电子垃圾不当处置的重金属和多氯联苯污染及其生态毒理效应

在广东清远市龙塘镇和石角镇焚烧迹地、拆解作坊附近和周边农田采集土壤样品,分析土样中重金属和多氯联苯浓度水平的同时,测定土壤酶活性,并采用聚合酶链式反应-变性梯度凝胶电泳技术(PCR-DGGE)解析土壤微生物群落结构。结果表明不同种类土壤酶对重金属和多氯联苯污染的响应存在较大差异,其中酸性磷酸酶活性与Pb、Cu和Zn含量在P0.01水平上显著负相关,与Cd和多氯联苯含量在P0.05水平上显著负相关,说明酸性磷酸酶对重金属和多氯联苯污染的响应最为敏感;酸性磷酸酶活性与土壤pH值在P0.01水平上显著负相关,过氧化氢酶活性与土壤pH值和全磷含量均在P0.01水平上显著正相关,说明土壤酶活性不仅受重金属和多氯联苯等污染物的影响,还与pH值、土壤养分等因素密切相关。焚烧迹地、拆解作坊附近及周边农田土样微生物多样性指数低于离拆解中心区域较远土壤样品微生物多样性指数,一定程度上反映了不当电子垃圾拆解污染对当地土壤微生物的损伤;变形菌门(Proteobaeteria)是拆解区土壤中优势微生物类群,占克隆总数的60%;部分克隆序列在Gen Bank中最相似序列与多氯联苯、多环芳烃等有机物降解和重金属抗性微生物有关。

Pollution of heavy metals and polychlorinated biphenyls by improper e-waste dismantling activities and its ecotoxicological effect

Longtang Town and Shijiao Town in Qingyuan City, Guangdong Province, South China, have been known for their improper e-waste importing and recycling, and their crude recycling activities have led to serious contamination of the surrounding environment. In the present work, enzyme activities and microbial communities of soil samples at the open burning site (OBS) and near the dismantling workshops (NDW), as well as enzyme activities and microbial communities of samples of farmland soil (FS) around the dismantling workshops, were analyzed. Results showed that different enzymes had different responses to pollution by heavy metals and PCBs. Significant negative correlations between acid phosphatase activity and concentration of Pb, Cu, Zn, Cd, or PCBs in the soil samples were observed (P<0.01 or P<0.05). Acid phosphatase was the most sensitive indicator of the reactions of five different enzymes to soil contamination by heavy metals and PCBs. Soil enzyme activities were not only influenced by pollutants, but also closely related to soil physical-chemical qualities such as soil nutrients, pH, and so on. Results of polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) experiments demonstrated that the Shannon index varied from 1.946 to 2.485 at different sites, and the indices at OBS, NDW, and farmland around the dismantling workshops were lower than those at farmland sites far away from the central dismantling area. A higher Shannon index indicates a more diversified bacterial community, therefore, the above result partly implied the damage to local soil microorganisms by pollution from improper e-waste dismantling activities. Proteobacteria was the most abundant bacterial lineage (60%). Some PCR-DGGE band sequences were highly similar with 16S rRNA genes from heavy metal-resistant microorganisms and PCB- and PAH-degrading microorganisms.