Responses Of Microbial Communities To Intrusion Of Acid Mine Drainage In Paddy Soils

The acid mine drainage?AMD?generates from sulfide ores exposed to air and water and usually characterized by low pH,a high concentration of sulphate and metal.AMD was a serious and global environmental threat to ecosystem of the mining regions,which can affect the quantity,quality and potential uses of water and soil.AMD pollution characterized by acidification and heavy metal hazard.Once these toxic acidic solutions invade agricultural soil,they may result in soil function degradation,heavy mental pollution,affect crop production,safety and threaten human health via incorporation into the food chain.Understanding the effects of AMD on soil factors and microbial communities will help to provide theoretical basis for restoring AMD contaminated agricultural soils.Therefore,we performed laboratory simulation experiment to evaluate the effect of AMD intrusion on paddy soil ecosystem.Using high-throughput sequencing to evaluate the possible succession mechanisms of microbes in paddy soil irrigated by AMD and AMD polluted soil irrigated by clear water.A comprehensive survey of diversity,structure and functional predictions of microbial community in paddy soil was conducted.This helps us to obtain a better insight of soil microbial communities and useful for the development of bioremediation strategies to combat AMD pollution in agriculture soil.The research results are as follows:?1?AMD intrusion significantly increased the content of SO₄^2-,Cd and Zn in soil,acidified the soil,decreased the diversity of bacterial community.Soil samples dominated by phylum Proteobacteria and abundant Fe/S related genus were detected,which play critical roles in iron and sulfur elements cycles.While clear water irrigation was beneficial to the remediation of AMD contaminated soils and increased the diversity of bacterial community.RDA analysis showed that soil pH and heavy mental?Pb and Cu?content were the key factors controlling the community structure.?2?The soil pH and microbial communities shown differentiation in different irrigation system along AMD pollution gradient:direct AMD pollution?AMD,pH=2.46?had significant impacts on soil pH,diversity,structure and metabolism function of microbial community,greatly enriched the phylum Proteobacteria and acidophilic genera?Acidibacter,Metallibacterium,Acidiphilium?.Moderate AMD pollution?AMD dilution,pH=3?had a certain influence on soil microbial communities,provided suitable environment for phylum Chloroflexi,genera Acidibacter and Rhodanobacter.While slight AMD pollution?AMD dilution,pH=4/5?had almost no effect on soil ecosystem.?3?The most contaminated system?direct AMD pollution?was selected to further analyse the characteristics of soil and bacteria communities.Under AMD pollution,heavy metals?Zn,Cd,Cu?infiltrated in soil mostly in form of exchangeable metal fraction.Meanwhile,abundant genera related to iron metabolism reduced ferric iron resulting in increase of soil Fe???content.The PICRUSt result demonstrated that the majority of bacteria KEGG pathways were affected by AMD intrusion,and various genes related to methane,nitrogen and sulfur metabolism detected in soil samples,confirming the important role of bacteria in C,N and S cycle.When confronting AMD disturbance,bacteria communities augmented mutual connections especially positive links to better resist the extremely environment.In summary,the alteration of soil ecosystem and possible succession mechanisms of microbes in paddy soils under AMD pollution gradient and AMD polluted soil irrigated by clear water were systematically investigated by the microcosm study.The results will useful for the development of bioremediation strategies to combat AMD pollution in agriculture soil.