Investigation Of Bioremediation Effect On Removal Of Polycyclic Aromatic Hydrocarbons And Dynamic Of Microbial Community Structure In Petroleum Contaminated Soils

In this paper,bioremediation of contaminated soils was performed by applying organic fertilizer and polycyclic aromatic hydrocarbon(PAHs)– degrading bacteria to petroleum-contaminated soils.The effect of bioremediation on removal of PAHs was investigated by researching the changes of petroleum hydrocarbon content in contaminated soils.The amount of ammonia-nitrogen,available,and PAHs-degrading bacteria and the shif of microbial communities in soils during the remediation process were also investigated and determined.After 18 weeks of remediation,by four kinds of treating processes,which were natural attenuation,applying organic fertilizer,adding the degradation bacteria,and adding organic fertilizer plus degradation bacteria processes,the removal rates of PAHs in soil were-9.7%,17.7%,11.5% and 25.0% respectively;The total oil hydrocarbon removal rates were 7.3%,17.5%,9.7% and 14.1% respectively;The removal rates of alkanes was 6.6%,15.6%,15.5% and 21.1% respectively.Compared with natural attenuation process,applying organic fertilizer,adding degradation bacteria and adding organic fertilizer + degradation bacteria processes can promote the degradation of different components of hydrocarbon in the soil and last one can obtain the best PAHs removal effect in soil.The initial concentration of ammonia nitrogen and effective phosphorus in petroleum contaminated soil was 2.20 and 9.40 mg/kg.The concentration of those two components in soil were changed significantly after applying organic fertilizer process.The concentration of the two contents increased to 14.10 and 122.00 mg/kg respectively,and remained unchanged during the adding organic fertilizer process.Illumia Miseq technique was used and the results showed that during natural attenuation process,shannon,ACE and Chao1 index of contaminated soils were 4.38,3327 and 2534 respectively.After adding organic fertilizer process,the those diversity index increased to 5.80,4828 and 4005 respectively.In adding PAHs-degradation bacteria process,indexes were changed to 4.02,3301 and 2603 respectively.Those indicated that in contaminated soil,microbial community diversity can be improved by adding organic fertilizer and it would be reversed though adding degrading bacteria.The dominant Phyla in petroleum contaminated soil were Actinobacteria,Proteobacteria and Firmicutes.The dominant bacterial genus mainly include Promicromonospora,Exiguobacterium,Nocardioides and Mycobacterium.After the application of adding organic fertilizer,the relative abundance of Actinobacteria and Bacteroidetes in the soil decreased from 47.34% to 25.80% and increased from 0.78% to 14.89% respectively.At the genus level,Promicromonospora dominated in original soil was reduced from 18.96% to 6.34%.Fertilization significantly changed the microbial community structure in soil,the relative abundance of Exiguobacterium was reduced to 3.44% from the initial 8.49%,while the abundance of the Promicromonospora was increased from 18.9% to 33.58%.The dominant Eumycophyta in petroleum contaminated soil were Ascomycota and Basidiomycota.The dominant bacterial genus mainly include Sistotrema,Acremonium,Niesslia,Emericella and Ochroconis.After the treatment of adding organic fertilizer,the relative abundance of Ascomycota in soil decreased from 73.26% to 781.35%.The abundance of Basidiomycota decreased from 26.67% to 18.93% and 17.06%.At the genus level,the abundance of Emericella dominated in original soil was reduced from18.18% to 8.29%.The relative abundance of some non-dominant strains of Chaetomium,Microascus and Penicillium increased significantly.