U.S. Department of the Interior 

U.S. Geological Survey 

Total Mercury and Methylmercury in Fish Fillets, 

Water, and Bed Sediments from Selected Streams 

in the Delaware River Basin, New Jersey, New York, 

and Pennsylvania, 1998–2001 

by Robin A. Brightbill, Karen Riva-Murray, Michael D. Bilger, and John D. Byrnes 

Water-Resources Investigations Report 03-4183 

New Cumberland, Pennsylvania 

2004 
U.S. DEPARTMENT OF THE INTERIOR 

GALE A. NORTON, Secretary 

U.S. GEOLOGICAL SURVEY 

Charles G. Groat, Director 

The use of product names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. 

For additional information Copies of this report may be 

write to: purchased from: 

District Chief U.S. Geological Survey 

U.S. Geological Survey Branch of Information Services 

215 Limekiln Road Box 25286 

New Cumberland, Pennsylvania 17070-2424 Denver, Colorado 80225-0286 

Email: dc_pa@usgs.gov Telephone: 1-888-ASK-USGS 

Internet Address: http://pa.water.usgs.gov 

ii 
FOREWORD 

The U.S. Geological Survey (USGS) is committed to serve the Nation with accurate and timely 

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

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

quality of the Nation's water resources is of critical interest to the USGS because it is so integrally linked to 

the long-term availability of water that is clean and safe for drinking and recreation and that is suitable for 

industry, irrigation, and habitat for fish and wildlife. Escalating population growth and increasing 

demands for the multiple water uses make water availability, now measured in terms of quantity and 

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

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

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

policy (http://water.usgs.gov/nawqa). Shaped by and coordinated with ongoing efforts of other Federal, 

State, and local agencies, the NAWQA Program is designed to answer: What is the condition of our 

Nation's streams and ground water? How are the 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. NAWQA results can contribute to informed decisions that result in practical and 

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

Since 1991, the NAWQA Program has implemented interdisciplinary assessments in more 

than 50 of the Nation's most important river basins and aquifers, referred to as Study Units 

(http://water.usgs.gov/nawqa/nawqamap.html). Collectively, these Study Units account for more than 

60 percent of the overall water use and population served by public water supply, and are representative 

of the Nation's major hydrologic landscapes, priority ecological resources, and agricultural, urban, and 

natural sources of contamination. 

Each assessment is guided by a nationally consistent study design and methods of sampling and 

analysis. The assessments thereby build local knowledge about water-quality issues and trends in a 

particular stream or aquifer while providing an understanding of how and why water quality varies 

regionally and nationally. The consistent, multi-scale approach helps to determine if certain types of 

water-quality issues are isolated or pervasive, and allows direct comparisons of how human activities and 

natural processes affect water quality and ecological health in the Nation's diverse geographic and 

environmental settings. Comprehensive assessments on pesticides, nutrients, volatile organic compounds, 

trace metals, and aquatic ecology are developed at the national scale through comparative analysis of the 

Study-Unit findings (http://water.usgs.gov/nawqa/natsyn.html). 

The USGS places high value on the communication and dissemination of credible, timely, and 

relevant science so that the most recent and available knowledge about water resources can be applied in 

management and policy decisions. We hope this NAWQA publication will provide you the needed 

insights and information to meet your needs, and thereby foster increased awareness and involvement in 

the protection and restoration of our Nation's waters. 

iii 
The NAWQA Program 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 a fully integrated 

understanding of watersheds and for cost-effective management, regulation, and conservation of our 

Nation's water resources. The Program, therefore, depends extensively on the advice, cooperation, and 

information from other Federal, State, interstate, Tribal, and local agencies, non-government 

organizations, industry, academia, and other stakeholder groups. The assistance and suggestions of all are 

greatly appreciated. 

Robert M. Hirsch 

Associate Director for Water 

iv 
CONTENTS


Page 

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


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


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


Description of study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3


Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3


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


Fish, streamwater, and bed-sediment sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3


Fish, streamwater, and bed-sediment laboratory analysis procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 7


Quality control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8


Data analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8


Distribution and concentrations of total mercury and methylmercury. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8


Patterns of distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8


Concentrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12


Human-health and wildlife criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13


Factors affecting concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13


Fish fillets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15


Streamwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16


Bed sediment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16


Differences among land-use groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19


Comparison of results with the National Mercury Pilot Program and other studies . . . . . . . . . . . . . 22


Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24


References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26


Appendix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29


v 
ILLUSTRATIONS


Page 

Figure 1. Map showing sites sampled for mercury in fish, streamwater, and bed sediment 

in the Delaware River Basin, New Jersey, New York, and Pennsylvania, 

1998 through 2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4


2-4. Maps showing: 

2. Distribution of mercury concentrations in fish fillets within the Delaware


River Basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9


3. 	Distribution of mercury and methylmercury concentrations in streamwater


within the Delaware River Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10


4. Distribution of mercury and methylmercury concentrations in bed sediment 

within the Delaware River Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11


5-17. Graphs showing:


5. 	Relation between mercury concentrations in smallmouth bass fillets


and latitude within the Delaware River Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . 12


6. 	Mercury concentrations in fish fillets, U.S. Environmental Protection Agency


human-health criteria, and U.S. Fish and Wildlife Service fish-eating


bird and wildlife criteria compared with land-use categories within the


Delaware River Basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13


7. Relation between total mercury concentrations in smallmouth bass fillets


and total mercury concentrations in bed sediment within the Delaware


River Basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16


8. 	Relation between total mercury concentrations in smallmouth bass fillets


and estimated population density within the Delaware River Basin. . . . . . . . 16


9. Relation between population density and total mercury concentrations in


streamwater samples within the Delaware River Basin . . . . . . . . . . . . . . . . . . . 17


10. Relation between population density and methylmercury concentrations


in streamwater samples within the Delaware River Basin. . . . . . . . . . . . . . . . . 17


11.	 Relation between population density and methylation efficiency in


streamwater samples within the Delaware River Basin . . . . . . . . . . . . . . . . . . . 18


12. Relation between population density and total mercury concentrations in


bed-sediment samples within the Delaware River Basin. . . . . . . . . . . . . . . . . . 18


13. Relation between population density and methylmercury concentrations


in bed-sediment samples within the Delaware River Basin . . . . . . . . . . . . . . . 18


14. Relation between methylmercury concentrations in bed-sediment samples


and wetlands within the Delaware River Basin. . . . . . . . . . . . . . . . . . . . . . . . . . 18


15. Relation between population density and methylation efficiency in bed-


sediment samples within the Delaware River Basin. . . . . . . . . . . . . . . . . . . . . . 19


16. 	Distribution of total mercury concentrations in smallmouth bass


fillets by land-use groups within the Delaware River Basin . . . . . . . . . . . . . . . 20


17. Distribution of streamwater and bed sediment forms of mercury 

(A) total mercury, (B) methylmercury, and (C) methylation efficiency,


by land-use groups within the Delaware River Basin . . . . . . . . . . . . . . . . . . . . 21


vi 
TABLES


Page 

Table 1. Sites where fish fillets, streamwater column, and bed-sediment samples were 

collected in the Delaware River Basin, New Jersey, New York, and 

Pennsylvania, 1998 through 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

2. A summary of mercury concentrations in fish fillets and exceedances of the 

U.S. Environmental Protection Agency human-health criteria, and the U.S. 

Fish and Wildlife Service fish-eating bird and wildlife criteria from selected 

sites in the Delaware River Basin, 1998 through 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

3. 	Results of Spearman rank correlation analysis between mercury concentration in 

smallmouth bass (Micropterus dolomieu) fillets and environmental and 

landscape variables for sites within the Delaware River Basin, New Jersey, 

New York, and Pennsylvania, 1998 through 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

4. 	Results of Spearman rank correlation analyses between environmental 

and landscape variables and mercury in streamwater samples for sites 

within the Delaware River Basin, New Jersey, New York, and Pennsylvania, 

1998 through 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

5. 	Results of Spearman rank correlation analyses between environmental 

and landscape variables and mercury in bed-sediment samples for sites 

within the Delaware River Basin, New Jersey, New York, and Pennsylvania, 

1998 through 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

6. 	Results of Kendall Tau correlation analyses among forms of mercury in fish fillets, 

streamwater, and bed-sediment samples, and environmental and landscape 

variables, within forested/low intensity-agricultural, agricultural, and urban 

land-use classes for sites within the Delaware River Basin, New Jersey, 

New York, and Pennsylvania, 1998 through 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

APPENDIX 

Appendix. Site information, sampling years, fish species, number of fish per sample, 

mercury and (or) methylmercury concentrations in fish, streamwater, and bed 

sediment, and Loss-On-Ignition for bed sediment for sites within the Delaware 

River Basin, New Jersey, New York, and Pennsylvania, 1998 through 2001 . . . . . . . . . . . 29 

vii 
CONVERSION FACTORS, DATUMS, AND ABBREVIATED WATER-QUALITY UNITS


Multiply By To obtain 

Length 

inch (in) 2.54 centimeter 

foot (ft) 0.3048 meter 

Area 

square mile (mi2) 2.590 square kilometer 

Temperature 

degree Fahrenheit (°F) °C=5/9 .(°F-32) degree Celsius 

Abbreviated water-quality units used in report: 

g, gram 

cm, centimeter 

m, meter 

mm, millimeter 

ng/L, nanogram per liter (ppb, parts per billion) 

ng/g, nanogram per gram (ppt, parts per trillion) 

μg/g, microgram per gram (ppm, parts per million) 

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 1927 (NAD 27). 

viii 
TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER,


AND BED SEDIMENTS FROM SELECTED STREAMS


IN THE DELAWARE RIVER BASIN,


NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998–2001


by Robin A. Brightbill, Karen Riva-Murray, Michael D. Bilger, and John D. Byrnes 

ABSTRACT 

Within the Delaware River Basin, fish-tissue 

samples were analyzed for total mercury (tHg). 

Water and bed-sediment samples were analyzed 

for tHg and methylmercury (MeHg), and methylation efficiencies were calculated. This study was 

part of a National Mercury Pilot Program conducted by the U.S. Geological Survey (USGS). The 

Delaware River Basin was chosen because it is part 

of the USGS National Water-Quality Assessment 

Program that integrates physical, chemical, and 

biological sampling efforts to determine status and 

trends in surface-water and ground-water 

resources. 

Of the 35 sites in the study, 31 were sampled 

for fish. The species sampled at these sites include 

smallmouth bass (Micropterus dolomieu), the target 

species, and where smallmouth bass could not be 

collected, brown trout (Salmo trutta), chain pickerel 

(Esox niger), largemouth bass (Micropterus salmoides), and rock bass (Ambloplites rupestris). There 

were a total of 32 fish samples; 7 of these exceeded 

the 0.3 μg/g (micrograms per gram) wet-weight 

mercury (Hg) concentration set for human health 

by the U.S. Environmental Protection Agency and 

27 of these exceeded the U.S. Fish and Wildlife Service criteria of 0.1 μg/g wet weight for the protection of fish-eating birds and wildlife. 

Basinwide analysis of Hg in fish, water, and 

bed sediment showed tHg concentration in fillets 

correlated positively with population density, 

urban land cover, and impervious land surface. 

Negative correlations included wetland land cover, 

septic density, elevation, and latitude. Smallmouth 

bass from the urban sites had a higher median concentration of tHg than fish from agricultural, low 

intensity-agricultural, or forested sites. Concentrations of tHg and MeHg in water were higher in 

samples from the more urbanized areas of the 

basin and were positively correlated with urbanization and negatively correlated with forested 

land cover. Methylation efficiency of water was 

negatively correlated with urbanization. Bed-sediment patterns were similar to those observed in 

water. Concentrations of tHg were higher in samples from the urbanized areas. In the more forested 

areas, MeHg concentrations were higher than in 

other land-use areas. Concentrations of tHg in bed 

sediment were positively correlated with urbanization factors (population, urban land cover, and 

impervious land surface) and negatively correlated 

with forested land cover and elevation. Forested 

land cover and latitude were positively correlated 

with concentrations of MeHg. The methylation 

efficiency was higher in samples from the forested 

areas and was negatively correlated with urbanization. 

Analyses within land-use groups showed 

that tHg concentrations in fish fillets from the 

urban sites were positively correlated with forested land cover and wetland cover. Urbanization 

factors within the agricultural group were positively correlated with tHg in fish; concentrations of 

tHg in fish from sites in the low intensity-agricultural group were negatively correlated with urbanization factors. Within the agricultural land-use 

group, tHg concentrations in water were negatively correlated with septic density, and MeHg 

concentrations were negatively correlated with elevation. In the forested and low intensity-agricultural groups, MeHg in water was negatively 

correlated with forested and agricultural land 

cover. Methylation efficiency in water also was 

negatively correlated with forested land cover but 

positively correlated with agricultural land cover. 

Bed sediment concentrations of tHg in the forested 

and low-agricultural groups were positively correlated with agricultural land cover and negatively 

correlated with forested land cover. Concentrations of MeHg in bed sediment were positively 

correlated with septic density and drainage area 

1 
and negatively correlated with forested land cover. 

Methylation efficiency was negatively correlated 

with population density, agricultural land cover, 

and sulfate concentrations in water. 

An urbanization effect was observed in all 

three media—fish, water, and bed sediment. Different factors, basinwide and within land-use 

groups, showed a complex relation. Additional 

sampling within these land-use groups could help 

characterize interrelations of Hg in the environment to fish in the Delaware River Basin. 

INTRODUCTION 

Mercury (Hg) is a naturally occurring metal 

found primarily in cinnabar (mercurysulfate) that 

is released through the weathering of rock and (or) 

volcanic activity (National Research Council, 

2000). However, the main source of Hg in the environment is from human activity through coal-combustion electrical power generation and industrial 

waste disposal (National Research Council, 2000; 

Stahl and Sobat, 2000). Environmental concentrations can be influenced by proximity to point 

sources such as sewage treatment plants and 

industrial discharges, and by geographic and 

physiographic factors that affect vulnerability to 

atmospheric deposition. Once Hg is released to the 

environment, it can be converted to a biologically 

toxic form of methylmercury (MeHg) by microorganisms found in soil and in the aquatic environment (National Research Council, 2000). MeHg is a 

potent neurotoxin that affects the central nervous 

system causing neurological damage, mental retardation, blindness, deafness, kidney malfunction, 

and, in some cases, death (National Research 

Council, 2000). 

Methylation of Hg is of concern because 

MeHg is absorbed easily into the food chain (U.S. 

Environmental Protection Agency, 1997). MeHg 

readily crosses biological membranes and can 

accumulate to harmful concentrations in the 

exposed organism and biomagnify up the food 

chain (Krabbenhoft and others, 1999). This biomagnification can cause high levels of Hg in top 

predator fishes and have a detrimental effect on 

humans and fish-eating wildlife (Krabbenhoft and 

others, 1999; National Research Council, 2000). 

The United States, along with other industrialized countries, has taken action to reduce Hg 

pollution; however, these reductions are not yet 

reflected in the air, soil, water, or fish (U.S. Environmental Protection Agency, 2001a). As of 1999, 

41 states had fish Hg advisories (limits on numbers 

of meals consumed by humans per month). Of 

these 41 states, 11 have statewide Hg advisories for 

lakes and streams (U.S. Environmental Protection 

Agency, 2000a), particularly in the northeastern 

United States (Bahnick and Sauer, 1994). 

The Delaware River Basin, located in the 

northeastern part of the United States, is included 

in the U.S. Geological Survey (USGS) National 

Water-Quality Assessment (NAWQA) Program. 

NAWQA is a long-term effort designed to evaluate 

the status of, and trends in, the quality of surfaceand ground-water resources in the United States 

through an integrated approach of physical, chemical, and biological factors (Hirsch and others, 

1988; Leahy and others, 1990; Gurtz, 1994; Gilliom 

and others, 1995). The NAWQA Program was 

designed to be conducted in more than 50 separate 

river basins and aquifer systems that account for 

about two-thirds of the water use and public water 

supply in the United States (Leahy and Wilber, 

1991). These basins constituted the framework for 

regional- and national-level assessments such as 

the National Mercury Pilot Program (NMPP) 

(Brumbaugh and others, 2001). 

The Delaware River Basin NAWQA study 

examined factors affecting Hg concentrations in 

samples of fish, water, and bed sediment and is 

part of the USGS NMPP. Factors examined 

included water quality and environmental and 

landscape conditions (Krabbenhoft and others, 

1999; Brumbaugh and others, 2001). The national 

study proposed a national tHg bioaccumulation 

model (Brumbaugh and others, 2001) and recommended additional research in urban areas and 

within various regions. Additional research is 

necessary to determine the applicability of the 

national model for different geographic regions of 

the country and to examine factors within each 

region that cause deviations in the model. 

This report (1) documents the occurrence 

and distribution of total mercury (tHg) and MeHg 

in game-fish tissue, water, and bed sediment in the 

Delaware River Basin, and (2) examines the relations among the three media and with environmental factors and watershed characteristics. 

Concentrations of tHg and MeHg also are compared to results from the NMPP. Any exceedances 

of the U.S. Environmental Protection Agency 

(USEPA) human-health criteria or the U.S. Fish and 

Wildlife Service’s fish-eating bird and wildlife criteria are noted. 

2 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 
Description of Study Area 

The Delaware River Basin drains approximately 12,700 mi2 and includes parts of Pennsylvania (6,460 mi2), New Jersey (2,970 mi2), New York 

(2,360 mi2), and Delaware (968 mi2) (fig. 1) (Fischer, 

1999). The entire basin, except for the Coastal Plain 

Physiographic Province and the tidal part of the 

estuary, are part of the NAWQA study area. The 

population of the study area, as determined by the 

1990 census, is over 7 million people (Fischer, 

1999). The Delaware River originates in the Catskill Mountains of New York and flows southward 

and eventually flows into the Atlantic Ocean. The 

Lehigh and Schuylkill Rivers in Pennsylvania are 

major tributaries of the Delaware River. 

The Delaware River flows through five physiographic provinces, from the Appalachian Plateau 

in the north, through the Valley and Ridge, the 

New England, the Piedmont, and the Coastal Plain 

in the south (fig. 1). Land use in the basin is about 

60 percent forested, 24 percent agricultural, 9 percent urban/residential, and 7 percent surfacewater bodies and miscellaneous land uses (Fischer, 

1999). In the forested northern half of the basin, 

which is mostly within the Appalachian Plateau 

Physiographic Province, altitudes range from 

about 1,000 ft to greater than 3,000 ft. This area 

includes the Catskill Mountains and the town of 

Port Jervis, N.Y. Major cities in the Valley and 

Ridge Physiographic Province include Stroudsburg, Easton, Allentown, and Reading, Pa. No 

major cities within the study area are in the New 

England Physiographic Province. 

The population density is highest in the 

urbanized south, primarily in the Piedmont (Trenton, N.J., and Philadelphia and Chester, Pa.) and 

Coastal Plain (Camden, N.J., and Wilmington, 

Del.) Physiographic Provinces, where the altitudes 

generally are below 330 ft. These provinces cover 

about 40 percent of the total study area, contain 

over 80 percent of the population, and have about 

40 percent urban land cover and less than 45 percent forest land cover (Fischer, 1999). 

During the 1998 through 2001 data-collection 

period, precipitation was below normal by 1 to 

4 in., and streamflows were near the 7-day, 10-year 

low-flow values. In particular, 1999 was an 

extremely dry year, and all four basin states 

declared drought emergencies. However, in September 1999, Hurricane Floyd provided relief by 

dropping considerable amounts of rain across the 

basin. The extreme conditions observed in 1999 

were not experienced in the other years of this 

study. 

Acknowledgments 

Many colleagues have contributed to this 

report, including USGS personnel who collected 

samples: Jeffrey Fischer, Ward Hickman, Jonathan 

Klotz, Timothy Oden, Susan Edwards, Paul Dunn, 

Kimberly Orlick, Gretchen Wall, and Brett Boehlert. We thank Michael Boyer and Richard Spear 

from the Pennsylvania Department of Environmental Protection and Steven Schubert from the 

U.S. Fish and Wildlife Service for their assistance in 

collecting data; David Krabbenhoft (USGS) and 

Mark Olsen (USGS) for their technical assistance; 

William Brumbaugh (USGS), Stephen Smith 

(USGS), and Barry Mower (Maine Department of 

Environmental Protection) for their review of the 

manuscript; and Kim Otto, James Bubb, Terriann 

Preston, and Leona McLanahan for helping to 

complete this report. 

METHODS 

Within the Delaware River Basin, a total of 

35 sites were sampled for a combination of either 

fish tissue, streamwater, and (or) bed sediments 

(table 1, fig. 1). Sites were selected to represent 

watersheds dominated by agricultural, forested, 

and urban land uses throughout much of the study 

area, and to include mixed land-use watersheds 

and several large-river (integrator) sites draining 

major parts of the Delaware River Basin. Most sites 

were in the more highly populated southern half of 

the study area. Basins upstream from sampling 

sites were characterized for land use and population density. Basins were delineated using 10 m 

digital-elevation data. Land-use data from 1992 

Landsat Satellite Thematic Mapper Imagery and 

population data from 1990 United States census 

data and 1997 estimates were then applied to each 

basin (Fischer, 1999). 

Fish, Streamwater,


and Bed-Sediment Sampling


Fish specimens were collected from 31 sites, 

streamwater samples from 25 sites, and bed-sediment samples from 30 sites. Because the same species of fish could not be collected at all sites, five 

different species were collected among the 31 sites. 

Smallmouth bass were collected at 21 of the 

31 sites. Water and bed-sediment samples were 

collected at 16 of the 21 smallmouth bass sites. 

These 16 sites were used for the analysis. 

IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 3 
Figure 1. Sites sampled for mercury in fish, streamwater, and bed sediment in the Delaware 

River Basin, New Jersey, New York, and Pennsylvania, 1998 through 2001. 

4 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 
Ta

ble 1. Sites where fish fillets, streamwater column, and bed-sediment samples were collected in the Dela

ware River Basin, New Jersey

Pennsylvania, 1998 through 2001 

Map 

locator 

number 

(fig. 1) 

Site name 

U.S. Geological 

Survey 

identification 

number 

Latitude Longitude 

Drainage 

area 

(square 

miles) 

People 

per 

square 

mile1 

Land-use cha

Percent 

forest2 

Percent Percent 

agriculture2 urban2 

1 Raccoon Creek near Swedesboro, N.J. 01477120 39°44′28′′ 75°15′33′′ 25.7 242 27.3 63.6 4.2 

2 Cooper River at Haddonfield, N.J. 01467040 39°54′11′′ 75°01′19′′ 17.5 2,414 24.9 7.5 56.9 

3 Darby Creek near Darby, Pa. 01475510 39°55′44′′ 75°16′22′′ 38 3,353 37.8 7.2 51.4 

4 Ridley Creek near Media, Pa. 01476470 39°55′57′′ 75°24′42′′ 27.5 734 59.2 28.5 11.4 

5 South Branch Pennsauken Creek at 01467081 39°56′30′′ 75°00′05′′ 8.8 3,088 14.8 12.5 66.2 

Cherry Hill, N.J. 

6 Schuylkill River at Philadelphia, Pa. 01474500 39°58′04′′ 75°11′20′′ 1,886 684 48.3 37.8 9.9 7 North Branch Rancocas Creek at 01467000 39°58′10′′ 74°41′05′′ 113 388 63.4 3.9 7.6 

Pemberton, N.J. 

8 Crum Creek at Goshen Road near 01475845 39°59′24′′ 75°26′16′′ 13 915 59.7 20.4 17.4 

Whitehorse, Pa. 

9 Darby Creek at Foxcroft, Pa. 01475430 39°59′45′′ 75°21′21′′ 16.2 1,692 50.2 12.7 35.2 

10 Wissahickon Creek below Walnut Lake 01473990 40°01′50′′ 75°11′54′′ 61 2,430 40.4 11.6 41.9 

near Manayunk, Pa. 

11 East Branch Brandywine Creek near 01480665 40°03′08′′ 75°43′28′′ 31.7 291 46.1 51.9 1.1 

Dorlan, Pa. 

12 Stony Creek at Steriger Street at 01473470 40°07′38′′ 75°20′43′′ 20.3 1,835 31.0 29.6 36.7 

Norristown, Pa. 

13 Pennypack Creek at Paper Mill, Pa. 01467040 40°08′24′′ 75°04′28′′ 23.5 3,308 23.2 4.6 63.2 

14 French Creek near Phoenixville, Pa. 01472157 40°09′05′′ 75°36′06′′ 58.9 159 63.1 34.5 1.0 

15 Pigeon Creek at Parker Ford, Pa. 01472100 40°11′48′′ 75°35′13′′ 14 393 50.6 45.8 3.3 

16 Dela

ware River at Trenton, N.J. 01463500 40°13′18′′ 74°46′42′′ 6,773 203 74.7 16.5 3.3 

17 Little Neshaminy Creek at Valley Road 01464907 40°13′45′′ 75°07′12′′ 27 989 35.6 32.0 25.7 

near Neshaminy, Pa. 

18 Hay Creek near Birdsboro, Pa. 01471668 40°15′04′′ 75°48′50′′ 21 128 76.3 20.6 .4 

19 Shabakunk Creek near Lawrenceville, N.J. 01463810 40°15′19′′ 74°44′17′′ 11.7 2,774 15.8 14.0 61.9 

20 Manatawny Creek near Pottstown, Pa. 01471980 40°16′22′′ 75°40′49′′ 85.5 226 55.9 41.0 1.6 

21 Pine Run at Chalfont, Pa. 01464710 40°17′20′′ 75°12′11′′ 11.8 684 37.4 48.8 12.1 

22 

Wyomissing Creek at West Reading, Pa. 01471520 40°19′41′′ 75°56′41′′ 16 1,964 43.4 24.8 31.1 

23 Pidcock Creek near New Hope, Pa. 01462100 40°19′46′′ 74°56′14′′ 12.7 199 60.8 36.9 .3 

24 

Tulpehocken Creek near Bernville, Pa. 01470779 40°24′48′′ 76°10′19′′ 70 282 13.1 82.3 3.6 

25 Little Lehigh Creek near East Texas, Pa. 01451425 40°32′34′′ 75°33′47′′ 51 384 23.4 68.0 7.5 

IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 5 
Ta

ble 1. Sites where fish fillets, streamwater column, and bed-sediment samples were collected in the Dela

ware River Basin, New Jersey

Pennsylvania, 1998 through 2001—Continued 

Map 

locator 

number 

(fig. 1) 

Site name 

U.S. Geological 

Survey 

identification 

number 

Latitude Longitude 

Drainage 

area 

(square 

miles) 

People 

per 

square 

mile1 

Land-use cha

Percent 

forest2 

Percent Percent 

agriculture2 urban2 

26 Jordan Creek near Schnecksville, Pa. 01451800 40°39′42′′ 75°37′38′′ 52 156 32.9 65.6 0.8 

27 Lehigh River at Glendon, Pa. 01454700 40°40′09′′ 75°14′12′′ 1,356 442 63.0 23.3 6.7 

28 Brodhead Creek at Stroudsburg, Pa. 01442500 40°59′14′′ 75°11′02′′ 256 273 83.3 7.4 4.5 

29 Bush Kill Creek at Bushkill, Pa. 01439500 41°05′17′′ 75°00′42′′ 126 57 86.6 .6 1.0 

30 Flat Brook near Flatbrookville, N.J. 01440000 41°06′24′′ 74°57′09′′ 65 38 88.0 7.0 .7 

31 Dela

ware River at Port Jervis, N.Y. 01434000 41°22′14′′ 74°41′52′′ 3,076 48 84.3 10.6 1.0 

32 Neversink River near Godeffroy, N.Y. 01437500 41°26′28′′ 74°36′08′′ 305 87 89.2 3.0 3.0 

33 Lacka

waxen River at Hawley, Pa. 01431500 41°28′34′′ 75°10′21′′ 288 84 74.6 18.8 .9 

34 Neversink River near Claryville, N.Y. 01435000 41°53′24′′ 74°35′25′′ 69 9 99.3 .5 .1 

35 

W.Br. Dela

ware River at Walton, N.Y. 01423000 42°09′58′′ 75°08′25′′ 331 45 75.4 23.1 .9 

1 U.S. Department of Commerce, 1990. 2 Fischer, 1999. 

TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 6 
Fish were collected using a direct current 

electrofishing backpack. A top predator species, 

usually smallmouth bass (Micropterus dolomieu), 

was targeted for collection. Chain pickerel (Esox 

niger), resident brown trout (Salmo trutta), largemouth bass (Micropterus salmoides), or rock bass 

(Ambloplites rupestris) were collected from sampling reaches lacking smallmouth bass. One to 

three specimens were collected at each site. Twoto three-year-old fish were needed for this study 

(Krabbenhoft and others, 1999). Age was estimated 

by size class during collection. In 1999, specimens 

were measured for total length (mm), weighed (g), 

placed in sealable plastic bags, put on dry ice, and 

shipped to the USGS Wisconsin Mercury Research 

Laboratory (WMRL) in Middleton, Wis., for analysis (Krabbenhoft and others, 1999). In 2000, specimens were measured for total length, weighed, 

filleted in the field, put on dry ice, and shipped to 

the WMRL for analysis. The fish were filleted in 

the field to avoid thawing of the fish and refreezing. In 2001, the same field procedures used in 2000 

were followed, and samples were sent to the USGS 

National Water Quality Laboratory (NWQL) for 

analysis. 

Streamwater samples for tHg and MeHg 

were collected using the trace-metal clean methods 

of Fitzgerald and Watras (1989). Personnel collecting the samples wore arm-length latex gloves. The 

persons doing the processing wore latex gloves 

and used the “clean-hands, dirty-hands” technique 

of Olsen and DeWild (1999). Samples were placed 

in teflon containers that had been hot acid cleaned, 

partially filled with 1 percent hydrochloric acid for 

storage purposes, and double bagged in sealable 

plastic bags (Krabbenhoft and others, 1999). The 

tHg samples were acidified to 1 percent hydrochloric acid by volume, and the MeHg samples were 

placed in a dark cooler until they could be frozen 

(Krabbenhoft and others, 1999) and shipped to the 

WMRL. 

Bed-sediment samples were collected using 

the trace-element sampling protocols from the 

NAWQA Program (Shelton and Capel, 1994). Personnel wearing latex gloves used a polypropylene 

scoop to sample the surficial layer (estimated at 

2-3 cm deep), which is assumed to be recently 

deposited sediment in the stream, from random 

locations within the designated sampling area. 

Approximately 50 scoops were placed in a bowl 

that had been cleaned in accordance with the traceelement sampling protocols. After the material was 

mixed thoroughly, an aliquot was removed, placed 

in a teflon vial, frozen, and sent to the WMRL for 

analysis of tHg, MeHg, and Loss-On-Ignition 

(LOI), a surrogate for organic carbon. 

Fish, Streamwater, and Bed-Sediment 

Laboratory Analysis Procedures 

Fish-fillet samples were placed into acidwashed borosilicate glass jars and freeze-dried. 

The dry product was homogenized and digested in 

a sealed teflon pressure vessel with microwave 

heating and the addition of nitric and hydrochloric 

acid, followed by hydrogen peroxide. Cold-vapor 

atomic absorption spectrophotometry with flow 

injection sample introduction and stannous chloride reduction was used to determine the concentration of tHg in the sample. A full description of 

laboratory procedures can be found in Brumbaugh 

and others (2001). 

The NWQL and WMRL used different 

USEPA methods (method 3052 and method 1631, 

respectively) for determination of tHg (J.R. Garbarino, U.S Geological Survey, written commun., 

2003). The primary difference that could affect 

comparability of results is a higher detection limit 

for the WMRL method (0.02 μg/g wet weight) 

(Brumbaugh and others, 2001) than for the NWQL 

method (0.001 μg/g dry weight) (J.R. Garbarino, 

U.S Geological Survey, written commun., 2003). 

This should not affect the results for the Delaware 

River Basin study because all sample concentrations were orders of magnitude higher than the 

method detection limit of either testing method. 

Streamwater samples were analyzed for tHg 

concentration using cold-vapor atomic-fluorescence spectroscopy (CVAFS) (Olson and DeWild, 

1999; Olson and others, 1997) at the WMRL. Water 

samples also were analyzed for MeHg concentration with the distillation and aqueous phase ethylation method of Horvat and others (1993) and 

with CVAFS. Method reporting limits (MRL) for 

concentrations of tHg and MeHg in water were 

0.04 and 0.025 ng/L, respectively (Olsen and 

DeWild, 1999). 

Bed-sediment samples were analyzed for 

concentrations of tHg using the CVAFS technique 

at the WMRL. These samples were predigested 

with nitric and sulfuric acids in a sealed teflon 

pressure vessel at 125°C for a minimum of 2 hours. 

The cooled sample was then diluted with a 5-percent bromochloride solution and oxidized at 50°C 

for a minimum of 12 hours (Krabbenhoft and others, 1999). The distillation and aqueous phase ethyIN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 7 
lation method of Horvat and others (1993) and 

CVAFS (Krabbenhoft and others, 1999) were used 

to determine MeHg concentrations. The MRLs for 

tHg and MeHg in bed sediments were 0.04 and 

0.025 ng/g, respectively (Olsen and DeWild, 1999). 

Quality Control 

Several types of quality-control samples 

were analyzed to assure a sound data set. No quality-control samples were done for fish other than 

the laboratory’s own quality control. No extra fish 

were taken as a replicate sample. In 1998, a split 

bed-sediment tHg sample was analyzed at the 

WMRL. In 1999, another split bed-sediment tHg 

sample was analyzed at the WMRL. An additional 

streamwater-column sample was analyzed for tHg 

and MeHg in 1999. 

Data Analysis 

Concentrations below the MRLs were set to 

one-half the reporting limit for statistical and 

graphical analysis. This technique has been used in 

reports by Bilger and others (1999) and by Stahl 

and Sobat (2000). Land-use and population factors 

were generated for each site. Methylation efficiencies (MeHg/tHg) of sediment and water samples 

were calculated according to Krabbenhoft and others (1999) and Brumbaugh and others (2001). For 

comparisons among land-use classes, sites were 

defined as follows: forested basins have greater 

than 80 percent forest, low intensity-agricultural 

basins have from 15 to 25 percent agricultural land 

and more than 65 percent forested land, agricultural basins have greater than 25 percent agriculture and less than 8 percent impervious surface, 

urban basins have 15 percent or greater impervious surface, and mixed basins have between 8 and 

14 percent impervious surface and less than 

80 percent forested land from 1992 satellite derived 

MAPPER land-use data (McMahon and Cuffney, 

2000). In addition, several large watersheds (drainage area greater than 800 mi2) with multiple land 

uses were classified as ‘integrator sites.’ 

Prior to data analysis, a Pearson correlation 

was run on the environmental data. This was done 

to reduce the multicollinearity within the data set. 

The correlated variable with fewer data points or 

that was less normally distributed was removed 

from the data set. The remaining variables were 

analyzed using statistical and graphical 

approaches. 

Fish-fillet data used for all statistical (and 

most graphical) analyses were limited to smallmouth bass. Limiting certain analyses to the largest 

single-species data set avoided the problem of 

interspecies differences in metabolism and in Hg 

accumulation rates (Goldstein and others, 1996; 

Brumbaugh and others, 2001). For sites having 

specimens ranging widely in size, the laboratory 

separated specimens into two separate batches 

prior to analysis. In these cases, only the sample 

with the larger mean length was retained for inclusion in this report. Dry-weight concentrations were 

converted to wet-weight concentrations by using 

percent moisture as the divisor, or, where percent 

moisture was not available, an estimate of 80 percent moisture was used. Hg concentrations in 

smallmouth bass fillets were normalized to mean 

sample total length prior to statistical and graphical analyses. Total length is related to age of fish, 

which has been shown in other studies to influence 

Hg concentrations. Concentration of tHg in bed 

sediment was normalized to LOI. 

DISTRIBUTION AND CONCENTRATIONS


OF TOTAL MERCURY AND


METHYLMERCURY


Fish tissue, water, and bed-sediment samples were obtained from streams throughout the 

Delaware River Basin. The West Branch Delaware 

River at Walton, N.Y., was the northernmost site. 

Raccoon Creek near Swedesboro, N.J., was the 

southernmost site. 

Concentrations of Hg were detectable in all 

fish-tissue samples. Concentrations of tHg were 

detected in all streamwater and bed-sediment samples. Samples from 19 of the 24 water-collection 

sites had detectable concentrations of MeHg. Of 

the 28 bed-sediment collection sites, all had detectable concentrations of MeHg. 

Patterns of Distribution 

The distribution of Hg was highly variable 

throughout the basin (figs. 2, 3, and 4). Fish-tissue 

concentrations that exceeded human health and 

wildlife criteria were found in the urbanized south 

and the forested north (fig. 2). A north-south plot 

of tHg concentrations in smallmouth bass (fig. 5) 

indicates a pattern of higher length-normalized 

tHg concentrations in the southern section, an area 

of higher population density and industrialization, 

and in the northern section, an area of relatively 

low population density. The lowest concentrations 

tended to be at sites in the middle section of the 

study area. 

8 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 
Figure 2. Distribution of mercury concentrations in fish fillets within the Delaware River Basin, New Jersey,


New York, and Pennsylvania, 1998 through 2001.


IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 9 
Figure 3. Distribution of mercury and methylmercury concentrations in streamwater within the Delaware River 

Basin, New Jersey, New York, and Pennsylvania, 1998 through 2001. 

10 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 
Figure 4. Distribution of mercury and methylmercury concentrations in bed sediment within the Delaware 

River Basin, New Jersey, New York, and Pennsylvania, 1998 through 2001. 

IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 11 
Figure 5. Relation between mercury concentrations in 

smallmouth bass fillets (normalized by total length) and 

latitude within the Delaware River Basin, New Jersey, 

New York, and Pennsylvania, 1998 through 2001. 

(Locations of towns and cities referred to are shown on 

figure 2.) 

Concentrations of tHg in the majority of the 

water samples were below the USEPA Maximum 

Contaminant Level (MCL) of 2 ng/L tHg in drinking water (U.S. Environmental Protection Agency, 

2002). Only six sites were above this MCL, and 

these were in the more highly urbanized area of 

the basin (fig. 3). However, the sites with higher 

concentrations of MeHg were in the more urbanized (southern) and the more forested (northern) 

areas of the basin. This pattern is similar to that 

observed with the fish-tissue Hg patterns. 

The distribution of Hg in bed-sediment samples was similar to that observed in the streamwater samples. The two sites under the Threshold 

Effect Concentration (TEC) of 18 ng/g tHg (MacDonald and others, 2000) were in the northern section of the Delaware River Basin (fig. 4). The three 

highest tHg concentrations were observed at sites 

in the more populated area of the basin. A northern, forested site and a middle, urban site had the 

two highest MeHg concentrations in the basin. The 

urbanized southern sites had the lowest MeHg 

concentrations. 

12 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 

Concentrations 

Fish-tissue tHg concentrations ranged from 

0.03 to 0.35 μg/g wet weight (Appendix). The 

internal quality-control tests performed at the 

WMRL for fish tissue indicated good accuracy and 

precision except when sample concentrations were 

very low (Brumbaugh and others, 2001). Method 

blanks were near or below the instrument detection limit for eight of the nine test blanks, resulting 

in a higher MRL of 0.020 μg/g wet weight (Brumbaugh and others, 2001). 

Streamwater tHg sample concentrations 

ranged from 0.43 to 22 ng/L (Appendix) and 

MeHg concentrations ranged from less than the 

MRL to 0.28 ng/L. The split sample for tHg in 

water from the 1999 survey (Flat Brook near Flatbrookville, N.J.) showed a 175-percent difference in 

results, with a sample tHg concentration of 

1.79 ng/L and a split tHg concentration of 

0.65 ng/L. The MeHg split sample from the same 

site showed a 250-percent error, with a sample 

MeHg concentration of 0.049 ng/L and a split sample MeHg concentration of 0.014 ng/L. The NMPP 

reported differences between split samples to be 

less than 50 percent at higher tHg and MeHg concentrations and differences greater than 100 percent for lower tHg and MeHg concentrations 

(Brumbaugh and others, 2001). 

Bed-sediment sample tHg concentrations 

ranged from 1.5 to 380 ng/g (Appendix) and 

MeHg concentrations ranged 0.01 to 8.7 ng/g. The 

bed-sediment quality-control split samples 

showed better results than the streamwater samples. Split sample tHg concentrations showed a 40 

and 43 percent difference between the first and second samples. The Little Neshaminy sample had 

concentrations of 40.1 and 66.9 ng/g (40 percent), 

and the French Creek sample had concentrations of 

77.7 and 54.3 ng/g for a difference of 43 percent. 

No MeHg split samples were collected for bed sediments. 
Human-Health and Wildlife Criteria 

Fish-fillet tHg data were compared to 

human-health and wildlife criteria to assess potential effects in the Delaware River Basin. Concentrations of tHg in fish fillets exceeded the USEPA 

human-health criteria of 0.3 μg/g wet-weight fillets (U.S. Environmental Protection Agency, 2001b) 

in 7 of the 32 samples (22 percent) from 31 sites 

(fig. 6, table 2). Of the seven samples that exceeded 

the USEPA human-health criteria, four were from 

streams near Philadelphia, Pa., one was from near 

Reading, Pa., and the other two were from the 

Pocono area in New York and New Jersey. 

Figure 6. Mercury concentrations in fish fillets, U.S. 

Environmental Protection Agency human-health criteria 

(U.S. Environmental Protection Agency, 2001b), and U.S. 

Fish and Wildlife Service fish-eating bird and wildlife 

criteria (Eisler, 1987) compared with land-use categories 

(Fischer, 1999) within the Delaware River Basin, New 

Jersey, New York, and Pennsylvania, 1998 through 2001. 

The U.S. Fish and Wildlife Service fish-eating 

bird and wildlife criteria of 0.1 μg/g wet weight in 

whole fish (Eisler, 1987) was exceeded in 27 of the 

32 fillet samples (84 percent) from the 31 sites 

where fish were collected. The criteria were set 

using whole fish; thus, a direct comparison to the 

criteria is not entirely valid, although most of the 

Hg in fish typically is in muscle (Wachs, 1985; 

Goldstein and others, 1996). Fillet samples just 

over the criteria limit may actually be below the 

criteria level if whole fish had been analyzed. 

A direct relation between fillet concentrations and 

whole-fish concentrations has been described by 

Goldstein and others (1996) and could be used to 

extrapolate fish-eating bird and wildlife criteria, 

but these regressions must be species-adjusted 

(Goldstein and others, 1996). 

Factors Affecting Concentrations 

Hg concentrations in fish fillets, water, and 

bed sediment have different distribution patterns 

along the length of the Delaware River Basin. Patterns tend to coincide with land use. The northern 

section of the basin is mostly forested, and the 

southern section is mostly urban; the area inbetween has mixed land uses. Within each land-use 

category, different factors influence the concentrations of Hg in fish fillets, water, and bed sediment. 

IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 13 
Table 2. A summary of mercury concentrations in fish fillets and exceedances of the U.S. Environmental Protection 

Agency human-health criteria, and the U.S. Fish and Wildlife Service fish-eating bird and wildlife criteria from selected 

sites in the Delaware River Basin, 1998 through 2001 

[USEPA, U.S. Environmental Protection Agency; USFWS, U.S. Fish and Wildlife Service; μg/g, micrograms per gram] 

Map 

locator 

number 

(fig. 1) 

Site name Fish species 

Number 

of fish in 

sample 

Mercury 

concentration 

(μg/g) 

Exceed 

USEPA’s 

human-health 

criteria? 1 

(fillet) 

(0.3 μg/g) 

Exceed 

USFWS 

fish-eating 

bird and wildlife 

criteria? 2 

(whole fish) 

(0.1 μg/g) 

1 Raccoon Creek near Swedesboro, N.J. Chain Pickerel 1 0.29 No Yes 

2 Cooper River at Haddonfield, N.J. Largemouth bass 3 .21 No Yes 

3 Darby Creek near Darby, Pa. Smallmouth bass 2 .35 Yes Yes 

4 Ridley Creek near Media, Pa. Rock bass 3 .31 Yes Yes 

5 South Branch Pennsauken Creek Largemouth bass 4 .09 No No 

at Cherry Hill, N.J. 

6 Schuylkill River at Philadelphia, Pa. Smallmouth bass 5 .32 Yes Yes 

9 Darby Creek at Foxcroft, Pa. Smallmouth bass 1 .19 No Yes 

Rock bass 2 .22 No Yes 

10 Wissahickon Creek below Walnut Lake near Smallmouth bass 1 .34 Yes Yes 

Manayunk, Pa. 

11 East Branch Brandywine Creek near Dorlan, Pa. Smallmouth bass 2 .14 No Yes 

12 Stony Creek at Steriger Street at Norristown, Pa. Smallmouth bass 3 .21 No Yes 

13 Pennypack Creek at Paper Mill, Pa. Rock bass 3 .13 No Yes 

14 French Creek near Phoenixville, Pa. Smallmouth bass 3 .20 No Yes 

15 Pigeon Creek at Parker Ford, Pa. Smallmouth bass 1 .15 No Yes 

16 Delaware River at Trenton, N.J. Smallmouth bass 5 .29 No Yes 

17 Little Neshaminy Creek at Valley Road near Smallmouth bass 2 .27 No Yes 

Neshaminy, Pa. 

18 Hay Creek near Birdsboro, Pa. Smallmouth bass 1 .33 Yes Yes 

19 Shabakunk Creek near Lawrenceville, N.J. Rock bass 2 .20 No Yes 

20 Manatawny Creek near Pottstown, Pa. Smallmouth bass 3 .17 No Yes 

22 Wyomissing Creek at West Reading, Pa. Brown trout 2 .03 No No 

24 Tulpehocken Creek near Bernville, Pa. Smallmouth bass 1 .24 No Yes 

25 Little Lehigh Creek near East Texas, Pa. Brown trout 3 .03 No No 

26 Jordan Creek near Schnecksville, Pa. Smallmouth bass 3 .06 No No 

27 Lehigh River at Glendon, Pa. Smallmouth bass 5 .13 No Yes 

28 Brodhead Creek at Stroudsburg, Pa. Smallmouth bass 2 .06 No No 

29 Bush Kill Creek at Bushkill, Pa. Smallmouth bass 2 .13 No Yes 

30 Flat Brook near Flatbrookville, N.J. Smallmouth bass 2 .33 Yes Yes 

31 Delaware River at Port Jervis, N.Y. Smallmouth bass 4 .33 Yes Yes 

32 Neversink River near Godeffroy, N.Y. Rock bass 2 .18 No Yes 

33 Lackawaxen River at Hawley, Pa. Smallmouth bass 2 .18 No Yes 

34 Neversink River near Claryville, N.Y. Brown trout 2 .12 No Yes 

35 West Branch Delaware River at Walton, N.Y. Smallmouth bass 2 .15 No Yes 

1 U.S. Environmental Protection Agency human-health criteria (U.S. Environmental Protection Agency, 2001b). 

2 U.S. Fish and Wildlife Service fish-eating bird and wildlife criteria (Eisler, 1987). 

14 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 
Fish fillets 

On a basinwide scale, length-normalized 

tHg concentrations in smallmouth bass fillets were 

not strongly correlated with any land-use or landscape factor (table 3). The only significant correlation (at p<0.05) was with percent impervious land 

surface. There was a weak correlation with LOInormalized tHg concentrations in bed sediments 

(fig. 8). However, this relation was strongly influenced by a few data points at the low and high 

ends of the range. Length-normalized tHg concentrations in smallmouth bass fillets vary greatly 

among the sparsely populated, northern basins 

and generally increase with population density in 

the middle and southern parts of the basin. Concentrations of tHg in fish fillets tend to be highest 

in the more densely populated areas where concentrations of tHg in bed sediments are relatively 

high (fig. 7). 

Thus, when the sparsely populated 

(<100 people per square mile), northern-region 

sites are excluded from the analysis, effects of 

urbanization are observed (table 3). Among sites in 

watersheds inhabited by 100 or more people per 

square mile, length-normalized tHg concentrations 

in smallmouth bass fillets were positively correlated with population density, percent urban land 

cover, LOI-normalized tHg concentrations in bed 

sediment, and impervious land surface. Concentrations of tHg (length-normalized) in fillets from 

sites in this group were negatively correlated with 

latitude, percent wetland, percent septic, and 

methylation efficiency in bed sediment; a weak 

negative correlation is observed with elevation. 

Concentrations of tHg in smallmouth bass fillets 

were not significantly correlated with MeHg concentrations in water or in bed sediments, either on 

a basinwide scale or after removal of the sparsely 

Table 3. Results of Spearman rank correlation analysis between mercury concentration in smallmouth 

bass (Micropterus dolomieu) fillets and environmental and landscape variables for sites within the Delaware River 

Basin, New Jersey, New York, and Pennsylvania, 1998 through 2001 

[**, p≤0.01; *, p=0.05; ns, not significant (p>0.05); LOI, Loss-On-Ignition; ≥ , greater than or equal to; <, less than; 

numbers of observations are shown in parentheses] 

Smallmouth bass fillets


Environmental and landscape variables 

Total mercury/mean sample total length


Sites in basins with Sites in basins with 

All sites ≥100 people per <100 people per 

square mile square mile 

Estimated population density for 19971 ns (21) 0.69** (16) ns (5) 

Forested land cover (percent of total area)2 ns (21) ns (16) ns (5) 

Agricultural land cover (percent of total area)2 ns (21) ns (16) ns (5) 

Urban land cover (percent of total area)2 ns (21) .61* (16) ns (5) 

Impervious land surface (percent of total area)2 0.47* (21) .65** (16) ns (5) 

Wetland land cover (percent of total area)2 ns (21) -.66** (16) ns (5) 

Septic density1 ns (21) ns (16) ns (5) 

Septic percent (percent of population)1 ns (21) -.56** (16) ns (5) 

Elevation ns (21) -.52* (16) ns (5) 

Latitude ns (21) -.70** (16) ns (5) 

Methylmercury in water ns (16) ns (13) ns (5) 

Methylmercury in bed sediments ns (16) ns (13) ns (5) 

Total mercury in water ns (16) ns (13) ns (5) 

Total mercury/ LOI in bed sediments .55* (17) .71** (13) ns (5) 

Methylation efficiency in water ns (16) ns (13) ns (5) 

Methylation efficiency in bed sediments ns (16) -.64* (12) ns (5) 

Sulfate in water ns (21) ns (16) ns (5) 

Dissolved organic carbon in water ns (21) ns (16) ns (5) 

pH ns (21) ns (16) ns (5) 

1 U.S. Department of Commerce, 1990. 

2 U.S. Geological Survey, 1992. 

IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 15 
Figure 7. Relation between total mercury 

concentrations in smallmouth bass fillets (normalized 

by total length) and total mercury concentrations in bed 

sediment (normalized by LOI) within the Delaware 

River Basin, New Jersey, New York, and Pennsylvania, 

1998 through 2001. [<, less than; ≥ greater than or 

equal to] 

Figure 8. Relation between total mercury concentrations in smallmouth bass fillets (normalized by total 

length) and estimated population density (1997) (U.S. 

Department of Commerce, 1990) within the Delaware 

River Basin, New Jersey, New York, and Pennsylvania, 

1998 through 2001. 

16 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 

populated northern sites (table 3). No significant 

and reasonably strong correlations were observed 

when a separate analysis was conducted on the 

small group of northern-region sites with less than 

100 people per square mile (table 3). 

Streamwater 

Streamwater-sample tHg concentrations 

were correlated with urban indicators, when 

viewed on a basin-wide scale. Concentrations of 

tHg were positively correlated with population 

density, impervious land surface, and urban land 

cover (table 4, fig. 9). There was a weak, positive 

correlation with sulfate concentrations in the water 

column. Concentrations of tHg were negatively 

correlated with forested land cover. There appears 

to be an upward trend in tHg as areas become 

more populated in the basin, even with the large 

error range on actual concentration values. There is 

also a weak positive correlation with dissolved 

organic carbon (DOC) at p<0.05 (table 4). 

Streamwater MeHg concentrations were not 

strongly correlated with any landscape or environmental variable (table 4, fig. 10). However, methylation efficiency of streamwater was negatively 

correlated with population density, impervious 

land surface, and urban land cover (table 4. fig. 11). 

This is the inverse of the correlation observed with 

tHg and population variables. The rate of change 

from tHg to MeHg appears to be higher in the 

more forested areas of the basin than the less forested areas. 

Bed sediment 

Bed-sediment tHg concentrations also were 

correlated with urban indicators similar to the 

results seen for tHg in streamwater. The positive 

correlations were with population density, impervious land surface, and urban land cover. The negative correlations were with forested land cover, 

latitude, and elevation (table 5, fig. 12). The tHg 

concentrations showed a positive relation with sulfate concentrations in the water column, similar to 

the water and sulfate interaction (table 5). 
Table 4. Results of Spearman rank correlation analyses between environmental and landscape variables and mercury 

in streamwater samples for sites within the Delaware River Basin, New Jersey, New York, and Pennsylvania, 1998 

through 2001 

[LOI, Loss-On-Ignition; ***, p≤0.001; **, p≤0.01; *, p=0.05; ns, not significant (p>0.05); —, same variable. Number of 

observations are shown in parentheses.] 

Environmental and landscape variables 

Streamwater column 

Total 

mercury 

Methylmercury 

Methylation 

efficiency 

Estimated population density 19971 0.63*** (24) ns (24) -0.54** (23) 

Forested land cover (percent of total area)2 -.69*** (24) ns (24) ns (23) 

Agricultural land cover (percent of total area)2 ns (24) ns (24) ns (23) 

Urban land cover (percent of total area)2 .67*** (24) ns (24) -.59** (23) 

Impervious land surface (percent of total area)2 .57** (24) ns (24) -.53** (23) 

Wetland land cover (percent of total area)2 ns (24) ns (24) ns (23) 

Septic density1 ns (24) ns (24) ns (23) 

Elevation ns (24) ns (24) ns (23) 

Latitude ns (24) ns (24) ns (23) 

Methylmercury in water ns (23) — ns (23) 

Methylmercury in bed sediments ns (23) ns (24) ns (23) 

Total mercury in water — ns (24) -.62** (23) 

Total mercury in bed sediments .65*** (24) ns (24) ns (23) 

Total mercury/ LOI in bed sediments .63*** (24) ns (24) ns (23) 

Methylation efficiency in water -.60** (23) ns (23) — 

Methylation efficiency in bed sediments ns (23) ns (24) ns (23) 

Sulfate in water .46* (24) ns (24) ns (23) 

Dissolved organic carbon in water .41* (24) ns (24) ns (23) 

pH ns (24) ns (24) ns (23) 

1 U.S. Department of Commerce, 1990. 

2 U.S. Geological Survey, 1992. 

Figure 9. Relation between population density and 

total mercury concentrations in streamwater samples 

within the Delaware River Basin, New Jersey, New 

York, and Pennsylvania, 1998 through 2001. 

Figure 10. Relation between population density and 

methylmercury concentrations in streamwater samples 

within the Delaware River Basin, New Jersey, New York, 

and Pennsylvania, 1998 through 2001. 

IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 17 
As in the water column, MeHg was not 

strongly correlated with any landscape or environmental variable (table 5, fig. 13). A slight decline 

with an increase in population density can be 

observed in figure 13 until the population density 

becomes greater than 1,000 people per square mile. 

A threshold response can be observed between 

MeHg concentrations in bed sediment and percent 

wetland (fig. 14). None of the higher-percentage 

wetland sites have low MeHg concentrations. 

Methylation efficiency in bed sediment was 

negatively correlated with population density, 

impervious land surface, agricultural land cover 

and urban land cover (table 5), similar to what was 

observed in the water-column interactions. 

Positive correlations included forested land cover, 

elevation, and latitude. This is the inverse of the 

correlations for tHg in bed sediment and is similar 

to the results observed for streamwater tHg and 

MeHg concentrations. Methylation efficiency in 

bed sediment is an upside-down, bell-shaped 

curve with methylation efficiencies being higher in 

the least populated sites and the most populated 

sites of the Delaware River Basin (fig. 15). This 

negative correlation between methylation 

efficiency and population density corresponds 

with an opposite trend in relation to latitude 

(table 5). 

Figure 11. Relation between population density and 

methylation efficiency in streamwater samples within the 

Delaware River Basin, New Jersey, New York, and 

Pennsylvania, 1998 through 2001.

Figure 12. Relation between population density and total 

mercury concentrations in bed-sediment samples within 

the Delaware River Basin, New Jersey, New York, and 

Pennsylvania, 1998 through 2001. 

Figure 13. Relation between population density and 

methylmercury concentrations in bed-sediment samples 

within the Delaware River Basin, New Jersey, New York, 

and Pennsylvania, 1998 through 2001. 

Figure 14. Relation between methylmercury 

concentrations in bed-sediment samples and wetlands 

within the Delaware River Basin, New Jersey, New York, 

and Pennsylvania, 1998 through 2001. 

18 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 
Figure 15. Relation between population density and 

methylation efficiency in bed-sediment samples within 

the Delaware River Basin, New Jersey, New York, and 

Pennsylvania, 1998 through 2001. 

Table 5. Results of Spearman rank correlation analyses between environmental and landscape variables and mercury 

in bed-sediment samples for sites within the Delaware River Basin, New Jersey, New York, and Pennsylvania, 1998 

through 2001 

[LOI, Loss-On-Ignition; ***, p≤0.001; **, p≤0.01; *, p=0.05; ns, not significant (p>0.05); —, same variable; ≤, less than 

or equal to; >, greater than. Numbers of observations are shown in parentheses.] 

Environmental and landscape variables 

Bed sediment 

Total mercury/ 

LOI Methylmercury 

Methylation 

efficiency 

Estimated population density 19971 0.74*** (30) ns (28) -0.62*** (28) 

Forested land cover (percent of total area)2 -.64*** (30) 0.45* (28) .63*** (28) 

Agricultural land cover (percent of total area)2 ns (30) ns (28) -.47** (28) 

Urban land cover (percent of total area)2 .69*** (30) ns (28) -.49** (28) 

Impervious land surface (percent of total area)2 .61*** (30) ns (28) -.43* (28) 

Wetland land cover (percent of total area)2 ns (30) ns (28) ns (28) 

Septic density1 ns (30) ns (28) -.55** (28) 

Elevation -.56** (30) ns (28) .56** (28) 

Latitude -.48* (30) .46* (28) .62*** (28) 

Methylmercury in water ns (24) ns (24) ns (24) 

Methylmercury in bed sediments ns (28) —- .82*** (28) 

Total mercury in water .63*** (24) -.41* (23) ns (23) 

Total mercury in bed sediments .67*** (30) ns (28) ns (28) 

Total mercury/ LOI in bed sediments —- ns (28) -.40* (28) 

Methylation efficiency in water ns (23) ns (23) ns (23) 

Methylation efficiency in bed sediments -.40* (28) .84*** (28) —­

Sulfate in water .64*** (29) ns (27) -.52** (27) 

Dissolved organic carbon in water ns (29) ns (27) ns (27) 

pH ns (30) ns (28) ns (28) 

1 U.S. Department of Commerce, 1990. 

2 U.S. Geological Survey, 1992. 

Methylation efficiency in bed sediment was 

negatively correlated with water-column sulfate 

concentrations. This is similar to the negative correlation between methylation efficiency in streamwater and water-column sulfate concentrations. 

The forested sites in the northern latitudes, plus a 

mixed land-use site in the Coastal Plain (low-gradient) streams, had the highest methylation efficiencies and the lowest sulfate concentrations. The 

agricultural, urban, and mixed land-use sites had 

higher sulfate concentrations and lower bed-sediment methylation efficiencies. 

Differences among land-use groups 

After studying occurrence and distribution 

of Hg in the basin as a whole, comparisons were 

made among sites grouped according to land use 

to determine which processes may affect the distribution of Hg within each group. All the forested 

and two of the three low intensity-agricultural 

basins are in the northern Appalachian region of 

IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 19 
the study area, and most urban basins are in the 

southern area. Agricultural basins span the entire 

study area, but most moderate to high agricultural 

land-use basins are in the middle and southern sections of the study area. Mixed land-use sites and 

large-river sites were not included in this analysis 

because of the multiplicity of land uses within each 

basin. 

The urban sites had the highest median concentration of tHg (length-normalized) in smallmouth bass (fig. 16). Next were the low-intensity 

agricultural group, the agricultural group, and the 

forested group. The forested and agricultural 

basins had greater ranges in tHg fillet concentrations than the other two land-use groups (fig. 16). 

Some land-use differences were observed in 

concentrations of tHg, MeHg, and the methylation 

efficiency in streamwater and bed-sediment samples (fig. 17A, 17B, and 17C, respectively). The 

urban land-use group had the highest tHg concentrations in streamwater and bed-sediment samples 

(fig. 17A). No patterns could be determined in concentrations of MeHg (fig. 17B). Methylation efficiency was lower in the urban group than the other 

groups (fig. 17C). 

Figure 16. Distribution of total mercury concentrations in 

smallmouth bass fillets by land-use groups within the 

Delaware River Basin, New Jersey, New York, and 

Pennsylvania, 1998 through 2001. 

Correlation analyses were used to determine 

the factors affecting Hg in fillets, streamwater, and 

bed-sediment samples among the different landuse groups (table 6). Sites from the forested and 

low intensity-agricultural groups were combined 

into a ‘forested/low intensity-agricultural’ group 

to provide a greater number of sites for data analysis. These results (table 6) suggest that each landuse group had different environmental factors 

affecting Hg concentrations in fish, water, and bed 

sediments. More data are needed within each landuse group to better characterize these factors. 

Within the forested/low-intensity agricultural group, increased urbanization was associated 

with decreased tHg concentrations in smallmouth 

bass (length-normalized). Increased population 

density was associated with decreased methylation 

efficiency in bed sediment. Increased agricultural 

land cover was associated with increased concentrations of tHg (normalized to LOI) in bed sediment and increased methylation efficiency in 

water. Increased agricultural land cover also was 

associated with decreased MeHg concentrations in 

water, and methylation efficiency in bed sediment 

is observed to increase with an increase in agricultural land cover (table 6). Methylation efficiency in 

bed sediment also was negatively correlated with 

sulfate concentration. 

Within the agricultural group, increased 

urbanization (denoted as urban land cover), 

impervious land surface, and population density 

were associated with increased tHg concentrations 

in smallmouth bass (length-normalized) (table 6). 

Increased septic-tank density was associated with 

decreased tHg concentrations in water (possibly 

reflecting the lower septic-tank density in towns 

and villages served by wastewater treatment 

plants). Increased elevation was associated with 

decreased methylation efficiency in the water. 

Within the urban group, increased forested 

land cover and wetland cover were associated with 

an increase in tHg concentration in smallmouth 

bass (length-normalized). Concentrations in smallmouth bass fillets were not significantly correlated 

with water or bed sediment tHg, MeHg, or methylation efficiency. Furthermore, no forms of Hg in 

fish, water, or bed sediment exhibited a significant 

correlation with pH, DOC, or sulfate concentration. 

20 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 
Figure 17. Distribution of streamwater and bed sediment forms of mercury (A) total mercury, 

(B) methylmercury, and (C) methylation efficiency, by land-use groups within the Delaware River Basin, 

New Jersey, New York, and Pennsylvania, 1998 through 2001. 

IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 21 
Table 6. Results of Kendall Tau correlation analyses among forms of mercury in fish fillets, streamwater, and bedsediment samples, and environmental and landscape variables, within forested/low intensity-agricultural, agricultural, 

and urban land-use classes for sites within the Delaware River Basin, New Jersey, New York, and Pennsylvania, 1998 

through 2001 

[LOI, Loss-On-Ignition; ***, p≤0.001; **, p≤0.01; *, p=0.05; ns, not significant (p>0.05). Only factors with one or more 

significant correlations are shown. Numbers of observations are shown in parentheses.] 

Mercury in Total mercury Methylmercury Methylation efficiency 

Environmental 

and landscape 

variables 

smallmouth 

bass fillets, 

normalized to 

mean total length 

Bed 

sediment Water (LOI 

normalized) 

Bed 

sediment Water (LOI 

normalized) 

Bed 

sediment Water (LOI 

normalized) 

Forested / low-intensity agricultural group 

1 Urban land cover -0.73* (6) ns (8) ns (8) ns (8) ns (8) ns (8) ns (8) 

Estimated population ns (6) ns (8) ns (8) ns (8) ns (8) ns (8) -0.57 (8) 

density 19972 

1 Forest land cover ns (6) ns (8) -0.64** (8) -0.76** (8) -0.76* (8) -0.71** (8) ns (8) 

1 Agricultural land cover ns (6) ns (8) .93** (8) -.76** (8) ns (8) .71** (8) -.57 (8) 

Septic-tank density (1990)2 ns (6) ns (8) ns (8) ns (8) .81* (8) ns (8) ns (8) 

Drainage area ns (6) ns (8) ns (8) ns (8) .81* (8) ns (8) ns (8) 

Sulfate ns (6) ns (8) ns (8) ns (8) ns (8) ns (8) -.64 (8) 

Agricultural group 

1 Urban land cover .73* (6) ns (7) ns (8) ns (7) ns (7) ns (7) ns (7) 

1 Impervious land surface .73* (6) ns (7) ns (8) ns (7) ns (7) ns (7) ns (7) 

Population density 19972 .87* (6) ns (7) ns (8) ns (7) ns (7) ns (7) ns (7) 

Septic-tank density (1990)2 ns (6) -0.81** (7) ns (8) ns (7) ns (7) ns (7) ns (7) 

Elevation ns (6) ns (7) ns (8) ns (7) ns (7) -.62* (7) ns (7) 

Urban group 

1 Forest land cover .80* (5) ns (6) ns (10) ns (7) ns (10) ns (6) ns (10) 

W 1 etland cover .80* (5) ns (6) ns (10) ns (7) ns (10) ns (6) ns (10) 

1 U.S. Geological Survey, 1992. 

2 U.S. Department of Commerce, 1990. 

Comparison of Results With the National 

Mercury Pilot Program and Other Studies 

Concentrations of tHg in fish fillets from the 

Delaware River Basin ranked eighth highest (geometric mean; 0.26 μg/g) of the 20 basins in the 

NMPP (Brumbaugh and others, 2001). The highest 

geometric mean was in the Nevada Basin and 

Range NAWQA study basin of Nevada and California (geometric mean, 3.34 μg/g) and the lowest 

was in Oahu Island, Hawaii, NAWQA study basin 

(geometric mean; 0.03 μg/g). These results, however, were calculated before this study was completed. The recalculated geometric mean for the 

Delaware River Basin is 0.17 μg/g, which would 

rank the basin around twelfth highest instead of 

eighth highest. 

Results of the NMPP indicate that tHg concentrations in fish fillets (length-normalized) 

increased with latitude, percent wetland, and the 

methylation efficiency of bed sediment (Brumbaugh and others, 2001). The Delaware study had 

the opposite results. If the Delaware study had 

more data and larger ranges within each category 

tested, similar to NMPP, maybe the results would 

have been similar between the two studies. The 

percentage of wetland in the Delaware River Basin 

ranged from 0 to 18, but the NMPP had a range of 

0 to 50 (Brumbaugh and others, 2001). Within the 

Delaware River Basin, the percentage of wetland in 

a given stream basin was estimated from satellite 

images. 

Concentrations of tHg in fish correlated with 

tHg concentrations in bed sediment, in contrast to 

the lack of correlation observed in the NMPP study 

(Brumbaugh and others, 2001). Several other studies also have seen the same relation between MeHg 

concentrations in bed sediment to concentrations 

of Hg in fish (Burns and others, 1997; U.S. Environmental Protection Agency, 1997; Australian and 

New Zealand Environment and Conservation 

Council, 2000a; New York State Department of 

Environmental Conservation, 2002). This differ22 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 
ence between NMPP and the Delaware River Basin 

could be because of the greater percentage of 

urban sites in the Delaware River Basin study as 

compared with NMPP. This difference also could 

be related to differences in deposition, or habitat, 

diet and uptake dynamics between smallmouth 

bass used for analysis in the Delaware River Basin 

and largemouth bass (Micropterus salmoides) used 

in the NMPP. The largemouth bass tHg concentrations correlated with MeHg in water and was the 

strongest influential variable on Hg concentration 

in fish noted in the NMPP (Brumbaugh and others, 

2001). 

Alkalinity and pH of the streams showed no 

significant relation with Hg in fish tissue. Many 

lake studies have found that Hg concentrations in 

fish are often inversely related to lake alkalinity or 

pH (Watras and Huckbee, 1994; Watras and Bloom, 

1992; Spry and Wiener, 1991; Cope and others, 

1990). However, this is not true for all lakes. 

In Little Rock Lake, Wis., for example, when calcium concentrations increased, the rate of MeHg 

uptake across the fish’s gill-membrane increased 

(Wiener and others, 1990). The calcium shift 

occurred when the pH was adjusted. Without the 

shift in calcium, the effect of pH on uptake of Hg 

by the fish in this lake is unclear. Another study 

conducted by Rodgers and others (1987) showed 

that MeHg uptake by rainbow trout and walleye 

did not differ among three different pH levels used 

in the study. Little is known about the relation 

between pH and the uptake of Hg by fish in flowing waters. 

Other studies have shown a correlation 

between DOC and the uptake of Hg by fish (U.S 

Geological Survey, 1995; Krabbenhoft and others, 

1999; U.S. Department of Interior, 1998; U.S. Environmental Protection Agency, 2000b). Above a 

threshold DOC concentration, bioaccumulation of 

Hg in fish appears to decrease (U.S. Department of 

Interior, 1998; U.S. Environmental Protection 

Agency, 2000b). However, in the Delaware River 

Basin, only a weak correlation between DOC and 

tHg concentrations in water was observed 

(table 4). The low median and relatively narrow 

range of DOC concentrations among the Delaware 

River Basin sites (median 2.1 ng/L, minimum 

0.7 ng/L, and maximum 9.5 ng/L) may account 

for the lack of correlation. A 74-percent decrease in 

MeHg uptake rate across the gills of Sacramento 

blackfish (Orthodon microlepidotus) when 2 mg/L 

DOC were present in the water was reported by 

the National Center for Environmental Research 

(2002). 

Weight, length, and age of the fish are highly 

correlated with Hg concentrations in fish tissue 

(Braune, 1987; Cope and others, 1990; Stahl and 

Sobat, 2000; Huggett and others, 2001). The Delaware River Basin studies focused on fish in the 

2- to 3-year age range to allow stronger correlations to be made between the environmental variables and Hg concentrations in fish rather than 

with fish age and size. 

Water temperature can be an important variable for uptake of Hg by fish. As water temperatures increase, bioaccumulation of Hg in fish fillets 

increases (Australian and New Zealand Environment and Conservation Council, 2000b) because of 

increased metabolic activity and increased Hg 

methylation efficiency. The temperature data collected as part of the Delaware River Basin study 

were collected during August and September, and 

little or no temperature variation was observed 

that would account for slower or faster uptake of 

Hg by the smallmouth bass analyzed. 

A USEPA study (1997) indicated that the 

Delaware River Basin has one of the highest deposition rates of Hg in the country; estimated atmospheric deposition rates of Hg are in excess of 

20 mg/m2/yr. Although methylation efficiency in 

the Delaware River Basin is relatively low, Hg concentrations in fish are relatively high. In the Delaware River Basin, precipitation rates are higher at 

the forested sites compared to the rest of the basin 

(Fischer, 1999). However, Pilgrim and others (1999) 

studied atmospheric deposition rates of Hg in forested and unforested areas and the concentration 

of Hg in fish. They determined no significant difference in atmospheric deposition or fish Hg concentrations between the two areas. 

In the Delaware River Basin, fish tissue from 

the urban sites had the highest median concentration of tHg of the four groups in the study, and fish 

from the forested group had the lowest tHg concentrations. These results differ from those of 

NMPP, in which the lowest median tHg concentration in fish tissue was from sites in the urban 

group, and the highest was in the forested/lowintensity agricultural group (Brumbaugh and others, 2001). 

With no apparent patterns observed in the 

present study among the land-use groups for 

MeHg concentrations, no comparisons with NMPP 

results were possible. The NMPP found that the 

MeHg concentrations in water were highest at forested/low-intensity agricultural sites and lowest at 

IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 23 
urban sites (Krabbenhoft and others, 1999), and 

MeHg concentrations in bed sediment were highest at the forested/low-intensity agricultural sites, 

the urban sites were next, and the agricultural sites 

had the lowest MeHg concentrations. 

The methylation efficiency pattern observed 

in the Delaware study is similar to what was 

observed in the NMPP. Both studies showed 

higher methylation efficiencies in streams flowing 

through mixed forested and agricultural landscapes than in streams flowing through urban 

landscapes (Krabbenhoft and others, 1999). 

Both studies suggest that regional and landuse factors are important in affecting the processing and bioavailability of Hg in the environment. 

High tHg concentrations in fish tissue and bed sediment are related to factors associated with urban 

landscapes. Human effects such as increased concentrations of tHg in fish tissue are observed as 

population density increases in urban areas of the 

Delaware River Basin. The source of the higher 

tHg fish-tissue concentrations observed in the forested areas could not be determined but may have 

to do with the higher amounts of rainfall in the 

area. Additional study with a larger number of 

sites using the urban gradient for site-selection 

purposes would be helpful in determining 

whether the urbanization effect is real or an artifact 

of a small number of sampling sites. 

SUMMARY AND CONCLUSIONS 

The nontidal part of the Delaware River 

Basin has been studied as part of the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program to integrate physical, 

chemical, and biological sampling efforts to determine the status and trends in surface- and groundwater resources. The Delaware River Basin also 

was included in the USGS National Mercury Pilot 

Program (NMPP). 

Fish species collected as part of the Delaware 

River Basin study included smallmouth bass 

(Micropterus dolomieu), brown trout (Salmo trutta), 

chain pickerel (Esox niger), largemouth bass 

(Micropterus salmoides), and rock bass (Ambloplites 

rupestris). Only total mercury (tHg) was analyzed 

in this study. The U.S. Environmental Protection 

Agency human-health criteria of 0.3 μg/g wetweight mercury (Hg) concentrations in fillets was 

exceeded in 7 of the 32 fillet samples collected from 

31 sites. With the exception of two samples collected in forested areas of the basin, these samples 

were collected from streams near the major cities 

within the basin. The U.S. Fish and Wildlife Service 

fish-eating bird and wildlife criterion of 0.1 μg/g 

wet weight in whole fish was exceeded in 27 of 

32 samples. Although comparing concentrations 

from fish fillets is not a truly valid comparison to a 

criterion established for whole fish, the fillets had 

higher levels of Hg than are safe for wildlife. 

Correlation analyses were completed comparing concentrations of Hg in smallmouth bass 

(length-normalized) with water and bed sediment 

tHg and methylmercury (MeHg) concentrations, 

methylation efficiencies, and other environmental 

variables. Only percent impervious surface and 

tHg concentration in bed sediment correlated with 

Hg concentrations in the smallmouth bass. 

A subgroup of the fish sites was analyzed 

with the environmental variables. This subgroup 

consisted of sites where the population was greater 

than or equal to 100 people per square mile. Within 

this group of sites, population density, urban land 

cover, impervious surface, and bed sediment tHg 

concentrations were positively correlated with tHg 

concentrations in smallmouth bass fillets. Wetland 

cover, percent septic systems, elevation, latitude, 

and bed sediment methylation efficiency were negatively correlated with tHg concentrations in 

smallmouth bass fillets. These correlations all indicate an urban effect on Hg concentrations in smallmouth bass fillets. 

Concentrations of tHg and MeHg in water in 

the more urbanized areas of the Delaware River 

Basin were higher than in other areas. Concentrations of tHg were positively correlated with urbanization factors and negatively correlated with 

forested land cover. No correlations were noted for 

concentrations of MeHg with any factors in this 

study. Methylation efficiency was negatively correlated with urbanization. 

Concentrations of tHg in bed sediments in 

the urbanized area of the basin were higher than in 

other areas, and concentrations of MeHg in the 

northern (more forested) area of the basin were 

higher than in other areas. Urbanization was positively correlated with tHg concentration in bed 

sediments; forested land cover and elevation were 

negatively correlated. Forested land cover was 

positively correlated with bed sediment MeHg 

concentrations. Methylation efficiency in bed sediment was higher in the forested areas and was negatively correlated with urbanization, similar to 

methylation efficiency in water. 

24 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 
There are several different land-use groups 

within the Delaware River Basin—urban, agricultural, low-intensity agricultural, and forested. Correlations within each group were analyzed to 

determine if different environmental variables 

played a role in fillet Hg concentrations among the 

four groups. The fillets from urban sites had the 

highest median concentration of tHg, followed by 

low-intensity agricultural sites, the agricultural 

sites, and the forested sites. Forested land cover 

and wetland cover correlated positively with Hg 

concentrations in fillets within the urban group. 

The Hg fillet concentrations in the agricultural 

group were positively correlated with urbanization 

factors (population, urban land cover, and impervious land), whereas forested and low-intensity 

agricultural groups had fillet Hg concentrations 

that were negatively correlated with urbanization. 

Concentrations of tHg in water from sites in 

the agricultural group were negatively correlated 

with septic-tank density, and methylation 

efficiency was negatively correlated with elevation. 

In the forested and low-intensity agricultural 

groups, MeHg concentrations were negatively 

correlated with forested land and agricultural land 

cover. Methylation efficiency in the forested and 

low-intensity agricultural group was negatively 

correlated with forested land cover and positively 

correlated with agricultural land cover. No significant correlations for tHg, MeHg, or methylation 

efficiency were noted for the urban group. 

Concentrations of tHg in bed sediment were 

positively correlated with agricultural land cover 

and negatively correlated with forested land cover 

in the forested and low-intensity agricultural 

groups. Concentrations of MeHg in bed sediment 

from the forested and low-intensity agricultural 

groups were positively correlated with septic-tank 

density and basin drainage area and negatively 

correlated with forested land cover. Methylation 

efficiency in forested and low-intensity agricultural sites was negatively correlated with population density, agricultural land cover, and sulfate 

concentration in the water. Bed sediment tHg concentrations in urban sites were not significantly 

correlated with any environmental variables tested 

as part of the study. 

All three media—fish, water, and bed sediments—reflected an urbanization effect, but the 

relation for each was different. Because of the limited number of samples, neither concentrations of 

MeHg in streamwater nor bed sediment were good 

predictors of tHg concentrations in smallmouth 

bass in the Delaware River Basin. Additional sampling would be needed to draw more precise conclusions. 

IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 25 
REFERENCES CITED 

Australian and New Zealand Environment and 

Conservation Council, and Agriculture and 

Resource Management Council of Australia 

and New Zealand, 2000a, National water 

quality management strategy—Australian 

and New Zealand guidelines for fresh and 

marine water quality—Aquatic ecosystems—Rationale and background 

information: Australia and New Zealand, 

Paper no. 4, v. 2, chap. 8, p. 8.3/128-132. 

_____2000b, National water quality management 

strategy—Australian and New Zealand 

guidelines for fresh and marine water quality—Primary industries—Rationale and 

background information: Australia and 

New Zealand, Paper no. 4, v. 3. chap. 9, 

p. 9.4/43. 

Bahnick, D., and Sauer, C., 1994, A national study 

of mercury contamination of fish—IV—Analytical methods and results: Chemosphere, 

v. 29, no. 3, p. 537-546. 

Bilger, M.D., Brightbill, R.A., and Campbell, H.L, 

1999, Occurrence of organochlorine compounds in whole fish tissue from streams of 

the lower Susquehanna River Basin, Pennsylvania and Maryland, 1992: U.S. Geological Survey Water-Resources Investigations 

Report 99-4065, 17 p. 

Braune, B.M., 1987, Mercury accumulation in relation to size and age of Atlantic Herring (Clupea harengus harengus) from the southwestern 

bay of Fundy, Canada: Archives of Environmental Contamination and Toxicology, v. 16, 

p. 311-320. 

Brumbaugh, W.G., Krabbenhoft, D.P., Helsel, D.R., 

Wiener, J.G., and Echols, K.R., 2001, 

A national pilot study of mercury contamination of aquatic ecosystems along multiple 

gradients—Bioaccumulation in fish: U.S. 

Geological Survey, USGS/BRD/BSR-2001­

0009, 28 p. 

Burns, T.P., Hadden, C.T., Cornaby, B.W., and Mitz, 

S.V., 1997, A food web model of mercury 

transfer from stream sediment to predators 

of fish for ecological risk based clean-up 

goals: American Society for Testing and 

Materials, ASTM STP 1317, p. 7-27. 

Cope, W.G., Wiener, J.G., and Rada, R.G., 1990, 

Mercury accumulation in yellow perch in 

Wisconsin seepage lakes—Relation to lake 

characteristics: Environmental Toxicology 

and Chemistry, v. 9, p. 931-940. 

Eisler, Ronald, 1987, Mercury hazards to fish, wildlife, and invertebrates—A synoptic review: 

U.S. Fish and Wildlife Service Biological 

Report 85, v. 1, no. 10, 90 p. 

Fischer, J.M., 1999, National Water-Quality Assessment Program—Delaware River Basin: 

U.S. Geological Survey Fact Sheet FS-056-99, 

6 p. 

Fitzgerald, W.F., and Watras, C.J., 1989, Mercury in 

surficial waters of rural Wisconsin 

lakes: Science of the Total Environment, 

v. 87/88, p. 223-232. 

Gilliom, R.J., Alley, W.M., and Gurtz, M.E., 1995, 

Design of the National Water-Quality 

Assessment Program—Occurrence and distribution of water-quality conditions: 

U.S. Geological Survey Circular 1112, 33 p. 

Goldstein, R.M., Brigham, M.E., and Stauffer, J.C., 

1996, Comparison of mercury concentrations 

in liver, muscle, whole bodies, and composites of fish from the Red River of the 

North: Canadian Journal of Fisheries and 

Aquatic Sciences, v. 53, p. 244-252. 

Gurtz, M.E., 1994, Design of biological components 

of the National Water-Quality Assessment 

(NAWQA) Program in Loeb, S.L., and Spacie, A., eds., Biological monitoring of aquatic 

systems: Boca Raton, Fla., Lewis Publishers, p. 323-354. 

Hirsch, R.M., Alley, W.M., and Wilber, W.G., 1988, 

Concepts for National Water-Quality Assessment Program: U.S. Geological Survey Circular 1021, 42 p. 

Horvat, M., Bloom, N.S., and Liang, L., 1993, Comparison of distillation with other current isolation methods for the determination of 

methylmercury compounds in low level 

environmental samples, Part I, Sediment: 

Analytica Chemica Acta, v. 281, p. 135-152. 

Huggett, D.B., Stevens, J.A., Allgood, J.C., Lutken, 

C.B., Grace, C.A., and Benson, W.H., 2001, 

Mercury in sediment and fish from North 

Mississippi Lakes: Chemosphere, v. 42, 

p. 923-929. 

26 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 
REFERENCES CITED—CONTINUED 

Krabbenhoft, D.P., Wiener, J.G., Brumbaugh, W.G., 

Olson, M.L., DeWilde, J.F., and Sabin, T.J., 

1999, A national pilot study of mercury contamination of aquatic ecosystems along multiple gradients: U.S. Geological Survey 

Water-Resources Investigations Report 99­

4018-B. 13 p. 

Leahy, P.P., Rosenshein, J.S., and Knopman, D.S., 

1990, Implementation plan for the National 

Water-Quality Assessment Program: U.S. 

Geological Survey Open-File Report 90-174, 

10 p. 

Leahy, P.P., and Wilber, W.G., 1991, National WaterQuality Assessment Program: U.S. Geological Survey Open-File Report 91-54, 2 p. 

MacDonald, D.D., Ingersoll, C.G., and Berger, T.A., 

2000, Development and evaluation of consensus-based sediment quality guidelines 

for freshwater ecosystems: Archives of 

Environmental Contamination and Toxicology, v. 39, p. 20-31. 

McMahon, Gerard, and Cuffney, T.F., 2000, Quantifying urban intensity in drainage basins for 

assessing stream ecological conditions: 

Journal of the American Water Resources 

Association, v. 36, p. 1,247-1,261. 

National Center for Environmental Research, 2002, 

Progress Report—Mercury uptake by fish: 

U.S. Environmental Protection Agency, 

Office of Research and Development, 

accessed April 17, 2002, at http://es.epa.gov/ 

ncer/progress/centers/cehr/aqua1apr.html 

National Research Council, 2000, Toxicological 

effects of methylmercury: Washington, 

D.C., National Academy Press, 344 p. 

New York State Department of Environmental 

Conservation, 2002, Mercury management in 

New York State: accessed January 31, 2002, 

at http://www.dec.state.ny.us/website/dshm/ 

redrecy/mercury.htm 

Olson, M.L., Cleckner, L.B., Hurley, J.P., Krabbenhoft, D.P., and Heelan, T.W., 1997, Resolution 

of matrix effects on analysis of total and 

methylmercury in aqueous samples from the 

Florida Everglades: Fresenius Journal of 

Analytical Chemistry, v. 358, p. 392-396. 

Olson, M.L., and DeWild, J.F., 1999, Low-level techniques for the collection and species-specific 

analysis of low levels of mercury in water, 

sediment, and biota, in Morganwalp, D.W., 

and Buxon, H.T., eds., U.S. Geological Survey Toxic Substances Hydrology Program 

Proceedings of the technical meeting, 

Charleston, S.C., March 8-12, 1999, v. 2, 

Contamination of hydrologic systems and 

related ecosystems: U.S. Geological Survey 

Water-Resources Investigations Report 99­

4018-B, 8 p. 

Pilgrim, Wilfred, Lucotte, Marc, Montgomery, 

Shelagh, Santos-Burgoa, Carlos, Uriarte, 

M.I.I., Abascal-Garrido, Francisco, Round, 

Margaret, and Porcella, Don, 1999, Meeting 

the challenges of continental pollutant pathways–Mercury–Case study: Environment 

Canada, Final Report to the Secretariat of the 

CEC, accessed April 17, 2002, at 

http://www.eman-rese.ca/eman/reports/ 

publications/99_mercurywkshp/page4.html 

Rodgers, D.W., Watson, T.A., Langan, J.S., and 

Wheaton, T.J., 1987, Effects of pH and feeding regime on methylmercury accumulation 

within aquatic microcosms: Environmental 

Pollution, v. 45, p. 261-274. 

Shelton, L.R., and Capel, P.D., 1994, Guidelines for 

collecting and processing samples of stream 

bed sediment for analysis of trace elements 

and organic contaminants for the National 

Water-Quality Assessment Program: U.S. 

Geological Survey Open-File Report 94-0458, 

p. 20. 

Spry, D.J., and Wiener, J.G., 1991, Metal bioavailability and toxicity to fish in low-alkalinity 

lakes—A critical review: Environmental 

Pollution, v. 71, p. 243-304. 

Stahl, J.R., and Sobat, S.L., 2000, Creek chub as sentinel indicator species for relative regional 

assessment of mercury contamination and 

monitoring pollutant trends in Indiana rivers and streams: Indiana Department of 

Environmental Management, 

IDEM/32/002/2000, 25 p. 

U.S. Department of Commerce, 1990, United States 

Census 1990: U.S. Census Bureau, accessed 

1997, at http://www.census.gov 

IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 27 
REFERENCES CITED—CONTINUED 

U.S. Department of Interior, 1998, Guidelines for 

interpretation of the biological effects of 

selected constituents in biota, water, and 

sediment—Mercury: National Irrigation 

Water Quality Program Information Report, 

no. 3, 22 p. 

U.S. Environmental Protection Agency, 1997, Mercury study report to congress - Volume III ­

Fate and transport of mercury in the 

environment: Office of Air Quality Planning and Standards, Office of Research and 

Development, EPA-451/R-97-005, 

243 p. + appendices. 

_____2000a, Update - National listing of fish and 

wildlife advisories: USEPA Office of Water, 

EPA-823-F-00-016, 6 p. 

_____2000b, Mercury transport and fate in 

watersheds: National Center for Environmental Research, Star Report 10, 8 p. 

_____2001a, Methylmercury: EPA-823-F-01-001, 

accessed November 11, 2001, at 

http://www.epa.gov/waterscience/criteria/ 

methylmercury/factsheet.html 

_____2001b, Mercury–General information–Frequently asked questions: accessed May 3, 

2001, at http://www.epa.gov/ 

mercury/information.htm#questions 

_____2002, 2002 Edition of the drinking water standards and health advisories: Washington, 

D.C., Office of Water, EPA 822-R-02-038, 

p. 19. 

U.S. Geological Survey, 1992, National Land Cover 

Characterization, accessed 1997, at 

http://landcover.usgs.gov/natllandcover.html 

_____1995, Mercury contamination of aquatic 

ecosystems: U.S. Geological Survey Fact 

Sheet, FS-261-95. 

Wachs, B., 1985, Bioindicators for the heavy metal 

load of river ecosystems: Symposia Biologica Hungarica, v. 29, p. 179-190. 

Watras, C.J., and Bloom, N.S., 1992, Mercury and 

methylmercury in individual zooplankton— 

Implications for bioaccumulation: 

Limelight and Oceanography, v. 37, p. 1,313­

1,318. 

Watras, C.J., and Huckabee, J.W., eds., 1994, Mercury pollution integration and synthesis: 

Boca Raton, Fla., Lewis Publishers, p. 153­

177. 

Wiener, J.G., Fitzgerald, W.F., Watras, C.J., and 

Rada, R.G., 1990, Partitioning and bioavailability of mercury in an experimentally acidified Wisconsin lake: Environmental 

Toxicology and Chemistry, v. 9, p. 909-918. 

28 TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 
Appendix. Site information, sampling years, fish species, number of fish per sample, mercury and (or) methylmercury concentrations in fi

sediment, and Loss-On-Ignition for bed sediment for sites within the Dela

ware River Basin, New Jersey, New York, and Pennsylvania, 199

[μg/g, micrograms per gram; ng/L, nanograms per liter; ng/g, nanograms per gram; LOI, Loss-On-Ignition; —, no data] 

Site name 

U.S. 

Geological 

Survey 

identification 

number 

Latitude Longitude 

Year of 

fillet 

sample 

Total 

mercury in 

fish fillets -

wet weight 

(μg/g) 

Fish species 

Number 

of fish 

per 

sample 

Year of 

water 

sample 

Total 

mercury 

in water 

(ng/L) 

Methyl 

mercury 

in water 

(ng/L) 

Year of 

bed 

sediment 

sample 

Raccoon Creek near Swedesboro, 01477120 394428 751533 11998 0.29 Chain pickerel 1 11998 1.1 0.05 11998 

N.J. 

Cooper River at Haddonfield, N.J. 01467040 395411 750119 11999 .21 Largemouth bass 3 11999 — .04 11999 Darby Creek near Darby, Pa. 01475510 395544 751622 11999 .35 Smallmouth bass 2 11999 3.5 .06 11999 Ridley Creek near Media, Pa. 01476470 395557 752442 22001 .31 Rock bass 3 11998 .86 — 2000 South Branch Pennsauken Creek 01467081 395630 750005 11999 .09 Largemouth bass 4 — — — 1999 

at Cherry Hill, N.J. 

Schuylkill River at Philadelphia, Pa. 01474500 395804 751120 11998 .32 Smallmouth bass 5 — — — — North Branch Rancocas Creek 01467000 395810 744105 — — — — — — — 11999 

at Pemberton, N.J. 

Crum Creek at Goshen Road 01475845 395924 752616 — — — — 11998 1.1 .04 12000 

near Whitehorse, Pa. 

Darby Creek at Foxcroft, Pa. 01475430 395945 752121 22001 .19 Smallmouth bass 1 11999 2.1 <.02 12000 

.22 Rock bass 2 

Wissahickon Creek below Walnut 01473990 400150 751154 11999 .34 Smallmouth bass 1 11999 1.6 .03 11999 

Lake near Manayunk, Pa. 

East Branch Brandywine Creek 01480665 400308 754328 22001 .14 Smallmouth bass 2 11998 .80 .03 12000 

near Dorlan, Pa. 

Stony Creek at Steriger Street 01473470 400738 752043 22001 .21 Smallmouth bass 3 11998 1.6 <.02 12000 

at Norristown, Pa. 

Pennypack Creek at Paper Mill, Pa. 01467040 400824 750428 11999 .13 Rock bass 3 — — — 11999 French Creek near Phoenixville, Pa. 01472157 400905 753606 11999 .20 Smallmouth bass 3 11999 1.8 .05 11999 Pigeon Creek at Parker Ford, Pa. 01472100 401148 753513 22001 .15 Smallmouth bass 1 — — — 12000 Dela

ware River at Trenton, N.J. 01463500 401318 744642 11998 .29 Smallmouth bass 5 — — — — 

Little Neshaminy Creek at Valley 01464907 401345 750712 11998 .27 Smallmouth bass 2 11998 4.1 .10 11998 

Road near Neshaminy, Pa. 

Hay Creek near Birdsboro, Pa. 01471668 401504 754850 11998 .33 Smallmouth bass 1 11998 .77 .04 11998 Shabakunk Creek near 01463810 401519 744417 22001 .20 Rock bass 2 11998 22 .28 12000 

Lawrenceville, N.J. 

Manatawny Creek near Pottstown, 01471980 401622 754049 11998 .17 Smallmouth bass 3 11998 1.4 .06 11998 

Pa. 

IN THE DELAWARE RIVER BASIN, NEW JERSEY, NEW YORK, AND PENNSYLVANIA, 1998-2001 29 
Appendix. Site information, sampling years, fish species, number of fish per sample, mercury and (or) methylmercury concentrations in fi

sediment, and Loss-On-Ignition for bed sediment for sites within the Dela

ware River Basin, New Jersey, New 

York, and 

Pennsylvania, 199

[μg/g, micrograms per gram; ng/L, nanograms per liter; ng/g, nanograms per gram; LOI, Loss-On-Ignition; —, no data] 

Site name 

U.S. 

Geological 

Survey 

identification 

number 

Latitude Longitude 

Year of 

fillet 

sample 

Total 

mercury in 

fish fillets ­

wet weight 

(μg/g) 

Fish species 

Number 

of fish 

per 

sample 

Year of 

water 

sample 

Total 

mercury 

in water 

(ng/L) 

Methyl 

mercury 

in water 

(ng/L) 

Year of 

bed 

sediment 

sample 

Pine Run at Chalfont, Pa. 01464710 401720 751211 — — — — 11998 13 0.06 12000 Wyomissing Creek at West 01471520 401941 755641 11999 0.03 Brown trout 2 — — — 11999 

Reading, Pa. 

Pidcock Creek near New Hope, Pa. 01462100 401946 745614 — — — — 11998 1.0 <.07 12000 Tulpehocken Creek near Bernville, 01470779 402448 761019 11998 .24 Smallmouth bass 1 11998 2.1 .09 11998 

Pa. 

Little Lehigh Creek near East 

Texas, 01451425 403234 753347 11998 .03 Brown trout 3 — — — — 

Pa. 

Jordan Creek near Schnecksville, 01451800 403942 753738 11999 .06 Smallmouth bass 3 11999 1.9 <.02 11999 

Pa. 

Lehigh River at Glendon, Pa. 01454700 404009 751412 11998 .13 Smallmouth bass 5 — — — — 

Brodhead Creek at Stroudsburg, 01442500 405914 751102 11999 .06 Smallmouth bass 2 11999 1.1 .05 11999 

Pa. 

Bush Kill Creek at Bushkill, Pa. 01439500 410517 750042 11999 .13 Smallmouth bass 2 11999 .82 .03 11999 Flat Brook near Flatbrookville, N.J. 01440000 410624 745709 11999 .33 Smallmouth bass 2 11999 .69 .03 11999 Dela

ware River at Port Jervis, N.Y. 01434000 412214 744152 11998 .33 Smallmouth bass 4 — — — — 

Neversink River near Godeffroy, 01437500 412628 743608 11999 .18 Rock bass 2 11999 1.2 <.03 11999 

N.Y. 

Lacka

waxen River at Hawley, Pa. 01431500 412834 751021 11999 .18 Smallmouth bass 2 11999 1.1 .06 11999 

Neversink River near Claryville, N.Y. 01435000 415324 743525 11999 .12 Brown trout 2 11999 .43 <.03 11999 W. Br. Dela

ware River at Walton, 01423000 420958 750825 11999 .15 Smallmouth bass 2 11999 1.4 .12 11999 

N.Y. 

1 Analyzed at the U.S. Geological Survey Wisconsin Mercury Research Laboratory. 2 Analyzed at the U.S. Geological Survey National Water Quality Laboratory. 

TOTAL MERCURY AND METHYLMERCURY IN FISH FILLETS, WATER, AND BED SEDIMENTS FROM SELECTED STREAMS 30