Contribution of Atmospheric Deposition to Pesticide Loads in Surface Water Runoff

A 3.5-year study was conducted to determine the signifcance of atmospheric deposition to the pesticide concentrations in runoff. Both wet and dry atmospheric depostion were collected at six sites in the central San Joaquin Valley, California. Wet deposition samples were collected during individual rain events and dry deposition samples were collected for periods ranging from three weeks to four months. Each sample was analyzed for 41 currently used pesticides and 23 transformation products, including the oxygen analogs of nine organophosphorus (OP) insecticides. Ten compounds in rainfall and 19 in dry deposition were detected in at least 50% of the samples. [Summary provided by the USGS.]