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The goal of my biodegradation research is to understand the processes controlling the rate of biodegradation of contaminants in the subsurface. This understanding will form the basis of methods to increase degradation rates without causing further degradation of groundwater quality. Recent work has focused on the fate of crude oil and agricultural nitrate contamination in the subsurface. Specific objectives for the crude oil research include: (a) determine the rate that contaminants are transported from the source zone; (b) provide an estimate of how long the spilled oil will continue to pollute the groundwater; and (c) determine the fate of products of biodegradation or so-called “secondary water quality impacts”...
To study the mechanisms, pathways, and rates of transformation of carbon and nitrogen compounds (natural and contaminant) mediated by microorganisms in aquatic habitats and identify factors controlling these transformations and to examine the effect that these transformations have upon other biogeochemical processes.
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In 1991, the U.S. Geological Survey (USGS) began a study of more than 50 major river basins across the Nation as part of the National Water-Quality Assessment (NAWQA) project of the National Water-Quality Program. One of the major goals of the NAWQA project is to determine how water-quality conditions change over time. To support that goal, long-term consistent and comparable monitoring has been conducted on streams and rivers throughout the Nation. Outside of the NAWQA project, the USGS and other Federal, State, and local agencies also have collected long-term water-quality data to support their own assessments of changing water-quality conditions. Data from these multiple sources have been combined to support...
Trends are identified changes over time in the characteristics of groundwater and (or) surface water. The characteristics analyzed can include descriptions of both quantity and quality. The calculated trends are dependent upon the available data and the methods used to identify trends. (Updated 12/23/2015)
Increased nutrient and sediment loading have caused observable changes in algal community composition, and thereby, altered the quality and quantity of food resources available to native freshwater mussels. Our objective was to characterize the relationship between nutrient conditions and mussel food quality and examine the effects on the fatty acid composition, growth and survival of juvenile mussels. Juvenile Lampsilis cardium and L. siliquoidea were deployed in cages for 28 d at four riverine and four lacustrine sites in the lower St. Croix River, Minnesota/Wisconsin, USA. Mussel foot tissue and food resources (four seston fractions and surficial sediment) were analyzed for quantitative fatty acid (FA) composition....


map background search result map search result map Water-quality and streamflow datasets used in the Weighted Regressions on Time, Discharge, and Season (WRTDS) models to determine trends in the Nation’s rivers and streams, 1972-2012(output) Water-quality and streamflow datasets used in the Weighted Regressions on Time, Discharge, and Season (WRTDS) models to determine trends in the Nation’s rivers and streams, 1972-2012(output)