USGS

Pesticide Concentrations in Water and in Suspended and Bottom Sediments in the New and Alamo Rivers, Salton Sea Watershed, California, April 2003

By Lawrence A. LeBlanc, James L. Orlando and Kathryn M. Kuivila

U.S. GEOLOGICAL SURVEY

Data Series 104

Sacramento, California 2004


ONLINE ONLY


Prepared in cooperation with the California State Regional Water Quality Control Board

Complete accessible text of report (835 KB PDF)

To view PDF documents, you must have the Adobe Acrobat Reader (free from Adobe Systems) installed on your computer.
(download free copy of Acrobat Reader).

Abstract

     This report contains pesticide concentration data for water, and suspended and bed sediment samples collected in April 2003 from twelve sites along the New and Alamo Rivers in the Salton Sea watershed, in southeastern California. The study was done in collaboration with the California State Regional Water Quality Control Board, Colorado River Region, to assess inputs of current-use pesticides associated with water and sediment into the New and Alamo Rivers. Five sites along the New River and seven sites along the Alamo River, downstream of major agricultural drains, were selected and covered the lengths of the rivers from the international boundary to approximately 1.5 km from the river mouths. Sampling from bridges occurred at seven of the twelve sites. At these sites, streamflow measurements were taken. These same sites were also characterized for cross-stream homogeneity by measuring dissolved oxygen, pH, specific conductance, temperature, and suspended solids concentration at several vertical (depths) and horizontal (cross-stream) points across the river.
    Large volume water samples (200300 L) were collected for isolation of suspended sediments by flow-through centrifugation. Water from the outflow of the flow-through centrifuge was sampled for the determination of aqueous pesticide concentrations. In addition, bottom sediments were sampled at each site. Current-use pesticides and legacy organochlorine compounds (p,p-DDT, p,p-DDE and p,p-DDD) were extracted from sediments and measured via gas chromatography/mass spectrometry (GC/MS). Organic carbon and percentage of fines were also determined for suspended and bottom sediments.
    Cross-stream transects of dissolved constituents and suspended sediments showed that the rivers were fairly homogeneous at the sites sampled. Streamflow was higher at the outlet sites, with the Alamo River having higher flow (1,240 cfs) than the New River (798 cfs).
    Twelve current-use pesticides, one legacy organochlorine compound (p,p-DDE), and the additive piperonyl butoxide were detected in water samples. Trifluralin was found in the highest concentration of all detected compounds (68.5599 ng/L) at all sites in both rivers, except for the international boundary sites. Atrazine was also detected in high concentration (51.0285 ng/L) at several sites. The outlet sites had among the highest numbers of pesticides detected and the international boundary sites had the lowest numbers of pesticides detected for both rivers. The numbers of pesticides detected were greater for the Alamo River than for the New River.
    Six current-use pesticides and two legacy organochlorines (p,p-DDE and p,p-DDD) were found associated with suspended and bed sediments. The DDT metabolite p,p-DDE was detected in all suspended and bed sediments from the Alamo River, but only at two sites in the New River. Dacthal, chlorpyrifos, pendimethalin, and trifluralin were the most commonly detected current-use pesticides. Trifluralin was the compound found in the highest concentrations in suspended (14.5120 ng/g) and bed (1.99.0 ng/g) sediments. The sites along the Alamo River had more frequent detections of pesticides in suspended and bed sediments when compared with the New River sites. The greatest number of pesticides that were detected in suspended sediments (seven) were in the samples from the Sinclair Road and Harris Road sites. For bottom sediments, the Alamo River outlet site had the greatest number of pesticide detections (eight).

CONTENTS

Abstract

Introduction

Hydrographic Setting

Purpose and Scope

Sample Collection Methods

Large Volume Water Samples

Isolation of Sespended Sediments

Water Samples for Aqueous Pesticide Analysis

Bed Sediment

Laboratory Methods

Water Analysis

Quality Assurance and Quality Control for Water Samples

Sediment Analysis

Quality Assurance and Quality Control for Sediment Samples

Instrument Analysis

Sediment Organic Carbon Analysis

Grain-Size Analysis

Results

Station Characteristics

Aqueous Pesticide Concentrations

Percentage of Organic Carbon and Percentage of Fines in Suspended and Bed Sediments

Pesticide Concentrations Associated with Suspended and Bed Sediments

References


Document Accessibility: Adobe Systems Incorporated has information about PDFs and the visually impaired. This information provides tools to help make PDF files accessible. These tools convert Adobe PDF documents into HTML or ASCII text, which then can be read by a number of common screen-reading programs that synthesize text as audible speech. In addition, an accessible version of Acrobat Reader 5.0 for Windows (English only), which contains support for screen readers, is available. These tools and the accessible reader may be obtained free from Adobe at Adobe Access.

 



Water Resources of California




U.S. Department of the Interior, U.S. Geological Survey
Persistent URL:
Page Contact Information: Contact USGS
Last modified: Monday, November 28 2016, 12:05:40 PM
FirstGov button  Take Pride in America button