The dynamic development of bacterial community following long-term weathering of bauxite residue

ABSTRACT:Bauxite residue disposal areas(BRDAs) aretypicallybare of vegetationwith highsalinity and alkalinity. However,spontaneous encroachmentofvegetation indicated that natural weathering processes hadtransformedtheresidue tailings into a soil-like material. Herewe investigatethedevelopment of bacterial communities and theirgeochemical driversin bauxite residue,using Illumina high-throughput sequencing technology. Bauxite residue fromweathered sites had lowerpH and exchangeable sodium percentages(ESP), butgreater organic carbon and nitrogenconcentrations. Followingnatural processes, the diversityof the bacterial community significantly increased and hierarchical clustering separated un-weatheredfrom olderweathered sites. Taxonomic analysis revealed that long-term weathering processesencouraged populationsofProteobacteria, Chloroflexi,AcidobacteriaandPlanctomycetes, whilstreducingpopulations of Firmicutesand Actinobacteria. LEfSe analysis revealed that the biomarker changed considerablyin olderweathered residuescomparedwith that of un-weathered residue. Amongstall the residue properties, variation intotal organic carbon (TOC),total nitrogen (TN), available phosphorus(AP) and pH,showed significanteffects on the diversity and structures of the bacterial community.The results have demonstrated that natural weathering processesstimulatethedynamic development of bacterial communities in bauxite residue, and mayprovide a hypotheticalbasisfor the applicationof microbes atdisposal areasto improve soil conditions