Submitted to: Water Environment Federation
Publication Type: Proceedings
Publication Acceptance Date: June 1, 1996
Publication Date: N/A
Interpretive Summary: All of us consume water, and we usually assume that the water is contaminant-free. To insure that drinking water supplies are safe and contaminant-free, scientific monitoring studies are implemented. To evaluate the impact of pesticides on ground and surface water quality in the agricultural intensive region of the eastern Coastal Plain region, the USDA-ARS has implemented a water quality demonstration project in Duplin Co, NC. Both ground and surface waters were monitored in a watershed. This type of study required that water samples be collected from ground water wells and streams and the pesticides measured using advanced analytical instruments. We examined ground water samples collected from 100 water quality wells and from several stream locations from 1993 to 1996. Most (95%) of our samples did not contain pesticides, and the detected amounts were usually very much less than the health advisory limit. This finding indicates that pesticides, if applied using best management practices, do not pose a threat to ground and surface water quality within this and similar watersheds.
Technical Abstract: Agricultural pesticides have some potential to migrate to ground and surface water sources, which may pose a threat to drinking water supplies. We have implemented a pesticide monitoring study in an agricultural intensive watershed located in the eastern Coastal Plain region of NC to evaluate the influence of pesticide best management practices (BMPs) on water quality in the watershed. Samples were collected from 1993 to 1996 from 100 ground water monitoring wells and thirteen stream locations and were extracted for pesticides commonly used within the watershed. The extracts were analyzed for pesticides using a combination of immunoassay and gas chromatography/mass spectrometry. Usually zero or very low amounts of pesticides were found in over 95% of the ground water wells sampled. Some pesticides were detected in one stream tributary, but the concentrations declined rapidly along the stream continuum. Among the pesticides assayed, alachlor was the most frequently (3%, total sample basis) confirmed pesticide in the ground water, while metolachlor (11%, total sample basis) was the most frequent pesticide detected in the stream. Overall, the high percentage of ground water wells with zero or very low concentrations of pesticides indicates that pesticide BMPs implemented by local farmers are effective in maintaining good water quality.