The Effect Of Bioremediation On Soil Enzymatic Activity And Microbial Community

Petroleum is one of the dominant energy sources to maintain the economic and social development of a country.During the production and transportation of crude oil,unsuitable operation and leakage may result in contamination of soil with petroleum hydrocarbons.Petroleum contamination causes significant environmental impacts and presents substantial hazards to human health.During the past decade,bioremediation of petroleum contaminated soil has been a hot issue in environmental research,and many bioremediation strategies have been developed and improved to clean up soils polluted with petroleum and its derivatives.The petroleum-contaminated soil used in this study was collected from Qingyang,Gansu province,China.Bioaugmentation plus Biostimulation were employed as remedial options for 18 weeks in a crude oil-contaminated soil.Petroleum concentrations,physical-chemical properties,and microbial community were measured,in order to(1)assess the effects of bioaugmentation combined with biostimulationon different fractions of hydrocarbon degradation;and(2)investigate the relationships between environmental factors and biological factors.Results showed that the total n-alkane and PAHs concentrations in the initial soil were 26000 and 5300 mg/kg dry soil,respectively.After the application of bioaugmentation plus biostimulation technique,the total n-alkane and PAHs contents decreased to 12800 and 2900 mg/kg,respectively.It could be concluded that the removal of n-alkanes and PAHs was enhanced in oil-polluted soil by combining of bioaugmentation with biostimulation.Results showed that the concentrations of total nitrogen,ammonia nitrogen,nitrate nitrogen decreased from 1830,35.62,45.43 mg/kg to 1600,1.22,7.17 mg/kg,respectively.The activities of dehydrogenase and polyphenol oxidase increased shortly,and then decreased significantly after several weeks of remediation.It was found that the activities of catalase and lipase were higher in the bioremediation treatment than throughout the experiment.This study demonstrated that the degradation efficiency of hydrocarbon can vary significantly in relation to concentrations of different kinds of nitrogen and enzyme activities.Illumina sequencing was used to detect the microbial community and diversity changes in the petroleum-polluted soil.Proteobacteria,Acidobacteria,Bacteroidetes,Firmicutes were predominant in all treatments.At genus level,high-sequencing results suggested that the abundance of Promicromonospora,Pseudomonas,Mycobacteriu,Altererythrobacter and Alkanibacter enhanced significantly after 18-week remediation.