| Antimony(sb),as a non-essential toxic heavy metal element,has been listed as a priority pollutant by the U.S.Environmental Protection Administration and the European Union.China has the most abundant antimony resources in the world and was the main producer,whose output accounts for 53% of the global antimony output.However,the reserve of antimony in Guizhou accounts for 10.2% of the whole country,and the content of antimony in the surrounding medium of antimony mine was much higher than the background value.Due to the joint action of surface runoff,biology,atmosphere and other factors,antimony was released into the surrounding supergene environment.Previous studies have found that heavy metal pollution was very easy to affect the distribution,composition and richness of soil microbial community.Despite the high toxicity of antimony,microorganisms can still reduce the impact of antimony pollution on the surrounding ecological environment through the biochemical processes of enrichment,efflux,methylation and oxidationreduction.The geochemical behavior of antimony in paddy soil and the adaptive mechanism of microorganism to antimony pollution are the key to microbial ecological restoration.In addition,earthworm,as the most important invertebrate in soil ecological function,is widely used in the monitoring of metal pollution in soil ecosystem.The feeding of earthworm and the excretion of earthworm excrement also have a great influence on the soil microorganism of rice field,however,there are few related researches at present.In order to find out the relationship between bacterial community and ecological function,physical and chemical factors,microbial community and ecological function of paddy soil and earthworm intestinal tract under antimony pollution.This study selected the paddy soil around the mining and smelting area of Banpo antimony mine in Guizhou Province as the research object,studied the soil profile of paddy field,the distribution characteristics of antimony components in the intestinal tract of earthworm,the relationship between microbial community structure and ecological function and its components.The response mechanism of microorganism to antimony pollution was revealed.The conclusions are as follows:(1)The sources of Sb and As are different in the profile of paddy field.Sb mainly comes from atmospheric deposition or artificial feeding.The concentration of Sb(III)and Sb(V)decreased with the increase of soil layer depth,the concentration of Sbaec and Sboxz increased with the increase of soil layer depth,and the concentration of Sbrec remained unchanged with the increase of soil layer depth,while in the as related contamination fraction,except As(III)concentration decreased with the increase of soil layer,the concentration of other contamination parts remained unchanged with the increase of soil layer.Sbtot and Sb(V)were significantly different in each group(ANOVA,P < 0.05),while Sbexe and Sbsrp in bioavailable Sb were significantly different in S100 and S200 groups,but the difference was not significant(P > 0.05).The bioavailability and microbial community structure of Sb can be affected by the biotransformation of Sb mediated by earthworm intestinal microflora.Sb(III)is the main component of earthworm intestinal contents,while Sb(V)mainly exists in the surrounding soil.(2)The lower concentration of Sb and As related contamination had little effect on the bacterial diversity of each soil layer.Chlorofloxi and Proteobacteria are the main dominant phylum of SL1(0-30cm),SL2(30-65cm)and SL3(65-100cm).Lefse analysis showed that different taxa were enriched in different soil layers,and the significant threshold value was more than 3.0,which indicated that the number of species was SL1 in hydroponic maturation layer,SL3 in plough bottom layer and SL2 in infiltration layer.RDA analysis and relative importance analysis showed that Sbrec,Asrec and Astot had a greater impact on the bacterial community at the taxonomic level than other polluted fractions,and Asace had a greater negative impact on Chlorofloxi,Proteobacteria was greatly affected by As related contamination fractions,while Sbrec had a negative impact on proteobacteria.According to the prediction of Tax4Fun2,it is found that the resilience of paddy soil to Sb and As contamination is SL1 >SL2 > SL3.RDA analysis,relative importance analysis and co-occurrence network analysis showed that environmental factors and bacterial community structure had an impact on the function of Sb and As related bacteria.For example,ACR3 is greatly affected by Sbrec,Sbtot and Asrec,while Anaeromyxobacter is negatively correlated with arsenate reductase(Ars C,ars C1 and ars C2).In addition,pls-pm analysis showed that as related contamination had a greater direct impact on bacterial community structure than Sb related contamination,while Sb related contamination had a greater direct impact on bacterial function than as related contamination.Sb and As related contamination had a positive effect on bacterial function,bacterial community structure had a positive effect on bacterial function,and environmental factors had a greater direct impact on bacterial function than bacterial community structure.(3)With the increase of Sb concentration,the diversity index increased,reaching the maximum in S200 group and the minimum in SC group.Relative importance analysis showed that Sb(III)and Sbsrp were the main Sb fractions affecting the diversity index of bacterial community.The results of principal coordinate analysis(PCo A)showed that there were significant differences between bacterial communities and soil communities polluted by Sb in the control group.The results showed that Proteobacteria,Actinobacteria and Bacteroidetes were the main dominant bacteria in soil polluted by Sb,and their enrichment and isolation were greater than other dominant bacteria.Static Bayesian network reasoning showed that Sbtot affected soil bacterial community by affecting Sphingomonaceae,Sbsrp by affecting Burkholderia,Xanthomadaceae and Acidobaracteriale,while sb(V)was mainly affected by Flavobacteriaceae,Rhodopirillaceae and Acidobaracteriale.(4)The bioavailability and microbial community structure of Sb can be affected by the biotransformation of Sb mediated by earthworm intestinal microflora.Sb(III)is the main component of earthworm intestinal contents,while Sb(V)mainly exists in the surrounding soil.There were differences in ace,Chao 1,Shannon and Simpson between the earthworm intestinal tract and the surrounding soil,but the differences were not significant,and showed that the soil flora was larger than the intestinal content flora,such as SC > GC,S100 > G100.In addition,Actinobacteria,Acidobacteria and Bacteroides were significantly different in the intestinal contents of earthworms and the surrounding paddy soil.Among them,Rhodospirillaceae(10.15%),Clostridiaceae(6.53%),Xanthobacteraceae(4.78%)and Mycobacterium(3.56%)are the most abundant species in the intestinal contents of earthworm,while only 2.28%,0.65%,2.46% and 0.70% in the surrounding soil bacterial community structure.The intestinal contents of earthworms and the surrounding soil bacteria are mainly involved in the process of Sb(V)reduction and Sb transport,while the functional genes of Sb(III)oxidation process are less abundant in the intestine and soil.To sum up,the different groups of sb disturbed the intestinal bacterial community structure of Eisenia foetida. |
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