Effect of species differences, pollutant concentration, and residence time in soil on the bioaccumulation of 2,2-bis (p-chlorophenyl)-1,1-dichloroethylene by three earthworm species.

Laboratory experiments were conducted to study the effects of species differences, soil concentration, and contaminant-residence time in soil on the bioaccumulation factor (BAF; dry-weight ratio of contaminant concentration in the tissue to that in the soil) of 2,2-bis (p-chlorophenyl)- 1,1-dichloroethylene (p,p'-DDE) for three species of earthworms. In four field-weathered soils, the BAF for Eisenia foetida, an epigeic species (surface habitat), was approximately 10-fold higher than those for Lumbricus terrestris, an anecic species (deep habitat) and Aporrectodea caliginosa, an endogeic species (habitat within the soil profile). Preliminary analysis indicates that BAF may decline with increasing pollutant concentration in soil. With regard to contaminant-residence time, the BAF for E. foetida was lower in weathered soils relative to that in freshly amended soils, but age of p,p'-DDE did not significantly alter the BAF for A. caliginosa. These data suggest total chemical concentration alone is not a reliable indicator of the toxicological significance of a contaminated soil and that species-specific differences and environmental factors significantly impact overall exposure and risk.