Monitoring of 15 Pesticides in Rainwater in Utsunomiya, Eastern Japan, 1999-2000<SUP>1</SUP>

Abstract

Residues of 15 pesticides in rainwater were investigated monthly from July 1999 to July 2000 at five sampling sites in Utsunomiya, eastern Japan. Additionally, the residues for each precipitation were measured at one site. Among pesticides applied mostly as granular formulations to paddy fields, simetryn, pretilachlor, mefenacet and iprobenfos with small Henry's law constants were infrequently detected. In contrast, the herbicides thiobencarb and esprocarb with large Henry's law constants were frequently detected outside of the application periods, suggesting that the volatilization from water and soil surfaces had continued for a long time. The annual (July 1999-June 2000) deposited amount as an average value among the sampling sites was largest for fenitrothion at 546 μg/m 2 , followed by thiobencarb at 196 μg/m 2 , esprocarb at 109 μg/m 2 , and fenobucarb, diazinon and phthalide at about 40 μg/m 2 each. The relative standard deviations of the deposited amounts among the sampling sites were 30% or less. Fenitrothion, fenobucarb and phthalide were applied mostly as wettable powder, emulsifiable concentrate and dust formulations, allowing the pesticides to easily enter the atmosphere during the spraying or dusting process. The less variable distribution of these three pesticides is ascribable in part to the application of the above three formulations in large quantities. The annual deposited amounts of the other pesticides were about 20 μg/m 2 or less, with marked variation among the sampling sites.