Ecotoxicological assessments of contaminated soil aim to understand the effect of introduced chemicals on the soil flora and fauna. Ecotoxicity test methods were developed and conducted on hydrocarbon‐contaminated soils (<5,000–30,000 mg/kg total petroleum hydrocarbon) and on adjacent uncontaminated control soils from eight field locations. Tests included 7‐d, 14‐d, and chronic survival tests and reproduction assays for the earthworm (Eisenia fetida) and seed germination, root length, and plant growth assays for corn, lettuce, mustard, and wheat. Species‐specific responses were observed with no‐observed effect concentrations (NOECs) ranging from <1 to 100% contaminated soil. The 14‐d earthworm survival NOEC was equal to or greater than the reproduction NOEC values for numbers of cocoons and juveniles, which were similar to one another. Cocoon and juvenile production varied among the control soils. Germination and root length NOECs for mustard and lettuce were less than NOECs for corn and wheat. Root length NOECs were similar to or less than seed germination NOECs. Statistically significant correlations (p < 0.05) for earthworm survival and seed germination as a function of hydrocarbon measurements were found. The 14‐d earthworm survival and the seed germination tests are recommended for use in the context of a risk‐based framework for the ecological assessment of contaminated sites.

Abstract-Ecotoxicological assessments of contaminated soils require an understanding of the impact of chemicals on the terrestrial ecosystem. Eight hydrocarbon-containing field soils were evaluated using physical-chemical, hydrocarbon, and ecotoxicological assays during 11 to 13 months of laboratory bioremediation. Ecotoxicity tests included earthworm (Eisenia fetida) 14-d survival and reproduction assays and seed germination and root length assays using corn, lettuce, mustard, and wheat seeds. During bioremediation, freon-extractable total petroleum hydrocarbon decreased by 26 to 84%, depending on the soil. In most soils, earthworm survival increased to or remained at 100% following bioremediation. Earthworm reproduction increased or remained the same relative to control soils. Lettuce and mustard seed germination increased following bioremediation except in two soils with high salt concentrations. Corn and wheat germination was high on most soils and did not change following bioremediation. Root length responses varied among seeds and soils, increasing in some soils and remaining unchanged in others. The responses of organisms to hydrocarbon-containing field soils directionally improved with bioremediation.