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Environmental Health - Toxic Substances


U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting, Charleston, South Carolina, March 8-12, 1999 -- 3 Volumes -- Water-Resources Investigations Reports 99-4018A, 99-4018B, and 99-4018C

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The U.S. Geological Survey (USGS) Toxic Substances Hydrology (Toxics) Program was initiated in 1982. The goal of the Program is to provide earth science information on the behavior of toxic substances in the Nation's hydrologic environments. Contamination of surface water, ground water, soil, sediment, and the atmosphere by toxic substances is among the most significant issues facing the Nation. Contaminants such as excessive nutrients, organic chemicals, metals, and pathogens enter the environment, often inadvertently, via industrial, agricultural, mining, or other human activities. The extent of their migration and their persistence often are difficult to ascertain. Estimates of the costs and time frames for cleanup of contamination and protection of human and environmental health can best be described as astounding, despite continual efforts by governments and industries worldwide to improve environmental technologies.

Contaminant sources and environmental occurrence have a wide range of scales. Some contaminants are released from point sources, such as leaks or discharges from industrial facilities. Some are released from multiple, closely spaced releases, such as domestic septic systems. Still others are released relatively uniformly over broad areas with similar land-use practices, such as agricultural and residential land uses. Contaminants are detected at high concentrations locally in the immediate vicinity of a release, at varied concentrations where multiple releases disperse within watersheds or regional hydrologic systems, and at relatively low (but still potentially toxic) concentrations where they enter systems from broad uniform sources. Common to contamination at all these scales is the need to:

  • Measure the contaminants and their transformation products in environmental samples;
  • Characterize the physical processes and properties that affect their propagation in the environment;
  • Define the chemical and microbial processes that transform or degrade the contaminants;
  • Describe contaminant-biota interactions that control their effects on ecosystems, the food chain, and human health;
  • Understand the ultimate fate of contaminants with the potential long-term implications for human and environmental health; and
  • Develop simulation models that enable prediction of potential exposure and effective design of waste disposal facilities, monitoring networks, and remediation alternatives.

To meet these needs, the Toxics Program provides information and technology to Federal and State resource-management agencies and industry. The Toxics Program: (1) conducts intensive field investigations of representative cases of subsurface contamination at local releases; (2) conducts watershed- and regional-scale investigations of contamination affecting aquatic ecosystems from nonpoint and distributed point sources; and (3) develops methods and models- - methods to detect, identify, and measure emerging environmental contaminants; and models to interpret the persistence and fate of contamination and to design waste-disposal and remediation strategies.

Intensive field investigations are established at sites contaminated with predominant types of environmental contamination, in commonly occurring geohydrologic and geochemical settings. Contamination types currently under investigation include chlorinated solvents, sewage effluent, toxic metals, radionuclides, and petroleum products, including fuel oxygenates. These long-term research projects are conducted by interdisciplinary research teams that comprehensively identify and characterize the physical, chemical, and biological processes that affect contaminant transport, transformation, and fate at the site. Through extensive characterization and field experimentation, the sites provide field-laboratory conditions that enhance research opportunities. Results from the sites are generalized by focused field and laboratory experiments at other sites that describe the range of field conditions for the controlling processes. Knowledge and methods produced at these representative sites improve the effectiveness and reduce the cost of characterization and remediation at similar sites across the Nation.

A unifying theme of these investigations is characterization of the natural response of hydrologic systems to contamination. This, when combined with comprehensive assessment of the processes that affect contaminant transport and fate, make assessing the potential of natural attenuation and remediation-performance monitoring undertakings in which the Toxics Program can excel. The long-term nature of the research provides a unique opportunity to evaluate the potential and limitations of natural-attenuation remediation alternatives.

Watershed- and regional-scale investigations are developed to address contamination problems typical of specific land uses or human activities that may pose a threat to human and environmental health throughout significant parts of the Nation. Current watershed- and regional-scale investigations address contamination from agricultural chemicals in the Midwest corn belt; cotton agriculture across the southern U.S.; human activities in estuarine ecosystems; historic hard-rock mining in watersheds in mountain terrain and southwestern alluvial basins; and mercury emissions on aquatic ecosystems.

In some cases, these investigations involve characterizing contaminant sources and their mechanisms for affecting aquatic ecosystems. This is the case in ongoing investigations of watersheds that may be affected by hundreds of abandoned mine sites. In some cases, watershed- and regional-scale investigations involve widespread detection of mixtures of contaminants or contaminant transformation products at levels near or below existing water-quality standards or advisories. This is the case in investigations of agricultural land uses which have documented that mixtures of pesticides and their metabolites accumulate to significantly higher levels than the individual parent compounds. In still other cases, these investigations identify chemicals in environmental samples for which standards have not yet been developed. In these cases, the Program provides information to resource managers and regulators that is useful for developing new water-quality standards or registering use of new chemicals, such as new pesticides or industrial chemicals.

These investigations complement the National Water-Quality Assessment (NAWQA) Program, which has the goal of assessing the status and trends of the quality of the Nation's ground- and surface-water resources. The Toxics Program watershed- and regional-scale investigations focus rapidly on new issues, emerging contaminants, and understanding the processes that affect whether a chemical may be of widespread concern. This information is used for planning future NAWQA Program activities.

New scientific models and methods are developed as part of both intensive field investigations and watershed- and regional-scale investigations. Simulation models provide tools to predict environmental occurrence and estimate exposure risks, as well as design remediation and monitoring strategies. A strength of models developed by the Toxics Program is that they are developed and applied to explain the complex field conditions at Program field sites. This makes them particularly well suited for application to real problems. New and improved water-quality analytical methods enable (1) detection of new chemicals in environmental samples, such as new pesticides and fuel oxygenates; (2) detection of chemicals at lower levels, which enables our understanding of the processes that control the environmental and human health effects of chemicals, such as mercury; and (3) identification of persistent transformation products of contaminants, such as pesticide metabolites. These methods and models are transferred to public and private practitioners for widespread use across the Nation.

Most scientists involved with Toxics Program activities are from the USGS National Research Program and District (state) Offices. However, as interdisciplinary approaches to solving contamination problems have become more successful, more ecologists, geologists, chemists, hydrologists, geochemists, and digital data-collection experts from across the USGS have become involved in Program activities. In addition, many scientists from universities, other Federal agencies, and industry are taking advantage of research opportunities afforded by the Program and its field sites, and are active members of the research teams.

Each project is steered by a core group of scientists from the research team. This core group, led by the project coordinator(s), guides the development of a research plan that integrates the multi-disciplinary activities at the site. They facilitate opportunities that become available for a wide range of related research. Although not an emphasis of the Toxics Program, many innovative, engineered-remediation technologies have been tested at the Program field sites because their extensive characterization provides a basis for effective evaluation of technology design and performance. Long-term data sets from the sites have been used by other Federal agencies to test decision-support software for site characterization or to test new hydrologic simulation models. Research plans for each project undergo periodic review by a panel of USGS and non-USGS scientists to improve the research approach and identify opportunities to enhance the research team. Field support for research projects is provided by experienced specialists located in the local USGS District Office.

The Toxics Program is coordinated with the U.S. Environmental Protection Agency, the U.S. Department of Agriculture, the Department of Defense, the Department of Energy, the Nuclear Regulatory Commission, and other U.S. Department of the Interior agencies to ensure that current and future research priorities are being addressed.

The long-term cooperation and assistance offered by the Federal, State, and local agencies, and by private entities that administer or own the Program's research sites has been essential to the success of the Toxics Program. Their continued support is greatly appreciated.

Herb Buxton
Coordinator, Toxic Substances
Hydrology Program

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