U.S. Department of the Interior

U.S. Geological Survey

Data Series 307

National Water-Quality Assessment Program

Toxic Substances Hydrology Program

Data on Mercury in Water, Bed Sediment, and Fish from

Streams Across the United States, 1998–2005
Cover photographs:

Top left, fish collection by electrofishing

Middle, stream-water processing

Bottom right, streambed sediment sampling

Background, cutthroat trout (Oncorhynchus clarkii)

All photographs by Dennis A. Wentz, U.S. Geological Survey
Data on Mercury in Water, Bed Sediment, 

and Fish from Streams Across the United 

States, 1998–2005

By Nancy J. Bauch, Lia C. Chasar, Barbara C. Scudder, Patrick W. Moran, 

Kerie J. Hitt, Mark E. Brigham, Michelle A. Lutz, and Dennis A. Wentz

Data Series 307

U.S. Department of the Interior

U.S. Geological Survey

National Water-Quality Assessment Program

Toxic Substances Hydrology Program
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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Suggested citation:

Bauch, N.J., Chasar, L.C., Scudder, B.C., Moran, P.W., Hitt, K.J., Brigham, M.E., Lutz, M.A., and Wentz, D.A., 2009, 

Data on mercury in water, bed sediment, and fish from streams across the United States, 1998–2005: U.S. Geological 

Survey Data Series 307, 33 p. 
iii

FOREWORD

The U.S. Geological Survey (USGS) is committed to providing the Nation with reliable scientific 

information that helps to enhance and protect the overall quality of life and that facilitates effective 

management of water, biological, energy, and mineral resources (http://www.usgs.gov/). Information 

on the Nation’s water resources is critical to ensuring long-term availability of water that is safe for 

drinking and recreation and is suitable for industry, irrigation, and fish and wildlife. Population growth 

and increasing demands for water make the availability of that water, measured in terms of quantity 

and quality, even more essential to the long-term sustainability of our communities and ecosystems.

The USGS implemented the National Water-Quality Assessment (NAWQA) Program in 1991 to 

support national, regional, State, and local information needs and decisions related to water-quality 

management and policy (http://water.usgs.gov/nawqa). The NAWQA Program is designed to answer: 

What is the quality of our Nation’s streams and ground water? How are conditions changing over 

time? How do natural features and human activities affect the quality of streams and ground water, 

and where are those effects most pronounced? By combining information on water chemistry, 

physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide 

science-based insights for current and emerging water issues and priorities. From 1991 to 2001, the 

NAWQA Program completed interdisciplinary assessments and established a baseline understanding 

of water-quality conditions in 51 of the Nation’s river basins and aquifers, referred to as Study Units 

(http://water.usgs.gov/nawqa/studyu.html). 

National and regional assessments are ongoing in the second decade (2001–2012) of the NAWQA 

Program as 42 of the 51 Study Units are selectively reassessed. These assessments extend the 

findings in the Study Units by determining water-quality status and trends at sites that have been 

consistently monitored for more than a decade and filling critical gaps in characterizing the 

quality of surface water and ground water. For example, increased emphasis has been placed on 

assessing the quality of source water and finished water associated with many of the Nation’s 

largest community water systems. During the second decade, NAWQA is addressing five national 

priority topics that build an understanding of how natural features and human activities affect water 

quality, and establish links between sources of contaminants, the transport of those contaminants 

through the hydrologic system, and the potential effects of contaminants on humans and aquatic 

ecosystems. Included are studies on the fate of agricultural chemicals, effects of urbanization 

on stream ecosystems, bioaccumulation of mercury in stream ecosystems, effects of nutrient 

enrichment on aquatic ecosystems, and transport of contaminants to public-supply wells. In addition, 

national syntheses of information on pesticides, volatile organic compounds (VOCs), nutrients, trace 

elements, and aquatic ecology are continuing. 

The USGS aims to disseminate credible, timely, and relevant science information to address practical 

and effective water-resource management and strategies that protect and restore water quality. 

We hope this NAWQA publication will provide you with insights and information to meet your needs 

and will foster increased citizen awareness and involvement in the protection and restoration of our 

Nation’s waters. 

The USGS recognizes that a national assessment by a single program cannot address all 

water-resource issues of interest. External coordination at all levels is critical for cost-effective 

management, regulation, and conservation of our Nation’s water resources. The NAWQA Program, 

therefore, depends on advice and information from other agencies—Federal, State, regional, 

interstate, Tribal, and local—as well as nongovernmental organizations, industry, academia, and 

other stakeholder groups. Your assistance and suggestions are greatly appreciated.

 Matthew C. Larsen

Associate Director for Water
iv

Contents

Foreword ........................................................................................................................................................iii

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

Introduction.....................................................................................................................................................1

Data Collection...............................................................................................................................................4

Site Selection.........................................................................................................................................4

Sample Collection and Processing....................................................................................................4

Stream-Water Sample Collection .............................................................................................4

Stream-Water Sample Processing.........................................................................................14

Bed-Sediment Sample Collection ...........................................................................................14

Bed-Sediment Sample Processing.........................................................................................14

Fish Sampling and Processing ................................................................................................14

Analytical Methods......................................................................................................................................15

Stream Water ......................................................................................................................................15

Bed Sediment ......................................................................................................................................15

Fish ........................................................................................................................................................16

Quality Assurance........................................................................................................................................16

Quality of Water and Bed-Sediment Data ......................................................................................16

Blanks ..........................................................................................................................................17

Replicates....................................................................................................................................17

Quality of Fish Data.............................................................................................................................23

Ancillary Data...............................................................................................................................................23

Geographic Information.....................................................................................................................23

Basin Hydrologic Estimates ..............................................................................................................25

Mercury Source Estimates ...............................................................................................................25

Acknowledgments.......................................................................................................................................26

References Cited..........................................................................................................................................26

Appendixes ...................................................................................................................................................31

Appendix Data..............................................................................................................................................32

Appendix 1. Water and sediment sample data ..........................................................................32

Appendix 2. Field-blank sample data ...........................................................................................32

Appendix 3. Field-replicate sample data.....................................................................................32

Appendix 4. Fish data......................................................................................................................32

Appendix 5. Ancillary data.............................................................................................................32
v

Figures

1. Map showing streams sampled for mercury, 1998–2005.......................................................2

2. Graph showing statistical distribution of field blanks and stream-water 

 environmental samples of (A) filtered total mercury (FTHg) concentrations 

 and (B) particulate total mercury (PTHg) concentrations, 1998–2005 ...............................20

Tables

1. U.S. Geological Survey National Water-Quality Assessment Program study 

 area abbreviations, study area names, and years sampled, 1998–2005 .............................3

2. Summary of samples collected and methods used for the determination of 

 field properties and streamflow, and laboratory analysis of mercury, organic 

 carbon, major ions, and suspended sediment in stream water, 1998–2005........................5

3. Summary of samples collected and methods used for sample collection 

 and processing and laboratory analysis of mercury, organic matter, sulfur, 

 and size characterization in bed sediment, 1998–2005 ..........................................................9

4. Summary of samples collected and methods used for sample collection 

 and processing and laboratory analysis of mercury in fish and fish age 

 determination, 1998–2005 ..........................................................................................................12

5. Summary of data for stream-water field-blank samples, 1998–2005.................................18

6. Estimates of variability for lower and higher concentration ranges of 

 stream water and bed sediment replicate samples, 1998–2005 .........................................21

7. Estimates of variability for stream water and bed sediment replicate 

 samples, 1998–2005 ....................................................................................................................22

8. Measured total mercury concentrations for certified and standard reference

 materials from the Columbia Environmental Research Center, National Institute 

 of Standards and Technology, and National Research Council Canada used 

 for laboratory quality assurance of fish samples, 1998–2005..............................................24
vi

Conversion Factors

Multiply By To obtain

Length

nanometer (nm) 3.937 10–8 inch (in.)

micrometer (μm) 3.937 10–5 inch (in.)

millimeter (mm) 0.03937 inch (in.)

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

foot (ft) 0.3048 meter (m)

Area

square kilometer (km2

) 0.3861 square mile (mi2)

Volume

liter (L) 33.82 ounce, fluid (fl. oz)

milliliter (mL) 0.03382 ounce, fluid (fl. oz)

Flow rate

cubic foot per second (ft3

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

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

milligram (mg) 3.527 10–5 ounce, avoirdupois (oz)

microgram (μg) 3.527 10–8 ounce, avoirdupois (oz)

nanogram (ng) 3.527×10–11 ounce, avoirdupois (oz)

Yield

kilogram per hectare (kg/ha) 0.893 pound per acre (lb/acre)

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

°F= (1.8×°C) +32

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

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

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25°C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L, 

or part per million), or nanograms per liter (ng/L, or part per trillion). Concentrations of chemical 

constituents in solid media (sediment and fish) are given either in micrograms per gram (μg/g, or 

part per million) or nanograms per gram (ng/g, or part per billion). 
vii

Abbreviations and Acronyms 

AVS acid-volatile sulfide 

BrCl bromine monochloride 

CERC Columbia Environmental Research Center 

CVAFS cold vapor atomic fluorescence

 spectroscopy 

DOC dissolved organic carbon 

DOLT dogfish (Squalus acanthias) liver 

DORM dogfish (Squalus acanthias) muscle 

FMeHg methylmercury in filtered water 

FTHg total mercury in filtered water 

GIRAS Geographic Information Retrieval and

 Analysis System 

GIS Geographic Information System 

> greater than 

HCl hydrochloric acid 

Hg mercury

ITIS Integrated Taxonomic Information System 

< less than 

LOI loss on ignition 

LULC Land Use and Land Cover 

MAS/MILS Mineral Availability System/Mineral

 Industry Location System 

MDL method detection limit 

MeHg methylmercury

MRDS Mineral Resources Data System

N normal (moles of equivalents per liter)

NADP National Atmospheric Deposition Program 

NAWQA National Water-Quality Assessment 

NFM National Field Manual 

NIST National Institute of Standards and

 Technology 

NLCD National Land Cover Data 

NRCC National Research Council Canada 

NRP OCTL National Research Program Organic

 Carbon Transformations Laboratory 

NWIS National Water Information System 

NWQL National Water Quality Laboratory 

PETG polyethylene terephthalate copolyester,

 glycol-modified 

PMeHg methylmercury in particulate matter 

PRISM Parameter-elevation Regressions on

 Independent Slopes Model 

PTHg total mercury in particulate matter 

QC quality control 

RSD relative standard deviation 

SD standard deviation 

SGL Sulfur Geochemistry Laboratory 

SMeHg methylmercury in bed sediment 

SnCl2 stannous chloride 

STATSGO State Soil Geographic 

STHg total mercury in bed sediment 

SUVA specific ultraviolet absorbance 

TEAM Trace Elements Analysis Model 

TERL Trace Element Research Laboratory (at

 Texas A&M University, College

 Station, Texas) 

THg total mercury 

μg/m2 microgram per square meter 

UMeHg methylmercury in unfiltered water 

USEPA U.S. Environmental Protection Agency 

USGS U.S. Geological Survey 

UTHg total mercury in unfiltered water 

WMRL Wisconsin Mercury Research Laboratory

Abstract

The U.S. Geological Survey (USGS) National WaterQuality Assessment (NAWQA) and Toxic Substances Hydrology Programs conducted the National Mercury Pilot Study 

in 1998 to examine relations of mercury (Hg) in water, bed 

sediment and fish in streams across the United States, including Alaska and Hawaii. Water and bed-sediment samples were 

analyzed for total Hg (THg), methylmercury (MeHg), and 

other constituents; fish were analyzed for THg. Similar sampling was conducted at additional streams across the country 

in 2002 and 2004–05. This report summarizes sample collection and processing protocols, analytical methods, environmental data, and quality-assurance data for stream water, bed 

sediment, and fish for these national studies. To extend the 

geographic coverage of the data, this report also includes four 

regional USGS Hg studies conducted during 1998–2001 and 

2004. The environmental data for these national and regional 

Hg studies are provided in an electronic format.

Introduction

In 1998, the U.S. Geological Survey (USGS) National 

Water-Quality Assessment (NAWQA) and Toxic Substances 

Hydrology Programs conducted the National Mercury Pilot 

Study with the goal of examining relations of mercury 

(Hg) in water, bed sediment, and fish in streams across 

the Nation, including Alaska and Hawaii (Krabbenhoft 

and others, 1999; Brumbaugh and others, 2001). At each 

stream site, investigators conducted a one-time sampling 

of water, bed sediment, and fish for the analysis of total Hg 

(THg), methylmercury (MeHg), and other constituents. This 

Pilot study was the first known study in which nationwide 

multimedia sampling occurred jointly with low-level Hg 

speciation analysis (Krabbenhoft and others, 1999). The 

USGS conducted similar national and regional studies at 

additional streams across the Nation during 1998–2001, 

2002, and 2004–05 (fig. 1, table 1). For the remainder of this 

report, results from the 1998 National Mercury Pilot Study are 

described together with results from the national and regional 

studies conducted during 1998–2005. 

This report describes sample collection and processing procedures, analytical methods, environmental data, 

and quality-assurance data for water, bed sediment, and fish 

samples collected from 266 stream sites in 42 NAWQA study 

areas during national studies conducted in 1998, 2002, and 

2004–05, and for samples collected from 101 stream sites 

during regional USGS studies in four study areas conducted 

in 1998–2001 and 2004. Water-quality, bed-sediment, and 

fish data, along with quality-assurance data and ancillary site 

data, are available for download on the Appendix Data page at 

http://pubs.usgs.gov/ds/307/. Analytical data for water include 

filtered THg (FTHg), filtered MeHg (FMeHg), particulate THg 

(PTHg), particulate MeHg (PMeHg), dissolved organic carbon 

(DOC) concentration, specific fractions and specific ultraviolet 

absorbance (SUVA) of DOC, sulfate and suspended-sediment 

concentrations, and suspended-sediment grain size. Bedsediment data include THg, MeHg, loss on ignition (LOI, a 

measure of organic carbon content of sediment), acid-volatile 

sulfide (AVS), and grain size. Fish data include THg, type 

of cut (whole fish, skin-on fillet, skin-off fillet), weight and 

length measurements, and fish age. Data on streamflow, field 

measurements (water temperature, pH, specific conductance, 

and dissolved oxygen concentration), and ancillary site information are provided. 

In all, 367 streams were sampled for national and 

regional studies combined. Fish Hg concentrations (715 

samples) are available for 291 streams; concentrations of Hg 

in water and bed sediment are available for 342 streams. All 

three media (water, bed sediment, and fish) were sampled at 

267 streams. Scudder and others (2009) describe the occurrence and spatial distribution of the Hg data in relation to 

regional and national gradients of Hg source strength and 

land-use/land-cover types; they also discuss associations 

among the Hg data and other measures of stream-water and 

bed-sediment chemistry. 

Data on Mercury in Water, Bed Sediment, and Fish from 

Streams Across the United States, 1998–2005

By Nancy J. Bauch, Lia C. Chasar, Barbara C. Scudder, Patrick W. Moran, Kerie J. Hitt, Mark E. Brigham, 

Michelle A. Lutz, and Dennis A. Wentz
0 400 MILES 0 400 KILOMETERS 170°W 140°W 50°N 0 100 MILES 0 100 KILOMETERS 160°W 156°W 22°N 18°N 110°W 80°W 40°N 20°N EXPLA

State bounStudy area 

(see table 

LERI Study sites 1998 natio

2002 natio2004–05 nCHEY regDELR regNECB regUMIS reg

0 200 200 

YELL CACI GAFL KANS MISE RIOG UMIS MOBL CAZB SANJ ALBE CNBR SPLT SACR LERI CHEY ACAD SOFL UCOL NROK SANT NECB TRIN ACFB WMIC ALMN GRSL CONN WILL DELR HDSN UIRB PUGT LINJ SOCA COOK OAHU TENN WHMI PODL CCYK NVBR

Base composited from National Atlas of the United States boundaries of the United States, 1:2,000,000, 2005; Hitt and Nakagaki National Water-Quality Assessment (NAWQA) study-unit investigations in the conterminous United States 1991-2001, 1:2,000,000, 2006; Hitt and Nakagaki National Water-Quality Assessment (NAWQA) study-unit investigations in the conterminous United States 2001-2012, 1:2,000,000, 2006. Continental United States in Albers Conical Equal Area Projection, referenced to North American Datum of 1983. Alaska in Alaska Albers, referenced to North American Datum of 1983. Hawaii in Hawaii State Plane zone 1 FIPS zone 5101, referenced to North American Datum of 1983.

Figure 1. Streams sampled for mercury, 1998–2005. (Regional studies are CHEY, Cheyenne–Belle Fourche River Basins, 1998–99; DELR, DelawRiver Basin, 1999–2001; NECB, New England Coastal Basins, 1999–2000; and UMIS, Upper Mississippi River Basin, 2004).
Introduction 3

Table 1. U.S. Geological Survey National Water-Quality Assessment Program study area abbreviations, study area names, and years 

sampled, 1998–2005. 

[--, not applicable]

Study area Study area name Year of national mercury study Year of regional mercury study

ACAD Acadian-Pontchartrain Drainages 1998, 2004–05 --

ACFB Apalachicola-Chattahoochee-Flint River Basin 2002 --

ALBE Albemarle-Pamlico Drainage Basin 2002 --

ALMN Allegheny and Monongahela River Basins 1998 --

CACI Canadian-Cimarron River Basins 2004–05 --

CAZB Central Arizona Basins 2004–05 --

CCYK Central Columbia Plateau–Yakima River Basin 2002 --

CHEY Cheyenne–Belle Fourche River Basins 1998 1998–99

CNBR Central Nebraska Basins 2002 --

CONN Connecticut, Housatonic, and Thames River Basins 2002 --

COOK Cook Inlet Basin 1998 --

DELR Delaware River Basin 1998 1999–2001

GAFL Georgia-Florida Coastal Plain 2002 --

GRSL Great Salt Lake Basins 1998 --

HDSN Hudson River Basin 2004–05 --

KANS Kansas River Basin 2004–05 --

LERI Lake Erie–Lake Saint Clair Drainages 2004–05 --

LINJ Long Island–New Jersey Coastal Drainages 1998, 2004–05 --

MISE Mississippi Embayment 2004–05 --

MOBL Mobile River Basin 1998 --

NECB New England Coastal Basins 1998 1999–2000

NROK Northern Rockies Intermontane Basins 1998 --

NVBR Nevada Basin and Range 1998, 2002 --

OAHU Island of Oahu 1998 --

PODL Potomac River Basin and Delmarva Peninsula 2002 --

PUGT Puget Sound Basin 2004–05 --

RIOG Rio Grande Valley 2004–05 --

SACR Sacramento River Basin 1998, 2004–05 --

SANJ San Joaquin–Tulare Basins 2002 --

SANT Santee River Basin and Coastal Drainages 1998, 2004–05 --

SOCA Southern California Coastal Drainages 1998 --

SOFL Southern Florida 2004–05 --

SPLT South Platte River Basin 2002 --

TENN Tennessee River Basin 1998 --

TRIN Trinity River Basin 1998, 2002 --

UCOL Upper Colorado River Basin 1998 --

UIRB Upper Illinois River Basin 1998 --

UMIS Upper Mississippi River Basin 2004–05 2004

WHMI White, Great and Little Miami River Basins 1998, 2002 --

WILL Willamette Basin 2002 --

WMIC Western Lake Michigan Drainages 2002 --

YELL Yellowstone River Basin 1998 --
4 Data on Mercury in Water, Bed Sediment, and Fish from Streams Across the United States, 1998–2005

Data Collection

Site Selection

The streams included in the 1998 National Mercury Pilot 

Study represent a diversity of environmental settings across 

the Nation. Sites were chosen to represent a range of values 

for a number of environmental variables, including wetland 

density and other land-use/land-cover characteristics, pH, 

sulfate, total organic carbon and DOC, and Hg loading (source 

type, strength, and extent). Streams for the 2002 and 2004–05 

studies were selected to include the same range in environmental variables as the 1998 National Mercury Pilot Study, as 

well as to extend geographic coverage, increase representation 

of key land-use and land-cover categories, and increase the 

range of DOC values (both concentration and SUVA). Additional factors considered in site selection were the availability 

of historical water-quality and ecological data and the presence of top predator fish. Because largemouth bass (Micropterus salmoides) is a widely distributed top predator fish, this 

species and other black bass species (Micropterus spp.) were 

emphasized as a first preference for collection.

Data for Hg in water, bed sediment, and fish from 101 

streams sampled during USGS regional Hg studies conducted 

from 1998 through 2001 and during 2004 in four NAWQA 

study areas are included in this report to extend the geographic 

coverage of data. The inclusion of these studies was based on 

availability of Hg data for water, bed sediment, and fish, with 

supporting field properties (water temperature, pH, specific 

conductance, dissolved oxygen concentration) and streamflow. 

The studies are defined as CHEY (Cheyenne–Belle Fourche 

River Basins) regional study (S.K. Sando, USGS, unpub. data, 

2005), DELR (Delaware River Basin) regional study (Brightbill and others, 2003), NECB (New England Coastal Basins) 

regional study (Chalmers and Krabbenhoft, 2001), and UMIS 

(Upper Mississippi River Basin) regional study (Christensen 

and others, 2006). For the first three regional studies, many 

streams were sampled more than once. Only one sample per 

site is included in the data tables to maintain consistency with 

the national studies and to avoid overweighing analysis and 

interpretation in favor of sites with more than one sample. 

For a site with multiple samples, the sample included in the 

data tables had the greatest number of constituents measured, 

was sampled during low flow in August, and(or) was sampled 

during the same week in August as most other samples for 

the regional study. Additional data for the DELR and NECB 

regional studies are available in Brightbill and others (2003) at 

http://nh.water.usgs.gov/projects/nawqa/sw_merc.htm, and on 

the USGS National Water Information System (NWIS) Web at 

http://waterdata.usgs.gov/usa/nwis/qw.

Sample Collection and Processing

Water samples compiled for this database were collected 

and processed for analysis of FTHg, FMeHg, PTHg, PMeHg, 

DOC, sulfate, and suspended sediment (concentration and 

grain size). Bed-sediment samples were collected and processed for analysis of THg and MeHg, LOI, AVS, and grain 

size. Fish samples were collected and processed for analysis 

of THg only; otoliths, scales, or spines were collected from 

fish for age determination. The types of samples collected 

during each study are summarized in tables 2–4. Field properties (water temperature, pH, specific conductance, dissolved 

oxygen concentration) were measured when water and bedsediment samples were collected (Wilde, variously dated). At 

most sites, streamflow also was measured (Rantz and others, 

1982). 

Stream-Water Sample Collection

USGS clean-sampling procedures (sometimes called trace 

element part-per-billion or ppb protocols) and ultra trace-level 

clean techniques (for Hg) were used to collect water samples. 

Detailed descriptions of these procedures and techniques are 

provided in the USGS National Field Manual (NFM) (U.S. 

Geological Survey, variously dated [chapters 1–4]); Fitzgerald 

and Watras (1989); U.S. Environmental Protection Agency 

(1996a); Olson and DeWild (1999); and Lewis and Brigham 

(2004). USGS scientists were trained in clean sampling 

techniques prior to sample collection and processing. Because 

low-level Hg samples are susceptible to contamination from 

many sources, specific measures were required for collecting 

Hg samples to prevent contamination (Lewis and Brigham, 

2004). Field personnel wore shoulder-length polyethylene 

gloves under powder-free, wrist-length nitrile or latex gloves. 

Particle-shedding clothing (for example, fleece jackets, wool 

sweaters, or soiled field clothing) was avoided; outerwear, if 

needed, was clean, nylon-shell (or comparable material) clothing. Field personnel were instructed to open sample containers 

while holding them upwind from themselves or with the container inside a sample-processing chamber (Lane and others, 

2003). 

Stream-water samples were collected during low-flow 

conditions between late spring and early fall, depending on 

the general geographic location. For streams known to be well 

mixed, dip samples for Hg, DOC, sulfate, and suspendedsediment analyses were obtained from the approximate 

centroid of flow. For streams not known to be well mixed, 

an isokinetic, depth-integrated sample or a multiple-vertical 

composite sample was collected (Wilde and others, 1999; 

Lewis and Brigham, 2004). At wadeable sites, the in-channel 

collection site was approached from downstream, and 

sample containers were extended upstream into the current 

to avoid disturbance of sample water by field personnel. At 

nonwadeable sites, samples were collected from the bow of 

a boat moving upstream at low speed; sample bottles and 
Table 2. Summary of samples collected and methods used for the determination of field properties and streamflow, and laboratory analysis of mercions, and suspended sediment in stream water, 1998–2005.[See Appendix 1 for definition of column names and units of measurement. The 1998 National Mercury Pilot Study was conducted with the U.S. Geological Survey Toxic SubNational Water-Quality Assessment Program. CHEY-reg, regional study of mercury in the Cheyenne–Belle Fourche River Basins; DELR-reg, regional study of mercury in the reg, regional study of mercury in the New England Coastal Basins; UMIS-reg, regional study of mercury in the Upper Mississippi River Basin; --, not applicable; USGS, U.S. Wisconsin Mercury Research Laboratory; NRP OCTL, National Research Program Organic Carbon Transformations Laboratory; 1998, National Mercury Pilot Study conductestudy of mercury conducted in 2004–05; NWQL, National Water Quality Laboratory; 2002, national study of mercury conducted in 2002. See text for methods used in sample 

Constituent

Column name 

from Appendix 1. 

Water and

sediment 

sample data

National mercury studies CHEY- reg DELR- reg NECB- reg UMIS- reg

Laboratory 

1998 2002 2004– 05 1998– 99 1999– 2000 1999– 2000 2004

Field properties and streamflow

Water temperature Temp yes yes yes yes yes yes yes -- WpH pH yes yes yes yes yes yes yes -- W

Specific conductance SC yes yes yes yes yes yes yes -- WDissolved oxygen DO yes yes yes yes yes yes yes -- R

Streamflow Q_inst yes yes yes yes yes yes yes -- W

Analytes

MercuryUnfiltered total 

mercury

UTHg yes no no yes yes yes no USGS WMRL U

OO

Filtered total mercury FTHg yes (CHEY only) yes yes yes no no yes USGS WMRL U

OO
Table 2. Summary of samples collected and methods used for the determination of field properties and streamflow, and laboratory analysis of mercions, and suspended sediment in stream water, 1998–2005.—Continued [See Appendix 1 for definition of column names and units of measurement. The 1998 National Mercury Pilot Study was conducted with the U.S. Geological Survey Toxic SubNational Water-Quality Assessment Program. CHEY-reg, regional study of mercury in the Cheyenne–Belle Fourche River Basins; DELR-reg, regional study of mercury in the reg, regional study of mercury in the New England Coastal Basins; UMIS-reg, regional study of mercury in the Upper Mississippi River Basin; --, not applicable; USGS, U.S. Wisconsin Mercury Research Laboratory; NRP OCTL, National Research Program Organic Carbon Transformations Laboratory; 1998, National Mercury Pilot Study conductestudy of mercury conducted in 2004–05; NWQL, National Water Quality Laboratory; 2002, national study of mercury conducted in 2002. See text for methods used in sample 

Constituent Column name from Appendix 1. Water and sediment sample data National mercury studies CHEY- reg DELR- reg NECB- reg UMIS- reg Laboratory 

1998 2002 2004– 05 1998– 99 1999– 2000 1999– 2000 2004 Mercury Unfiltered methyl- mercury UMeHg yes no no yes yes yes no USGS WMRL B

HOD

Filtered methyl­ mercury FMeHg yes (CHEY only) yes yes yes no no yes USGS WMRL B

HOD

Particulate total mercury PTHg no yes yes no no no yes USGS WMRL U

O

Particulate methyl- mercury PMeHg no yes yes no no no yes USGS WMRL D

D
Table 2. Summary of samples collected and methods used for the determination of field properties and streamflow, and laboratory analysis of mercions, and suspended sediment in stream water, 1998–2005.—Continued[See Appendix 1 for definition of column names and units of measurement. The 1998 National Mercury Pilot Study was conducted with the U.S. Geological Survey Toxic SubNational Water-Quality Assessment Program. CHEY-reg, regional study of mercury in the Cheyenne–Belle Fourche River Basins; DELR-reg, regional study of mercury in the reg, regional study of mercury in the New England Coastal Basins; UMIS-reg, regional study of mercury in the Upper Mississippi River Basin; --, not applicable; USGS, U.S. Wisconsin Mercury Research Laboratory; NRP OCTL, National Research Program Organic Carbon Transformations Laboratory; 1998, National Mercury Pilot Study conductestudy of mercury conducted in 2004–05; NWQL, National Water Quality Laboratory; 2002, national study of mercury conducted in 2002. See text for methods used in sample 

Constituent

Column name 

from Appendix 1. 

Water and

sediment 

sample data

National mercury studies CHEY- reg DELR- reg NECB- reg UMIS- reg

Laboratory 

1998 2002 2004– 05 1998– 99 1999– 2000 1999– 2000 2004

Organic carbonDissolved organic 

carbon

DOC yes yes yes yes yes yes yes USGS NRP OCTL 

(1998; 2004–05, 

NECB-reg, UMISreg); USGS WMRL 

(CHEY-reg)

A

USGS NWQL (2002, 

DELR-reg)

B

Hydrophobic acid 

fraction

HPOA_FRAC_PCT yes no yes no no no yes USGS NRP OCTL A

Hydrophilic acid 

fraction, low molecular weight

HPI_FRAC no no yes no no no yes USGS NRP OCTL A

Transphilic organic 

acid fraction

TPIA_FRAC no no yes no no no yes USGS NRP OCTL A

Hydrophilic acid 

fraction

HPIA_FRAC yes no no no no no no USGS NRP OCTL A

Specific ultraviolet 

absorbance

SUVA yes no yes no no no yes USGS NRP OCTL W
Table 2. Summary of samples collected and methods used for the determination of field properties and streamflow, and laboratory analysis of mercions, and suspended sediment in stream water, 1998–2005.—Continued [See Appendix 1 for definition of column names and units of measurement. The 1998 National Mercury Pilot Study was conducted with the U.S. Geological Survey Toxic SubNational Water-Quality Assessment Program. CHEY-reg, regional study of mercury in the Cheyenne–Belle Fourche River Basins; DELR-reg, regional study of mercury in the reg, regional study of mercury in the New England Coastal Basins; UMIS-reg, regional study of mercury in the Upper Mississippi River Basin; --, not applicable; USGS, U.S. Wisconsin Mercury Research Laboratory; NRP OCTL, National Research Program Organic Carbon Transformations Laboratory; 1998, National Mercury Pilot Study conductestudy of mercury conducted in 2004–05; NWQL, National Water Quality Laboratory; 2002, national study of mercury conducted in 2002. See text for methods used in sample 

Constituent Column name from Appendix 1. Water and sediment sample data National mercury studies CHEY- reg DELR- reg NECB- reg UMIS- reg Laboratory 

1998 2002 2004– 05 1998– 99 1999– 2000 1999– 2000 2004 Major ions Sulfate Sulfate yes yes yes yes yes yes yes USGS WMRL; USGS NWQL; USGS Atlanta, Ga. (NECB-reg, 1999 samples) F

Suspended sediment Concentration SS yes yes yes yes yes no no USGS Sediment Labora- tory (Vancouver, Wash.; Iowa City, Iowa) G

Grain size (percent fines) SS_Pct_063 yes yes yes yes no no no USGS Sediment Labora- tory (Vancouver, Wash.; Iowa City, Iowa) G
Table 3. Summary of samples collected and methods used for sample collection and processing and laboratory analysis of mercury, organic mattecharacterization in bed sediment, 1998–2005.[See Appendix 1 for definition of column names and units of measurement. The 1998 National Mercury Pilot Study was conducted with the U.S. Geological Survey Toxic SubNational Water-Quality Assessment Program. CHEY-reg, regional study of mercury in the Cheyenne–Belle Fourche River Basins; DELR-reg, regional study of mercury in the reg, regional study of mercury in the New England Coastal Basins; UMIS-reg, regional study of mercury in the Upper Mississippi River Basin; USGS, U.S. Geological SurveyResearch Laboratory; 1998, National Mercury Pilot Study conducted in 1998; SGL, Sulfur Geochemistry Laboratory; 2002, national study of mercury conducted in 2002; 2004conducted in 2004–05]

Analyte

Column name from 

Appendix 1. Water 

and sediment 

sample data

National mercury studies CHEY- reg DELR- reg NECB- reg UMIS- reg Sample collection and processing 

reference

Labora

1998 2002 2004–05 

1998– 99 1999– 2000 1999– 2000 2004

MercuryTotal mercury STHg yes yes yes yes yes yes yes Krabbenhoft, D.P., 

Wiener, J.G., Brumbaugh, W.G., Olson, M.L., DeWild, J.F., and Sabin, T.J., 1999

USGS W

Lutz, M.A., 

Brigham, M.E., and Marvin-DiPasquale, Mark, 2008

Methylmercury SMeHg yes yes yes yes yes yes yes Krabbenhoft, D.P., 

Wiener, J.G., Brumbaugh, W.G., Olson, M.L., DeWild, J.F., and Sabin, T.J., 1999

USGS W

Lutz, M.A., 

Brigham, M.E., and Marvin-DiPasquale, Mark, 2008
Table 3. Summary of samples collected and methods used for sample collection and processing and laboratory analysis of mercury, organic mattecharacterization in bed sediment, 1998–2005.—Continued [See Appendix 1 for definition of column names and units of measurement. The 1998 National Mercury Pilot Study was conducted with the U.S. Geological Survey Toxic SubNational Water-Quality Assessment Program. CHEY-reg, regional study of mercury in the Cheyenne–Belle Fourche River Basins; DELR-reg, regional study of mercury in the reg, regional study of mercury in the New England Coastal Basins; UMIS-reg, regional study of mercury in the Upper Mississippi River Basin; USGS, U.S. Geological SurveyResearch Laboratory; 1998, National Mercury Pilot Study conducted in 1998; SGL, Sulfur Geochemistry Laboratory, 2002; national study of mercury conducted in 2002; 2004conducted in 2004–05] Analyte Column name from Appendix 1. Water and sediment sample data National mercury studies CHEY- reg DELR- reg NECB- reg UMIS- reg Sample collection and processing reference Labora

1998 2002 2004–05 

1998– 99 1999– 2000 1999– 2000 2004 Organic matter Loss on ignition LOI yes yes yes no yes yes yes Krabbenhoft, D.P., Wiener, J.G., Brumbaugh, W.G., Olson, M.L., DeWild, J.F., and Sabin, T.J., 1999 USGS W

Lutz, M.A., Brigham, M.E., and Marvin-Di- Pasquale, Mark, 2008 Sulfur Acid-volatile sulfide AVS_DryWt, Pct_ AVS_WetWt yes yes yes no no yes yes Krabbenhoft, D.P., Wiener, J.G., Brumbaugh, W.G., Olson, M.L., DeWild, J.F., and Sabin, T.J., 1999 USGS W

(1998, 

re

Lutz, M.A., Brigham, M.E., and Marvin-Di- Pasquale, Mark, 

2008
Table 3. Summary of samples collected and methods used for sample collection and processing and laboratory analysis of mercury, organic mattecharacterization in bed sediment, 1998–2005.—Continued[See Appendix 1 for definition of column names and units of measurement. The 1998 National Mercury Pilot Study was conducted with the U.S. Geological Survey Toxic SubNational Water-Quality Assessment Program. CHEY-reg, regional study of mercury in the Cheyenne–Belle Fourche River Basins; DELR-reg, regional study of mercury in the reg, regional study of mercury in the New England Coastal Basins; UMIS-reg, regional study of mercury in the Upper Mississippi River Basin; USGS, U.S. Geological SurveyResearch Laboratory; 1998, National Mercury Pilot Study conducted in 1998; SGL, Sulfur Geochemistry Laboratory, 2002; national study of mercury conducted in 2002; 2004conducted in 2004–05]

Analyte

Column name from 

Appendix 1. Water 

and sediment 

sample data

National mercury studies CHEY- reg DELR- reg NECB- reg UMIS- reg Sample collection and processing 

reference

Labora

1998 2002 2004–05 

1998– 99 1999– 2000 1999– 2000 2004

Sulfur

Krabbenhoft, D.P., 

Wiener, J.G., Brumbaugh, W.G., Olson, M.L., DeWild, J.F., and Sabin, T.J., 1999

USGS SG

and 20

UMI

Lutz, M.A., 

Brigham, M.E., and Marvin-DiPasquale, Mark, 2008

Size characterizationGrain size (percent fines) Bed_Pct_063 yes yes yes no yes no no Krabbenhoft, D.P., Wiener, J.G., 

Brumbaugh, W.G., Olson, M.L., DeWild, J.F., and Sabin, T.J., 1999

USGS Sed

Laborat(VancouWash.; ICity, Iow

Lutz, M.A., 

Brigham, M.E., and Marvin-DiPasquale, Mark, 2008
Table 4. Summary of samples collected and methods used for sample collection and processing and laboratory analysis of mercury in fish and fish 1998–2005. [See Appendix 4 for definition of column names and units of measurement. The 1998 National Mercury Pilot Study was conducted with the U.S. Geological Survey Toxic SubNational Water-Quality Assessment Program. CHEY-reg, regional study of mercury in the Cheyenne–Belle Fourche River Basins; DELR-reg, regional study of mercury in the reg, regional study of mercury in the New England Coastal Basins; UMIS-reg, regional study of mercury in the Upper Mississippi River Basin; --, not applicable; USGS, U.S. Columbia Environmental Research Center; NWQL, National Water Quality Laboratory; TERL, Trace Element Research Laboratory; WMRL, Wisconsin Mercury Research La

Analyte Column name from Appendix 4. Fish data National mercury studies CHEY-reg DELR-reg NE

1998 2002 2004–05 1998–99 1999 2001 199

Mercury in fish Total mercury in fish tissue THg_Dry, THG_Wet yes yes yes No samples collected yes yes 

Laboratory -- USGS CERC USGS NWQL Texas A&M Uni- versity TERL -- USGS WMRL USGS NWQL USGS 

Reference -- Scudder, B.C., Chasar, L.S., DeWeese, L.R., Brigham, M.E., Wentz, D.A., and Brum- baugh, W.G., 2008 Scudder, B.C., Chasar, L.S., DeWeese, L.R., Brigham, M.E., Wentz, D.A., and Brumbaugh, W.G., 2008 Scudder, B.C., Chasar, L.S., DeWeese, L.R., Brigham, M.E., Wentz, D.A., and Brum- baugh, W.G., 2008 -- Scudder, B.C., Chasar, L.S., DeWeese, L.R., Brigham, M.E., Wentz, D.A., and Brumbaugh, W.G., 2008 Scudder, B.C., Chasar, L.S., DeWeese, L.R., Brigham, M.E., Wen- tz, D.A., and Brumbaugh, W.G., 2008 Scudd

ChDeWL.RBriM.ED.ABruW.G

Brumbaugh, W.G., Krabbenhoft, D.P., Helsel, D.R., Wie- ner, J.G., and Echols, K.R., 2001 U.S. Environmen- tal Protection Agency, 1996b U.S. Environmen- tal Protection Agency, 1998 Brumbaugh, W.G., Krab- benhoft, D.P., Helsel, D.R., Wiener, J.G., and Echols, K.R., 2001 U.S. Envi- ronmental Protection Agency, 1996b Brum

W.GbenD.PD.RnerEch200

Olson, M.L., and 

DeWild, J.F., 1999

U.S. Environmental Protection 

Agency, 1996c

Olson, M.L., 

and DeWild, J.F., 1999

U.S. Environmental 

Protection Agency, 1996c

Olson

and J.F.
Table 4. Summary of samples collected and methods used for sample collection and processing and laboratory analysis of mercury in fish and fish 1998–2005.[See Appendix 4 for definition of column names and units of measurement. The 1998 National Mercury Pilot Study was conducted with the U.S. Geological Survey Toxic SubNational Water-Quality Assessment Program. CHEY-reg, regional study of mercury in the Cheyenne–Belle Fourche River Basins; DELR-reg, regional study of mercury in the reg, regional study of mercury in the New England Coastal Basins; UMIS-reg, regional study of mercury in the Upper Mississippi River Basin; --, not applicable; USGS, U.S. Columbia Environmental Research Center; NWQL, National Water Quality Laboratory; TERL, Trace Element Research Laboratory; WMRL, Wisconsin Mercury Research La

Analyte

Column name 

from Appendix 

4. Fish data

National mercury studies CHEY-reg DELR-reg NE

1998 2002 2004–05 1998–99 1999 2001 199

Mercury in fishOtoliths, 

scales, spines

Age, Ave_Age yes yes yes No samples 

collected

No samples collected No samples collected No sa

col

Laboratory -- USGS CERC USGS South 

Carolina Cooperative Wildlife Research Unit Laboratory

USGS South 

Carolina Cooperative Wildlife Research Unit Laboratory

-- -- -- 

Reference -- Scudder, B.C., 

Chasar, L.S., DeWeese, L.R., Brigham, M.E., Wentz, D.A., and Brumbaugh, W.G., 2008

Scudder, B.C., 

Chasar, L.S., DeWeese, L.R., Brigham, M.E., Wentz, D.A., and Brumbaugh, W.G., 2008

Scudder, B.C., 

Chasar, L.S., DeWeese, L.R., Brigham, M.E., Wentz, D.A., and Brumbaugh, W.G., 2008

-- -- -- 

Brumbaugh, W.G., 

Krabbenhoft, D.P., Helsel, D.R., Wiener, J.G., and Echols, K.R., 2001

Brumbaugh, W.G., 

Krabbenhoft, D.P., Helsel, D.R., Wiener, J.G., and Echols, K.R., 2001

Brumbaugh, 

W.G., Krabbenhoft, D.P., Helsel, D.R., Wiener, J.G., and Echols, K.R., 2001

Jearld, A., Jr., 

1983

Jearld, A., Jr., 1983 Jearld, A., Jr., 

1983

Porak, W., Coleman, W.S., and 

Crawford, S., 1988.

Porak, W., Coleman, W.S., and 

Crawford, S., 1988.

Porak, W., Coleman, W.S., and 

Crawford, S., 1988.
14 Data on Mercury in Water, Bed Sediment, and Fish from Streams Across the United States, 1998–2005

containers were positioned in front of the boat and extended 

upstream into the current. Samples from nonwadeable 

sites were also collected from bridges using the reed-andsuspension method and dip or isokinetic, depth-integrated 

methods on the upstream side of the bridge (Wilde and others, 

1999). 

Dip samples were collected for THg and MeHg in 

fluorocarbon polymer (Teflon®) bottles supplied by the 

USGS Wisconsin Mercury Research Laboratory (WMRL) 

in Middleton, Wis., or in new polyethylene terephthalate 

copolyester, glycol-modified (PETG) containers; the latter 

were typically used in 2002 and beyond. All fluorocarbon 

polymer sample bottles were rigorously cleaned by the 

WMRL (Olson and DeWild, 1999), partially filled with 1 

percent hydrochloric acid (HCl, OmniTraceTM) and shipped 

in double zip-seal plastic bags. All PETG bottles (Nalgene®) 

were new (cap seals intact) and were stored in double zipseal plastic bags until use. Dip samples for DOC and sulfate 

analysis were collected using a Teflon® bottle or from the 

PETG bottles that were used for the Hg sample. Samples for 

suspended-sediment concentration and grain-size analysis 

were collected in widemouth 1-liter plastic bottles or other 

appropriate suspended-sediment sampling bottle, using 

methods comparable to those used for the other water-quality 

samples (as noted above, either dip in approximate centroid of 

flow, or with an isokinetic sampler).

Stream-Water Sample Processing

Stream-water samples were processed for the analysis 

of unfiltered THg (UTHg) and unfiltered MeHg (UMeHg) or 

for FTHg, FMeHg, PTHg, and PMeHg. The type of analysis 

for each study is shown in table 2. In this report, “filtered” 

refers to constituents that pass through a filter, and includes 

dissolved and filter-passing colloidally bound constituents. 

“Particulate” refers to constituents retained on the filter and 

includes sediment and organic detritus.

Stream-water samples collected for the analysis of UTHg 

were preserved in the field by addition of 6 N HCl to a final 

concentration of approximately 1 percent by volume. Samples 

collected for UMeHg analysis were frozen immediately on dry 

ice until analysis. Samples collected for analysis of FTHg and 

FMeHg were vacuum filtered through combusted, 47 millimeter (mm), 0.7-micrometer (μm) quartz-fiber filters in the 

field in a sample processing chamber (Lane and others, 2003); 

preserved with 6 N HCl to a concentration of approximately 1 

percent by volume; double bagged in zip-seal bags; and stored 

in a closed dark cooler until analysis (Olson and DeWild, 

1999; Lewis and Brigham, 2004). The volume of water filtered 

through a filter was recorded for subsequent conversion of 

particulate amount to mass per volume. The quartz-fiber filters 

were transferred to Teflon® Petri dishes, double-bagged in 

new plastic zip-seal bags, and immediately placed on dry ice; 

filters were maintained frozen until analysis of PTHg and 

PMeHg.

Samples collected for the analysis of DOC and sulfate 

were processed in the field as directed by the USGS NFM 

(Lane and others, 2003; Wilde and others, 2004). DOC samples were filtered through combusted, 0.7-μm glass fiber filters, chilled, and stored at 4° Celsius (C). Sulfate samples were 

filtered through 0.45-μm membrane or polysulfone capsule 

filters, and stored until analysis. Unfiltered and unpreserved 

suspended-sediment samples were stored in original collection 

bottles until analysis. 

Bed-Sediment Sample Collection

Detailed descriptions of bed-sediment sampling methods 

for all USGS NAWQA Hg sampling efforts and regional Hg 

studies are provided in Krabbenhoft and others (1999) and 

Lutz and others (2008). Clean sampling methods were adapted 

from Shelton and Capel (1994). An acid-cleaned Teflon® 

or plastic scoop was used to collect the top (approximately) 

2 centimeter (cm) of bed sediment from 5 to 10 depositional 

areas; these samples were composited in acid-cleaned 

Teflon®, plastic, or glass containers into one sample for each 

stream site. 

Bed-Sediment Sample Processing

Bed-sediment composites were immediately homogenized by stirring with a Teflon spatula and subsampled in 

the field. Bed-sediment subsamples for analysis of total Hg 

(STHg) and MeHg (SMeHg) were placed in acid-cleaned 

polypropylene or Teflon® vials and stored frozen until analysis. AVS subsamples were placed in clean polypropylene jars, 

and samples for the 1998 and 2002 national studies and NECB 

regional study were preserved with 0.3 milliliter of zinc 

acetate. All AVS samples were stored frozen until analysis. 

Subsamples for the analysis of bed-sediment grain size were 

placed in polypropylene jars and stored until analysis. Detailed 

descriptions of the steps for processing bed-sediment samples 

are available in Krabbenhoft and others (1999) and Lutz and 

others (2008). 

Fish Sampling and Processing

Fish sampling and sample processing methods are 

detailed in Scudder and others (2008). Field personnel 

collected up to eight largemouth bass or other black bass 

(Micropterus spp.), approximately 3 to 4 years old, whenever 

possible, at each sampling site. If bass were difficult to collect 

in the target age range or were not present in a study area, 

alternate predator fish (piscivorous or insectivorous) species 

were chosen from a priority list provided in Scudder and others (2008). Multiple sampling methods were used, including 

electrofishing, seining, and hook and line. 

Fish samples collected during the 1998 National Mercury Pilot Study were rinsed in stream water, measured as 

individual samples for weight and length, placed whole in 
Analytical Methods 15

double zip-seal bags, and frozen until they were analyzed 

(Brumbaugh and others, 2001). For the 2002 and 2004–05 

national studies and the NECB regional study, fish were 

weighed, measured and processed in the field to obtain axial 

muscle (skinless fillet) tissue, as detailed by Scudder and others (2008). Fillets were rinsed with deionized water, placed in 

double zip-seal bags, and frozen until analysis. For the DELR 

regional study, fish were weighed and measured in the field 

and processed either in the laboratory or field to obtain fillet 

samples. Fish collected during the UMIS regional study were 

stored on wet ice in plastic bags with sample water from the 

collection site until transfer to refrigerators. After length and 

weight measurements in a laboratory setting, fish were frozen 

until analysis (Christensen and others, 2006). Fish samples 

were not collected during the CHEY regional study.

Otoliths, scales, or spines were obtained from each fish 

collected during the national studies for age determination. 

Similar materials were not obtained from fish collected during 

the DELR, NECB, and UMIS regional studies.

Analytical Methods

Multiple analytical laboratories were used for the national 

and regional Hg studies; a summary of methods and laboratories is provided in tables 2–4.

Stream Water

All samples for unfiltered, filtered, and particulate THg 

and MeHg were analyzed by the WMRL. The analytical 

procedures for determining THg in unfiltered and filtered 

water are detailed in U.S. Environmental Protection Agency 

(USEPA) Method 1631 (U.S. Environmental Protection 

Agency, 2002), as adapted by the WMRL (Olson and others, 

1997; Olson and DeWild, 1999). Briefly, THg samples were 

oxidized with bromine monochloride (BrCl) under acidic 

conditions, treated with stannous chloride (SnCl2

) to reduce 

ionic Hg to elemental Hg, and quantified with cold vapor 

atomic fluorescence spectroscopy (CVAFS). Samples were 

analyzed for MeHg by distillation, aqueous phase ethylation, 

purge and trap of volatile ethylmercury derivatives, gaschromatographic separation, pyrolization, and CVAFS 

determination (Bloom, 1989, as modified by Horvat and 

others, 1993; Olson and DeWild, 1999; DeWild and others, 

2002). Concentrations of PTHg and PMeHg were determined 

by analyzing the 0.7-μm quartz-fiber filters obtained from 

the stream-water filtration for FTHg and FMeHg. Filters for 

PTHg analysis were thawed and placed in Teflon bottles, 

and BrCl was added. Samples were oxidized, treated with 

SnCl2

, and analyzed according to USEPA Method 1631 using 

CVAFS (U.S. Environmental Protection Agency, 2002; Olund 

and others, 2004). Filters for PMeHg analysis were placed 

in Teflon bottles for distillation and reagents were added. 

Samples were distilled, and the distillates were analyzed 

following the procedures described for aqueous MeHg 

(DeWild and others, 2002; DeWild and others, 2004). 

Concentrations of DOC for the 1998 and 2004–05 

national studies and the NECB and UMIS regional studies 

were determined by the USGS National Research Program 

Organic Carbon Transformations Laboratory (NRP OCTL) 

in Boulder, Colo., using a persulfate wet oxidation method 

as described in Aiken (1992). DOC samples for the CHEY 

regional study were analyzed at the WMRL using the same 

wet oxidation method. Water samples for the 2002 national 

study and the DELR regional study were analyzed for DOC 

concentration at the USGS National Water Quality Laboratory 

(NWQL) in Denver, Colo., following a UV-promoted persulfate oxidation and infrared spectroscopy (Brenton and Arnett, 

1993). For samples analyzed by the NRP OCTL, carbon fractions of DOC (hydrophobic organic acids, hydrophilic acids, 

and transphilic acids) were measured by a modified version 

of the XAD-8 and XAD-4 methods (Aiken and others, 1992). 

SUVA was calculated by measuring the UV absorbance at 254 

nanometers and dividing by the DOC concentration (Weishaar 

and others, 2003). 

Water samples were analyzed for sulfate by the WMRL 

(1998 National Mercury Pilot Study), the NWQL (2002 and 

2004–05 NAWQA national studies; CHEY, DELR, NECB, 

and UMIS regional studies), and the USGS laboratory in 

Atlanta, Ga. (1999 NECB regional study). All laboratories 

used ion chromatography for analysis (Fishman and Friedman, 

1989).

Suspended-sediment samples were analyzed by the 

USGS sediment laboratories in Vancouver, Wash., and Iowa 

City, Iowa, for concentration and grain size (percent fines) 

(Guy, 1969). 

Bed Sediment

Bed-sediment samples were analyzed by the WMRL for 

STHg and SMeHg concentrations using similar analytical procedures as those described above for aqueous and particulate 

samples, with some modification (DeWild and others, 2004; 

Olund and others, 2004). The WMRL also determined LOI, a 

measure of organic carbon content of sediment, as described 

by Heiri and others (2001), and sediment dry weight (percent 

solids) by drying wet sediment at 105°C. 

AVS was analyzed by the WMRL (1998 National Mercury Pilot Study, NECB regional study) and by the USGS 

Sulfur Geochemistry Laboratory (SGL) (2002 and 2004–05 

national studies, UMIS regional study) in Reston, Va. The 

WMRL procedure required acidification of each sample with 

6 N HCl, trapping released sulfide in an antioxidant buffer, 

and determination of sulfide by ion-specific electrode (Allen 

and others, 1991). At the SGL, AVS was separated using an 

HCl extraction and reprecipitation as silver sulfide. Percent by 

weight of AVS in the sediment sample was subsequently determined gravimetrically (Canfield and others, 1986; Tuttle and 

others, 1986; Allen and others, 1991; Bates and others, 1993). 
16 Data on Mercury in Water, Bed Sediment, and Fish from Streams Across the United States, 1998–2005

Bed sediment was analyzed for grain size (percent fines) by 

the USGS sediment laboratories in Vancouver, Wash., and 

Iowa City, Iowa (Guy, 1969). 

Fish

Fish samples collected during the 1998 National Mercury Pilot Study were processed and analyzed at the USGS 

Columbia Environmental Research Center (CERC) in Columbia, Mo. Fish less than approximately 50 grams (g) in weight 

were analyzed whole or whole minus head; fish greater than 

50 g were filleted to obtain a sample of skin-off axial muscle 

(Brumbaugh and others, 2001). All whole fish and fish muscle 

tissue were freeze-dried to a constant weight, finely ground, 

and stored in a dessicator until analysis. For each site, samples 

from the same species and of similar size were composited 

and analyzed as one sample. Fish samples were analyzed for 

THg using an acid/microwave digestion, BrCl oxidation, and 

CVAFS (Olson and DeWild, 1999; Brumbaugh and others, 

2001). Only THg was analyzed because approximately 95 

percent of Hg in fish is MeHg (Huckabee and others, 1979; 

Bloom, 1992; Wiener and Spry, 1996). 

Fillet samples for the 2002 national study were analyzed 

at the NWQL. Each sample was freeze-dried to constant 

weight and finely ground, and fish of a single species from 

each site were analyzed as one composite sample. THg was 

determined using acid/microwave digestion, BrCl oxidation, 

and CVAFS in accordance with USEPA method 3052 for 

digestion (U.S. Environmental Protection Agency, 1996b) and 

USEPA method 7474 (U.S. Environmental Protection Agency, 

1996c) for Hg analysis. 

Fillet samples collected during the 2004–05 national 

study were analyzed for THg at the Texas A&M University 

Trace Element Research Laboratory (TERL) in College Station, Tex. Each sample was freeze-dried to constant weight, 

finely ground, and analyzed individually (1–13 fish per site) 

using USEPA method 7473 (combustion-trapping-atomic 

absorption; U.S. Environmental Protection Agency, 1998).

Skin-off fillet samples collected during the DELR 

regional study in 1999 and during the NECB regional study 

were analyzed at the WRML using a process similar to that 

used by CERC to analyze the 1998 National Mercury Pilot 

Study fish samples. The skin-off fillets collected during the 

2001 DELR regional study were analyzed by the NWQL 

according to methods described for the 2002 national fish 

samples. 

Fish collected for the UMIS regional study were analyzed 

as composites samples of whole fish, skin-on fillets, or skin-off 

fillets by the River Studies Center, University of Wisconsin, 

La Crosse, Wis. (Christensen and others, 2006). Subsamples 

from composite samples were digested using a modification of 

USEPA Method 1631 (U.S. Environmental Protection Agency, 

2002; Christensen and others, 2006). Digested subsamples 

were analyzed by flow-injection CVAFS.

For the national studies and the UMIS regional study, 

moisture content (percent water) was determined by weight 

loss upon freeze-drying and is reported as the weight percentage of the original wet sample. Moisture content was not 

reported for the DELR and NECB regional studies. Fish ages 

were estimated from sagittal otoliths, scales, or spines by the 

CERC (1998 National Mercury Pilot Study) or the USGS 

South Carolina Cooperative Fish and Wildlife Research Unit 

(2002 and 2004–05 national studies) (Jearld, 1983; Porak and 

others, 1988; Brumbaugh and others, 2001; Scudder and others, 2008). 

The Integrated Taxonomic Identification System (ITIS) 

codes (http://www.itis.gov/) for all fish species sampled are 

included in Appendix 4.

Quality Assurance

The quality of stream-water, bed-sediment, and fish 

data was assured through a variety of quality-control (QC) 

samples collected in the field and laboratory. These included 

blank and replicate samples, spike recoveries, and certified 

and standard reference materials. Blank and replicate field QC 

samples were used to assess the bias and variability that may 

be introduced by sample collection, processing, and analysis. 

Laboratory QC samples were routinely analyzed to calibrate 

instruments, identify procedural problems, validate data, and 

provide defensible analytical data. Field QC samples will be 

discussed for water and bed sediment only; information on 

laboratory QC samples for water and bed sediment is available 

in references listed in tables 2–4. Field QC samples were not 

collected for fish because the nature of this medium does not 

allow collection of true field blanks or replicates. Laboratory 

QC samples to be discussed for fish include blanks, replicate 

and spiked samples, and reference materials. Summary and 

analysis of QC data are grouped by analyte and laboratory. 

Quality of Water and Bed-Sediment Data

Field-blank samples for water were collected using 

inorganic- and organic-free water that contained no detectable 

concentrations of the analytes of interest. The blank water was 

processed in the field and analyzed identically to environmental samples. Field-blank samples were used to determine if 

contamination of samples occurred during sampling, processing, and analysis. 

Most field-replicate samples were two or more samples 

collected in sequence, processed, and analyzed using identical methods. Two separate field samples were split into 

subsamples to make two replicate sets. For filtered samples, 

the filter was changed before the processing of each sample. 

Replicate sample data (environmental sample and additional 

QC samples) yield information on overall precision of the field 

and laboratory methods. 
Quality Assurance 17

Blanks

Data for field-blank samples are summarized in table 5. 

UMeHg, FMeHg, PMeHg, and sulfate were not detected in 

any blank samples. DOC concentrations in blank samples 

from the 2002 national study were not detected above the 

method detection limit (MDL); six samples had concentrations 

that were detected at or below the MDL.

Concentrations of UTHg, FTHg, PTHg, and DOC 

(2004–05 national study) were greater than the respective 

MDLs in multiple blank samples. All six blank samples for 

UTHg had concentrations greater than the MDL of 0.04 

nanogram per liter (ng/L). Concentrations of UTHg in all 

environmental samples for the 1998 National Mercury Pilot 

Study and the CHEY, DELR, and NECB regional studies were 

greater than the maximum blank concentration of 0.22 ng/L. 

For these studies, UTHg concentrations were measured values 

for unfiltered samples. Concentrations of UTHg for the 2002 

and 2004–05 national studies and UMIS regional study were 

calculated values (sum of FTHg and PTHg); blank values are 

not reported for calculated UTHg.

Most (25 of 27) blank samples for FTHg had concentrations detected above the MDL of 0.04 ng/L, with concentrations ranging from 0.02 to 0.4 ng/L. There was, however, little 

overlap between concentrations of FTHg in blank samples 

and most environmental samples (fig. 2A). Concentrations of 

PTHg were detected in less than 50 percent (8 of 18) of the 

blank samples. Overlap of some of the higher PTHg concentrations in blanks with concentrations in environmental 

samples may indicate positive bias of PTHg for some environmental data values (fig. 2B).

For the 2004–05 national study, only two blank samples 

were available for DOC and SUVA analysis. To increase 

sample size for analysis, data for these two samples were 

combined with blank sample DOC data collected between 

2003 and 2006 from site-specific Hg studies conducted by 

the NAWQA Program (Brigham and others, 2008). The 

site-specific studies used essentially the same collection, 

processing, and analytical methods as the 2002 and 2004–05 

national studies. Twelve of 15 blank samples for DOC from 

the combined studies were detected at concentrations greater 

than the MDL; however, only one environmental sample for 

the 2004–05 national study had a DOC concentration less 

than the maximum blank concentration. Concentrations of 

DOC in all remaining environmental samples for the 2004–05 

national study were at least three times greater than the maximum blank concentration. Blank-sample data for SUVA are 

included in this report even though SUVA is a calculated value 

(UV absorbance at 254 nanometers divided by DOC concentration). Only two environmental samples from the 2004–05 

national study had SUVA concentrations that were less than 

or equal to the maximum blank concentration of 1.7 liters per 

milligram carbon per meter. SUVA data can be useful in interpretation and analysis of Hg and DOC data.

Replicates

Replicate data for water and bed-sediment samples are 

summarized in tables 6–7. Variability in sample data can be 

estimated by analyzing the distribution of replicate data using 

the standard deviation (SD) or the relative standard deviation 

(RSD, standard deviation divided by the mean concentration). 

For many water-quality analytes, the SD of replicate sets generally is uniform at low concentrations, but SD increases with 

increasing concentration. At higher concentrations, the RSD 

generally is uniform (Mueller and Titus, 2005). Variability of 

an analyte with a wide range of concentrations can be estimated by dividing the data into low- and high-concentration 

ranges based on the distribution of the SD or the RSD (Anderson, 1987). For low-concentration ranges, the mean SD of replicates is used to estimate variability; for high-concentration 

ranges, the mean RSD is used (Mueller and Titus, 2005). 

For all replicate data, only replicate pairs with detected 

concentrations for each sample were used to estimate variability. As the first step in assessing variability of data collected during the national and regional studies, the SD and 

the RSD for each analyte were plotted (ordinate) against the 

mean replicate concentration (abscissa). The values at which 

concentrations were divided into low- and high-concentration 

ranges were estimated by fitting a loess [local regression 

nonparametric smoothing technique (S-Plus 7.0 for Windows, 

Insightful Corporation, Seattle, Wash.)] curve through the data 

and visually examining the SD or RSD plots for gaps in mean 

concentration and a change in the slope of the loess curve. For 

some analytes, there was no obvious difference in SD or RSD 

throughout the range of mean replicate concentration. Variability for these analytes was estimated by the RSD for the entire 

range of concentrations, which may overestimate the variability for a low range of concentration data. 

In general, SDs for FTHg and FMeHg in the lower 

concentration ranges were similar to, though numerically 

slightly less than, the respective values for PTHg and PMeHg 

(table 6). In the higher concentration ranges, the RSD for 

FTHg was about one-third that for PTHg, whereas the RSD 

for FMeHg was about twice that for PMeHg (table 6). Moreover, RSD values for UTHg and UMeHg were as much as 4–5 

times greater than the respective values of filtered or particulate values (tables 6, 7). These data suggest that the presence 

of particulate matter can have important effects on analyte 

variability.

SDs for DOC and sulfate in stream water in the low range 

of concentrations were 0.08 and 0.09 mg/L, respectively. RSD 

values for DOC, sulfate, and SUVA in high-concentration 

ranges also were low, less than or equal to 2.5 percent. RSD 

values for bed-sediment samples of LOI for the entire concentration range and AVS for the high-concentration range were 

8.4 and 18.3 percent, respectively.
Table 5. Summary of data for stream-water field-blank samples, 1998–2005. [See Appendix 2 for definition of column names. MDL, method detection limit; >, greater than; ng/L, nanogram per liter; CHEY-reg, regional study of mercury in the CheyennUSGS, U.S. Geological Survey; WMRL, Wisconsin Mercury Research Laboratory; < less than; --, not applicable; 2002 and 2004–05, national studies of mercury conducted in reg, regional study of mercury in the Upper MIssissippi River Basin; mg/L, milligram per liter; NWQL, National Water Quality Laboratory; E, estimated; NRP OCTL, NationaCarbon Transformations Laboratory; L mgC–1 m–1, liter per milligram carbon per meter] Analyte Column name from Appendix 2. Field-blank sample data Unit Study Laboratory MDL Number of blanks Number of blanks > MDL Concen

Minimum 9

perc

Mercury Unfiltered total mercury UTHg ng/L CHEY-reg USGS WMRL 0.04 6 6 0.05 

Unfiltered methylmercury UMeHg ng/L CHEY-reg USGS WMRL 0.04 6 0 <0.001 

Filtered total mercury FTHg ng/L 2002 and 2004–05; CHEY- reg; UMIS-reg USGS WMRL 0.04 27 25 0.02 

Filtered methylmercury FMeHg ng/L 2002 and 2004–05; CHEY- reg; UMIS-reg USGS WMRL 0.04 29 0 0.002 Particulate total mercury PTHg ng/L 2002 and 2004–05; UMIS-reg USGS WMRL variable1 18 8 <0.062 

Particulate methylmercury PMeHg ng/L 2002 and 2004–05; UMIS-reg USGS WMRL variable1 21 0 <0.008 

Organic carbon Dissolved organic carbon DOC mg/L 2002 USGS NWQL 0.3 13 0 E 0.2 

Dissolved organic carbon DOC mg/L 2004-052 USGS NRP OCTL 0.2 15 12 0.1 

Specific ultraviolet absor- bance SUVA L×mgC –1 m–1 2004-052 USGS NRP OCTL none3 11 -- 0.1 
Table 5. Summary of data for stream-water field-blank samples, 1998–2005.—Continued[See Appendix 2 for definition of column names. MDL, method detection limit; >, greater than; ng/L, nanogram per liter; CHEY-reg, regional study of mercury in the CheyennUSGS, U.S. Geological Survey; WMRL, Wisconsin Mercury Research Laboratory; < less than; --, not applicable; 2002 and 2004–05, national studies of mercury conducted in reg, regional study of mercury in the Upper MIssissippi River Basin; mg/L, milligram per liter; NWQL, National Water Quality Laboratory; E, estimated; NRP OCTL, NationaCarbon Transformations Laboratory; L mgC–1 m–1, liter per milligram carbon per meter]

Analyte

Column name 

from Appendix 

2. Field-blank 

sample data

Unit Study Laboratory MDL Number of blanks Number of blanks > MDL Concen

Minimum 9

perc

Major ionsSulfate Sulfate mg/L 2002 USGS 

NWQL

0.1 12 0 <0.1 

Sulfate Sulfate mg/L 2004–05; 

UMIS-reg

USGS 

NWQL

0.18 4 0 <0.18 

1 Analytical results for PTHg and PMeHg are reported on a ng/L basis by dividing the mass of PTHg or PMeHg on a filter by the volume of stream water filtered. The MDL 

of water filtered (DeWild and others, 2004; Olund and others, 2004). See Appendix 2 for detection limits.

2 Only two blank samples for DOC and SUVA were available for the 2004–05 national study. These data were combined with DOC and SUVA blank data from detailed USG

from 2003 through 2006 to increase sample size for analysis. 

"3 No MDL; SUVA is a calculated value: UV absorbance at 254 nanometers divided by DOC concentration.
20 Data on Mercury in Water, Bed Sediment, and Fish from Streams Across the United States, 1998–2005

Figure 2. Statistical distribution of field blanks and stream-water environmental samples 

of (A) filtered total mercury (FTHg) concentrations and (B) particulate total mercury (PTHg) 

concentrations, 1998–2005.

FIELD BLANKS ENVIRONMENTAL

SAMPLES

CONCENTRATION, 

IN NANOGRAMS PER LITER

CONCENTRATION, 

IN NANOGRAMS PER LITER

0.01

0.1

1

10

100

10

100

1,000

0.1

0.01

1

A. Filtered total mercury

B. Particulate total mercury

27 189

18 155

FIELD BLANKS ENVIRONMENTAL

SAMPLES

75th percentile

Median

25th percentile

10th percentile

90th percentile

Censored data point 

Data point

EXPLANATION

155 Number of samples

Maximum detection limit

Minimum detection limit
Table 6. Estimates of variability for lower and higher concentration ranges of stream water and bed sediment replicate samples, 1998–2005.[See Appendix 3 for definition of column names. SD, standard deviation; RSD, relative standard deviation; ng/L, nanogram per liter; 2002, national study of mercury conductestudy of mercury in the Cheyenne–Belle Fourche River Basins; UMIS-reg, regional study of mercury in the Upper Mississippi River Basin; USGS, U.S. Geological Survey; WResearch Laboratory; mg/L, milligram per liter; NRP OCTL, National Research Program Organic Carbon Transformations Laboratory; NWQL, National Water Quality Laboraof mercury conducted in 2004–05; SGL, Sulfur Geochemistry Laboratory]

Analyte

Column name 

from Appendix 3. 

Fieldreplicate 

sample data

Unit Study Laboratory

Low-concentration range High-co

Number 

of 

replicate 

sets

Range Variability (mean SD)

Number 

of 

replicate 

sets

Stream water

MercuryFiltered total 

mercury

FTHg ng/L 2002; CHEYreg; UMISreg USGS WMRL 18 0.22–1.37 0.09 5 

Filtered methylmercury FMeHg ng/L 2002; CHEY- reg, UMISreg USGS WMRL 10 0.05–0.45 0.01 1 Particulate total 

mercury

PTHg ng/L 2002; UMIS-reg USGS 

WMRL

17 0.123–2.34 0.111 6 1

Particulate methylmercury PMeHg ng/L 2002; UMIS-reg USGS WMRL 17 0.023–0.287 0.014 1 Organic carbonDissolved 

organic carbon

DOC mg/L UMIS-reg1 USGS 

NRP OCTL

16 0.9–11.1 0.08 2 4

Major ionsSulfate Sulfate mg/L 2002; CHEYreg; UMISreg USGS WMRL, USGS 

NWQL

14 1.8–69.6 0.09 1 807–

Bed sediment

SulfurAcid-volatile 

sulfide

Pct_AVS_ WetWt percent 2002 and 

2004–05; UMIS-reg

USGS 

SGL

9 6.46–17–4.16–4 6.51–5 7 

1Only one replicate set for DOC was available for the UMIS regional study. These data were combined with DOC replicate data from detailed USGS mercury studies conduc

to increase sample size for replicate analysis. 
Table 7. Estimates of variability for stream water and bed sediment replicate samples, 1998–2005. [See Appendix 3 for definition of column names. RSD, relative standard deviation; ng/L, nanogram per liter; CHEY-reg, regional study of mercury in the Cheyenne–Belle FourU.S. Geological Survey; WMRL, Wisconsin Mercury Research Laboratory; mg/L, milligram per liter; 2002, national study of mercury conducted in 2002; NWQL, National WL×mgC–1×m–1, liter per milligram carbon per meter; UMIS-reg, regional study of mercury in the Upper Mississippi River Basin; NRP OCTL, National Research Program Orga

tions Laboratory; ng/g, nanogram per gram; 2004–05, national study of mercury conducted in 2004–05; DELR-reg, regional study of mercury in the Delaware River Basin] Analyte Column name from Appendix 3. Field- replicate sample data Units Study Laboratory Number of replicate sets Rang

Stream Water Mercury Unfiltered total mercury UTHg ng/L CHEY-reg USGS WMRL 5 2.36

Unfiltered methylmercury UMeHg ng/L CHEY-reg USGS WMRL 3 0.06Organic carbon Dissolved organic carbon DOC mg/L 2002 USGS NWQL 13 1.2–Specific ultraviolet absor- bance SUVA L×mgC–1×m-1 UMIS-reg1 USGS NRP OCTL 10 2.5–

Streambed sediment Mercury Total mercury STHg ng/g 2002 and 2004–05; CHEY-reg; DELR- reg2; UMIS-reg USGS WMRL 20 2.34

Methylmercury SMeHg ng/g 2002 and 2004–05; CHEY-reg; UMIS-reg USGS WMRL 12 0.05Organic matter Loss on ignition LOI percent 2002 and 2004–05; UMIS-reg USGS WMRL 17 0.00

1 Only one replicate set for SUVA was available for the UMIS regional study. These data were combined with SUVA replicate data from detailed USGS mercury studies con

2006 to increase sample size for replicate analysis. 2 The two replicate samples for the DELR regional study were split samples.
Ancillary Data 23

Quality of Fish Data

Laboratory QC samples for fish included procedural 

blanks, replicate samples, spiked samples, and certified and 

standard reference materials. Procedural blanks measure the 

amount of Hg that may be introduced in a sample during 

sample processing in the laboratory. Replicate samples, created by taking subsamples from the original homogenized fish 

sample, were used to measure the variability in the analytical 

procedures for fish analysis. Laboratory spiked samples were 

used to measure the bias and precision of analytical methods 

by determining the amount of spike recovery in a sample. 

Low recovery of the spiked analyte can indicate Hg degradation, analytical interference from the sample matrix, and (or) 

poor analytical recovery. Reference materials from the USGS 

CERC, the National Institute of Standards and Technology 

(NIST), and the National Research Council Canada (NRCC) 

were used to assess the accuracy of analytical methods. Reference materials used were CERC whole striped bass (material 

I.D. STB), NIST albacore tuna fillet (SRM 50) and mussel tissue (SRM 2976), NRCC dogfish (Squalus acanthias) muscle 

(DORM-1 and DORM-2), NRCC dogfish liver (DOLT-2), and 

NRCC lobster hepatopancreas (TORT-2) (table 8). Laboratory 

QC samples were available for the national studies and the 

UMIS regional study.

QC results for fish sampled during the 1998 National 

Mercury Pilot Study and analyzed at the CERC are discussed 

in Brumbaugh and others (2001) and are summarized here. 

Concentrations in eight of nine method blank samples were 

near or less than the instrument detection level. The one 

elevated blank sample resulted in an increased MDL for 

samples analyzed in the digestion block, but virtually all 

sample concentrations were considerably greater than the 

blank concentration. As a result, there was no indication of 

systematic contamination of samples due to sample collection, 

processing, and analysis. The RSDs for the triplicate samples 

ranged from 0.6 to 7.5 percent (n=8) and averaged 2.6 percent. 

Percent recoveries for the predigestion spikes of MeHg 

averaged 102.3 percent (SD 4.2, n=16). Percent recoveries 

for the postdigestion spikes of divalent Hg (Hg2+) averaged 

98.5 percent (SD 5.1, n=25). Measured concentrations of the 

reference tissue samples for the CERC whole striped bass, 

NIST albacore tuna fillet, and NRCC DORM-1 materials were 

in good agreement with the certified ranges (table 8). Overall, 

QC results for the 1998 National Mercury Pilot Study fish 

samples analyzed at the CERC indicated low bias and good 

reproducibility. 

QC data for the 2002 fish samples analyzed for Hg at the 

NQWL included concentrations measured in blank samples 

and recoveries of reference tissue samples (J.R. Garbarino, 

USGS, written commun., 2007). Concentrations of Hg in 11 

blank samples were less than or equal to the MDL. For reference samples analyzed from February 2002 through February 

2003, measured concentrations of the reference tissue samples 

for NRCC DOLT-2 and NRCC DORM-2 were within one 

SD of certified ranges (table 8). For the same time period, 

recoveries averaged 115.5 percent (SD 34.9 percent, n=10) for 

DOLT-2 and 88.5 percent (SD 17.4 percent, n=9) for DORM2. Overall, the quality-control results associated with the 2002 

fish samples analyzed at the NWQL indicated low bias and 

moderate variability. 

For the 2004–05 fish samples analyzed at the TERL, 

8 of 19 procedural blanks had Hg concentrations that were 

slightly greater than the MDL. These detections of Hg in 

blank samples with concentrations equal to or slightly greater 

than the MDLs do not affect the interpretation of Hg in the 

243 fish samples analyzed at the TERL because the minimum 

sample concentration (0.056 microgram per gram ([μg/g]), 

dry weight) was at least 6 times greater than the highest blank 

equivalent concentration (0.009 μg/g, dry weight). The RSDs 

for the replicate samples were between 0 and 8 percent (n=23), 

with an average of 2 percent. Percent recoveries for the spike 

samples averaged 99.7 percent (SD 3.3, n=23). Measured 

concentrations of the reference tissue samples for the NRCC 

DOLT-2 and DORM-2 materials were within certified ranges 

(table 8). Average percent recoveries for the reference materials were 104.2 percent (SD=6.6 percent, n=19) for DOLT-2 

and 99.7 percent (SD 2.5, n=19) for DORM-2. QC results for 

the 2004–05 national study fish samples analyzed at the TERL 

indicated low bias and good reproducibility. 

QC results for fish sampled during the UMIS regional 

study and analyzed at River Studies Center, University of 

Wisconsin, La Crosse, Wis., are discussed in Christensen and 

others (2006) and are summarized here. The average RSD for 

60 triplicate subsamples of homogenized fish was 4.5 percent, 

and values ranged from 0.4 to 8.3 percent. Percent recoveries of predigestion subsamples of homogenized fish averaged 

96.5 percent (n=60) and ranged from 84.1 to 112.1 percent. 

Measured concentrations of reference tissue samples of NIST 

mussel tissue, NRCC lobster hepatopancreas, and NRCC dogfish muscle were within the certified ranges (table 8). The QC 

results for the UMIS regional study fish samples analyzed at 

the University of Wisconsin, La Crosse, River Studies Center 

indicated low bias and good reproducibility.

Ancillary Data

Selected ancillary data for geographic information, basin 

hydrologic estimates, and Hg source estimates are available 

for the basins upstream from most Hg study sites. Ancillary 

data are not included for 18 sites because specific land-cover 

data were not available or basin boundaries were not determined. The 18 sites are listed in Appendix 5. 

Geographic Information

Boundaries representing the basin upstream from study 

sites were delineated by USGS personnel from a variety of 

sources. Most basin boundaries were previously compiled 

for the USGS NAWQA Program from 1:24,000-scale to 
24 Data on Mercury in Water, Bed Sediment, and Fish from Streams Across the United States, 1998–2005

1:250,000-scale digital topographic and hydrologic maps 

(Nakagaki and Wolock, 2005). Other basin boundaries were 

generated using 30-meter (m) resolution Elevation Derivatives 

for National Applications reach catchments (U.S. Geological 

Survey, 2002). All digital basin boundaries were managed both 

as vector data sets (hereinafter referred to as “coverages”) and 

as 30-m resolution raster data sets (hereinafter referred to as 

“grids”). Drainage areas for the basins were calculated from 

the coverages. 

Several ancillary data sets were processed in a Geographic Information System (GIS) to characterize natural 

features and human influences within the Hg study basins. The 

basin boundaries gridded at 30-m resolution for most variables 

were intersected with each national ancillary data layer to calculate a basin average for the ancillary data feature. For land 

cover, percentages of land-cover classes were calculated. The 

basin boundary coverages were used to calculate total stream 

length and number of historical and active Hg and gold mining 

sites in the basin. 

Land-cover information was obtained from 30-m 

National Land Cover Data (NLCD) (U.S. Geological Survey, 

1999), which were based on satellite imagery from the early 

to mid-1990s (Vogelmann and others, 2001), and USGS Land 

Use and Land Cover (LULC) data (Price and others, 2007), 

which were derived from aerial photography from the 1970s 

to mid-1980s. The NLCD was enhanced with selected landuse categories of LULC data, as described in Nakagaki and 

Wolock (2005), because the LULC data were a better source 

for some land categories that are difficult to distinguish using 

only satellite imagery. This “enhanced” NLCD includes 21 

land-cover classifications from the original NLCD plus an 

additional four categories from the LULC (LULC tundra, 

Table 8. Measured total mercury concentrations for certified and standard reference materials from the Columbia Environmental 

Research Center, National Institute of Standards and Technology, and National Research Council Canada used for laboratory quality 

assurance of fish samples, 1998–2005.

[μg/g, micrograms per gram; wt, weight; CERC, Columbia Environmental Research Center; USGS, U.S. Geological Survey; NIST, National Institute of 

Standards and Technology; NRCC, National Research Council Canada; DORM, dogfish (Squalus acanthias) muscle; DOLT, dogfish liver; NWQL, National 

Water Quality Laboratory; TERL, Trace Element Research Laboratory, Texas A&M University; UMIS, Upper Mississippi River Basin; RSC, River Studies 

Center, University of Wisconsin, La Crosse, Wis. Data for 1998 from Brumbaugh and others (2001); data for UMIS regional study from Christensen and others (2006)]

Reference material Laboratory Number 

of samples

Measured concentration, μg/g, dry wt Certified 

concentration 

range, μg/g, dry wt

Mean Standard 

deviation

1998 National Mercury Pilot Study

CERC whole striped bass USGS CERC 3 2.21 0.01 2.26 ± 0.51

NIST albacore tuna fillet 3 0.99 0.04 0.95 ± 0.10

NRCC DORM-1 3 0.9 0.06 0.80 ± 0.07

2002 national study

NRCC DOLT-2 USGS NWQL 10 2.47 0.75 2.14 ± 0.28

NRCC DORM-2 9 4.11 0.81 4.64 ± 0.26

2004–05 national study

NRCC DOLT-2 TERL 19 2.23 0.14 2.14 ± 0.28

NRCC DORM-2 19 4.63 0.12 4.64 ± 0.26

UMIS regional study

Reference material Laboratory Number 

of samples

Mean,

μg/g, dry wt

95-percent 

confidence 

interval,

μg/g, dry wt 

Certified 

concentration 

range, μg/g, dry wt

NIST mussel tissue RSC 12 0.0605 0.0575–0.0641 0.061 ± 0.0036

NRCC lobster 

hepatopancreas 12 0.258 0.242–0.274 0.27 ± 0.06

NRCC dogfish muscle 11 0.841 0.795–0.887 0.798 ± 0.074
Ancillary Data 25

NLCD/LULC forested residential, LULC residential, and 

LULC orchards/vineyards/other) (Nakagaki and Wolock, 

2005). 

The enhanced NLCD was used to derive percentages of 

land-cover classes in each basin. The enhanced NLCD also 

was classified into broader categories representing urban, 

agriculture, forest, wetland, undeveloped, and other land 

cover. To address the possibility that conditions observed at 

a sampling site were influenced more by land cover closer to 

the site than by land cover farther from the site, land-cover 

percentages weighted by the inverse distance from the site also 

were calculated and are included in the ancillary database. 

Key soil characteristics, including percent organic 

matter content by weight, soil erodibility factor, percent land 

surface slope, depth to seasonally high water table, percent 

hydric soils, soil porosity, and soil drainage class, were 

compiled from State Soil Geographic (STATSGO) data (U.S. 

Department of Agriculture, 1994). Percent organic matter, 

soil erodibility factor, and land surface slope were obtained 

from the tabular data files presented in Wolock (1997) and 

were linked by mapping unit identification code to a 100-m 

resolution national grid of STATSGO geographic mapping 

units. Hydric soils and soil porosity were calculated for 

each mapping unit using methods from Wolock (1997). Soil 

drainage class was compiled from Schwarz and Alexander 

(1995), who converted the categorical classes into numeric 

values. Hydric soils, soil porosity, and soil drainage class 

also were linked to the 100-m soils mapping unit grid. For 

each basin, a weighted average was calculated for each soil 

characteristic based on the areas of the soils mapping units 

within the basin.

Elevation data at 30-m resolution were extracted from 

USGS National Elevation Data (U.S. Geological Survey, 

2001). The 30-m data were resampled to 100-m resolution, 

and the 100-m data were used to calculate the elevation of 

each sampling site and the mean and maximum elevation 

of each basin. Stream segments from the 1:100,000-scale 

medium-resolution National Hydrography Dataset (U.S. 

Geological Survey and U.S. Environmental Protection 

Agency, 2003) were clipped to the study basin boundaries to 

calculate total stream length within each basin. 

The 2000 Census block group boundaries (U.S. Census 

Bureau, 2001) gridded at 30-m resolution were used with 2000 

block group population density calculated from the Census 

Summary File 1 published by GeoLytics (2001) to derive a 

weighted average 2000 population density by block group 

for each basin. The source of impervious surface area was 

a 1-kilometer (km) resolution grid prepared by Elvidge and 

others (2004). 

Basin Hydrologic Estimates

Mean annual precipitation at 1-km resolution was derived 

from the Parameter-elevation Regressions on Independent 

Slopes Model (PRISM). PRISM uses point data, a digital 

elevation model, and other spatial data to generate estimates of 

precipitation and other climatic parameters (Daly and others, 

1994; Daly and others, 1997). PRISM mean annual precipitation (1961–1990) at 2-km resolution was obtained from the 

Spatial Climate Analysis Service at Oregon State University. 

Mean annual precipitation was estimated for each basin by 

using the PRISM data. 

National 1-km resolution grids (D.M. Wolock, USGS, 

written commun., 2007) were used to calculate a mean for 

each basin for base-flow index, potential and actual evapotranspiration, and topographic wetness index. Base-flow index 

is the ratio of base flow (component of streamflow that can 

be attributed to ground-water discharge into streams) to total 

flow, expressed as a percentage. The base-flow index grid 

was created by interpolating base-flow index point values 

estimated for USGS streamflow gages (Wolock, 2003a, 

2003b). PRISM temperature data (Daly, 2006) and the Hamon 

equation (Hamon, 1961) were used by Wolock to generate a 

1-km grid of mean annual potential evapotranspiration (D.M. 

Wolock, USGS, written commun., 2007). PRISM climate data 

also were used in a water-balance model to estimate actual 

evapotranspiration (Wolock and McCabe, 1999). Average 

topographic wetness index was developed from 1-km resolution digital elevation model data (Wolock and McCabe, 2000). 

Mean annual runoff (1951–1980) characteristics were derived 

from Gebert and others (1987).

Mercury Source Estimates

Data from the National Atmospheric Deposition Program 

(NADP) provided information about measured Hg and sulfate 

wet deposition. Annual wet deposition data for 2000–2003 for 

sites in the Mercury Deposition Network (Roger Claybrooke, 

Illinois State Water Survey, written commun., 2005) were 

averaged for 2000–2003. The station averages were converted 

to a grid surface by using inverse distance weighting interpolation for the eastern part of the United States. Data were 

available for only seven sites in the western part of the United 

States, and this was deemed insufficient for interpolation. 

Instead, the mean deposition of those seven sites was assigned 

to the western part of the country. Digital isopleths maps 

of annual sulfate wet deposition data for 2000–2003 were 

downloaded from the NADP (National Atmospheric Deposition Program, 2006). One surface map representing an average 

sulfate wet deposition for 2000–2003 was generated using GIS 

software to compute the mean from the four individual sulfate 

maps. The average Hg and sulfate wet deposition maps for 

2000–2003 were clipped to the basin boundaries to calculate 

basin mean wet deposition of Hg and sulfate. 

Modeled wet and dry Hg deposition rates were estimated using results from the Trace Elements Analysis Model 

(TEAM) (Seigneur and others, 2004). The resolution of each 

TEAM grid cell was 100-km 100-km. 

Large-scale potential sources of Hg from past or current mining operations were extracted from the Mineral 
26 Data on Mercury in Water, Bed Sediment, and Fish from Streams Across the United States, 1998–2005

Availability System/Mineral Industry Location System (MAS/

MILS) (V.C. Stephens, USGS, written commun., 2004), which 

is part of the Mineral Resources Data System (MRDS) (U.S. 

Geological Survey, 2004). Mining sites in each basin were 

identified as (1) Hg mining operations, in general, (2) Hg 

“producers,” (3) gold mining operations, in general, and (4) 

gold “producers.” Producers included current or past producer 

mining operations.

Acknowledgments

This study was supported by the following USGS 

programs and disciplines: National Water-Quality Assessment, 

Toxic Substances Hydrology, and National Research 

Programs; and Water, Biology, and Geology Disciplines. We 

thank many USGS scientists and field staff for assistance in 

site selection, technical input, and careful sample collection. 

We especially wish to thank the following USGS employees: 

Rod DeWeese, for assistance in initial planning of the study; 

George Aiken and Kenna Butler, for DOC sample planning 

and analyses; William Brumbaugh, for assistance with the use 

of fish results from the 1998 National Hg Pilot Study; John 

Garbarino, for assistance with the use of fish results from the 

2002 national study; Robert Taylor (Trace Element Research 

Laboratory, Texas A&M University), for assistance with the 

use of fish results from the 2004-05 national study; Kerie Hitt, 

Naomi Nakagaki, and Dave Wolock, for GIS data compilation 

and preparation; Douglas Causey, William Ferguson, and Cory 

Stephens, for assistance with retrieval of data from the MRDS 

and MAS/MILS mining databases; John DeWild, Mark 

Olson, and Shane Olund of the Wisconsin Mercury Research 

Laboratory, for their expertise and guidance in multimedia 

Hg sampling; and John DeWild and Norm Spahr, for their 

technical review of an earlier version of this manuscript.

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Appendixes
Appendix Data

These data files are included as part of U.S. Geological Survey (USGS) Data Series 307 and are available for download at 

http://pubs.usgs.gov/ds/307/. See report text for details about the study and for information on sources and compilation of ancillary data. The data tables are available for download in two file formats, Microsoft© Excel (.xls) and comma-separated values 

(.csv) text. The Excel files are formatted to properly display the data. Users with software that reads Excel files are encouraged 

to download the Excel versions of the data files. If you cannot read Excel files, .csv files are provided. The first row of each data 

table contains USGS National Water Information System (NWIS) numeric and alpha parameter codes and parameter descriptions (example, P_63745_Total mercury, biota, tissue, recoverable, dry weight, nanograms per gram). The second row contains 

abbreviated parameter descriptions (example, THG_TIS_DW). Analytes with no parameter code listed are not entered in NWIS.

Five data tables are included in this data series:

Appendix 1. Water and sediment sample data.

Mercury and methylmercury sample data for water and streambed sediment, including field parameters and additional waterquality analytes, collected during 1998–2005 at stream and river sampling sites. The Excel file can be accessed at 

ds307_Appendix01.xls. The .csv files can be accessed at ds307_Appendix01.notes.csv and ds307_Appendix01.data.csv.

Appendix 2. Field-blank sample data.

Feld-blank sample data for mercury and methylmercury in water, and additional water-quality analytes. The Excel file can be 

accessed at ds307_Appendix02.xls. The .csv files can be accessed at ds307_Appendix02.notes.csv and 

ds307_Appendix02.data.csv.

Appendix 3. Field-replicate sample data.

Field-replicate sample data for mercury and methylmercury in water and streambed sediment, and additional water-quality 

analytes. The Excel file can be accessed at ds307_Appendix03.xls. The .csv files can be accessed at ds307_Appendix03.notes.csv

and ds307_Appendix03.data.csv. 

Appendix 4. Fish data.

Mercury sample data, including physical characteristics and additional sample information, for fish collected during 1998–2005 

at stream and river sampling sites. The Excel file can be accessed at ds307_Appendix04.xls. The .csv files can be accesssed at 

ds307_Appendix04.notes.csv and ds307_Appendix04.data.csv.

Appendix 5. Ancillary data.

Selected data for geographic information, basin hydrologic estimates, and mercury source estimates for basins upstream from 

most study sites. The Excel file can be accessed at ds307_Appendix05.xls. The .csv files can be accessed at 

ds307_Appendix05.notes.csv and ds307_Appendix05.data.csv.

32 Data on Mercury in Water, Bed Sediment, and Fish from Streams Across the United States, 1998–2005
Publishing support provided by: 

Denver Publishing Service Center

For more information concerning this publication, contact:

Director, USGS Colorado Water Science Center

Box 25046, Mail Stop 415

Denver, CO 80225

(303) 236-4882

Or visit the Colorado Water Science Center Web site at:

http://co.water.usgs.gov/
Bauch and others— Data on Mercury in Water, Bed Sediment, and Fish From Streams Across the United States, 1998–2005—Data Series 307