Effects of Petroleum-Contaminated Soil on Lethality and Avoidance Behavior of the Earthworm Eisenia foetida
石油污染土壤对蚯蚓的致死效应及回避行为的影响

The contamination of petroleum hydrocarbons in soil is now seriously threatening ecosystem safety and human health, and therefore the diagnosis and risk assessment of petroleum-contaminated soil is becoming one of the hot topics in the field of environmental science. In this study, the earthworm Eisenia foetida was exposed to the soil contaminated with different concentrations of petroleum, which was obtained by mixing the natural contaminated soil with the clean background soil. The acute lethality and avoidance response were adopted as endpoints to evaluate the toxic effects of petroleum-contaminated soil on earthworms. Results showed that the values of 7d-LC50 and 14d-LC50 were 32.5 and 29.4 g·kg-1, respectively. However, when the concentration of petroleum hydrocarbons in the soil achieved 8.0 g·kg-1, the earthworm showed significant avoidance behavior (avoidance rate = 80%). The former two endpoints were 3.7 to 4.1 times as much as the latter one. It was demonstrated that the avoidance endpoint was more sensitive than the mortality endpoint while evaluating ecological risk of petroleum-contaminated soil. The avoidance response of Eisenia foetida can serve as a sensitive indicator for assessing the petroleum pollution of soil.