A Feasibility Study Of Application Of Protein In Soil Contamination Biological Assessment

With the development of industries in China, the issue of soil pollution is becoming increasingly serious and some measurements have been taken to recover the ecological functions of contaminated soil. There is an urgent need to select an appropriate indicator in the process of assessing soil pollution, choosing remediation methods, and evaluating the effect of remediation. Consequently, we chose soil contaminated by polychlorinated biphenyls (PCBs) and heavy metals as study objects to explore the changes of soil biological indicators under pollutants stress. Firstly we compared two soil protein extract methods that were used most to investigate their extract efficiency for following researches. Comparing with some conventional biological indicators by combining traditional biological technology (e.g. enzymes activity, microbial biomass carbon, etc.) and modern molecular biotechnology (e.g. genomics, proteomics, etc.), the potential of soil protein as an indicator for soil pollution was discussed. In order to provide theoretical basis for using protein as an indicator for natural soil contamination, we did some preliminary work about the variations of microbial community structure and soil protein under contaminant stress. The main conclusions are as follows:(1) Compared with NaOH extraction, Citrate-SDS extraction can remove soil organic matter effectively and obtain more soil protein. The Citrate-SDS extraction is a relative high efficiency extract method for soil protein.(2) Acid phosphatase, protease, and polyphenol oxidase activity increased significantly (p<0.05) in soil contaminated by PCBs. Furthermore, the polyphenol oxidase activity was significantly positively correlated (p<0.05) with PCBs concentration. On the contrast, the content of soil protein was significantly negatively correlated (p<0.01) with PCBs concentration. The protein was separated by SDS-PAGE showed that with PCBs concentration increasing, there were less large molecular weight proteins and more low molecular weight proteins. Compared with polyphenol oxidase, the relationship between protein and PCBs was more closely. Therefore, it is more reliable to be an assessment indicator for soil contaminated by PCBs.(3) Soil acid phosphatase and dehydrogenase were inhibited by heavy metals, the dehydrogenase was more sensitive to heavy metals. Dehydrogenase was significantly negatively correlated (p<0.05) with Cu, Zn and Pb. Similarly, soil microbial biomass carbon (MBC) and soil protein were significantly negatively correlated (p<0.05) with Cu, Zn, Pb and Cd. Moreover, soil protein decreased sharply once the soil slightly contaminated by heavy metals. Subsequently, the variations of soil bacteria and actinomycete community structures were studied by modern molecular biological methods (e.g. SDS-PAGE, PCR-DGGE, etc.). The microbial community structures changed significantly under heavy metals stress. With the increase of heavy metals concentration, the Shannon index decreased and there were more low molecular weight proteins in soil. Compared with the responses of acid phosphatase, dehydrogenase, MBC and protein to heavy metals, protein is more suitable to be an indicator for soil polluted by heavy metals.