Study On The Influence Of Heavy Metal Pollution On The Variability Of Rhizosphere Bacterial Communities In Haloxylon Ammodendron In East Mining Area

Xinjiang’s Jungdong coalfield is China’s largest energy planning cross-border power transmission and gas supply.The total area of the mining area is about 1.5×10⁴km²,220 km long from east to west,and 60 km wide from north to south.The proven reserves of coal resources are 2.14×10⁸t.At present,large-scale coal mining,coal power and coal chemical industry parks such as Wucaiwan,Dajing,Jiangjunmiao,Beishan and Wuhu have been established in the area.It has been reported that mining in the Zhundong Mining Area has caused a certain degree of heavy metal pollution in the local soil.Heavy metals not only cause a certain degree of damage to the ecological environment around the mining area,especially to the vegetation,but certain microorganisms enhance the plant’s resistance to heavy metals and promote plant growth.Such characteristics,is conducive to plant fixation of pollutants,thereby reducing the destruction of heavy metals with the environment.Therefore,the high-throughput sequencing technology was used to explore the characteristics of bacterial diversity in the rhizospheric soil of Haloxylon,a dominant species in coal mining areas.Multivariate statistical methods were used to analyze the effects of heavy metals and other physical and chemical properties on the bacterial diversity in Haloxylon ammodendron.At the same time,the spatial distribution of heavy metal content in soil was analyzed using the buffer module in GIS.The main work and conclusions are as follows:（1）Main work:In this study,the rhizosphere microbiological sampling points are based on the distance from the mining area,and a total of six sampling units are determined.The rooting method and the wording method are used in each sampling unit to perform Haloxylon 0-20 cm and 20-40 cm rhizosphere sampling,collected samples were tested 16s RNA,heavy metals,available heavy metals,water content,conductivity and p H and other indicators,using multivariate statistical methods for data analysis;soil heavy metal sample sampling points in accordance with based on the distance from the mining area,a total of 36 soil sampling units were set up.Each sampling unit used a multi-point mixing method to take 0-20 cm soil samples.The sample was tested for heavy metals and moisture content,conductivity and p H.Statistical methods for analysis.（2）Characteristics of soil heavy metals:The contents of heavy metals in the soil of Zhundong Mining Area ranged from Cd(3.6-11.8 mg·kg^-1),Hg(0.01-3.4 mg·kg^-1),and As(13.97-87.79 mg·kg^-1),Cr(25.5-95.3 mg·kg^-1),Cu(11-46.2 mg·kg^-1),Zn(25.78-281.96 mg·kg^-1),Pb(28-96 mg·kg^-1)The over-standard rates of Cd,Hg,As,and Zn reached 100%,2.3%,79%,and 2.3%,respectively,and the correlation analysis showed that the heavy metal Cr has a high positive correlation with Cu and Zn,indicating that it may have Associated relationships or belong to the same source of pollution.（3）Horizontal bacterial abundance in the rhizosphere of Haloxylon ammodendron:levels of Actinobacteria（40.04%）,Proteobacteria（23.78%）,Gemmatimonadetes（7.67%）,Bacteroidetes（8.88%）,Acidobacteria（5.74%）as the dominant bacteria In the family level,bacterium（23.16%）,Streptomycetaceae（4.00%）,Cytophagaceae（3.70%）,and Sphingomonadaceae（3.60%）were the predominant bacteria;the levels of bacterium（47.86%）,Streptomyces（3.91%）,Nocardioides（2.22%）,Sphingomonas（1.16%）,Novosphingobium（2.03%）,Adhaeribacter.sp（1.58%）were dominant genus.（4）Characteristics of soil microbial diversity:Shannon and Chao indices indicate that the diversity and abundance of bacteria in rhizosphere of Haloxylon ammodendron are greater than non-rhizosphere,and the bacterial diversity in the rhizosphere of 20-40 cm Haloxylon ammodendron is greater than 0-20 cm.The bacterial diversity and abundance in the rhizosphere of two-year-old artificial Haloxylon ammodendron was less than that of the natural perennial Haloxylon ammodendron in the mining area.（5）RDA analysis of environmental factors:The order of environmental factors on rhizosphere bacterial diversity in Haloxylon ammodendron was:Pb>DTPACd>Cu>Hg>DTPAPb>water>Cr>Cd>Zn>p H>As;and Gemmatimonadetes,Firmicutes,Verrucomicrobia,Actinobacteria have a positive correlation with various heavy metals.（6）RDA analysis of environmental factors:The order of environmental factors on the bacterial diversity in the rhizosphere of Haloxylon ammodendron was:DTPACd>Pb>As>Hg>DTPApb>Cu>water>Cd>Zn>Cr>p H;Sphingomonadaceae,Micromonosporaceaer,Streptomycetaceae and Nocardioidaceae are positively related to various heavy metals.（7）RDA analysis of genus level environment factors:The effect of environmental factors on the bacterial diversity in the rhizosphere of Haloxylon ammodendron was:DTPACd>p H>As>Pb>Hg>DTPAPb>water>Cr>Zn>Cd>Cu>Pb;Pseudarthrobacter.sp,Nocardioides,Glycomyces,Streptomyces and Solirobrobacter have a positive correlation with various heavy metals.（8）The PCA results show that the development of the mining area has a significant impact on the bacterial structure of the rhizosphere soil of Haloxylon ammodendron.The artificial planting of Haloxylon ammodendron has a certain succession process for the natural perennial Haloxylon ammodendron,further combining Shannon,Chao index and RDA analysis results.Together,it can be proved that the heavy metal pollution brought about by human resource development has changed more than the natural environment in the structure of the roots of Haloxylon ammodendron.（9）Spatial analysis of soil heavy metals:Soil heavy metals As,Cu,Cd,and Pb pollution levels are positively correlated with the distance from the mining area.Heavy metals Cu,Zn,Cd,and Pb are all present at maximum values around the mining area,with heavy metals Cd gradually decreasing with distance.Farther lower,other heavy metals are present in the Wuhu area.The mining area is located in the sensitive area of the heavy metal Cd pollution and potential ecological risk in the mining area from 0 to 30 km along the highway to the village of Yanren.The above results indicate that the heavy metal pollution caused by resource extraction is the main factor that causes the change of bacterial community structure in the rhizosphere soil of Haloxylon ammodendron.The bacteria in the Rhizoctonia rhizosphere soil of Zhundong Mining Area are Gemmatimonadetes,Firmicutes,Verrucomicrobia,Actinobacteria,Pseudarthrobacter,Nocardioides,Glycomyces.The genus Streptomyces and Solirobrobacter have a positive correlation with various heavy metals.In order to provide theoretical support for the subsequent research on the transfer and transformation of heavy metals by Haloxylon ammodendron,the relevant departments shall formulate relevant measures for prevention and control of heavy metals and adopt effective protective measures to protect the affected population and provide reference.