Trends in pesticide concentrations in streams of the western United States, 1993-2005

Journal of the American Water Resources Association
By: , and 



Trends in pesticide concentrations for 15 streams in California, Oregon, Washington, and Idaho were determined for the organophosphate insecticides chlorpyrifos and diazinon and the herbicides atrazine, s‐ethyl diproplythiocarbamate (EPTC), metolachlor, simazine, and trifluralin. A parametric regression model was used to account for flow, seasonality, and antecedent hydrologic conditions and thereby estimate trends in pesticide concentrations in streams arising from changes in use amount and application method in their associated catchments. Decreasing trends most often were observed for diazinon, and reflect the shift to alternative pesticides by farmers, commercial applicators, and homeowners because of use restrictions and product cancelation. Consistent trends were observed for several herbicides, including upward trends in simazine at urban‐influenced sites from 2000 to 2005, and downward trends in atrazine and EPTC at agricultural sites from the mid‐1990s to 2005. The model provided additional information about pesticide occurrence and transport in the modeled streams. Two examples are presented and briefly discussed: (1) timing of peak concentrations for individual compounds varied greatly across this geographic gradient because of different application periods and the effects of local rain patterns, irrigation, and soil drainage and (2) reconstructions of continuous diazinon concentrations at sites in California are used to evaluate compliance with total maximum daily load targets.

Publication type Article
Publication Subtype Journal Article
Title Trends in pesticide concentrations in streams of the western United States, 1993-2005
Series title Journal of the American Water Resources Association
DOI 10.1111/j.1752-1688.2010.00507.x
Volume 47
Issue 2
Year Published 2011
Language English
Publisher American Water Resources Association
Contributing office(s) California Water Science Center, Oregon Water Science Center
Description 22 p.
First page 265
Last page 286
Country United States
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