Characteristics Analysis Of Microbial Communities Under The Abnormal Accumulation Of Soil Organic Carbon At Farmland Contaminated With Pb-Zn Tailing Sand Contamination

Pb-Zn tailing sand has adverse effects on soil biological functions,including the size,activity and diversity of the soil microbial community,which is relating to soil organic carbon metabolic activity.However,the abnormal accumulation of soil organic carbon at karst farmland is not clear with the soil functional 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,two kinds of land use types in the Pb-Zn tailing dam area in Sidi village,Yangshuo,Guangxi Zhuang Autonmous region,China are selected.In the laboratory,the soil samples are tested for some soil characteristics parameters,including the content of Pb,Zn,Cu and Cd,and the Total Nitrogen(TN),Available Nitrogen(AN),Cation Exchange Capacity(CEC)and pH;a part of the fresh soil samples for the carbon sources utilization ratios of soil microbe and the abundance of the microbial community.The technology of PCR-DGGE is used for detecting the fungal diversity function.Further more,in the experiment the diversity of bacterial community structure is examed by the technology of 16 S rRNA high-throughput sequencing.The SPSS software is applied to concentration of total and available heavy metal in soils.It is found that concentration of total and available Zn and Pb were increased since 1986.Content of DTPA-Zn and DTPA-Pb are increased in proportion to total Zn and Pb.It is found that the content level of Pb,Zn,Cu and Cd in paddy fields is the highest and has the significant statistical differences with dry land(maize fields and citrus orchards).The result indicates that heavy metal pollution in the region is getting worse;the soil in this region is not suitable for cultivation of crops.The distribution of heavy metals in different land use types is regularity.Land use type is one of the main factors that drive the spatial distribution of heavy metals differences.Analysising of organic carbon content between different land use types,the study find that organic carbon content in dry land is lower than the control group significantly,however,the organic carbon content in paddy fields is higher than the control group significantly.By adopting biolog method,it is explored the situation of microbial metabolism of carbon source.It is found that comparing with dry land,the average well color development(AWCD),dominance index,eveness index and diversity index of microbial community are significantly lower in the paddy fields.The metabolic characteristic of microorganism which in heavy metal pollution region has a significant difference with the control group and the variation was mainly reflected in the metabolic patterns of the utilization rate of amine and esters.The results of Fluorescence quantitative PCR show that abundance of soil bacteria,actinomyce in paddy fields increased and fungi decreased greatly in paddy fields compared with dry land.Combining with redundancy analysis,it is found that soil organic carbon content is significantly associated with abundance of bacteria and actinomycetes.One tentative proposal is a high concentration of heavy metal stress for a long time inhibited the microbial carbon cycle,it reduced abundance of fungi,and lead to abnormal accumulation of organic carbon in the paddy fields.it is assumed that the missing fungi in the paddy belonge to types of microorganism which involved in organic carbon metabolic activity.However,the level of bacterial abundance in polluted soil is increased because of the bacteria in the soil generated heavy metal resistance.Based on application of PCR-DGGE and gene sequencing,the soil microbial community function diversity was detected.The result showed that Polyporales and Polyporales which couldn’t survive in the heavy metal pollution are found in soil of control group.All evidence candidate that Polyporales and Polyporaleswere are feasibility key functional microorganism.In addition,there are multiple types of path oganic fungi including Hypocreales,Pleosporales and Eurotiales in the heavy metal pollution.Indicating that heavy metal pollution is result in descent of soil quality.By using high-throughput DNA sequencing techniques for 16 S rRNA show that bacterial richness decrease significantly with heavy metal content increased.The relative abundance of Proteobacteria,Chloroflexi and Nitrospirae decrease with heavy metal content increased,in contrary,the relative abundance of Acidobacteria is increase.Informing that original dominant species are displaced by bacteria which with ability of heavy metal resistance.Content of Zn,Pb,Cd and pH value were dominant factor which cause the change of microbial diversity.