Atrazine in Our Streams
Atrazine concentrations are decreasing while concentrations of breakdown product increase
From 2002 to 2012, concentrations of atrazine decreased in more than one-half of 60 U.S. streams and rivers studied and increased in only about one-third of these streams, according to a new study by the U.S. Geological Survey National Water Quality Program. The streams and rivers are in a range of land-use settings.
Atrazine is the second-most widely used weed killer in the United States, after glyphosate. The overall trend patterns indicate that regulatory changes starting in the early 1990s intended to decrease concentrations of atrazine in streams and encourage the breakdown of atrazine have had some success.
In contrast, more streams had an upward trend in concentrations of deethylatrazine (DEA), a major atrazine breakdown product, than a downward trend. This could be the result of successful actions to prevent atrazine transport by rainfall runoff, leading to more breakdown of atrazine into DEA in soils.
The study used Structural Equation Modeling (SEM) to test hypotheses concerning the causes, in addition to atrazine use, of the upward and downward trends in concentrations of atrazine and DEA at the sampled sites. Changes in corn acreage were important in explaining trends in atrazine concentration, but the presence of tile drains, amount of groundwater supply, changes in moisture supply, and corn acreage all contributed to explaining trends in DEA.
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The Nation's rivers and streams are a priceless resource, but pollution from urban and agricultural areas pose a threat to our water quality. To understand the value of water quality, and to more effectively manage and protect the Nation's water resources, it's critical that we know the current status of water-quality conditions, and how and why those conditions have been changing over time.Water-Quality Trends
Is water quality getting better or worse? Answering this deceptively simple question has been a fundamental objective of the USGS National Water-Quality Assessment Project’s research. Learn about trends in contaminants in the nation’s streams and rivers, trends in contaminants that collect in the bed sediment of streams and lakes, and changes in the quality of the nation’s groundwater. - Data
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