Microbial Diversity Of The Xikuangshan Surrounding Environment And Biodissolution Mechanism Of Stibnite

China is the richest country in the world in terms of antimony（Sb）ore resources,and has serious Sb pollution of soil and water sources in mining areas due to the massive mining and smelting extraction of Sb ores.The pollution of Sb ore areas mainly originates from the decomposition of Sb-containing minerals under the action of a series of chemical or biochemical reactions,in which the interaction of acidophilic microbial and Sb-containing sulfide is an essential factor to accelerate the decomposition and transformation of Sb-containing minerals.It is important to understand the mechanism of Sb/sulfur（S）transformation during acidophilic microbial-stibnite（Sb₂S₃）interaction to investigate the release regulation of Sb from antimony sulfide mines and to develop antimony pollution management and rehabilitation technology.Existing studies have mainly focused on alkaline and neutral environmental conditions,and less on extremely acidic conditions.Therefore,in this thesis,based on the typical Sb-bearing mineral Sb₂S₃,acidophilic enrichment of Xikuangshan and the typical acidophilic bacterium Acidithiobacillus ferrooxidans,we constructed the acidophilic enrichment-Sb₂S₃ and acidophilic bacterium A.ferrooxidans-Sb₂S₃ interaction systems to study the changes of phase succession,Sb/S morphology transformation,microbial community structure and metabolic characteristics in the above interaction system by combining various methods such as spectroscopy and microscopy,microbiomics,electrochemistry and DFT calculation,etc.,on the basis of studying and revealing the correlation between microbial diversity and elemental geochemistry in the surrounding environment of typical Sb mine.The specific research contents and main results are as follows:（1）Based on the environmental survey of Xikuangshan（XKS）in Hunan Province,we investigated the correlation between microbial diversity and elemental geochemical cycling in the surrounding environment by sequencing bacterial 16S r DNA,archaeal 18S r DNA and fungal ITS amplicons.The results showed that the bacteria in Xikuangshan were mainly Proteobacteria,followed by Bacteroidetes and Acidobacteria;fungi are mainly Ascomycota;Archaea are mainly Thaumarchaeota.The heavy metals in XKS mainly exist in the residue state,followed by the oxidizable and reducible states,and the weak acid dissolved state was the least.The comprehensive physical and chemical characterization,mineral phase transformation and microbial community structure analysis revealed that the microbial community structure is intimately related to p H,ORP,and the morphology and content distribution of various elements.p H and ORP are the main environmental influences,while the content and morphology distribution of Sb and As elements also have relatively obvious effects.（2）Based on XKS surrounding environmental samples,conducted microbial enrichment culture and investigated the enrichment-Sb₂S₃interaction.Combining the results of mineral surface morphology,physical phase and elemental composition analysis,it was found that the enrichment could promote the dissolution of Sb₂S₃ and the transformation of antimony-sulfur elements,and accelerate the change of mineral surface morphology.Based on 16S r DNA analysis of acidophilic microorganisms cultured by the columnar device,it was found that the community structure of the enrichment was mainly composed of Alicyclobacillus,Mycobacterium,Leptospirillum,Acidithiobacillus and so on.During the continuous cultivation process,the community structure of microorganisms changed significantly,of which the abundance of Leptospirillum,Acidiphilium increased significantly,especially Acidthiobacillus became the most abundant microorganism.（3）The dissolution mechanism of Sb₂S₃ mediated by A.ferrooxidans has been studied.The results show that A.ferrooxidans could promote the dissolution process of stibnite under extremely acidic conditions,and its adsorbed on the surface of stibnite to form biofilm and significantly reduced the p H values and increased the ORP values of the solution,accompanied by the formation of secondary products such as Sb₂O₃/Sb O₂^-、Sb₂O₅/Sb O₃^-,SO₄^2-and intermediates S⁰,S₂O₃^2-,etc.In contrast to the sulfur culture system,A.ferrooxidans in the Sb₂S₃ system showed the increasing in expression of catalytic activity,transporter protein activity,molecular carrier activity,electron transfer and other related functional genes,indicating that A.ferrooxidans could enhance the oxidative dissolution process of pyroxene under extremely acidic conditions.（4）The dissolution mechanism of Sb₂S₃ mediated by FeS₂/FeAs S-A.ferrooxidans has been studied.Both FeS₂ and FeAs S promoted the A.ferrooxidans-Sb₂S₃ interaction where FeAs S promoted the interaction more rapidly and FeS₂ promoted it more significantly.After 30 d of interaction,the surface of the Sb₂S₃ residue in both systems were oxidized with similar elemental speciation composition.In contrast to the A.ferrooxidans-Sb₂S₃ interaction,in both FeS₂ and FeAs S-added systems the expressions of functional genes related to cell metabolism,cell transport,binding activity and catalytic activity of A.ferrooxidans during Sb₂S₃ dissolution were up-graded,and more significantly in the FeS₂-added system.Electrochemical analysis showed that both FeS₂ and FeAs S generated a galvanic effect with Sb₂S₃ which accelerated the dissolution of stibnite.DFT calculations showed that when Sb₂S₃ was mixed with FeS₂/FeAs S,the surface structure of Sb₂S₃ changed,the work function decreased and the surface activity increased,and after adsorbed glucose molecules,the surface structure of Sb₂S₃ was changed,and such a change became more obvious when Sb₂S₃ was mixed with FeS₂/FeAsS.