USGS Fact Sheet 067-97:
Pesticides in Selected Small Streams
in the Puget Sound Basin, 1987-1995
Factors Influencing Pesticide Concentrations and Detections
Detections and concentrations of pesticides in
streams are influenced by many factors, including the amount of
pesticide used, the environmental persistence of the pesticide, and the
analytical methods used. In the Puget Sound Basin, the most
commonly detected pesticides were among the most heavily applied.
Eleven of the 18 pesticides that are most heavily used were
detected in water or bed sediments (see table below). Application
practices in urban and agricultural areas are important in determining
whether pesticides reach streams. Pesticides are used around urban
households, businesses, and parks, and application practices of urban
users differ widely. Urban use of pesticides (about 1.1
million pounds/year) was more than three times greater than
agricultural use (Tetra Tech, 1988). This may explain in part
why the number of different pesticides found in urban streams is
greater than in agricultural streams.
Chemical characteristics of
pesticides are a major factor in environmental persistence. The
majority of currently used pesticides break down relatively rapidly
after application. Consequently, pesticide detections occur most
frequently in the weeks following periods of heaviest pesticide
application, which usually are in spring and early summer in the basin.
Detections of pesticides have also increased over time as analytical
methods improve and smaller concentrations can be measured.
Click here for a table of commonly used
pesticides in the Puget Sound Basin
Puget Sound Basin NAWQA home page is
This page is http://
Last modified: Mon Jun 9 17:25:40 1997
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