德兴铜矿尾矿重金属污染对土壤中微生物多样性的影响

Impact on microbial diversity of heavy metal pollution in soils near Dexing copper mine tailings

摘要:

【目的】为更好地了解重金属污染与微生物多样性之间的相互作用关系, 以江西德兴铜矿4 #尾砂库为研究对象, 采集野外实地样品共16件进行分析(包括尾砂样品以及周围农田和菜地土壤样品)。【方法】一方面对样品中可培养异养细菌进行平板计数, 一方面采用变性梯度凝胶电泳(Denaturing gradient gel electrophoresis, DGGE)对样品中可培养和不可培养微生物分子生态多样性进行研究; 同时采用PCA (Principle component analysis)方法分析样品理化性质、重金属及主要元素与可培养细菌数量及微生物多样性之间的相互关系。【结果】元素分析结果表明该尾矿区样品受到不同程度重金属Cu、Cd、Zn、Ni、Pb和Cr的污染; 可培养异养细菌在尾砂样品中数量最少, 在菜地和农田土壤样品中有明显增加; 多样性指数(Shannon-Weaver index H)计算结果发现H最大值出现在距离尾矿中等距离、重金属浓度在中等程度的样品中。PCA分析结果表明可培养异养菌数量与理化性质如有机碳、有机质、含水率等相关性较大, 重金属影响不明显; 而多样性指数H除与上述理化性质相关性较大外, 还受到重金属Ag、Zn、As、Pb、Ni、Cr等的影响, 而在样品中含量普遍比较高的重金属如Cu、Cd等并不成为影响微生物多样性的主要因素。【结论】从这些长期受重金属污染的野外实地样品来看, 以上结果说明不同重金属浓度对微生物多样性的影响可能并不是实验室研究的简单的线性关系。

Abstract:

[Objective] In order to understand the interaction between heavy metal contamination and microbial diversity better, 16 wild field samples including tailing samples, near grain and vegetable soil samples were obtained from the 4 # tailing site of Dexing copper mine, Jiangxi province, China. On the one hand, number of culturable heterotrophic bacteria in samples was counted by plate method. [Methods] On the other hand, the diversity of culturable and unculturable microbial communities was further investigated by denaturing gradient gel electrophoresis (DGGE). Principle component analysis (PCA) was used to reveal the influences of physico-chemical characteristics, contents of chemical/heavy metal elements on the diversity of culturable heterotrophic bacteria and microbial community. [Results] Results of elemental analysis revealed that these samples subjected to different levels of contamination by heavy metals Cu, Cd, Zn, Ni, Pb and Cr. Number of culturable heterotrophic bacteria was the least in tailing samples, and increased significantly in vegetable and grain soil samples. The diversity index of the samples (Shannon-Weaver index H) was calculated, and it found the greatest diversity of microbial community present in samples, which were at middle distance away from the mine tailing site and had middle level of heavy metal concentrations. PCA analysis showed that the number of culturable heterotrophic bacteria had significant relativity to the physic-chemical properties such as organic carbon, organic matter, moisture content and so on, except for heavy metals. For diversity index H, except above physico-chemical properties, some heavy metals such as Ag, Zn, As, Pb, Ni and Cr had significant influences on it. While heavy metals such as Cu and Cd, which were present in the samples with relatively high concentrations, did not become major factors affecting microbial diversity. [Conclusion] The results from these long-term heavy metals contaminated wild field samples, may indicate that the influence of different heavy metals on microbial diversity is not laboratory studied simple linear relationship with their concentrations.