Dissolved pesticide concentrations in the lower Sacramento River and its source waters, California, 2016

Open-File Report 2018-1153
Prepared in cooperation with the Sacramento Regional County Sanitation District
By: , and 



As part of a collaborative study designed to better understand water-quality conditions in the Sacramento River, surface-water samples were collected from the lower Sacramento River and five of its tributaries and then analyzed by the U.S. Geological Survey for a suite of 162 current-use pesticides and pesticide degradates. Samples were collected in May and October 2016 at 16 sites on the Sacramento River and its tributaries. Samples were analyzed for pesticide concentrations by using gas chromatography with mass spectrometry and liquid chromatography with tandem mass spectrometry laboratory methods.

A total of 27 pesticides and pesticide degradates were detected in the water samples collected during the study (12 herbicides, 9 insecticides, 5 fungicides, and 1 synergist). Two herbicides were detected in the suspended sediments filtered from the water samples. Pesticides were detected in 100 percent of the water samples, and mixtures of two or more pesticides were detected at all sites and in all but four samples. The pesticides detected most frequently in the May and October sampling periods were the herbicides hexazinone (detected in 88 percent of the water samples), and diuron (84 percent), and the fungicide azoxystrobin (84 percent). Pesticide concentrations ranged from below the method detection limits to 576 nanograms per liter (clomazone). All pesticides were detected at concentration levels lower than the U.S. Environmental Protection Agency’s aquatic life benchmarks (U.S. Environmental Protection Agency, 2017).

During the May sampling period, the fungicides boscalid and azoxystrobin (both 94 percent); the herbicides clomazone, diuron, and hexazinone (all 94 percent); thiobencarb (88 percent); and metolachlor (81 percent) were the most frequently detected compounds. During the October sampling period, the herbicides hexazinone (81 percent) and diuron (75 percent) and the herbicide degradates 3,4-dichloroaniline (75 percent) and N-3,4-dichlorophenyl-N-methyl-urea (50 percent), along with the fungicide azoxystrobin (75 percent) and the insecticide methoxyfenozide (63 percent), were the most frequently detected compounds.

Suggested Citation

Stout, S.M., Orlando, J.L., McWayne, M., Sanders, C., and Hladik, M., 2018, Dissolved pesticide concentrations in the lower Sacramento River and its source waters, California, 2016: U.S. Geological Survey Open-File Report 2018–1153, 24 p., https://doi.org/10.3133/ofr20181153.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Procedures and Methods
  • Quality-Control Methods and Results
  • Results
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Dissolved pesticide concentrations in the lower Sacramento River and its source waters, California, 2016
Series title Open-File Report
Series number 2018-1153
DOI 10.3133/ofr20181153
Year Published 2018
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) California Water Science Center
Description vi, 24 p.
Country United States
State California
Other Geospatial Lower Sacramento River
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details