Toxicological Effects Of Naphthalene And Copper On Eisenia Fetida In Soil

As influence of human activities on soil environment develops increasingly, production in industry and agriculture leads to soil contamination. Researches on toxicological test and applied teconology of terrestrial ecology are given more attention in the need of ecological risk assessment and ecological function diagnosis of contaminated soil. Earthworm Eisenia fetida is one of the most important biological indicators of soil quality. Naphthalene is one of 16 PAHs as priority pollutants by U.S.EPA. And Copper is regarded as dominant heavy-metal pollutant in many industrial contaminated sites for its wide use and discharge. Naphthalene and copper have been selected as representatives of PAHs and heavy metal polltants. Toxic effects to the Eisenia fetida of naphthalene and copper in different concentrations were studied.Using OECD soil, black soil from Jilin, fluvo-aquic soil from Beijing and red earth from Hunan, the standardized avoidance tests were carried out to investigate the behavioral response of earthworm Eisenia fetida to naphthalene-spiked soils and copper-spiked soils. The results showed significant repellent effects at a concentration of 50 mg/kg naphthalete and 125 mg/kg copper in all kinds of soils.An acute lethal test was also conducted to determine the 50% lethal concentrations (LC₅₀) of naphthalene and copper. LC₅₀ to Eisenia fetida of naphthalene and copper is respectively 173.8 mg/kg and 229.2 mg/kg in OECD soil,which is both higher than in fluvo-aquic soil from Beijing(LC₅₀,nap=97.3 mg/kg,LC₅₀,copper=187.4mg/kg) .Through subacute toxicity test and reproductive toxicology test, we found that the influnce of sublethal pollutant concentrations on survival rates of Eisenia fetida was not so sensitive, whereas the effects of concentrations on body weight, cocoon number, average weight of cocoon and number of juvenile worms per cocoon were severe, which is more sensitive to describe the harm of pollutants than LC₅₀. Therefore, they can be used as indicators in ecological risk assessment. The growth and reproduction of Eisenia fetida were inhibited in high concentration contaminated soils. Body weight and average weight of cocoon were reduced; cocoon number and number of juvenile worms per cocoon were decresed as concentration rose.The toxicological response of Eisenia fetida towards pollutants was observed through the basic toxicology effect. After exposed in pollutants, the earthworms showed sluggish pace and dull skin color. The movement ability was declined, and the body turned to become long and thin, or even broke off.It possesses a lot of strengths to use toxic tests of earthworm in soil ecological function assessment, such as the easy operation, low cost, facil observation, sensitive reaction and ecological test endpoints. Therefore, it is regarded as one of powerful and effective tools for toxicology assessment. The results will provide methodological support for soil contamination ecological risk assessment in China, and also provide scientific basis for establishment of soil guide values and eco-toxicological diagnosis system of soil pollution.