<b>Study on Atmospheric Dry Deposition of Insecticides to Surface Waters </b><b>in the Isogo Ward of Yokohama </b>

Abstract

Summar y Dichlorvos and fenitrothion were detected frequently in rainwater collected at Yokohama Environmental Science Research Institute located in the Isogo ward of Yokohama in 2001 and 2002. Further, some rainwater samples in 2003 had a lethal effect on Daphnia magna after adding minerals. Thus, toxic potency of insecticide in rainwater (wet deposition) was considered to be an important problem for environmental protection. However, there were few studies on the atmospheric dry deposition of organophosphorous insecticides in Japan. Therefore, atmospheric deposition of dichlorvos and fenitrothion were determined by gas chromatograph mass spectrometer (GC/MS). Average atmospheric deposition amount of dichlorvos was 7.0 ng/m 2 /hr and that of fenitrothion was 6.3 ng/m 2 /hr. The highest concentration of insecticides in the aqueous solution exposed to air overnight was less than 0.05 μg/L, although the concentraions of dichlorvos and fenitrothion in rainwater sampled on October 1 st , 2014 were more than 0.10. μg/L. The toxic potency of insecticides in aqueous solution exposed to air overnight might be less than that in rainwater sampled on October 1 st , 2014. However, the concentrations of dichlorvos and fenitrothion in the solution exposed to air overnight were not less than PNEC (predicted no-effect of concentration). Therefore the atmospheric deposition of insecticides was considered to be one of important ecological problems for environmental protection as well as wet deposition of them.