| Mine tailings and its related pollutants diffused through the wind and water erosion,which has become an important source of soil,water and air pollution.Revegetation is the main method of ecological restoration for mine tailings,however,the decreased pH was caused by the oxidization process of iron and sulfur in mine tailings for a long time,and it is very difficult to revegetation.We all know that the presence of iron and sulfur oxidizing bacteria accelerates the oxidization of metal sulfides in mine tailings,and microbial nitrogen transformation process also inhibits the development of polymetallic tailings ecosystem.Thus,we urgently need to comprehend whether ecological restoration process influence the iron and sulfur oxidization and nitrogen transformation in mine tailings.In the study,microbial communities composition and functional microorganisms in Shuimuchong mine tailings were analyzed to discuss the effect of ecological restoration on iron and sulfur oxidization and nitrogen transformation.The main results were shown as follows:1.Glucose-induced respiration was employed to assess the microbiome activities,and high-throughput sequencing revealed significant shifts of putatively active microbiomes.Results showed that microcosm incubation with 8 mg C/g glucose addition only hardly increased the microbial activities in pH 7.5 but increased the heterotrophic microbiological activities in mine tailings with pH 5.5 and pH 3;microcosm incubation of mine tailing with only glucose addition significant increased 3.4-fold and 2.8-fold CO2 efflux in tailing with pH 5.5 and pH 3,respectively,and microcosm incubation of mine tailing with glucose-ammonium nitrate(8mg C/g glucose and 1mg N/g ammonium nitrate)addition also distinctly increased 9.1-fold CO2 efflux in pH 5.5 and 39.1-fold CO2 efflux in pH 3.In tailings with pH 7.5,the glucose addition increased the number of dominant(relative abundance>1%),secondary-dominant(0.1%<relative abundance<1%)and non-dominant(relative abundance<0.1%)genera all of which were belonging to phyla Proteobacteria,Acidobacteria,Actinobacteria,Bacteroidetes,Firmicutes,Planctomycetes,etc.However with the pH decreased to pH 5.5 and pH 3,the active microbial communities were mainly belonging to dominant and secondary dominant genera which assigned to Proteobacteria and Actinobacteria.2.The oxidization characteristics,bacterial communities structure and nitrogen transformation functions of the tailings in the presence of various plant species were investigated.The results showed that revegetation main influenced the mine tailings in the 0-20-cm interval.Compared to the bare wasteland,revegetation alleviated the acidification of mine tailings,possessed the lesser free iron oxides contend and higher reducing sulfur content,and was capable of decreasing the abundance of iron and sulfur oxidization bacteria.On the other hand,revegetation altered the bacterial communities in surface mine tailings,therein significant differences existed in the relative abundance of the phyla Alphaproteobacteria,Deltaproteobacteria,Acidobacteria,Firmicutes and Nitrospira.In parallel,the abundance and activity analysis of nifH genes also explained the elevated nitrogen fixation rate and soil nitrogen contents.Besides,Imperata cylindrica is the most effective in reducing the number of iron-and sulfur-oxidizing bacteria and enhancing the transcription of nifH gene,which could be widely used as the pioneer plants to prevent the oxidization of sulfide minerals and promote the expression of nitrogen fixation bacteria.3.Bacterial communities along a 60 cm profile were investigated in mine tailings during ecological restoration of two revegetation strategies(directly revegetation and native soil covered)with different plant species.The mine tailings were covered by native soils as thick as 40 cm for more than 10 years,and the total nitrogen,total organic carbon,water content and heavy metal(Fe,Cu and Zn)contents in the 0-40 cm intervals of profiles were changed.In addition,increased microbial diversity and changed microbial community structure were also found in the 10-40cm intervals of profiles in soil covered area.Soil-covered strategy rather than plant species and soil depth was the main factor influencing the bacterial community,which explained the largest portion(29.96%)of the observed variation.Compared to directly revegetation,soil-covered strategy exhibited the higher relative abundance of Acidobacteria and Deltaproteobacteria and the lower relative abundance of Bacteroidetes,Gemmatimonadetes,Betaproteobacteria and Gammaproteobacteria.PICRUSt analysis further demonstrated that soil covered caused energy metabolic functional changes in carbon,nitrogen and sulfur metabolism.Given all this,the soil covered strategy may be used to fast-track the establishment of native microbial communities and is conducive to the rehabilitation of biogeochemical processes for establishing native plant species.In summary,the additional soil organic carbon in ecological restoration for mine tailings did not lead to the intensification of mine tailings acidification;directly revegetation could inhibit the oxidization of mineral sulfide and improve the biochemical properties in mine tailings to some extent;pioneer plants such as I.Cylindrica could be widely used in ecological restoration for mine tailings which could inhibit the sulfide oxidization and increase the nitrogen content of mine tailings to the greatest extent;amendments such as soil-covered could accelerate the stability of surface mine tailings. |
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