USE OF PLANT AND EARTHWORM BIOASSAYS TO EVALUATE REMEDIATION OF SOIL FROM A SITE CONTAMINATED WITH POLYCHLORINATED-BIPHENYLS

Soil from a site heavily contaminated with polychlorinated biphenyls ( PCBs) was treated with a pilot-scale, solvent extraction technology. B ioassays in earthworms and plants were used to examine the efficacy of the remediation process for reducing the toxicity of the soil. The ea rthworm toxicity bioassays were the 14-d survival test and 21-d reprod uction test, using Lumbricus terrestris and Eisenia fetida andrei. The plant bioassays included phytotoxicity tests for seed germination and root elongation in lettuce and oats, and a genotoxicity test (anaphas e aberrations) in Allium cepa (common onion). Although the PCB content of the soil was reduced by 99% (below the remediation goal), toxicity to earthworm reproduction remained essentially unchanged following re mediation. Furthermore, phytotoxicity and genotoxicity were higher for the remediated soil compared to the untreated soil. The toxicity rema ining after treatment appeared to be due to residual solvent introduce d during the remediation process, and/or to heavy metals or other inor ganic contaminants not removed by the treatment. Mixture studies invol ving isopropanol and known toxicants indicated possible synergistic ef fects of the extraction solvent and soil contaminants. The toxicity in plants was essentially eliminated by a postremediation, water-rinsing step. These results demonstrate a need for including toxicity measure ments in the evaluation of technologies used in hazardous waste site r emediations, and illustrate the potential value of such measurements f or making modifications to remediation processes.