Accumulative characteristics of pesticide residues in organs of bivalves (Anodonta woodiana and Corbicula leana) under natural conditions.

Accumulative characteristics of pesticide residues in the gill, midgut gland, gonad, and the remaining tissues of the bivalve mollusks Anodonta woodiana and Corbicula leana were examined during the rice planting seasons of 1992 and 1994. Although seven pesticides, except thiobencarb, were accumulated all at ppb levels in the midgut gland (liver) and gonad of both bivalves during their application period, thiobencarb was accumulated in C. leana at extremely high levels of 15.70 microg g(-1) in 1992 and 12.45 microg g(-1) in 1994 in the midgut gland and 15.80 microg g(-1) in 1992 and 16.40 microg g(-1) in 1994 in the gonad, respectively. These levels were about 100 times higher than those in A. woodiana. Thiobencarb and molinate in A. woodiana and chlornitrofen (CNP) and molinate in C. leana remained in the gonad and midgut gland longer than in the gill and remaining tissues, while thiobencarb in organs of C. leana remained at ppm levels until the end of the experiments. The present study suggests that these interspecies differences can be attributed to differences between the two species in their ability to eliminate pesticides.