Ecotoxicity assessment of aged petroleum sludge using a suite of effects-based end points in earthworm Eisenia fetida

Laboratory investigations were conducted to test the toxicity of aged petroleum sludge collected from Shengli Oil Field, the second largest oilfield in China, to earthworm Eisenia fetida. Various end points were measured in the earthworms, including mortality, growth, cocoon output, juvenile production, and avoidance behavioral response, to determine their comparative sensitivity for assessing harmful effects of petroleum-hydrocarbon-contaminated soil. The results showed that all these assays responded in a concentration-dependent manner, and two chronic end points, juvenile production and cocoon output, as well as avoidance behavioral response appeared to be sensitive end points for detecting toxicity of petroleum-hydrocarbon-contaminated soil. Comparatively, juvenile production exhibited similar sensitivity to avoidance behavior response, both of which were more sensitive than cocoon output, while mortality and adult growth were proposed as the least sensitive parameters. It was suggested that large amounts of petroleum sludge deposited in Shengli Oil Field may pose a potential threat to the local ecosystem, and the utility of multiple effects-based end points in earthworm E. fetida is useful to facilitate ecological risk assessments in hydrocarbon-contaminated sites.