Overview

The NAWQA Pesticide National Synthesis Project, which began in 1992, is a national-scale assessment of the occurrence and behavior of pesticides in streams and ground water of the United States and the potential for pesticides to adversely affect drinking-water supplies or aquatic ecosystems.

Features

• Prediction of Atrazine Concentrations: Estimate atrazine concentrations in your stream with this interactive model and mapping tool.
  Watershed Regressions for Pesticides (WARP) Atrazine Model (BETA demonstration)
• The Quality of Our Nation's Waters
  Pesticides in the Nation's Streams and Ground Water, 1992-2001
  Released March 2, 2006

• Full Report
• Fact Sheet
• Frequently Asked Questions
• Supporting Information

• Recent Publications

• Comparison of pesticide concentrations in streams at low flow in six metropolitan areas of the United States: Environmental Toxicology and Chemistry, Vol. 27, No. 2, pp. 288–298
  
• Relative toxicity and occurrence patterns of pesticide mixtures in streams draining agricultural watersheds dominated by corn and soybean production: Integrated Environmental Assessment and Management, v.3, n.1, pp. 90-100 (2007)
• Response of stream chemistry during base flow to gradients of urbanization in selected locations across the conterminous United States: USGS SIR 2007-5083 (2007)
• Pesticides in the Nation's Streams and Ground Water; Environmental Science and Technology, v. 41, n.10, pp. 3408–3414 (2007)
• The geochemistry of pesticides. In: Environmental Geochemistry (ed. B. S. Lollar), Volume 9 of Treatise on Geochemistry (eds. H.D.Holland and K.K. Turekian), Elsevier—Pergamon, Oxford, UK, on-line edition, 43 p. (2007)
• How well can we predict the toxicity of pesticide mixtures to aquatic life? Integrated Environmental Assessment and Management, v. 3, n.3, pp. 364-372 (2007)
• Development and application of health-based screening levels for use in water-quality assessments: USGS SIR 2007-5106, 12 p. (2007)

This graph is an overview of results from hundreds of stream and ground-water samples collected across the U.S., which shows how concentrations of one of atrazine's primary degradation products, deethylatrazine (DEA), tend to increase in proportion to atrazine with increased residence time in the hydrologic system. The biotransformation of atrazine, which forms DEA and several other degradates, primarily occurs in the shallow subsurface (especially in the soil root zone), where microbial populations, organic-carbon content and temperatures tend to be higher than at greater depths, or in streams. The ratio of DEA to atrazine, therefore, tends to increase with atrazine residence time in the soil and unsaturated zones. In streams, the DEA-to-atrazine ratios increased with the time elapsed between atrazine applications and sampling, but were usually less than 1 (DEA less than atrazine). In ground water, DEA-to-atrazine ratios were markedly greater than those in streams, and were frequently greater than 1 (DEA greater than atrazine), especially in water collected from major aquifers, which contain water that is deeper and older than water collected from shallow wells.

For further details, see: http://pubs.usgs.gov/circ/2005/1291/pdf/circ1291_chapter5.pdf

Posted on October 24, 2008