Pesticides in water and fish from rivers flowing into Lake Biwa.

Abstract

Surveys of twelve herbicides were performed for water and fish samples obtained from seven rivers flowing into Lake Biwa from April in 1994 to March in 1996. Eleven herbicides were detected at high frequency for molinate, simazine, bromobutide, simetryne, benthiocarb, preti‐lachlor, oxadiazon and mefenaset but at low frequency for terbucarb, butachlor and CNP. Molinate, simetryne, benthiocarb, oxadiazon and mefenaset were detected in ayu sweetfish, pale chub and dark chub but not for simazine, butachlor, pretilachlor and CNP in spite of their detections in the river water. These are probably due to their low bioconcentration potential or temporary contamination. The bioconcentration factors (BCF) of molinate, benthiocarb, oxadiazon and simetryne in the three species of fish calculated from the field data were approximately consistent with the BCF values from the laboratory data on willow shiner or topmouth gudgeon. However, the difference of fish species should be considered for the evaluation of the fiel...