Impacts Of Bioremediation On Soil Micro-Ecological Environment And Petroleum Hydrocarbons Degradation

A laboratory study was conducted to investigate the impacts of bioremediation on microbial communities and the degradation characteristics of petroleum hydrocarbons in contaminated soil.Results showed that the degradation efficiency of total petroleum hydrocarbon(TPH)in control(CK),bioaugmentation(BA),and biostimulation treatments(BS)were 18%,10%,and 21%,respectively;the degradation efficiency of alkanes in soil were 6%,7%,and 22%,respectively;the degradation efficiency of PAHs were 46%,20%,and 45%,respectively.Biostimulation was the best methods for removal of petroleum hydrocarbon among three different treatments.Through determination of physicochemical characteristics including ammonium nitrogen,nitrate nitrogen,total nitrogen and available phosphorus contents,results showed that the contents of different forms of nitrogen and available phosphorus decreased during the bioremediation.In addition,the number of hydrocarbon-degrading bacteria was also determined in the study.It was found that the biostimulation treatment increased the number of hydrocarbon-degrading bacteria,and bioaugmentation treatment could increase the number of degrading bacteria in a short period but decrease shortly.The correlations between hydrocarbon degradation and various physicochemical and biological factors were analyzed by SPSS.The results showed that there was a certain correlation between the effect of petroleum hydrocarbon degradation and total nitrogen,ammonium nitrogen,available phosphorus and hydrocarbon-degrading bacteria in soil in soil treated with biostimulation.The results of high-throughput sequencing indicated that the microbial communitystructure changed greatly by bioremediation.The richness and evenness index of soil microbial community were control > biostimulation > bioaugmentation.The dominant phylum in control(CK)treatment were Actinobacteria(47.34%),Proteobacteria(37.44%)and Firmicutes(9.16%).The dominant genus was Promicromonospora(18.96%)and Exiguobacterium(8.49%).Other subdominant genus species include Nocardioides,Citrobacter,Mycobacterium,Acinetobacter,Leifsonia,et al.Compared with the control(CK)treatment,the basic structure of the soil microbial community after the optimal biostimulation treatment(the first week)have major changes.After one week of biostimulation treatment,Firmicutes became the most dominant phylum in the soil,its abundance increased to 58.36%;Actinobacteria and Proteobacteria were still in the soil.The dominant bacteria group,but its proportion decreased to 17.82% and 18.96%,respectively.In addition,the abundances of Gemmatimonadetes and Verrucomicrobia increased in the soil treated with biostimulation(the first week).In addition,the dominant genera of soil microorganisms mainly include: dominant genus-Bacillus,31.59%;Paenisporosarcina,Promicromonospora,and Fictibacillus are subdominant groups in the soil,and abundance ratios were 7.93%,6.34%,and 4.36%,respectively.In addition,after one week of biostimulation,it appeared a new genus,Planococcaceae_incertae_sedis,accounted for 6.64% of the soil,and the Arthrobacter abundance increased in the soil treated with biostimulation(the first week).After one week of bioaugmentation treatment,Proteobacteria became the most dominant phylum in the soil,its abundance increased to 96.26%,and the abundance of Actinobacteria and Firmicutes decreased to 4.08% and 3.71%,respectively;Pseudomonas became the most dominant genus in soil,its abundance increased from2.99% to 75.24%;Achromobacter and Bacillus became the subdominant genus in soil,and its abundance increased to 8.81% and 3.35%,respectively.