| Heavy metal pollution in soil has become one of the most serious environmental problems.Microbial community is an important part of soil system,Heavy metal pollution may soil biochemical processes,microbial community and activity,thus probably further affects soil carbon cycling.However,the abnormal accumulation of soil organic carbon is not clear with the soil microorganism groups.In order to reveal the impact of Pb-Zn tailing sand on the soil functional microorganism groups relating to soil organic carbon metabolic,different land use types in the Pb-Zn tailing dam area in Sidi village,Yangshuo,Guangxi Zhuang Autonmous region,China were selected.In this study,many contents,including heavy metals pollution,the accumulation and mineralization of soil organic carbon(SOC),biology community structureand and soil functional microorganism groups were identified by using molecular biology method and stable isotope probing(SIP)of DNA with the 13 C.Thorough a large number of field work and laboratory experiments,the major resides are as follows:(1)It is found that the content level of Pb,Zn,Cu and Cd in paddy fields is the highest.The geoaccumulation method and potential ecological risk index method were employed to evaluate the pollution level of 4 elements(Pb,Zn,Cu and Cd)in the target area soil.Both results show show that the potential hazard sequence is as follows: Cd>Pb>Zn>Cu.The result indicates that heavy metal pollution in the region is getting worse,the soil in this region and is not suitable for cultivation of crops.(2)Under the effect of Pb–Zn tailings,the low the microbial biomass carbonbut the high the particulate organic carbon compared to the control group.In contrast,metal pollution increased metabolic quotient and decreased microbial quotient in the target area soil.According to the results of factor analysis and multivariate linear(stepwise)regression model,soil organic carbon mineralizatn,basal respiration,microbial quotient and metabolic quotient might be changed by metal pollution.Microbial biomass carbon might be changed by metal pollution and its own properties on due to the decrease of carbon used efficiency of microorganism.(3)The results of Fluorescence quantitative PCR show that abundance of soil bacteria and fungi in paddy fields increased compared with other land.Combining with redundancy analysis,it is found that soil organic carbon content is significantly associated with abundance of bacteria.By using high-throughput DNA sequencing techniques for 16 S r RNA show that Proteobacteria,Acidobacteria,and Chloroflexi were dominant at bacterial communities the control group,corn field,citrus field and paddy field.The relative abundance of Acidobacteria decreased with heavy metal content in control group,corn field and citrus field,in contrary,the relative abundance of Proteobacteria and Actinobacteria increased.The structures of archaea communities were included Euryarchaeota,Thaumarchaeota,Marine Hydrothermal Vent Group(MHVG,ect.in phyla.Analysis of PLS-PM shows that heavy metal pollution directly affected microorganisms and organic carbon,and also undirectly affected microbial communities and organic carbon by changing other factors.Organic carbon can also directly affected on microbial communities.(4)In this study,active members of the bacterial community in the dry field(citrus field)and the paddy fields,with special emphasis on C utilizers,were identified by using molecular biology method and stable isotope probing(SIP)of DNA with the 13 C 1abeled C substrates glucose.Target microorganisms were detected in dry field.Analyses of partical 16 S r RNA genes revealed the dry field contain diverse glucose population,many of which were Actinobacteria,Pseudomonas,Escherichia-Shigella,Methylobacterium and Burkholderia. |
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