Bioavailability to Earthworms of Aged DDT, DDE, DDD, and Dieldrin in Soil

A study was conducted to determine the bioavailability of several pesticides that have persisted for various periods in soils in the field and the laboratory. Based on the concentrations or the percentages of the compound in soil samples that were found in the earthworm Eisenia foetida, ca. 30, 12, 34, and 20% of DDT, DDE, DDD, and a total of the three compounds were bioavailable in a soil treated in the field with DDT 49 years earlier. Only 28 or 43% of dieldrin aged for 49 years was bioavailable based on concentrations in E. foetida or percentages of the compound assimilated by the worms, respectively. Comparably low percentages of DDT, DDE, and DDD but not dieldrin were assimilated by the worms from samples of soil from a waste-disposal site receiving the insecticide ca. 30 years earlier. Aging for 190 days in Kendaia loam in the laboratory markedly reduced the availability to E. foetida of DDT and DDE but not DDD. The amounts of aged or unaged DDT, DDE, and DDD but not dieldrin that were removed from the soils by solid-phase extraction with Tenax TA beads were generally greater with increasing amounts assimilated by the earthworms. The results show that aging markedly reduces the bioavailability of these compounds.