Prediction of Environmental Fate of Organochlorine Pesticides in a Specific Area

Environmental pollution by pesticides became a major issue. In this study, the environmental fate of representative organochlorine pesticides were predicted to evaluate their environmental safety by a kinetic model from physicochemical parameters such as air-water partition coefficient and adsorption constant to soil and biological parameters such as aerobic biodegradation rate constant. The subject area of prediction is Tokyo metropolis, surrounding three prefectures and Tokyo Bay. The average concentrations at steady state in the case of continuous loading of ten pesticides and the concentration time profiles of two herbicides in the case of momentary loading were predicted. The results obtained were as follows; (1) Soil compartment tends to be a major polluted compartment in the case of continuous loading for many pesticides. Air is also a major polluted compartment for chloropicrin, dichlorvos and DCIP whose air-water partition coefficients are relatively high, and water is a major p lluted compartment for trichlorfon, dichlorvos and DCIP whose adsorption constants to soil are relatively low. (2) Although sediment is not a major polluted compartment, the concentrations of several pesticides and their biodegraded intermediates in sediment are predicted to be high. (3) On the time profiles of chlornitrofen and thiobencarb in the case of momentary loading, the concentrations in soil are calculated to be decreased according to the first-order rate equation, whereas those in water are calculated to be increased for 10-30 days after loading and are decreased slowly. (4) Estimation of man intakes of pesticides showed that the levels of intakes were not serious for the relatively large area such as Tokyo area, and it was considered that the pollution in small area should be directed attention.