 29

Table 3. Mercury and associated major and minor elements in sediment, precipitates, Clyde Mine, 2010............. 30

Table 4. Mercury and associated major and minor elements in sediment, precipitates, Elgin Mine. 2010. ............. 31

Table 5. Concentration of anions and selected cations in filtered water at the Clyde and Elgin mines, 2010.......... 32

Table 6. Concentrations of relevant geochemical constituents in samples of filtered water from the 

Freshwater Branch of Sulphur Creek adjacent to the Clyde Mine. .......................................................................... 33

Table 7. Concentrations of relevant geochemical constituents in samples of unfiltered water from the 

Freshwater Branch of Sulphur Creek adjacent to the Clyde Mine, 2010. ................................................................ 34

Table 8. Concentrations of relevant geochemical constituents in samples of filtered water from the 

West Fork of Sulphur Creek near the Elgin Mine, 2010........................................................................................... 35

Table 9. Concentrations of relevant geochemical constituents in samples of unfiltered water from the 

West Fork of Sulphur Creek near the Elgin Mine, 2010........................................................................................... 36

Table 10. Total mercury (HgT) and monomethyl mercury (MMeHg) concentrations (μg/g ww) in biota 

collected from the Clyde and Elgin mines, 2010...................................................................................................... 37
v

Conversion Factors , Datum, and Abbreviations and Definitions

Conversion Factors

Multiply By To obtain

Length

inch (in) 2.54 centimeter (cm)

inch (in) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

acre 4,047 square meter (m2)

acre 0.4047 hectare (ha)

acre 0.004047 square kilometer (km2

)

Volume

gallon (gal) 3.785 liter (L)

gallon (gal) 0.003785 cubic meter (m3)

cubic inch (in3) 16.39 cubic centimeter (cm3)

cubic inch (in3) 0.01639 liter (L)

cubic foot (ft3) 0.02832 cubic meter (m3)

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram 2.205 pound, avoirdupois (lb)

microgram (μg) 0.0000000353 ounce, avoirdupois (oz)

milligram (mg) 0.0000353 ounce, avoirdupois (oz)

nanogram (ng) 0.0000000000353 ounce, avoirdupois (oz)

ounce, avoirdupois (oz) 28.35 gram (g)

pound, avoirdupois (lb) 0.4536 kilogram (kg)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8×°C) +32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C = (°F-32)/1.8
vi

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L, parts per million), micrograms per

liter (μg/L, parts per billion), or nanograms per liter (ng/L, parts per trillion).

Concentrations of chemical constituents in tissues are given in micrograms per gram (μg/g, parts per million). Concentrations 

of chemical constituents in sediment are given in micrograms per gram (μg/g, parts per million) or nanograms per gram (ng/g, 

parts per billion)

Datum

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Acronyms and Definitions

Au gold

As arsenic

Ba barium

CDFG California Department of Fish and Game

CERCLA U.S. Environmental Protection Agency’s Comprehensive Environmental Response, Compensation, and Liability 

Act

CVAFS cold‐vapor atomic‐fluorescence spectroscopy

CVAAS cold‐vapor atomic‐absorption spectroscopy

DOC dissolved organic carbon

DOM dissolved organic matter

Flask 34.5 kg or 76 lb of Hg

GC gas chromatographic

GMWL Global Meteoric Water Line

HCl hydrochloric acid

HDPE high-density polyethylene

H2SO4 sulfuric acid

Hg Mercury; does not denote speciation

HgF total mercury (inorganic plus organic) in a filtered sample (either 0.1 or 0.45 μm, as specified in the text)

HgT total mercury (inorganic plus organic)

ICP‐AES inductively‐coupled plasma atomic‐emission spectroscopy

ICP‐MS inductively‐coupled plasma‐mass spectroscopy

KOH potassium hydroxide

MDL mean detection limit

MMeHg monomethyl mercury, methylmercury, and monomethylmercury ion (CH3Hg+

)

Na sodium

ng/g nanogram per gram, equivalent to parts per billion

NIST National Institute of Standards and Technology

ng/L nanogram per liter, equivalent to parts per trillion

ORP oxidation-reduction potential

ppm parts per million, equivalent to mg/kg or μg/g

QA/QC quality assurance/quality control

Rb rubidium

RPD relative percent difference

RSI Removal Site Investigation

Sb antimony

SC specific (electrical) conductivity, reported in units of millisiemens per centimeter (mS/cm) or microsiemens per 

centimeter (μS/cm) at 25 °C

SOP standard operating procedure
vii

Sr strontium

Tl thallium

USBLM U.S. Bureau of Land Management

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

W tungsten

ww wet weight

Acknowledgments

This field investigation was funded by the Bureau of Land Management. The California 

Department of Fish and Game granted permission to collect specimens for this study. 

W. Perry of the Dixon Field Station, USGS, prepared the map. We appreciate the excellent 

reviews of earlier versions of this report by J. Fleck, J. May, and T. Kimball.
viii

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1

Assessment of Mercury and Methylmercury in 

Water, Sediment, and Biota in Sulphur Creek in 

the vicinity of the Clyde Gold Mine and the Elgin 

Mercury Mine, Colusa County, California

By Roger L. Hothem,1 James J. Rytuba,2 Brianne E. Brussee,1 and Daniel N. Goldstein2

Abstract

At the request of the U.S. Bureau of Land Management, we performed a study during 

April–July 2010 to characterize mercury (Hg), monomethyl mercury (MMeHg), and other 

geochemical constituents in sediment, water, and biota at the Clyde Gold Mine and the Elgin 

Mercury Mine, located in neighboring subwatersheds of Sulphur Creek, Colusa County, 

California. This study was in support of a Comprehensive Environmental Response, 

Compensation, and Liability Act - Removal Site Investigation. The investigation was in response 

to an abatement notification from the California Central Valley Regional Water Quality Control 

Board to evaluate the release of Hg from the Clyde and Elgin mines. Samples of water, sediment, 

and biota (aquatic macroinvertebrates) were collected from sites upstream and downstream from

the two mine sites to evaluate the level of Hg contamination contributed by each mine to the 

aquatic ecosystem. Physical parameters, as well as dissolved organic carbon, total Hg (HgT), and 

MMeHg were analyzed in water and sediment. Other relevant geochemical constituents were 

analyzed in sediment, filtered water, and unfiltered water. Samples of aquatic macroinvertebrates 

from each mine were analyzed for HgT and MMeHg. The presence of low to moderate 

concentrations of HgT and MMeHg in water, sediment, and biota from the Freshwater Branch of 

Sulphur Creek, and the lack of significant increases in these concentrations downstream from the 

Clyde Mine indicated that this mine is not a significant source of Hg to the watershed during low 

flow conditions. Although concentrations of HgT and MMeHg were generally higher in samples 

of sediment and water from the Elgin Mine compared to the Clyde Mine, concentrations in 

comparable biota from the two mine areas were similar. It is likely that highly saline effluent 

from nearby hot springs contribute more Hg to the West Fork of Sulphur Creek than the mine 

waste material at the Elgin Mine. 

1

U.S. Geological Survey, Dixon, California.

2

U.S. Geological Survey, Menlo Park, California.
2

Introduction

The U.S. Bureau of Land Management (USBLM) received an abatement notification from the 

Central Valley Regional Water Quality Control Board to address release of mercury (Hg) from the 

Clyde Gold Mine and the Elgin Mercury Mine. In response, the USBLM requested that the U.S. 

Geological Survey (USGS) measure and characterize Hg and other geochemical constituents in 

sediment, water, and biota at the Clyde and Elgin mines in support of a Comprehensive Environmental 

Response, Compensation, and Liability Act (CERCLA) - Removal Site Investigation (RSI). The RSI 

applies to removal of Hg-contaminated mine waste from the Elgin and Clyde mines, as well as nearby 

Harley Gulch. Because the two mines, located in adjacent subwatersheds in the headwaters of Sulphur 

Creek, are within the California Coast Range mercury mineral belt (Rytuba, 2000), it is likely that Hg 

contamination could originate from both naturally occurring and anthropogenic sources.

The Clyde Gold Mine is a small, relatively low production mine about 6 km northwest of Wilbur 

Springs on land managed by the USBLM in the headwaters of the Sulphur Creek Watershed, Colusa 

County, California (fig. 1). Gold (Au) was discovered near the Clyde Mine in the 1860s, mine workings 

were constructed in the 1880s, and mining continued sporadically until 1890. The Clyde Mine 

reportedly produced about “$200 per day” of Au in the late 1880s, but it was abandoned by 1890 when 

prohibitive amounts of groundwater were encountered (Watts, 1893). Ore was processed on-site with a 

3.5-foot Huntington mill until 1890, at which point a 5-foot Huntington mill was installed to process 

ore. A trommel-type Au recovery system was installed in the 1970s, presumably to reprocess old waste 

material on-site. This trommel system is believed to have caused the tailings pile and small ponds 

visible on-site today. The on-site processing of Au ore produced waste material that could have 

contributed Hg to Freshwater Branch, a small creek that flows through the mine site. Workings at the 

Clyde Mine include three partially open adits containing standing water, several cuts and trenches to the 

west and southeast of the adits, and a stormwater retention pond southeast of the adits.

The mineralized area at the Clyde Mine is hosted within serpentinite and shales of the Great 

Valley Sequence in the west part of the mine area. The Au mineralizes in fracture zones in a northwestsoutheast trending, silicified body of serpentinite. Native Au and pyrite are reportedly found at the mine 

site in decomposed soft slate and shale.

The Elgin Mercury Mine is about 1.6 km south of the Clyde Mine and about 4.75 km northwest 

of Wilbur Springs on West Fork of Sulphur Creek, Colusa County, California (fig. 1). Part of the mine 

is on land managed by the USBLM. Mercury was discovered near the Elgin Mine in the 1870s, and at 

least 52 flasks (about 1,800 kg) of Hg were produced in 1875 (Mining and Scientific Press, 1875). Ore 

assaying about 1.8 percent Hg was mined intermittently until 1916 (Huguenin, 1917). The high 

temperature water and rock present in the area prohibited further exploration and mining. Compared to 

other Hg mines in the area, total production at the Elgin Mine was minimal. The nearby Abbott-Turkey 

Run Mine produced over 50,000 flasks of Hg from 1862 to 1971 (U.S. Bureau of Mines, 1965). 

Workings include three adits, 500 feet of underground workings that have since collapsed, and 

two areas containing significant surface disruption (Tetra Tech, 2003). Ore was processed with a 10-

pipe retort equipped with a furnace and Griffin mill to concentrate cinnabar (HgS), the principal ore 

mineral. Waste-rock piles exist around the open cuts, with an estimated total volume of 1,000-4,000 

cubic yards (Churchill and Clinkenbeard, 2003). A small tailings pile is present on the west side of West 

Fork of Sulphur Creek.

The country rock in the Elgin Mine region comprises serpentinite and shale of the Great Valley 

Sequence. The principal Hg mineralization product, cinnabar, is primarily found where serpentinite is 

in fault contact with shale. Cinnabar is concentrated in fracture zones in silicified serpentinite and 

locally leached by acidic fluids in the near surface (Tetra Tech, 2003).
3

This report summarizes data obtained from field sampling in the Sulphur Creek Watershed near 

the Clyde and Elgin mine areas that took place in 2010 to provide an assessment of Hg and related 

chemical constituents in water, sediment, and biota in the study area.

Methods

Sample Locations 

Clyde Mine

Samples were collected to assess the concentration of Hg and biogeochemically relevant 

constituents affecting Hg transport and methylation of Hg in Freshwater Branch, a stream that runs next 

to the Clyde Mine and is a tributary to the East Fork of Sulphur Creek (fig. 1, table 1). Water, sediment, 

and biota were sampled from Freshwater Branch, upstream and downstream from the mine workings, to 

characterize the amount of Hg contributed to the watershed by waste material from the Clyde Mine

during low-flow conditions (fig. 1, table 1). Sites sampled for biota were centered approximately on the 

locations listed in table 1, but sampling normally included as much as 50 meters (m) of stream. Unless

otherwise specified, biota sites overlapped sites sampled for water and sediment. Sample sites 10CL1 

(water and sediment, fig. 2) and CLUS (biota) were upstream from the mine workings in Freshwater 

Branch (fig. 1). Water and sediment site 10CL2 (fig. 3) was about 130 m upstream from the 

corresponding biota site (CLMN), but both were in Freshwater Branch downstream from the minewaste piles (fig. 1). Site 10CL3 (water and sediment) was about 330 m downstream from biota site 

CLDS (fig. 4), but both were in similar habitats on the Freshwater Branch downstream from the Clyde 

Mine. Site 10CL4 (water and sediment) and CLOK (biota, fig. 5) were in Oak Cove, a small tributary to 

Freshwater Branch downstream from the other sample sites (fig. 1).

Elgin Mine

Samples for water, sediment, and biota were collected at four locations in the Elgin Mine area

(fig. 1, table 1). Three of the sites were on the West Fork of Sulphur Creek, which flows adjacent to the 

Elgin Mine. Sites 10EL1 (water and sediment) and ESUS (biota, fig. 6) were near one another upstream 

from the confluence of West Fork Sulphur Creek and Salt Branch (fig. 1), and 10EL2 (water and 

sediment) and ESDS (biota, fig. 7), were just downstream from that confluence. Site 10EL3 (fig. 8A), a 

water and sediment site, was about 400 m downstream from the corresponding biota site, EWSU (fig. 

8B). One site, ESLT, on Salt Branch, about 975 m upstream from West Fork Sulphur Creek, was 

considered a reference site. Only biota was collected from ESLT (fig. 9).

Field Methods

Sediment

Wet sediment samples were collected from the streams and placed in 250 mL polycarbonate jars 

for analysis of monomethyl mercury (MMeHg) and total mercury (HgT). These samples were stored on 

wet ice in the field and shipped overnight on dry ice to the analytical laboratory where they were kept 

frozen until analysis. The temperature of samples arriving at the analytical facilities was ≤ −25oC. 

A dry sediment sample was collected in a Ziploc® bag for analysis of major and minor elements, 

stored at ambient temperature, and shipped to the analytical laboratory at ambient temperature without 

preservation. Replicate sediment samples were not collected for this study. 
4

Water

Water variables, including pH, conductivity, temperature, dissolved oxygen, and oxidationreduction potential (ORP) were measured in the field by placing the probe of a battery-powered 

Hydrolab Sonde directly into the flowing stream water (Gibs and others, 2007).

Water samples were then collected from the streams by using a peristaltic pump equipped with

ultraclean tubing and an inline filter (0.45-μm pore size) for analysis of anions and alkalinity. During 

every sampling event, a field blank was collected by processing de-ionized water and performing the 

same analyses (except for alkalinity) following the same procedures as were used for the field samples. 

Samples for major- and minor-element determinations in filtered and unfiltered water samples were 

acidified to less than pH 2 with trace metal (Ultrex, J.T. Baker)-grade nitric acid (HNO3) and stored in 

acid-washed, high-density polyethylene (HDPE) bottles. Subsamples for anion and alkalinity 

measurements were filtered, stored in HDPE bottles, and chilled to approximately 4°C until analysis, in 

accordance with USGS protocols for trace metals (U.S. Geological Survey, 2006).

Samples for HgT, total Hg in filtered water samples (HgF), and MMeHg analyses were collected 

in trace metal-free-certified 250-ml fluoropolymer bottles (Nalgene ICHEM) with no headspace. All 

samples were collected from the stream at the same time, but the HgF samples were filtered with a 0.45-

micron filter. The MMeHg bottles contained a preservative of hydrochloric acid (HCl) provided by the 

analytical laboratory, Frontier Global Sciences (Seattle, Wash.). Procedures for HgT analysis followed 

ultra-clean sampling and handling protocols (Bloom, 1995; Gill and Fitzgerald, 1987) during the 

collection of field samples and analysis to avoid introduction of Hg. Samples were kept on ice until 

shipped. Samples were shipped on ice packs and arrived the next morning at the analytical facilities at 

temperatures ranging from 1 to 4o C, as specified by U.S. Environmental Protection Agency (EPA)

Method 1631E to minimize biologically induced phase changes and MMeHg degradation (U.S. 

Environmental Protection Agency, 2002).

Biota

Aquatic invertebrates can serve as excellent indicators of metal contamination (bioindicators; for 

example, Cain and others, 1992). Predatory insects were the target macroinvertebrates (Merritt and 

Cummins, 1995) for this study, with primary taxa dependent on abundance and availability at sampling 

sites. Invertebrate taxa collected in 2010 from the Clyde Mine were adult water striders (order 

Hemiptera, family Gerridae), larval dragonflies (order Odonata, families Aeshnidae, Cordulegastridae, 

Gomphidae, and Libellulidae), and larval dobsonflies (order Megaloptera, family Corydalidae). Taxa 

collected from the Elgin Mine were larval damselflies (order Odonata, family Coenagrionidae), adult 

water striders, predaceous diving beetles (order Coleoptera, family Dytiscidae), larval water scavenger 

beetles (order Coleoptera, family Hydrophilidae), and larval dobsonflies.

Aquatic invertebrates were collected by using dip nets and by hand and placed in Ziploc® plastic 

bags with native water (Alpers and others, 2005). Samples were kept in a cooler and allowed to depurate 

in native water on wet ice for 4–24 hours before processing. Individuals were sorted by family and 

placed in disposable dishes by using TeflonTM-coated forceps or by hand while wearing disposable latex 

gloves. Organisms were rinsed clean with deionized water, patted dry with a clean paper towel, and 

composited by family, with the goal of obtaining a minimum of 1 gram (g) wet biomass. Each 

invertebrate sample consisted of 1–23 individuals of the same family (0.38–3.57 g total mass). Samples 

were weighed on an electronic balance (± 0.01 g), placed into chemically cleaned glass jars (VWR 

TraceCleanTM) with Teflon-lined lids, and stored frozen until they were shipped on dry ice to the 

contract laboratory for analysis within 30 days after processing. The samples were analyzed for HgT and 

MMeHg at Frontier Global Sciences, Inc., in Seattle, Wash. 
5

Analytical Methods

Sediment

Multi-element analyses for all dry-sediment samples were performed at ALS Chemex

laboratories (Reno, Nev.). Bulk samples were ground in a zirconia ring mill and subjected to a near-total 

four-acid digestion. Major elements were determined by inductively coupled-atomic emission 

spectroscopy (ICP-AES). Minor elements, other than Hg, were determined by ICP–mass spectroscopy

(ICP-MS). Mercury was determined by cold vapor atomic absorption spectroscopy (CVAAS) following 

methods similar to those described by Crock (1996) and O’Leary and others (1996).

Mercury and MMeHg analyses for all wet sediment were done at Frontier Global Sciences. For 

HgT, the sediment was leached with cold aqua regia, followed by stannous chloride (SnCl2) reduction, 

two-stage Au amalgamation, and cold vapor atomic fluorescence spectroscopy (CVAFS) detection. 

MMeHg was obtained by acid bromide/methyl chloride extraction, followed by aqueous-phase 

ethylation, isothermal gas chromatographic (GC) separation, and CVAFS detection (Horvat and others, 

1993). Results were reported on both a wet- and dry-weight basis.

Water

Analyses for anions and alkalinity were performed at the USGS laboratory in Denver, Colo. 

Anion (sulfate, chloride, nitrate, and fluoride) concentrations were determined by ion chromatography 

(Fishman and Pyen, 1979). Alkalinity as calcium carbonate (CaCO3) was determined by using Gran’s 

titration with sulfuric acid (H2SO4; Orion Research, Inc., 1978), within 2–4 days after sample collection. 

Cations were determined by using ICP–AES and ICP–MS. The ICP-AES analyses were 

determined in USGS laboratories under the direction of Paul Briggs. Duplicate water samples, blank 

samples, and USGS Water Resource Division standard reference waters were analyzed with the data set.

Mercury analyses in surface waters were performed at Frontier Global Sciences Inc. 

(Seattle, Wash.). Samples were handled in a Class-100 clean-air station, and ultra-clean Hg 

trace-metal protocol was followed. Primary standards used in the laboratory were NIST-certified, 

or traceable to NIST-certified materials and calibrated against DORM-2 (National Research 

Council of Canada Institute for National Measurement Standards, 1999). USEPA Method 1631 

was used (U.S. Environmental Protection Agency, 2002). Total Hg was determined by bromine 

monochloride (BrCl) oxidation followed by Tin(II) Chloride (SnCl2) reduction, two-stage gold 

amalgamation, and detection by CVAFS (Bloom and others, 1988). MMeHg was liberated from 

water by using an all-Teflon® distillation system and analyzed by using aqueous phase ethylation 

with purging onto CarbotrapTM, isothermal GC separation, and CVAFS detection (Bloom, 1989). 

Quality-assurance measures were employed with the following minimum frequencies: laboratory 

duplicates, one per ten samples; method blanks, three per analytical batch; filtration blanks, one 

per ten samples; and spike recovery or standard reference material, one per ten samples.

Biota

At Frontier Global Sciences, benthic samples were rinsed with reagent water and blotted with 

clean laboratory wipes prior to being homogenized. Homogenized samples were digested for HgT

analysis with concentrated sulfuric and nitric acids according to Frontier Global Sciences’ SOP FGS011, a modification of USEPA method 1631. Total Hg in digested tissues was analyzed by SnCl2

reduction, dual Au amalgamation, and CVAFS detection according to FGS-069, a modification of 

USEPA method 1631.
6

Homogenized samples were digested for MMeHg analysis by a heated 25 percent potassium 

hydroxide (KOH) solution, followed by dilution with methanol, according to FGS-010. MMeHg in 

digested tissues was analyzed by CV-GC-AFS (aqueous phase ethylation, isothermal GC separation, 

and CVAFS detection) according to Frontier Global Sciences’ SOP FGS-070, a modified EPA 1630 

procedure. 

All results are presented on a wet-weight basis, but, where sufficient sample mass was available, 

percentage moisture is presented to allow for dry-weight calculations.

QA/QC

Sediment

Procedural blanks, matrix spiked (MS) samples, and laboratory control samples (LCS) were 

analyzed to assure the accuracy of the methods. To assure that no analyte was added during the 

processing of the sample, procedural blanks were analyzed at a rate of 5 percent of the total samples, 

with at least one per matrix per analytical run. In all blanks for HgT (n=3) and for MMeHg (n=3), the 

analyte was undetected, although included in the analysis. All blank results met the acceptable criterion

of less than twice the mean detection limit (MDL; HgT = 0.36 ng/g; MMeHg = 0.008 ng/g).

Duplicate sediment samples were analyzed at a rate of 5 percent, with at least one duplicate per 

matrix per analytical run to estimate the precision of the methods. The relative percentage differences 

(RPDs) for HgT duplicates were 0.119 and 0.787, both less than the 25 percent acceptable criterion, but 

the RPDs for MMeHg duplicates were 4.73 and 136 percent. The one RPD exceeded the 25 percent 

criterion because the sample matrix was not homogeneous. However, the batch quality control was 

accepted on the basis of LCS/laboratory control sample duplicates (LCS/LCSD) RPD.

Matrix spikes and MS duplicates (MSDs) of HgT and MMeHg used to verify that the matrix 

characteristics did not interfere with the analytical results were analyzed at a rate of 5 percent, with at 

least one spike per matrix per analytical run. The HgT MS and MSD recoveries (n=4) ranged from 84.7 

to 2,850 percent, only two of which were within the acceptable criteria of 75–125 percent. According to 

Frontier Global Sciences, the two recoveries were outside the acceptable limits because the spike 

concentration was less than two times the sample concentration; however, the batches were acceptable 

because LCS and LCSD recoveries were within control limits. The RPDs (n=2) were 13.3 and 180 

percent. The one RPD exceeded the 25 percent criterion likely because the sample matrix was not 

homogeneous; however, the batch quality control was accepted on the basis of LCS/LCSD RPD.

The MMeHg MS and MSD recoveries (n=2) were 117 and 118 percent, both within the 

acceptable criteria (65–130 percent). The RPD was 0.872, well below the acceptable criterion of 25

percent. 

LCS and LCSDs were analyzed at a rate of 5 percent to insure that the method worked with 

naturally incorporated Hg. Recoveries of HgT in LCS and LCSDs (n = 2) were 102 and 104 percent, 

well within the criterion of 75–125 percent. The LCS RPD for HgT was 1.69 percent, meeting the 

criterion of ≤ 25 percent. For MMeHg, LCS and LCSD recoveries (n = 2) were 72.4 and 76.4 percent, 

within the criterion of 70–130 percent. The LCS RPD was 5.39 percent, meeting the criterion of ≤ 25 

percent.
7

Water

As with sediment, procedural blanks were analyzed for water at a rate of 5 percent of the total 

samples, with at least one per matrix per analytical run. In all blanks for HgT (n=10), and for MMeHg 

(n=6), the analyte was undetected, although included in the analysis. All blank results were less than the 

acceptable criteria of twice the MDL (HgT = 0.50 ng/L; MMeHg = 0.050 ng/L).

Duplicate water samples were analyzed at a rate of 5 percent, with at least one duplicate per 

matrix per analytical run to estimate the precision of the methods. The RPDs for HgT and MMeHg 

duplicates were all less than 25 percent, the acceptable criterion. 

Matrix spike samples and MSDs of HgT and MMeHg were analyzed at a rate of 5 percent, with 

at least one spike per matrix per analytical run. The HgT MS and MSD recoveries (n=12) ranged from 

84.5 to 116 percent, all within the acceptable criteria of 75–125 percent. The RPDs (n=6) ranged from 

0.049 to 7.41 percent, all less than the acceptable criterion of 25 percent. 

The MMeHg MS and MSD recoveries (n=4) ranged from 115 to 127 percent, all within the 

acceptable criteria of 65-130 percent. The RPDs (n=2) ranged from 2.59 to 10.4 percent, well below the 

acceptable criterion of 25 percent. 

LCS and LCSDs were analyzed at a rate of 5 percent to insure that the method worked with 

naturally incorporated mercury. Recoveries of HgT in LCS and LCSDs (n = 8) ranged from 94.4 to 98.5

percent, well within the criterion of 80–120 percent. RPDs for HgT ranged from 0.074 to 1.00 percent, 

less than the 25 percent criterion. For MMeHg, LCS and LCSD recoveries (n = 4) ranged from 79.7 to 

121 percent, within the criterion of 70–130 percent. LCS RPDs (n = 2), however, were 27.8 and 30.7 

percent, both exceeding the acceptable limit of 25 percent. Frontier Global Sciences reported that the 

batch quality control was acceptable because the matrix duplicate and MS/MSD RPD values were 

within control limits.

Biota

As with sediment and water samples, procedural blanks were analyzed for biota at a rate of 5

percent of the total samples, with at least one per matrix per analytical run. No HgT (n=9) or MMeHg 

(n=12) was detected in any of the procedural blanks that were analyzed. All blank results were less than 

the acceptable criteria of twice the MDL (HgT = 0.142 ng/g; MMeHg = 0.40 ng/g).

Duplicate biota samples were analyzed at a rate of 5 percent, with at least one duplicate per 

matrix per analytical run to estimate the precision of the methods. The RPDs for two of the HgT

duplicates (6.92–18.5 percent) were less than the acceptance criterion (25 percent), but the RPD for the 

third duplicate, 38.4 percent, exceeded the acceptable criterion. Nevertheless, the quality control for this 

analytical run was acceptable because MSD and LCS/LCSD RPD values were within control limits. The 

RPDs for two of the MMeHg sample duplicates (12.0 and 20.9 percent) were less than the acceptance 

criterion (25 percent), but the RPD for the third duplicate, 25.5 percent, barely exceeded the acceptable 

criterion. 

MS and MSDs of HgT and MMeHg were analyzed at a rate of 5 percent, with at least one spike 

per matrix per analytical run. Spikes were samples fortified with a known quantity of analyte and 

analyzed as part of the run. The HgT MS and MSD recoveries (n=6) ranged from 81.3 to 119 percent, all 

within the acceptable criteria of 75–125 percent. The RPDs (n=3) ranged from 19.4 to 31.4 percent, one 

falling outside the acceptable criterion of less than 25 percent. Although the one RPD was outside of 

acceptance limits, the analytical-run quality control was deemed acceptable on the basis of MSD or 

LCS/LCSD RPD values, or both, that were within control limits.
8

The MMeHg MS and MSD recoveries (n=12) ranged from 46.0 to 249 percent, and all but three 

were within the acceptable criteria of 65–135 percent. The RPDs (n=5) ranged from 4.27 to 80.8

percent, with two greater than the acceptable criterion of 25 percent. However, these two recoveries 

were outside the acceptable limits because the spike concentration was less than twice the sample 

concentration. The third recovery (249 percent) and its RPD (80.8 percent) were greater than the 

acceptable limits because of a lack of sample homogeneity. All analytical runs were accepted, however, 

on the basis of LCS/LCSD recoveries that were within control limits and, when analysis permitted, 

acceptable analytical samples and analytical sample duplicates (AS/ASD).

LCS and LCSDs were analyzed at a rate of 5 percent to insure that the method worked with 

naturally incorporated mercury. Recoveries of HgT in LCS and LCSDs (n = 4) ranged from 95.9 to 100

percent, well within the criterion of 75 to 125 percent. RPDs for HgT were 0.246 and 0.413 percent, 

below the criterion of 25 percent. For MMeHg, LCS and LCSD recoveries (n = 5) ranged from 81.4 to 

128 percent, within the criterion of 70 to 130 percent. LCS RPDs (n = 3) ranged from 0.573 to 5.92

percent, less than the criterion of 25 percent. 

The ratio of HgT to MMeHg in biological samples ranged from 43.4 to 126.8 percent at the 

Clyde Mine and from 8.8 to 171.2 percent at the Elgin Mine. The percentage of MMeHg in these 

samples exceeded 100 percent in 8 of 18 samples at the Clyde Mine and in 4 of 11 samples at the Elgin

Mine. However, we considered only those that were greater than 120 percent MMeHg to be 

problematic: two at Elgin Mine and three at Clyde Mine. According to Bloom (1992), nearly all of this 

variability can be explained by the analytical variability of HgT and MMeHg. Poorly homogenized 

samples showed greater variability, primarily because HgT and MMeHg are measured on separate 

aliquots, which vary in Hg concentration, not speciation. We considered the results of the analyses of 

MMeHg in biota, the biologically incorporated form of Hg, to be the more reliable than HgT for the 

purposes of this report.

Results

Mercury and Monomethyl Mercury in Sediment 

Clyde Mine

Sediment in the Freshwater Branch upstream from the Clyde Mine waste piles (site 10CL1, fig. 

2) did not have elevated HgT concentrations (259 nanograms per gram [ng/g]; table 2) compared to local 

background levels. Immediately downstream from the mine waste piles at sample site 10CL2 (fig. 3), 

HgT levels were lower (188 ng/g) than the upstream site, indicating that Hg was not being released in 

bulk sediment from the mine wastes into the creek during the sampling period. Further downstream 

from the mine workings at sample site 10CL3, the HgT concentration was higher (352 ng/g) than the 

most upstream site. At the sample site in the Oak Cove tributary to Freshwater Branch (10CL4), the HgT

concentration in sediment was the lowest, at 109 ng/g. The concentration observed at sample site 10CL4 

was representative of background in this watershed. The low concentrations of HgT (table 2) and other 

trace metals (table 3) in the sediment indicated that Hg-bearing sediment was not present in the stream 

reach near the Clyde Mine during low-flow conditions encountered at the time of sampling. 
9

MMeHg concentrations in sediment sampled from the Freshwater Branch were not significantly 

elevated, and their pattern was generally similar to the concentration of Hg in the sediment at the four 

sample sites (table 2). At sample site 10CL1, upstream from the mine tailings, the MMeHg 

concentration was 0.49 ng/g. Just below the mine wastes at site 10CL2, the MMeHg concentration was 

lower (0.07 ng/g). The MMeHg concentration increased at sample site 10CL3, but only moderately to 

0.52 ng/g. The concentration of MMeHg at sample site 10CL4 (0.15 ng/g) was near background levels. 

The percentage MMeHg in sediment (table 2) was indicative of the net MMeHg production on a 

site-specific basis when the concentration of MMeHg was normalized to the total concentration of Hg 

(Drott and others, 2008). The percentage MMeHg was derived by dividing the measured concentrations 

of MMeHg by the measured concentrations of Hg in sediment at the same site: 

Percentage of MMeHg = [(MMeHg in sediment, ng/g)/(Hg total in sediment, ng/g)]*100

The percentage of MMeHg levels in samples near the Clyde Mine were relatively constant and 

low, averaging from 0.19 percent upstream from the tailings input at site 10CL1 and varying slightly to 

0.04 percent at site 10CL2, 0.15 percent at site 10CL3, and 0.14 percent at site 10CL4 (table 2). These 

low values indicated that limited MMeHg was being produced in the Freshwater Branch of Sulphur 

Creek at the time of sampling. 

Elgin Mine

Sediment in the West Fork upstream from the main tailings piles at the Elgin Mine (site 10EL3) 

contained elevated HgT concentrations (2,800 ng/g; see table 2). Immediately downstream from the 

tailings piles, at sample site 10EL1, HgT concentrations were significantly higher at 16,400 ng/g. 

Furthest downstream from the mine area, at sample site 10EL2, HgT concentrations were the lowest 

observed locally, at 761 ng/g. The West Fork of Sulphur Creek receives uncontaminated water and 

sediment from Salt Fork, upstream from sample site 10EL2, which likely dilutes HgT in sediment at this 

site. These levels of HgT in sediment indicated that the tailings piles at the Elgin Mine were contributing 

significant amounts of HgT -enriched sediment to the West Fork of Sulphur Creek at the time of 

sampling.

MMeHg concentrations in West Fork sediment were moderate and showed a trend similar to 

HgT, with highest concentrations just downstream from the mine and lowest concentrations furthest

downstream (table 2). Upstream from the mine tailings (10EL3), MMeHg levels were moderate, at 0.97 

ng/g, but below the mine tailings piles, at site 10EL1, MMeHg levels (4.04 ng/g) were four times 

higher. As observed for HgT, the MMeHg concentration was lowest at the most downstream site (0.67

ng/g). 

The percentage of MMeHg levels were relatively constant and low in samples collected from the 

West Fork, at 0.03 percent both upstream from the tailings input at site 10EL3 and at sample site 

10EL1, and 0.09 percent at site 10EL2. These low values demonstrated that MMeHg production was 

limited in the West Fork of Sulphur Creek during the time of sampling. 
10

Water Chemistry 

Clyde Mine

The water in the Freshwater Branch of Sulphur Creek was slightly alkaline to neutral, with pH 

ranging from 7.37 to 7.89 (table 2). The water had low conductivity, ranging from 730 to 998 

microsiemens per centimeter (μS/cm). Sulfate levels were slightly elevated, 11.4–23.0 parts per million 

(ppm), and carbonate concentrations were high, ranging from 416.5 to 583.5 ppm (table 5). Dissolved 

organic carbon (DOC) levels were relatively low in the Freshwater Branch compared to the West Fork 

(table 2). Oxygen and deuterium stable-isotope levels plotted near the Global Meteoric Water Line 

(GMWL), indicating that the water in the Freshwater Branch of Sulphur Creek was predominantly 

meteoric, with some evaporation causing the minor shift away from the GMWL (fig. 10). 

Concentrations of metals typically associated with Au deposits, such as As, Sb, Tl, and W, were all 

present at low levels in both filtered (table 6) and unfiltered (table 7) water samples from all four 

samples sites.

Elgin Mine

The water in the West Fork of Sulphur Creek was slightly alkaline, ranging in pH from 7.57 to 

8.56 (table 2). The water was highly saline, with conductivity ranging from 23,097 to 25,899 μS/cm. 

Sulfate levels were elevated, ranging from 439 to 469 ppm, and carbonate concentrations were high, 

ranging from 2,765 to 3,380 ppm (table 5). Oxygen and deuterium stable-isotope levels plotted off the 

GMWL (fig. 10), indicating that the creek water was composed primarily of effluent from the numerous 

hot springs present in the area of the Elgin Mine. Slightly elevated levels of As, Ba, Na, Rb, Sr, and W 

were measured in the West Fork of Sulphur Creek (tables 8 and 9).

Mercury and Monomethyl Mercury in Water

Clyde Mine

The HgT levels in water in the Freshwater Branch of Sulphur Creek were low compared to other 

mine areas, with only one sample (10CL1) exceeding 50 nanograms per liter (ng/L) and the rest less 

than or equal to 16.0 ng/L (table 2). At sample site 10CL1, upstream from the mine tailings, the 

concentration of HgT was 16 ng/L, while the HgF was 9.45 ng/L. Just downstream from the Clyde Mine 

tailings (site 10CL2), HgT levels were relatively high (76.1 ng/L), but HgF (7.81 ng/L) was comparable 

to the upstream site. Further downstream from the mine at site 10CL3, HgT, and HgF declined to very 

low levels (3.45 and 3.14, respectively), similar to that found at the Oak Cove site (10CL4; table 2). The 

low values downstream demonstrated that much of the particulate Hg in upstream waters was not 

transported to the downstream site during the flow conditions in which we sampled. The relatively 

higher levels of total and dissolved HgT in the mine area could reflect Hg introduced into the 

mineralized area during formation of the Au deposit, or could represent Hg introduced to the system 

during amalgamation in gold recovery. The lack of specific mining records precludes definitive 

identification of the Hg source.
11

Elgin Mine

The Hg levels in all filtered and unfiltered water samples from the West Fork of Sulphur Creek 

were elevated (table 2). At sample site 10EL3, upstream from the main mine tailings, water had 

concentrations of 1,450 ng/L of HgT and 305 ng/L of HgF. Downstream from the mine area at site 

10EL1, HgT increased to 1,580 ng/L and HgF increased to 394 ng/L. At the sample site furthest 

downstream from the mine, 10EL2, levels decreased to 1,200 ng/L HgT and 362 ng/L HgF. The high Hg 

concentrations in unfiltered water downstream from the mine indicated that Hg was being transported 

into the West Fork of Sulphur Creek from the Elgin Mine during the period of sampling. However, high 

concentrations of HgF indicated that the geothermal, saline spring source of water to Sulphur Creek in 

this area could contribute significant amounts of naturally occurring Hg to the system.

Mercury and Monomethyl Mercury in Biota

Clyde Mine

Concentrations of MMeHg and HgT in the invertebrates collected from the area of the Clyde 

Mine were far lower than concentrations documented at nearby Harley Gulch in 2002 (Rytuba and 

others, 2011). Concentrations in Clyde Mine invertebrates, however, were similar to those in 

comparable taxa from Harley Gulch after the remediation of the Abbott and Turkey Run Mines in 2010 

and 2011. Water striders (Gerridae) had similar MMeHg concentrations at the three Freshwater Branch 

sampling sites (table 10). Larval dragonflies were collected from all four sampling sites in the Clyde 

Mine area, and MMeHg concentrations in two dragonfly families, Gomphidae and Aeshnidae, were not 

different among sites (fig. 11). Dobsonfly larvae collected from the site in Freshwater Branch farthest 

downstream from the mine (CLDS) were the exception, with five times more MMeHg (0.32 μg/g) than 

dobsonflies from the Oak Cove reference site (CLOK: 0.06 μg/g; table 10). As expected, the 

invertebrates collected from CLOK had MMeHg concentrations that were lower than, or similar to, the 

same taxa collected from the Freshwater Branch sites. With the exception of the CLDS dobsonflies, 

there were no apparent trends in concentrations of MMeHg or HgT in any taxon of aquatic invertebrate 

from Freshwater Branch.

Elgin Mine

Wide ranges of concentrations of HgT (0.01–1.62 μg/g) and MMeHg (0.01–1.90 μg/g) were 

present in invertebrate samples collected from the Elgin Mine area (table 10, fig. 12). The trend was for 

lower concentrations of both HgT and MMeHg at the site above the Elgin Mine (EWSU) and at the 

reference site (ESLT), with higher concentrations at the two sites below the Elgin Mine, ESUS and 

ESDS. The exception was water striders (Gerridae) which had a moderate concentration of MMeHg 

(0.12 μg/g) at EWSU, the site upstream from the mine, compared with lower concentrations just 

downstream from the mine (ESUS: 0.07 μg/g) and downstream from the confluence with Salt Branch 

(ESDS: 0.07 μg/g). Water striders were not collected from the reference site (ESLT).
12

MMeHg concentrations in both predaceous diving beetles (0.059 μg/g) and Dobsonflies (0.006 

μg/g) collected from ESLT were the lowest found in the Elgin Mine area, indicating the site was 

suitable for use as a reference. The concentration of MMeHg in beetles from ESLT was about half that 

found at the Harley Gulch reference site in 2011 (Rytuba and others, 2011), while the concentration of 

MMeHg in dobsonfly larvae at ESLT was about one-fourth that found at the Harley Gulch reference in 

2008 (Rytuba and others, 2011). The mean concentration of MMeHg in 2 samples of dobsonflies from 

EWSU (0.062 μg/g; SE = 0.0245) was 10 times greater than the sample from ESLT, and MMeHg in the 

composite sample of diving beetles from ESDS was more than 300 times greater than the sample from 

ESLT. 

The one composite sample of water scavenger beetle larvae (Hydrophilidae) collected from the 

Elgin Mine area (ESDS) had the second highest concentration of MMeHg (0.56 μg/g) observed for 

either mine, and it was higher than any larval hydrophilids collected at Harley Gulch during 2007–2011

(Rytuba and others, 2011). Damselfly larvae (Coenagrionidae) had elevated concentrations of HgT at 

both ESUS (1.62 μg/g) and ESDS (0.96 μg/g), but the MMeHg concentrations, 0.142 and 0.086 μg/g, 

respectively, were similar to concentrations observed at the Harley Gulch reference site in 2008 (Rytuba 

and others, 2011). The resulting percentages of MMeHg for those two sites were consistently low, 8.8

percent and 8.9 percent for ESUS and ESDS, respectively. Damselfly larvae from the Elgin Mine area 

had concentrations of HgT and MMeHg that were similar to those found in the wetlands of Harley 

Gulch, where the concentration of HgT ranged from 0.46 to 9.94 μg/g, the MMeHg concentration ranged 

from 0.02 to 0.23 μg/g, and the percent MMeHg ranged from 2.29 to 4.56 percent (Rytuba and others, 

2011). 

Conclusions

This report evaluates the potential Hg contamination of Sulphur Creek by two historical 

mines, one a mercury mine (Elgin Mine) and the other a gold mine (Clyde Mine), located within 

the California Coast Range mercury mineral belt. Sampling carried out during low-flow 

conditions in late spring and early summer of 2010 demonstrated that concentrations of MMeHg 

were lower in both water and sediment in Freshwater Branch near the Clyde Mine than near the 

Elgin Mine. This could indicate that available concentrations of DOC and Hg were insufficient 

to produce significant amounts of MMeHg in the Freshwater Branch. 

Data from the West Fork of Sulphur Creek near the Elgin Mine showed elevated HgT, 

HgF, and MMeHg levels in water and sediment. Concentrations of Hg ranged from 32 to 175 

times higher at the Elgin Mine sample sites than at the Clyde Mine sites in filtered water (HgF). 

In unfiltered water, HgT ranged between 16 and 629 times higher at the Elgin Mine sample sites. 

The differences between MMeHg in water at the two mine sites were less extreme, ranging from 

1.3 to 13 times higher at Elgin Mine sample sites than the Clyde Mine sites. Hg concentrations in 

sediment were 2–150 times higher at Elgin Mine sites than Clyde Mine sites, while MMeHg 

concentrations in sediment were 1.3–59 times higher at Elgin Mine sites than Clyde Mine sites. 

With the exception of one sample of larval dobsonflies, there were no apparent trends

toward increasing concentrations of HgT or MMeHg in biota collected in the Freshwater Branch. 

The elevated concentrations in the dobsonflies appeared to be an outlier and did not indicate a 

trend toward increased Hg bioaccumulation downstream from the mine. 
13

Changes in HgT and HgF concentrations in water collected from the West Fork of Sulphur 

Creek near the Elgin Mine were relatively consistent as they progressed downstream, increasing 

from 10EL3 to 10EL1, and then decreasing downstream to 10EL2. HgF concentrations were 70–

79 percent lower than HgT concentrations at corresponding sample sites. MMeHg in water, 

however, was highest at the upstream site and appeared to decline in a downstream direction, 

with the concentration just below the mine site the lowest of the three sampled, and the 

concentration at the lowest site in between the two. 

Unlike the trend observed for water, concentrations of both HgT and MMeHg in sediment 

were considerably higher (by a factor of 6 and 4, respectively) at the site just downstream from 

the Elgin Mine than at the upstream site. Concentrations of both HgT and MMeHg at the site 

furthest downstream were lower than upstream from the mine. Sulfate concentrations were 20–

40 times higher at Elgin Mine than at Clyde Mine. Concentrations of MMeHg in water and 

sediment at Elgin Mine were higher than at the Clyde Mine, where dissolved organic carbon 

(DOC) and HgT concentrations were likely limiting MMeHg formation.

Despite the close proximity of the two mines, few invertebrates of the same taxon were 

collected in both subwatersheds, making inter-watershed comparisons difficult. Three composite 

samples of water striders collected from each mine area indicated no significant differences 

between sites for either HgT or MMeHg. Larval dobsonflies were collected from two upperwatershed sites at Elgin Mine and three downstream Clyde Mine sites, and the concentrations of 

both MMeHg and HgT were greater at Clyde Mine sites than at Elgin Mine sites. Larval 

damselflies, larval water scavenger beetles, and adult predaceous diving beetles were collected 

only from the West Fork of Sulphur Creek (Elgin Mine), and their concentrations of HgT and 

MMeHg were higher compared with the other collected taxa. Larval dragonflies (families 

Gomphidae, Libellulidae, Aeshnidae, and Cordulegastridae) were collected only from 

Freshwater Branch (Clyde Mine), and an analysis of their concentrations of HgT and MMeHg 

revealed no significant trends.

The presence of relatively low to moderate concentrations of Hg and MMeHg in water, 

sediment, and biota in the Freshwater Branch, and the lack of significant increases in 

concentrations downstream from the mine wastes indicated that the Clyde Mine is not a 

significant source of Hg to the watershed during low-flow conditions. This conclusion is in 

accordance with previous research on this section of the Sulphur Creek watershed (Churchill and 

Clinkenbeard, 2003). 

Streamflow in Freshwater Branch was dominated by meteoric water, in contrast with 

West Fork Sulphur Creek, where high-salinity thermal spring effluent represented a significant 

component of creek water. The conductivity of this hot-spring source was about 20–30 times 

higher than meteoric waters present near the Clyde Mine. This hot-spring effluent is likely a 

natural source of Hg to the watershed because the thermal water formation is likely related to the 

mineralization. The West Fork also contained elevated levels of Hg, MMeHg, and other 

geochemical constituents before interacting with mine-waste material. It is possible, therefore,

that natural sources contribute significantly more Hg to the West Fork of Sulphur Creek than 

does mine-waste material from the Elgin Mine. 
14

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16

Figure 1. Study sites sampled in 2010 in the Clyde Gold Mine area and the Elgin Mercury Mine area in the 

headwaters of Sulphur Creek, California.
17

Figure 2. Clyde Mine sample site 10CL1, just downstream from biota site CLUS (see fig. 1). Photo by James Rytuba, USGS.
18

Figure 3. Clyde Mine sample site 10CL2, 130 meters upstream from biota site CLMN, below the main surface disruption 

of Clyde Mine (see fig. 1). Photo by James Rytuba, USGS.
19

Figure 4. Biota site CLDS, 380 meters upstream from water and sediment sample site 10CL3 (see fig. 1).

Photo by Roger Hothem, USGS.
20

Figure 5. Biota sample site CLOK near water and sediment sample site 10CL4 (see fig. 1).

Photo by Brianne Brussee, USGS.
21

Figure 6. Water and sediment sample site 10EL1 (A) and nearby biota sample site ESUS (B) on the West Fork of Sulphur Creek, Elgin Mine area, 

2010 (see table 1 and fig. 1). Photos by James Rytuba (A) and Roger Hothem (B), USGS.

A B
22

Figure 7. Water and sediment sample site 10EL2 (A) and nearby biota sample site ESDS (B) on the West Fork of 

Sulphur Creek, Elgin Mine area, 2010 (see table 1 and fig. 3). Photos by James Rytuba (A) and Roger Hothem (B), 

USGS.

A

B
23

Figure 8. Water and sediment sample site 10EL3 (A), located about 200 meters (m) upstream from 10EL1 and 

upstream from input from the Elgin Mine. Photo by James Rytuba, USGS. The comparable biota site, EWSU (B), is 

located upstream from the Elgin Mine input and 400 m upstream from 10EL3 (see table 1 and fig. 1). Photo by

Roger Hothem, USGS.

B

A
24

Figure 9. Biota sample site ESLT looking upstream at Salt Branch, Elgin Mine area, 2010 (see table 1 and fig. 1). 

Photo by Roger Hothem, USGS.
25

Figure 10. Plot showing oxygen and deuterium stable isotope levels in Clyde Mine and Elgin Mine water samples.
26

Figure 11. Total mercury (HgT) and monomethyl mercury (MMeHg) concentrations (μg/g ww) in invertebrate samples collected from Clyde Mine on 

April 29, 2010.
27

Figure 12. Total mercury (HgT) and monomethyl mercury (MMeHg) concentrations (μg/g ww) in invertebrate samples collected from Elgin Mine on May 12, 

2010. 
28

Table 1. Sample locations for water, sediment, and biota for the Clyde Gold Mine and Elgin Mercury Mine, 2010.

[°, degrees; ', minutes; ", seconds]

Biota Water and sediment

Site description

Site 

name

Sampling 

date Latitude Longitude Site name

Sampling 

date Latitude Longitude

CLYDE MINE

Freshwater Branch 

upstream Clyde Mine

CLUS 4/29/2010 39° 04' 17.7" 122° 28' 47.1" 10CL1 7/2/2010 39° 04' 17.5" 122° 28' 46.7"

Freshwater Branch at 

Clyde Mine

CLMN 4/29/2010 39° 04' 11.6" 122° 28' 45.8" 10CL2 7/2/2010 39° 04' 14.8" 122° 28' 46.4"

Freshwater Branch 

downstream Clyde Mine

CLDS 4/29/2010 39° 04' 03.8" 122° 28' 20.0" 10CL3 7/2/2010 39° 04' 09.0" 122° 28' 08.0"

Oak Cove tributary to 

Freshwater Branch

CLOK 4/29/2010 39° 04' 13.2" 122° 28' 10.1" 10CL4 7/2/2010 39° 04' 13.3" 122° 28' 10.3"

ELGIN MINE

Salt Branch upstream from 

road

ESLT 5/13/2010 39° 03' 17.5" 122° 28' 43.9" Not 

sampled

West Fork Sulfur Creek 

upstream Elgin Mine

EWSU 5/13/2010 39° 03' 36.6" 122° 28' 25.7" Not 

sampled

West Fork Sulphur Creek 

upstream Elgin Mine 

tailings pile

Not 

sampled

10EL3 6/30/2010 39° 03' 30.4" 122° 28' 12.4"

West Fork Sulphur Creek 

upstream Salt Branch

ESUS 5/13/2010 39° 03' 28.0" 122° 28' 08.0" 10EL1 6/30/2010 39° 03' 26.9" 122° 28' 05.6"

West Fork Sulphur Creek 

downstream Salt Branch

ESDS 5/13/2010 39° 03' 26.0" 122° 27' 52.0" 10EL2 6/30/2010 39° 03' 25.1" 122° 27' 52.0"
29

Table 2. Physical and selected chemical parameters and total mercury (HgT), monomethyl mercury (MMeHg), and dissolved organic carbon (DOC) 

concentrations in waters and sediment from the Clyde and Elgin mines, 2010.

[μS/cm, microsiemens per centimeter; °C, degrees Celsius; O2, Oxygen; ng/L, nanograms per liter; DOC, dissolved organic carbon; mg/L, milligrams per liter]

Water Sediment

Sample site

Sampling 

date

Conductivity

(μS/cm) pH

Temperature 

(°C)

Dissolved 

O2 (ppm)

HgT

(ng/L) HgF (ng/L)

MMeHg 

(ng/L)

DOC

(mg/L)

HgT

(ng/g)

MMeHg 

(ng/g)

MMeHg/Hg

(percent)

CLYDE MINE

10CL1A 7/2/2010 750 7.37 17.21 6.91 16.0 9.45 0.226 2.1 259 0.485 0.187

10CL2A 7/2/2010 781 7.62 17.51 7.80 76.1 7.81 0.085 2.5 188 0.068 0.036

10CL3A 7/2/2010 998 7.89 18.90 8.58 3.45 3.14 0.232 2.6 352 0.518 0.147

10CL4A 7/2/2010 730 7.82 19.21 9.33 2.51 2.25 0.101 3.0 109 0.15 0.138

ELGIN MINE

10EL1A 6/30/2010 25129 8.50 29.78 7.00 1580 394 0.307 4.3 16400 4.04 0.025

10EL2A 6/30/2010 23097 7.57 28.98 7.57 1200 362 0.531 6.6 761 0.667 0.088

10EL3A 6/30/2010 25899 8.56 25.47 1.40 1450 305 1.11 4.1 2800 0.968 0.035
30

Table 3. Mercury and associated major and minor elements in sediment, precipitates, Clyde Mine, 2010.

[ppm, parts per million]

Sample 

site

Hg

(ppm)

Ag

(ppm)

Al

(percent)

As

(ppm)

Ba

(ppm)

Be

ppm

Bi

(ppm)

Ca

(percent)

Cd

(ppm)

Ce

(ppm)

Co

(ppm)

Cr

(ppm)

Cs

(ppm)

Cu

(ppm)

Fe

(percent)

Ga

(ppm)

10CL1S2 0.81 0.05 7.67 8.9 600 1.30 0.19 0.67 0.15 36.1 54.3 1330 4.00 53.1 6.34 18.7

10CL2S2 3.63 0.07 7.09 7.6 540 1.29 0.13 0.45 0.14 31.4 58.1 806 3.71 47.8 5.94 16.4

10CL3S2 1.41 0.07 5.99 5.8 500 1.01 0.10 0.51 0.14 26.6 66.3 960 12.9 45.1 5.73 13.6

Sample 

site

Ge

(ppm)

Hf

(ppm)

In

(ppm)

K

(percent)

La

(ppm)

Li

(ppm)

Mg

(percent)

Mn

(ppm)

Mo

(ppm)

Na

(percent)

Nb

(ppm)

Ni

(ppm)

P

(ppm)

Pb

(ppm)

Rb

(ppm) S (percent)

10CL1S2 0.23 2.5 0.066 1.52 17.5 61.0 5.74 828 0.76 0.88 7.0 658 490 13.5 66.8 0.01

10CL2S2 0.19 2.3 0.058 1.36 14.7 93.7 7.50 893 0.69 0.79 6.1 835 450 11.4 56.1 0.01

10CL3S2 0.21 1.9 0.049 1.08 11.8 59.1 8.65 977 0.62 0.79 5.2 994 410 9.40 46.0 0.02

Sample 

site

Sb

(ppm)

Sc

(ppm)

Se

(ppm)

Sn

(ppm)

Sr

(ppm)

Ta

(ppm)

Te

(ppm)

Th

(ppm)

Ti

(percent)

Tl

(ppm)

U

(ppm)

V

(ppm)

W

(ppm)

Y

(ppm)

Zn

(ppm)

Zr

(ppm)

10CL1S2 2.56 20.9 2 1.6 84.1 0.50 0.09 5.5 0.359 0.46 1.6 171 1.8 15.8 131 75.2

10CL2S2 5.62 19.1 1 1.3 72.8 0.43 0.08 4.9 0.328 0.61 1.4 154 1.3 13.3 111 70.5

10CL3S2 2.75 17.1 1 1.1 66.1 0.37 0.07 3.9 0.305 0.36 1.1 132 2.5 12.4 102 58.9
31

Table 4. Mercury and associated major and minor elements in sediment, precipitates, Elgin Mine. 2010.

[ppm, parts per million]

Sample site

Hg

(ppm)

Ag

(ppm)

Al

(percent)

As

(ppm)

Ba

(ppm)

Be

(ppm)

Bi

(ppm)

Ca

(ppm)

Cd

(ppm)

Ce

(ppm)

Co

(ppm)

Cr

(ppm)

Cs

(ppm)

Cu

(ppm)

Fe

(percent)

Ga

(ppm)

10EL1S2 292 0.05 6.90 5.3 1850 0.85 0.08 2.62 0.15 28.2 38.2 2520 80.4 45.1 5.90 15.35

10EL2S2 130 0.06 6.80 5.6 2260 0.98 0.11 1.39 0.18 28.2 46.7 3720 61.1 46.7 6.45 16.35

10EL3S2 30.4 0.07 6.75 5.2 1440 0.96 0.09 1.37 0.32 25.2 40.1 846 72.0 44.6 6.17 15.25

Sample site

Ge

(ppm)

Hf

(ppm)

In

(ppm)

K

(percent)

La

(ppm)

Li

(ppm)

Mg

(percent)

Mn

(ppm)

Mo

(ppm)

Na

(percent)

Nb

(ppm)

Ni

(ppm)

P

(ppm)

Pb

(ppm)

Rb

(ppm)

S

(percent)

10EL1S2 0.18 2.4 0.055 1.27 13.1 79.2 4.08 836 0.68 1.81 5.1 305 590 8.0 62.0 0.11

10EL2S2 0.19 2.7 0.062 1.30 12.8 79.9 5.16 831 0.84 1.74 5.9 420 640 7.7 60.3 0.21

10EL3S2 0.16 2.5 0.058 1.32 11.7 74.5 5.23 823 0.83 2.00 5.3 436 630 7.4 59.8 0.22

Sample site

Sb

(ppm)

Sc

(ppm)

Se

(ppm)

Sn

(ppm)

Sr

(ppm)

Ta

(ppm)

Te

(ppm)

Th

(ppm)

Ti

(percent)

Tl

(ppm)

U

(ppm)

V

(ppm)

W

(ppm)

Y

(ppm)

Zn

(ppm)

Zr

(ppm)

10EL1S2 0.89 20.5 1 1.9 529 0.36 0.08 3.0 0.476 0.27 1.0 183 10.3 17.5 117 73.7

10EL2S2 1.22 22.0 1 1.2 207 0.42 0.08 3.4 0.507 0.33 1.1 197 15.7 19.0 128 81.8

10EL3S2 1.16 20.5 2 1.2 196 0.38 0.07 3.2 0.506 0.32 1.0 189 14.4 17.3 113 76.0
32

Table 5. Concentration of anions and selected cations in filtered water at the Clyde and Elgin mines, 2010.

[ppm, parts per million; mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than]

Cl F NO3 SO4 CaCO3 Ca Fe K Li Mg Na

Sample site (ppm) (ppm) (ppm) (ppm) (ppm) (mg/L) (μg/L) (mg/L) (μg/L) (mg/L) (mg/L)

CLYDE MINE

10CL1C 10.2 < 0.04 < 0.08 22.4 418.0 24.2 NA 0.678 36.0 82.8 5.20

10CL2C 10.3 < 0.04 < 0.08 23.0 438.5 24.9 NA 0.746 56.7 86.7 5.15

10CL3C 18.9 < 0.04 < 0.08 11.4 583.5 19.6 NA 0.703 47.8 118 13.8

10CL4C 10.0 < 0.04 < 0.08 12.0 416.5 25.6 NA 0.575 17.0 78.4 6.17

ELGIN MINE

10EL1C 8379 14.9 398 441.0 3082.4 21.3 71.1 307 7390 69.3 5120

10EL2C 8090 15.1 406 468.8 2765.5 25.0 39.1 283 6560 69.7 4770

10EL3C 8394 14.8 348 439.1 3380.3 22.8 85.0 326 7270 71.3 5750
33

Table 6. Concentrations of relevant geochemical constituents in samples of filtered water from the Freshwater Branch of Sulphur Creek adjacent to the 

Clyde Mine.

[μg/L, micrograms per liter; mg/L, milligrams per liter, <, less than]

B Ba Ca Cs K Li Mg Na Ni Rb SiO2 Sr W Y

Sample site (μg/L) (μg/L) (mg/L) (μg/L) (mg/L) (μg/L) (mg/L) (mg/L) (μg/L) (μg/L) (mg/L) (μg/L) (μg/L) (μg/L)

10CL1B 108 56.4 24.2 < 0.2 0.678 36.0 82.8 5.20 4.8 0.30 74.3 395 5.3 0.12

10CL2B 95.4 85.1 24.9 < 0.2 0.746 56.7 86.7 5.15 5.4 0.22 70.5 475 < 5 0.10

10CL3B 574 64.3 19.6 0.58 0.703 47.8 118 13.8 5.5 0.86 76.5 382 7.53 0.15

10CL4B 179 39.2 25.6 < 0.2 0.575 17.0 78.4 6.17 < 4 0.20 68.8 290 < 5 0.14

Not detected (in μg/L) : Ag <10, Al <20, As <10, Be <0.5, Bi <2, Cd <0.2, Ce <0.1, Co <0.2, Cr <10, Cu <5, Dy <0.05, Er <0.05, Eu <0.05, Fe <500, Ga <0.5, Gd <0.05, 

Ge<0.5, Ho <0.05, La <0.1, Lu <1, Mn <2, Mo <20, Nb <2, Nd <0.1, P<0.1, Pb <0.5, Pr <0.1, Sb <3, Sc <6, Se <10, Sm <0.1, SO4 <20, Ta <0.2, Tb <0.05, Th <2, Ti <5, 

Tl <1, Tm <0.05, U <1, V <5, Yb <0.05, Zn <5, Zr <2
34

Table 7. Concentrations of relevant geochemical constituents in samples of unfiltered water from the Freshwater Branch of Sulphur Creek adjacent to the 

Clyde Mine, 2010.

[μg/L, micrograms per liter; mg/L, milligrams per liter, <, less than]

Al B Ba Ca Ce Co Cs Dy Fe Ge K Li

Sample site (μg/L) (μg/L) (μg/L) (mg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (mg/L) (μg/L)

10CL1A 20.7 110 55.2 24.3 < 0.1 <0.2 < 0.2 < 0.05 < 20 < 0.5 < 0.3 14.7

10CL2A 926 82.3 89.3 25.4 0.62 1.4 < 0.2 0.071 1710 < 0.5 0.3 41.4

10CL3A 25.8 565 63.8 20 < 0.1 0.33 0.6 < 0.05 37.2 < 0.5 0.42 17.6

10CL4A < 20 150 40.9 25.4 < 0.1 <0.2 < 0.2 0.057 < 20 < 0.5 < 0.3 < 1

Mg Mn Na Nd Ni Rb SiO2 Sr W Y Zn

Sample site (mg/L) (μg/L) (mg/L) (μg/L) (μg/L) (μg/L) (mg/L) (μg/L) (μg/L) (μg/L) (μg/L)

10CL1A 80.2 < 2 5.00 < 0.1 6.40 0.30 74.6 385 5.05 0.12 < 5

10CL2A 86.6 46 4.84 0.24 24.5 0.86 74.3 467 < 5 0.24 6.2

10CL3A 117 < 2 13.8 < 0.1 9.80 0.80 78.2 367 6.85 0.16 < 5

10CL4A 76.7 < 2 5.87 0.18 < 4 0.21 67.3 283 < 5 0.23 < 5

Not detected (in μg/L): Ag <10, As <10 , Be <0.5, Bi <2, Cd <0.2, Cr <10, Cu <5, Er <0.05, Eu <0.05, Ga <0.5, Gd < 0.05, Ho <0.05, La <0.1, Lu <1, Mo <20, Nb <2, 

P<0.1 m, Pb <0.5, Pr <0.1, Sb <3, Sc <6, Se <10, Sm <0.1, SO4 <20, Ta <0.2, Tb <0.05, Th <2, Tl <1, Tm <0.05, U <1, V <5, Yb <0.05, Zr <2
35

Table 8. Concentrations of relevant geochemical constituents in samples of filtered water from the West Fork of Sulphur Creek near the Elgin Mine, 2010.

[μg/L, micrograms per liter; mg/L, milligrams per liter, <, less than]

Al As B Ba Ca Ce Co Cs Dy Eu Fe Gd

Sample site (μg/L) (μg/L) (mg/L) (μg/L) (mg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L)

10EL1B 27.2 32.2 157 1160 21.3 0.27 2.13 617 0.080 0.052 71.1 0.057

10EL2B 22.4 29.0 144 799 25.0 0.13 2.12 557 0.057 0.064 39.1 < 0.05

10EL3B 21.4 29.0 151 1280 22.8 0.17 1.85 626 0.098 0.066 85.0 0.089

Ge K Li Mg Mn Na Nd Ni P Pb Rb Sb

Sample site (μg/L) (mg/L) (μg/L) (mg/L) (μg/L) (mg/L) (μg/L) (μg/L) (mg/L) (μg/L) (μg/L) (μg/L)

10EL1B 24.7 307 6700 69.3 50.6 5120 0.23 30.0 0.1 0.57 970 6.23

10EL2B 20.2 283 6300 69.7 15.3 4770 < 0.1 27.0 0.1 <0.5 895 5.65

10EL3B 26.3 326 6940 71.3 66.2 5750 0.18 29.4 0.1 <0.5 1010 6.30

Sc Se SiO2 Sr Ti V W Y Yb Zn

Sample site (μg/L) (μg/L) (mg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L)

10EL1B 6.7 100 77.6 1140 6.5 6.1 1610 0.62 < 0.05 8.4

10EL2B 5.9 96 72.0 1360 7.0 7.1 1530 0.30 < 0.05 <5

10EL3B 6.5 108 80.5 1240 7.0 5.6 1720 0.52 0.07 <5

Not detected (in μg/L): Ag <10, Be <0.5, Bi <2, Cd <0.2, Cr <10, Cu <5, Er <0.05, Ga <0.5, Ho <0.05, La <0.1, Lu <1, Mo <20, Nb <2, Pr <0.1, Sm <0.1, Ta <0.2, Tb 

<0.05, Th <2, Tl <1, Tm <0.05, U <1, Zr <2
36

Table 9. Concentrations of relevant geochemical constituents in samples of unfiltered water from the West Fork of Sulphur Creek near the Elgin Mine, 

2010.

[μg/L, micrograms per liter; mg/L, milligrams per liter, <, less than]

Al As B Ba Ca Cd Ce Co Cs Dy Er Eu Fe

Sample site (μg/L) (μg/L) (mg/L) (μg/L) (mg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L)

10EL1A 465 32.6 137 1270 21.2 < 0.2 0.62 2.90 637 0.180 0.093 0.094 997

10EL2A 289 29.1 138 843 26.5 < 0.2 0.36 2.36 566 0.075 0.056 < 0.05 554

10EL3A 483 32.8 164 1320 24.2 0.32 0.54 2.41 623 0.200 0.100 < 0.05 905

Gd Ge K La Li Mg Mn Na Nd Ni P Rb Sb

Sample site (μg/L) (μg/L) (mg/L) (μg/L) (μg/L) (mg/L) (μg/L) (mg/L) (μg/L) (μg/L) (mg/L) (μg/L) (μg/L)

10EL1A 0.160 27.9 298 0.19 6880 80.7 71.8 4900 0.62 43.6 0.2 1010 7.37

10EL2A 0.095 20.8 293 0.29 6440 79.3 27.7 5240 0.21 34.8 0.2 910 6.19

10EL3A 0.130 27.0 333 0.16 7170 79.3 84.0 5470 0.57 41.5 0.1 1020 7.00

Sc Se SiO2 Sm Sr Ti V W Y Zn

Sample site (μg/L) (μg/L) (mg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L) (μg/L)

10EL1A 8 102 72.3 0.23 1200 13.3 7.7 1480 1.06 15.3

10EL2A 7 94.4 77.2 < 0.1 1410 10.9 7.8 1510 0.60 8.2

10EL3A 8 102 84.3 0.12 1280 9.2 6.1 1570 1.02 10.9

Not detected (in μg/L): Ag <10, Be <0.5, Bi <2, Cd <0.2, Cr <10, Cu <5, Ga <0.5, Ho <0.05, Lu <1, Mo <20, Nb <2, Pr <0.1, Sm <0.1, Ta <0.2, Tb <0.05, Th <2, Tl <1, 

Tm <0.05, U <1, Zr <2
37

Table 10. Total mercury (HgT) and monomethyl mercury (MMeHg) concentrations (μg/g ww) in biota collected from the Clyde and Elgin mines, 2010.

[ave., average; g, grams; μg/g, micrograms per gram; ww, wet weight; NA, not analyzed]

Site 

code Common name Order Family Number

Mass 

(g)

Ave. mass 

(g)

HgT

(μg/g)

MMeHg 

(μg/g)

MMeHg

(percent)

Moisture

(percent)

CLYDE MINE

CLOK Dragonfly larvae Odonata Gomphidae 4 1.21 0.30 0.155 0.171 110.3 76.8

CLOK Dragonfly larvae Odonata Aeshnidae 8 3.57 0.45 0.098 0.089 91.1 82.4

CLOK Dragonfly larvae Odonata Cordulegastridae 1 0.93 0.93 0.098 0.096 97.5 73.5

CLOK Dobsonfly larvae Megaloptera Corydalidae 2 0.65 0.33 0.131 0.057 43.4 NA

CLUS Dobsonfly larvae Megaloptera Corydalidae 2 1.15 0.58 0.196 0.169 86.2 77.4

CLUS Water strider adults Hemiptera Gerridae 11 0.72 0.07 0.169 0.089 52.6 NA

CLUS Dragonfly larvae Odonata Aeshnidae 4 2.16 0.54 0.157 0.081 51.7 77.7

CLUS Dragonfly larvae Odonata Gomphidae 2 0.62 0.31 0.166 0.170 102.4 NA

CLUS Dragonfly larvae Odonata Cordulegastridae 2 2.80 1.40 0.118 0.144 122.0 76.2

CLMN Dragonfly larvae Odonata Aeshnidae 6 3.37 0.56 0.122 0.090 73.4 76.2

CLMN Water strider adults Hemiptera Gerridae 23 1.72 0.07 0.123 0.139 113.0 65.0

CLMN Dragonfly larvae Odonata Libellulidae 9 1.73 0.19 0.074 0.070 94.3 84.2

CLMN Dragonfly larvae Odonata Cordulegastridae 1 1.44 1.44 0.090 0.086 96.0 74.6

CLMN Dragonfly larvae Odonata Gomphidae 2 0.60 0.30 0.144 0.177 122.9 NA

CLDS Dragonfly larvae Odonata Gomphidae 2 0.51 0.26 0.161 0.165 102.5 NA

CLDS Dragonfly larvae Odonata Cordulegastridae 3 2.48 0.83 0.123 0.156 126.8 71.9

CLDS Dobsonfly larvae Megaloptera Corydalidae 2 0.38 0.19 0.536 0.323 60.3 NA

CLDS Water strider adults Hemiptera Gerridae 15 1.07 0.07 0.113 0.127 112.4 NA

ELGIN MINE

ESDS Water strider adults Hemiptera Gerridae 21 1.45 0.069 0.180 0.068 38.0 81.2

ESDS Damselfly larvae Odonata Coenagrionidae 30 1.65 0.055 0.962 0.086 8.9 NA

ESDS Water scavenger beetle larvae Coleoptera Hydrophilidae 11 1.14 0.104 0.737 0.556 75.4 NA

ESDS Predaceous diving beetle adults Coleoptera Dytiscidae 11 0.66 0.060 1.110 1.900 171.2 60

ESUS Water strider adults Hemiptera Gerridae 13 0.86 0.066 0.099 0.068 69.1 NA

ESUS Damselfly larvae Odonata Coenagrionidae 12 0.55 0.046 1.620 0.142 8.8 NA

EWSU Dobsonfly larvae Megaloptera Corydalidae 5 1.17 0.234 0.051 0.037 72.0 60.8

EWSU Dobsonfly larvae Megaloptera Corydalidae 1 1.02 1.020 0.073 0.086 118.6 NA

EWSU Water strider adults Hemiptera Gerridae 6 0.39 0.065 0.103 0.118 114.6 NA

ESLT Predaceous diving beetle adults Coleoptera Dytiscidae 35 1.79 0.051 0.038 0.059 155.1 NA

ESLT Dobsonfly larvae Megaloptera Corydalidae 2 1.16 0.580 0.008 0.006 72.7 NA
38