Between 1992 and 1999 samples of untreated groundwater were analyzed from about 1500 primarily domestic drinking-water wells as part of the National Water-Quality Assessment Program of the U.S. Geological Survey. Wells were sampled to define the quality of the ground-water resource; consequently, they were geographically distributed across large aquifers primarily in rural areas. Up to 60 volatile organic compounds (VOCs), 83 pesticides, and nitrate were analyzed in each sample. Nitrate concentrations ³ 3 mg/L were assumed to have an anthropogenic origin. Seventy percent of the samples had at least one VOC, pesticide, or anthropogenic nitrate; 46% had at least two compounds; and 33% had at least three compounds. The total concentration of VOCs and pesticides ranged from about 0.001 to 100 µg/L, with a median of 0.02 µg/L. About 12% of the sampled wells exceeded health criteria, primarily due to nitrate concentrations exceeding the maximum contaminant level of 10 mg/L. Although VOCs were detected more frequently (44%) than pesticides (38%) or anthropogenic nitrate (28%), the most frequently detected mixtures consisted of persistent pesticides and nitrate that are commonly applied together, or sequentially, on row crops. VOCs, on the other hand, tended to co-occur with a wider variety of compounds. See wwwsd.cr.usgs.gov/nawqa/vocns/
Learning Objectives: At the conclusion of the session the participant will be able to describe common mixtures of pesticides and other contaminants in source water used for public water supplies in the U.S.
Keywords: Drinking Water Quality, Pesticide Contamination
Presenting author's disclosure statement:
Organization/institution whose products or services will be discussed: U.S. Geological Survey
I have a significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.
Relationship: Employment