Antimony Migration And Transformation And Microbial Community Characteristics In Sediments Of Lengshuigou Reservoir

Guizhou Duliu River Basin is rich in mineral resources.However,the surrounding water environment and soil environment of the mining area are seriously polluted by antimony as a result of the long-term active mining and metallurgical activities of antimony and other mineral resources,causing a potential threat to the ecological security of the basin.The Lengshuigou Reservoir in this watershed is considered to be the"sink"and"source"of heavy metal pollutants such as antimony in the water environment because of its role in intercepting pollutants.In order to explore the feature of migration and transformation of antimony in reservoir sediments and the characteristics of microbial communities under the influence of antimony mines,this article takes Lengshuigou Reservoir as the research object,and uses simulation experiments and Illumina high-throughput sequencing technology to analyze the release law of antimony and the characteristics of bacterial community composition in the sediments and water-level-fluctuating zone soils.The specific research contents and results are as follows:（1）The average concentration of antimony in the reservoir is 71.68μg/L,which is14 times of the drinking water limit（5μg/L）.Antimony pollution in the sediments is serious,reaching 180-213 times of the background value of river sediments in Guizhou Province（1.35 mg/kg）;the pollution load index evaluation results show that the reservoir area is heavily polluted by heavy metals(I_PLZONE>3);The concentration of antimony between different sampling points in the water-level-fluctuating zone soil is quite different（29.89-493.45 mg/kg）,and the highest antimony content reaches 220times of the soil background value in Guizhou Province（2.24 mg/kg）.Antimony in sediments and shore soils mainly exists in the form of residues.（2）The effects of different environmental factors such as pH,DO,DOC and temperature on the release of antimony in sediments were studied through batch experiments.The results show that pH has a great influence on the release of antimony in sediments.The order of antimony release in sediments under different initial pH conditions is:neutral conditions（pH=7）>weak acid and weak alkaline conditions（pH=5,9）>under strong acid conditions（pH=1,3）.Higher temperature and higher DOC are beneficial to the release of antimony into the water.In this experiment,when T=30℃and DOC=32 mg/L,the release of antimony is the largest.Dissolved oxygen mainly affects the content of antimony in the easily reducible fraction and oxidizable fraction in the sediment,thereby affecting the release of antimony.When DO<1 mg/L,the release of antimony is the largest,followed by DO>15 mg/L.Without aeration treatment（DO≈7 mg/L）,the release of antimony in the sediment is the smallest.（3）The effects of different environmental factors such as pH,DO,DOC and temperature on the release of antimony in the soil of the fluctuating zone were studied through batch experiments.The results show that the effect of different initial pH on the release of antimony in shore soil is quite different from that of sediments.The release of antimony in shore soil decreases with the increase of pH.When pH was 1,the release of antimony is the largest.The effects of temperature,DOC and dissolved oxygen on the release of antimony in shore soil are the same as those on sediments.（4）Analysis of the characteristics of bacterial community structure showed that the bacteria in Lengshuigou Reservoir mainly consists of 81 phyla such as Proteobacteria,Bacteroidota,Desulfobacterota,etc.;Dechloromonas,Flavobacterium and other 570 genera.Antimony in different extraction fractions and water-soluble antimony are significantly correlated with bacterial communities under different classification levels.The bacterial functions of Lengshuigou Reservoir are mainly chemical heterotrophic,nitrogen-carbon-sulfur and other bio-earth cycle-related functions,as well as human pathogenic functions.（5）The release law of antimony from sediments in static water was studied through a columnar reactor.The results show that the concentration of antimony in the overlying water tends to be stable;the concentration of antimony in the interstitial water fluctuates greatly,and the overall manifestation is diffusion from the surface to the deep layer.The pH of the overlying water and the interstitial water eventually tends to 7.0;the ORP of the overlying water fluctuates in a small range and the gap between the layers is small,while the ORP in the interstitial water rises at a slow rate during the experimental period;it is not completely airtight.In the experimental device of,the DO in the overlying water changed greatly.The DO in the interstitial water quickly dropped to 0mg/L after the start of the experiment,and then basically maintained at 0 mg/L;the DOC in the interstitial water was significantly higher than the DOC in the overlying water.The DOC in the overlying water decreased after the experiment started,and then remained basically unchanged,while the DOC in the interstitial water changed greatly.The weak acid extraction state of antimony in the surface sediments showed a downward trend during the experiment period;the reducible antimony first decreased,then increased,and then gradually decreased;the oxidizable antimony showed a gradual increase trend.