Pesticide transport in the San Joaquin River Basin

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Pesticide occurrence and concentrations were evaluated in the San Joaquin River Basin to determine potential sources and mode of transport. Land use in the basin is mainly agricultural. Spatial variations in pesticide occurrence were evaluated in relation to pesticide application and cropping patterns in three contrasting subbasins and at the mouth of the basin. Temporal variability in pesticide occurrence was evaluated by fixed interval sampling and by sampling across the hydrograph during winter storms. Four herbicides (simazine, metolachlor, dacthal, and EPTC) and two insecticides (diazinon and chlorpyrifos) were detected in more than 50 percent of the samples. Temporal, and to a lesser extent spatial, variation in pesticide occurrence is usually consistent with pesticide application and cropping patterns. Diazinon concentrations changed rapidly during winter storms, and both eastern and western tributaries contributed diazinon to the San Joaquin River at concentrations toxic to the water flea Ceriodaphnia dubia at different times during the hydrograph. During these storms, toxic concentrations resulted from the transport of only a very small portion of the applied diazinon.

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Publication type Conference Paper
Publication Subtype Conference Paper
Title Pesticide transport in the San Joaquin River Basin
DOI 10.1021/bk-2000-0751.ch020
Volume 751
Year Published 2000
Language English
Description 17 p.
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title Agrochemical fate and movement
First page 306
Last page 322
Country United States
State California
Other Geospatial San Joaquin River Basin
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