MONITORING PESTICIDE AND NITRATE IN VIRGINIAS GROUNDWATER - A PILOT-STUDY

Between October 1992 and February 1993, a total of 359 private wells i n Northampton County were sampled and data on water-quality variables (temperature, pH, and conductivity), well construction, and site chara cteristics were collected The groundwater samples were analyzed for al dicarb, alachlor, atrazine, carbofuran, linuron, methomyl, metolachlar , metribuzin, napropamide, pendimethalin, pronamide, simazine, and nit rate. The wells were stratified into shallow wells, withdrawing water from the unconfined aquifer, and deep wells, withdrawing water from th e deeper confined aquifers. The study was undertaken as a pilot study to demonstrate the applicability of a recently developed framework for evaluating the extent of pesticide contamination in Virginia's ground water. Pesticides were detected in 14% of the shallow wells and in 7% of the deep wells sampled. Pesticide detection was associated with the well depth, with a higher probability of detecting a pesticide in the shallow unconfined aquifer than in the deeper aquifers. Nitrate above the U.S. EPA drinking wafer standard of 10 mg/L was found in 17% of t he shallow and 1% of the deep wells. Pesticide and nitrate detections were not significantly related to well and site characteristics, such as crop type, location of well head, and distance to the nearest water body.