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U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 00-4203

Pesticides in Surface Water Measured at Select Sites in the Sacramento River Basin, California, 1996–1998

National Water-Quality Assessment Program
By Joseph Domagalski

Abstract

Pesticides were measured in one urban stream, one agricultural stream, one site on the Sacramento River, and one large flood control channel over a period of 18 months during 1996–1998. All sites were located within the Sacramento River Basin of California. Measurements were made on 83 pesticides or pesticide transformation products by either gas chromatography/mass spectrometry or by high performance liquid chromatography with ultraviolet light spectrometry. Some pesticides were detected frequently at the agricultural stream and downstream in the Sacramento River and at the flood control channel of the Sacramento River. These were pesticides related to rice farming (molinate, carbofuran, thiobencarb, and bentazon); herbicides used both agriculturally or for roadside maintenance (diuron, simazine, and metolachlor); or insecticides used on orchards and row corps (diazinon and chlorpyrifos). No pesticide concentrations above enforceable water quality criteria were measured at either the agricultural site or the Sacramento River sites. In contrast to the agricultural site, insecticides used for household, lawn, or garden maintenance were the most frequently detected pesticides at the urban site. Diazinon, an organophosphate insecticide, exceeded recommended criteria for the protection of aquatic life, and the diazinon levels were frequently above known toxic levels for certain zooplankton species at the urban site. Because of the low discharge of the urban stream, pesticide concentrations were greatly diluted upon mixing with Sacramento River water.

Contents

Abstract
Introduction
Sampling Collection and Analysis
Detection Frequency
Storm-Water Runoff
Comparison of Sampling Frequencies
Summary and Conclusions
References Cited

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Send questions or comments about this report to the author, Joseph Domagalski,, (916) 278-3077.