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Pixie A. Hamilton

Publications and source records attributed to Pixie A. Hamilton.

31 records · Page 2Linked to original sources
USGS2005

Parking lot sealcoat: a major source of polycyclic aromatic hydrocarbons (PAHs) in urban and suburban environments

Collaborative studies by the City of Austin and the U. S. Geological Survey (USGS) have identified coal-tar based sealcoat—the black, shiny emulsion painted or sprayed on asphalt pavement such as parking lots—as a major and previously unrecognized source of polycyclic aromatic hydrocarbon (PAH) contamination. Several PAHs are suspected human carcinogens and are toxic to aquatic life. Studies in Austin, Texas, showed that particles in runoff from coal-tar based sealcoated parking lots had concentrations of PAHs that were about 65 times higher than concentrations in particles washed off parking lots that had not been sealcoated. Biological studies, conducted by the City of Austin in the field and in the laboratory, indicated that PAH levels in sediment contaminated with abraded sealcoat were toxic to aquatic life and were degrading aquatic communities, as indicated by loss of species and decreased numbers of organisms. Identification of this source of PAHs may help to improve future strategies for controlling these compounds in urban water bodies across the Nation where parking lot sealcoat is used.

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USGS2004

Water Quality in the Nation's Streams and Aquifers Overview of Selected Findings, 1991-2001

This report accompanies the publication of the last 15 of 51 river basin and aquifer assessments by the USGS National Water-Quality Assessment (NAWQA) Program during 1991?2001. It highlights selected water-quality findings of regional and national interest through examples from river basins and aquifer systems across the Nation. Forthcoming reports in the USGS series ?The Quality of Our Nation?s Waters? will present comprehensive national syntheses of information collected in the 51 study units on pesticides in water, sediment, and fish; volatile organic compounds in major aquifers used for domestic and public supply; nutrients and trace elements in streams and ground water; and aquatic ecology. This report, summaries of the 51 water-quality assessments, and a 1999 national synthesis of information on nutrients and pesticides, are available free of charge as USGS Circulars and on the World Wide Web at http://water.usgs.gov/nawqa/nawqa_sumr.html.

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USGS2004

Studies by the U.S. Geological Survey on sources, transport, and fate of agricultural chemicals

The U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program is assessing the sources, transport, and fate of chemicals applied to crops in agricultural basins across the Nation (referred to as "study units," see map). Chemicals selected for study include nutrients (nitrogen and phosphorus) and about 50 commonly used pesticides and their transformation products, including triazine and acetanilide herbicides such as atrazine and metolachlor, and organophosphorus insecticides such as chlorpyrifos and diazinon. The basins in the studies represent a range of agricultural settings—with varying crop types and agricultural practices related to tillage, irrigation, artificial drainage, and chemical use—as well as a range of landscapes with different geology, soils, topography, climate, and hydrology. Consistent methodology and analysis allow comparisons among the different basins. This study design leads to an improved understanding of the many factors that can affect the movement of water and chemicals in different agricultural settings (see "Complex factors," next page). Information from these studies will help with decision-making related to chemical use, conservation, and other farming practices that are used to reduce runoff of agricultural chemicals and sediment from fields. This information also will benefit the U.S. Environmental Protection Agency, the Department of Agriculture, local and regional water managers, and agricultural chemical manufacturers who are involved in managing chemical use and pesticide registration.

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USGS2003

Mercury in stream ecosystems -- New studies initiated by the U.S. Geological Survey

Mercury can adversely affect humans and wildlife through consumption of contaminated fish, particularly by sensitive individuals, such as children and women of childbearing age. Mercury is currently the leading cause of impairment in the Nation’s estuaries and lakes and was cited in nearly 80 percent of fish-consumption advisories (2,242 of 2,838) reported by states in 2000. The geographic extent of mercury advisories covers more than 10 million acres of lakes and more than 400,000 stream miles—increases of about 7 and 48 percent, respectively, over advisories reported in 1998 (U.S. Environmental Protection Agency, 2002a).

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USGS2003

New studies initiated by the U.S. Geological Survey - Effects of nutrient enrichment on stream ecosystems

In 2001, the U.S. Geological Survey’s National Water-Quality Assessment (NAWQA) Program began an intensive study of nutrient enrichment elevated concentrations of nitrogen and phosphorus in streams in five agricultural basins across the Nation (see map, p. 2). This study is providing nationally consistent and comparable data and analyses of nutrient conditions, including how these conditions vary as a result of natural and human-related factors, and how nutrient conditions affect algae and other biological communities. This information will benefit stakeholders, including the U.S. Environmental Protection Agency (USEPA) and its partners, who are developing nutrient criteria to protect the aquatic health of streams in different geographic regions. Nutrient enrichment is one of five national priority topics addressed by NAWQA in its second decade of studies, which began in 2001. During its first round of assessments in 51 major river basins (referred to as “Study Units”), NAWQA scientists collected data on water chemistry, stream hydrology and habitat, and biological communities; currently, NAWQA is revisiting selected basins and focusing on (1) trends, (2) factors that affect water quality and aquatic health, and (3) national priority water issues related to, for example, the development of nutrient criteria, source-water protection strategies, and stream restoration plans. The nutrient enrichment study has four major objectives that address nutrient conditions, dissolved oxygen, aquatic communities, and geographic and landscape features in agricultural basins (see inset). The focus on agricultural streams is a starting point. As the study progresses, streams draining other land uses, such as those in residential and urban areas, will likely be added.

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USGS1998

Natural processes for managing nitrate in ground water discharged to Chesapeake Bay and other surface waters: More than forest buffers

Ground-water discharge is a significant source of nitrate load to tidal creeks, coastal estuaries, and Chesapeake Bay. Different studies have found that forest buffers greater than 200 feet wide remove most of the nitrate from passing ground water. These buffers are commonly included in regional nutrient-management strategies. Results of a U.S. Geological Survey study on the Eastern Shore of Virginia, however, indicate that the presence of forest buffers alone may not significantly decrease nitrate load in ground-water discharge. The effectiveness of forest buffers largely depends on the composition of local soils and ground-water flow paths. Study results also indicate that large amounts of nitrate are removed from ground water by the natural process of denitrification, which may occur independently of the presence or absence of forest buffers. The results of this study indicate that in addition to the presence of forest buffers, a range of other natural factors, such as soil texture and organic matter content and ground-water flow paths, affect the fate of nitrate in ground water. These factors are important to include along with forest buffers in developing comprehensive nutrient-management strategies.

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