U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2010–3011

May 2010

USGS Toxic Substances Hydrology Program, 2010

Contamination of surface water, groundwater, soil, sediment, and the atmosphere by toxic substances is 

among the most significant issues facing the Nation. Nutrients, organic chemicals, metals, and pathogens 

enter the environment, often inadvertently, by way of industrial, agricultural, mining, domestic, municipal, 

and other waste sources. Contaminant migration and persistence in the environment, and the potential 

human and ecological health impact are difficult to ascertain. The USGS Toxic Substances Hydrology 

Program conducts research to provide reliable and objective scientific information and tools that explain the 

occurrence, behavior, and effects of toxic substances in the natural environment. These products are used by 

resource managers, regulators, industry, and the public to help avoid exposure, to mitigate environmental 

deterioration, to enable cost-effective cleanup, and to establish efficient waste-disposal strategies.

The U.S. Geological Survey 

(USGS) Toxic Substances Hydrology 

Program adapts research priorities to 

address the most important contamination issues facing the Nation and to 

identify new threats to environmental 

health. The Program investigates two 

major types of contamination problems:

•	 Subsurface Point-Source

Contamination, and

•	 Watershed and Regional

Contamination.

Research objectives include 

developing remediation methods that 

use natural processes, characterizing 

and remediating contaminant plumes in 

fractured-rock aquifers, identifying new 

environmental contaminants, characterizing new and understudied pesticides 

in common pesticide-use settings, 

explaining mercury methylation and 

bioaccumulation, and developing 

approaches for remediating watersheds 

affected by active and historic mining. 

Subsurface Point-Source 

Contamination

The goal of these investigations 

is to improve capabilities to describe, 

manage, and remediate subsurface 

contamination from local releases that 

affect aquifers and local receiving 

waters. The contamination sources 

studied include chemical spills, leaking 

storage tanks, industrial discharges, and 

leakage from landfills and other waste 

facilities. 

Research is conducted at sites 

representative of common contamination problems and geohydrologic 

settings. The investigations are longterm, field-based studies conducted 

by interdisciplinary research teams. 

Results from these field laboratories 

are generalized to similar sites 

across the Nation to improve the cost 

effectiveness of characterizing and 

remediating other contaminated sites. 

A unifying research theme is 

defining the response of the natural 

environment to contamination, 

making these studies ideally suited 

for assessing potential long-term 

impacts, evaluating natural remediation alternatives, and designing 

remediation-performance monitoring. 

A multi-point sampling array installed at the Cape Cod Research Site, Mass., helps 

evaluate subsurface physical and geochemical heterogeneities in a contaminant plume. 

Printed on recycled paper
Current Subsurface Point-Source 

Investigations

• Solvents in Fractured Rock—

Naval Air Warfare Center, New

Jersey. The research focuses on the 

movement of water and dissolved 

and separate-phase solvents in 

fractured rock aquifers, including 

the role of fractures, contaminant 

residual in pore spaces, and 

remediation performance.

• Waste Disposal in the Arid

Southwest—Amargosa Desert

Research Site, Nevada. Research 

on the movement of moisture and 

chemicals, including radioactive 

and organic contaminants in the 

thick unsaturated zone between the 

land surface and the water table, is 

improving knowledge of the extent 

and mechanisms of contaminant 

migration in environments often used 

for waste disposal and isolation.

• Landfill Leachate—Norman

Municipal Landfill, Norman,

Oklahoma. Biogeochemical 

controls on the migration and fate of 

complex chemical mixtures found 

in landfill leachate are studied with 

special emphasis on the processes 

at geochemical and hydrologic 

interfaces, such as the fringe of the 

contaminant plume and where the 

plume discharges to surface water.

• Sewage-Contaminated Ground

Water—Cape Cod, Massachusetts.

Research at a treated sewage 

effluent plume is characterizing the 

fundamental processes that affect 

contaminant transport and fate in 

sand and gravel aquifers. Tracer 

studies and other field experiments 

are improving models of the subsurface movement and attenuation of 

contaminant mixtures.

• Crude Oil Contamination—

Bemidji, Minnesota. Studies 

are characterizing the long-term 

geochemical evolution of a plume 

of petroleum hydrocarbons and 

the performance of natural cleanup 

processes. One emphasis is the 

potential for residual product in the 

unsaturated zone to prolong cleanup, 

promote down-gradient expansion of 

the plume, and threaten the efficacy 

of natural cleanup strategies. 

Watershed and Regional 

Contamination

The goal of these investigations 

is to improve knowledge of the factors 

that affect the environmental fate and 

effects of contaminants that enter 

the environment from nonpoint and 

distributed point sources.

Watershed and regional 

contamination problems are typical 

of widespread land uses or human 

activities that may pose a threat to environmental health throughout large areas 

of the Nation. These investigations help 

(1) determine the extent, levels, and 

mixtures of widely used chemicals in 

the environment; (2) characterize the 

relative contributions from different 

contaminant sources; (3) identify the 

processes that control contaminant 

dispersal within the hydrologic cycle 

(including transformation of contaminants into less toxic or potentially more 

toxic chemicals); (4) define the effects 

on aquatic ecosystems; and (5) develop 

approaches and modeling tools that aid 

management decision making. 

Current Watershed and Regional-Scale 

Investigations

• Watershed Contamination from

Hard Rock Mining—Our western 

landscapes are dotted with thousands 

of hard-rock (gold, copper, and 

zinc) mines. This research focuses 

on the processes controlling migration of contaminants from mine 

A vertical shaft at the Amargosa Desert 

Research Site, Nev., provides access for 

measuring soil moisture and vapor in the 

unsaturated zone.

USGS scientist prepares a slurry containing contaminant-degrading bacteria for an 

injection experiment at the former Naval Air Warfare Center, New Jersey. Test results 

help design engineered bioremediation treatments in fractured-rock aquifers.
USGS scientists have developed sensitive methods to measure the pyrethroid 

insecticides in stream water and sediments, and are applying them in the field.

dumps, tailing piles (ore processing 

residuum), and unmined mineral 

deposits to local ground and surface 

waters. A watershed approach 

enables realistic restoration goals and 

resource investments where they will 

do the most good.

•	 Mercury in Aquatic Ecosystems—

Mercury in its most toxic form, 

methylmercury, is a neurotoxin 

that can be concentrated in simple 

organisms and accumulate in the 

food chain. Our studies provide 

an improved understanding of 

the relation between atmospheric 

mercury loading (including changes 

from emission reduction) and 

accumulation in aquatic plants 

and animals, and assessments of 

the relative sensitivity of aquatic 

ecosystems across the Nation to 

accumulation of methylmercury. 

•	 Environmental Pesticide

Contamination—This research 

advances understanding of the 

environmental occurrence, fate, and 

effects of new and understudied 

pesticides, the accompanying 

chemical additives, and their 

degradation byproducts. This 

knowledge is essential to product 

registration and responsible use. 

Studies focus on ecosystems adjacent 

to common pesticide-use settings 

across the Nation. 

• Chemicals of Emerging

Environmental Concern

(Emerging Contaminants)—More 

and more chemicals used daily in 

our homes and businesses, such 

as pharmaceuticals, household 

and personal care products, and 

industrial chemicals, are entering 

the environment. Studies develop 

methods to measure new contaminants, define important sources and 

the associated contaminant mixtures, 

identify environmental settings that 

are susceptible to contamination, 

characterize ecological effects, and 

provide data essential to defining 

human exposure. 

• Human Stresses on Sensitive

Aquatic Ecosystems—This research

evaluates the broad range of chemical stressors associated with human 

development on the landscape. 

Studies focus on sensitive ecosystems, such as water quality and ecosystem health in San Francisco Bay 

and the Chesapeake Bay drainages. 

Recent Program Contributions 

Framework for Assessing the Sustainability of Natural Attenuation—Natural 

attenuation employs natural processes 

Emerging contaminants were measured in biosolids (the solid byproduct of wastewater 

treatment), soil amended with biosolids, and earthworms living in the soil.
to clean up contamination and offers 

significant cost advantages over engineered approaches. USGS Circular 1303 

provides environmental managers with a 

blueprint for monitored natural attenuation at toxic waste sites (http://pubs.usgs.

gov/circ/circ1303/).

Antidepressants in Fish Brains—

Pharmaceutical antidepressants were 

detected in stream water, stream sediment, and fish neural tissue downstream 

of two wastewater treatment plants 

(Boulder, Colo., and Ankeny, Iowa). 

The results indicate that specific antidepressants are selectively taken up by 

brain tissues and occurrence in water or 

sediment does not necessarily indicate the 

presence in fish brain tissue. 

Tracer Test Quantifies Active

Microbial Processes at Contamination

Sites—Comparing the levels of injected 

dissolved hydrogen gas and a conservative tracer in groundwater enables 

scientists to identify the active microbial processes (iron-reducing, sulfatereducing, or methane-producing bacteria) 

and to estimate the rate of microbial 

degradation. The test enables performance assessment of active or passive 

bioremediation.

New Source of Mercury in the North

Pacific Ocean—Mercury in the open 

ocean was believed to be of geologic origin, associated with deep-sea vents. We 

now know that mercury deposited from 

the atmosphere settles to ocean depths of 

200 to 700 meters where decomposition 

of organic matter also results in unintentional conversion of mercury to methylmercury, which is bioavailable to ocean 

fish. This knowledge is useful to public 

health managers seeking ways to minimize human mercury exposure.

Evaluating Pre-mining Conditions

in Historically Mined Watersheds—

A field- and modeling-based approach 

to estimate pre-mining conditions was 

developed. It enables resource managers 

to evaluate whether historical waterquality conditions in highly mineralized 

watersheds supported healthy fish populations. This information is essential for 

making effective resource investments 

in restoration and establishing realistic 

restoration targets. 

By Herbert T. Buxton

Additional program contributions are 

available at 

http://toxics.usgs.gov/highlights/.

A searchable bibliography of over 

5,000 program publications is 

available at 

http://toxics.usgs.gov/bib/.

For more information on the activities 

of the USGS Toxic Substances 

Hydrology Program 

Visit the Web site:

 http://toxics.usgs.gov/

Or call: 609-771-3944

Male fathead minnows exposed to municipal wastewater effluent in an onsite field 

laboratory at Boulder Creek, Colo., exhibited intersex—internal and external female 

characteristics. 

A subsurface tracer test at the Norman Landfill Research Site, Okla., measures dissolved 

hydrogen gas to define how microbial processes affect contaminant transport.