In cooperation with the Texas Natural Resource Conservation Commission
Volatile Organic Compound and Pesticide Data for Public Water-Supply Reservoirs and Wells, Texas, 1999–2001
By B.J. Mahler, M.O. Gary, M.G. Canova, Eric W. Strom, Lynne Fahlquist, and Michael E. Dorsey
U.S. Geological Survey
Open-File Report 02–093
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Contents
Abstract
Introduction
Purpose and Scope
Site Selection
Acknowledgments
Volatile Organic Compound and Pesticide Data
Collection of Samples
Reservoir Samples
Well Samples
Quality-Control Samples
Analysis of Data
Methods
Environmental Samples
Reservoirs
Wells
Quality-Control Samples
Reservoirs
Wells
Summary
References Cited
Figures
| 1. | Map showing locations of public water-supply reservoirs sampled in Texas, June–July 1999 |
| 2. | Map showing locations of public water-supply wells sampled in Texas, November 1999–January 2001 |
| 3. | Boxplots showing percent recovery of spikes and surrogates for reservoir samples |
| 4. | Graph showing comparison of concentrations of pesticides detected in environmental and replicate samples from reservoirs |
| 5. | Boxplots showing percent recovery of spikes and surrogates for well samples |
| 6. | Graph showing comparison of concentrations of pesticides detected in environmental and replicate samples from wells |
Tables
| 1. | Concentrations of volatile organic compounds in public water-supply reservoirs sampled in Texas, June–July 1999 |
| 2. | Concentrations of soluble pesticides in public water-supply reservoirs sampled in Texas, June–July 1999 |
| 3. | Summary of soluble pesticides in samples collected from public water-supply reservoirs in Texas, June–July 1999 |
| 4. | Concentrations of volatile organic compounds, nitrite plus nitrate, and tritium in public water-supply wells sampled in Texas, November 1999–January 2001 |
| 5. | Concentrations of soluble pesticides in public water-supply wells sampled in Texas, November 1999–January 2001 |
| 6. | Summary of soluble pesticides in samples collected from public water-supply wells in Texas, November 1999–January 2001 |
Abstract
To provide data for the Texas Source-Water Assessment and Protection Program, the U.S. Geological Survey conducted a synoptic survey of 48 public water-supply reservoirs and 174 public water-supply wells during 1999–2001. The surface-water samples were analyzed for volatile organic compounds and soluble pesticides. The ground-water samples were analyzed for volatile organic compounds and soluble pesticides, as well as nitrite plus nitrate nitrogen and tritium.
One or more volatile organic compounds were detected in 75 percent of the reservoirs and in 9 percent of the wells. Methyl tert-butyl ether was detected most frequently in reservoirs, and toluene was detected most frequently in wells. One or more pesticides were detected in 96 percent of the reservoirs and in 33 percent of the wells. Atrazine or its breakdown product deethylatrazine was the most frequently detected pesticide.
Volatile organic compounds and pesticides were not detected at concentrations exceeding the maximum contaminant level allowed in drinking water. The only constituent sampled for that exceeded its maximum contaminant level (10 milligrams per liter) was nitrate nitrogen (in 8 percent of the 174 wells).