FATE AND IMPACT OF PESTICIDES APPLIED TO POTATO CULTURES - THE NICOLET-RIVER BASIN

The fate of cash-crop (potato) pesticides was monitored from the field s on which they were applied to the nearby streams. The investigation took place in the Nicolet River basin in the province of Quebec, Canad a. The main pesticides under study were aldicarb, fenvalerate, metribu zin, and phorate. Aldicarb was never detected in any of the samples. T he other pesticides were all detected in soils at low concentrations. Only fenvalerate and metribuzin were detected in tile drain. Metribuzi n concentrations of up to 0.25 mu g/g were detected in the soil giving rise to a concentration of 1.3 mu g/liter in tile drain and 47.1 mu g /liter in surface runoff. Low concentrations of metribuzin up to 0.41 mu g/liter were detected in the nearby streams. The CREAMS model simul ating pesticide movement in the fields overestimated metribuzin losses in the runoff at a concentration of 107 mu g/liter. The subsurface EX PRES model using a PRZM time series adequately estimated a metribuzin held subsurface runoff concentration of 0.5 mu g/liter. According to t he Canadian Water Quality Guideline for the protection of aquatic life , the concentrations of pesticides found in surface waters of this pot ato-growing region of Quebec do not have a potential to impact on the aquatic life in these systems. (C) 1996 Academic Press, Inc.