Bio-Toxicity Diagnosis Of Soil In Chordane And Mirex Contaminated Sites

Chlordane and mirex are persistent organic pollutants (POPs) which are recalcitrant in the environment and pose high risk to human health. Although the production of chlordane (Chlordane) and Mirex (Mirex) in China have been ceased, strong attention must be paid to the remediation and risk management of the contaminated sites.This work chose Liyang organic chemical contaminated site as the study area, in which mirex and chlordane were priority pollutants. The International Organization for Standardization (ISO) recommended test earthworm species-Eisenia fetida was used as test soil animal. Common local agricultural plants, including rice, wheat, corn and Chinese cabbage were chosen as test plants. Acute toxicity test and diagnosis methods were established for the contaminated site. The feasibility of the methods were tested by comparing the results with chemical analysis in practical applications.Through research, the paper established a set of bio-toxicity diagnosis methods for organic contaminated sites. Ecotoxicity experiments were performed using earthworm (Eisenia fetida) as the test organism. Effects of chlordane and mirex contaminated soil on body weight, activities of superoxide dismutase (SOD) andcatalase (CAT), and protein levels of earthworm (Eisenia foetida) were investigated. Seed germination rates and root elongation rates of the four selected plants (wheat, cabbage, corn and rice) were measured using the chlordane and mirex contaminated soil from the site.From the earthworm toxixity test, results showed that body weight of the earthworm was significantly inhibited by chlordane and mirex with increase in exposure time. Protein levels in vivo, and SOD and CAT activities in response to chlordane and mirex exhibited different sensitivities in the following order:CAT>SOD>protein. According to a dose-response relationship in this study, chlordane at14.13mg kg-1soil and mirex at4.14mg·kg-1soil may be critical concentrations which lead to the highest activity of CAT and obvious inhibition of SOD activity in earthworm. Ecotoxicity effects on earthworm may occur when the critical concentrations of chlordane and mirex in the soil are exceeded. From the plant toxicity tests,results showed that under the same concentrations of chlordane or mirex in soil, root elongation rates were more significantly inhibited than seed germination rates in all four types of plants. Thus, root growth could be more sensitive to the contamination level than seed germination. Seed germination sensitivity followed the order wheat> Chinese cabbage> rice> corn. Wheat can be used as a sensitive plant indicator for the contaminated site.The results of this study showed that earthworms and plant seeds had different levels of response to chlordane/mirex contaminated soil. Selected sensitive biological toxicity indicators with appropriate diagnostic methodsprovided a rapid, practical and effective way for hazard identification and ecological risk screening. Combined with chemical analysis and other evaluation methods, a comprehensive risk assessment of the contaminated site can be archieved, which will further benefit the planning of remediation.