PESTICIDES AND METABOLITES IN THE SHALLOW GROUNDWATER OF AN EASTERN COASTAL PLAIN WATERSHED

摘要

The occurrence of pesticides in drinking water sources is a public concern because of potential adverse health effects. We report the results of a three-year study to assess the occurrence of pesticides and metabolites in shallow groundwater in a USDA Water Quality Demonstration Project (WQDP). The Herrings Marsh Run (HMR) watershed is located in the eastern Coastal Plain region of North Carolina and has similar characteristics of other regional agricultural-intensive watersheds. Ninety-two shallow groundwater wells were installed on farms around the watershed in late 1992 and early 1993. Water samples were collected monthly from March 1993 to March 1995 and collected quarterly for the remainder of 1995 and early 1996. The samples (n = 2598) were initially screened for 11 pesticides (8 triazines, 2 chloroactamides, 1 methylester) using immunoassay techniques. The positive detections (n = 266) were further analyzed by gas chromatographic (GC) and GC/MS (mass spectrometric) procedures. During the study period, we found that the majority (91%) of the wells had no detections for 11 compounds commonly used in the watershed. Pesticides were consistently detected in four wells, but the concentrations were usually below the health advisory limit (HAL). Overall, alachlor was the most frequently detected pesticide. The lack of 11 commonly used pesticides in a high number of wells suggests that these pesticides have had a minimal impact on the quality of HMR shallow groundwater.