石油污染土壤对蚯蚓的致死效应及回避行为的影响

土壤石油污染对生态系统和人类健康有严重影响,其毒害诊断和风险评价的研究日益受到重视。以赤子爱胜蚓(Eiseniafoetida)为受试生物,利用受石油污染的实际土壤,将高浓度污染的土壤与清洁土壤混合,配制成不同污染水平的石油污染土壤,通过直接暴露的方式,分别以蚯蚓急性毒性死亡率和回避反应作为测试终点,评价了石油污染土壤对蚯蚓的生态毒性。结果显示,石油烃污染土壤对蚯蚓的7d-LC50和14d-LC50分别为32.5和29.4g·kg-1,而土壤中石油烃的浓度为8.0g·kg-1时,蚯蚓即有明显回避反应(回避率达80%),前两者为后者的3.7～4.1倍。可见,与急性毒性实验的测试终点LC50相比,行为测试终点对石油烃的响应更灵敏。蚯蚓的回避反应可更加及时地反映出土壤受石油污染的状况,发挥更好的指示作用。

Effects of Petroleum-Contaminated Soil on Lethality and Avoidance Behavior of the Earthworm Eisenia foetida

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.