Ecotoxicological Diagnosis Of Metal Contaminated Soil By Eisenia Fetida And The Identification Of Potential Biomarkers

With the rapid development of urbanization and industrialization, the problem of soil heavy metal contamination has become more and more serious. The metal smelter is an important source of heavy metal contamination in soil. The large emission of toxic and hazardous pollutants generated in the production process got into soils through various channels such as atmospheric deposition. And lead to the heavy metal contamination in soils around the smelter.In this paper, we determined the heavy metal contents in10soil samples collected from Nanjing steel plant and its surrounding farmland. Compared with the clean soil, the results showed that all soil samples of Nanjing steel plant were contaminated by heavy metals in different levels, and they were characterized by different Cu-Ni, Pb-Zn combined pollution. The integrated pollution indexes of heavy metals in soil samples ranged from1.285to4.364, and some soil samples were heavily polluted. The soils collected from surrounding farmland were still clean. The integrated pollution indexes were greater than0.1and less than1, belonging to the alert level.This study evaluated the biochemical responses, DNA damage, body metal contents and avoidance responses of Eisenia fetida exposed to two multi-metal-contaminated soils in Nanjing steel plant and a natural reference soil in Zijin Mountain. Results showed that three enzyme activities, including superoxide dismutase (SOD), acetylcholinesterase (AChE), and cellulase, in earthworm in metal-contaminated soils were significantly different from those of the reference soil. Cellulase and AChE were more sensitive than SOD to soil contamination. The results of the comet assay demonstrated the genotoxicity of metal contaminated soils. And a DNA repair process in earthworm was observed as the exposure time prolonged. And the comet assay is capable of examining the genotoxicity of soils. The results of heavy metal accumulation test showed that earthworms were capable of accumulating different heavy metals. In the avoidance response test, the avoidance behaviour of earthworm was not occurred.We collected earthworms from metal-contaminated soils, the metal contents in earthworms were determined and biological accumulation factor (BAF) was calculated. The activity of AChE and cellulase in earthworms were also assayed. The results showed that the metal contents in earthworms and AChE, cellulase activities were able to indicate the soil metal contamination.In summary, AChE, cellulase and DNA damage levels in earthworm can be used as potential biomarkers for the evaluation of metal-polluted soils, while metal contents in earthworm can be used as an indirect indicator of heavy metal contamination in soils.