Abstract
With an aim to evaluate ecological effects of fenitrothion (MEP) sprayed aerially over a forest for control of pine sawyer beetles, residues of MEP in soil and aquatic systems (water, sediment, fish) were investigated. In soil, MEP concentration was 2.87-56.3ppm in the organic horizon on the 2nd day after application, and decreased to 0.164-0.546ppm after one year, which was 178-1060 times as high as that in the mineral horizon. MEP residues after one year were estimated to be 0.16-0.25% of the applied dosage. In water, maximum MEP concentrations were 93.9ppb in streams on the application day, 24.4ppb at the first rainfall after application, 2.31ppb in estuaries, 508ppb in a pond. MEP dropped in the streams ran off rapidly, and the remaining MEP in the forest ran off with the first rainfall after application. MEP effusions were estimated to be 0.71% and 0.0092% of the applied dosage with an 89mm rainfall on the 2nd day and with a 36mm rainfall on the 5th day after another application, respectively. MEP concentration in the small pond was relatively high, decreasing exponentially with a half-life of 1.1-2.4 days. Little MEP remained in sediments. MEP in carp changed in proportion to the concentration in the water, maximum concentrations being 2.33ppm in the carp in the streams and 20.6ppm in the carp in the pond. The ratios of MEP concentration in the carp to the water were 5.2-2000 in the streams and 70-690 in the pond.
