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

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.