Effect Of Biochar Amendment On Adsorption And Biodegradation Of BTEX In Soils

BTEX including benzene,toluene,ethylbenzene and three isomers of xylene are important monoaromatic hydrocarbons in petroleum contaminanted soils.Owing to their strong toxicity and mutagenic,carcinogenic,teratogenic effect on human and organisms in soil,it is necessary to control and treat BTEX in soils.Biochar has pore structure and large specific surface area,therefore its not only can change soil physical and chemical properties,but also microbial community structure and diversity,leading to the migration and transformation of organic pollutants in soil.In the present study,BTEX contaminated soil was used to investigate the effect and mechanism of rice straw biochar on adsorption and degradation of BTEX in soil.The results provide the theoretical basis to tackle with BTEX contaminated soil.The major results were as the following:(1)The adsorption of soil on benzene and toluene were significantly increased with biochar amendment(p<0.01).The soil adsorption with biochar prepared at500? had a better effect on benzene and toluene.The adsorption isotherms of benzene and toluene on soils with different proportions of biochar prepared at 500 ?were well described by the Freundlich or Linear model.(2)One bacterial strain of BTEX biodegradation designated as FB1 was isolated from BTEX contaminated agricultural soil near one coking plant with selective inorganic salt basal medium.The Strain FB1 was able to degrade benzene,toluene and ethylbenzene,but not xylene.Based on morphology analysis and 16 S rDNA sequence,the strain FB1 was identified as Pseudomonas sp..The optimal growth temperature and pH of strain FB1 ranged from 25 ? to 30 ? and from 6.0 to 8.0,respectively.Its optimal degradation efficient appeared at 30? and pH 6.0.The strain FB1 was able to effectively degrade both benzene and toluene with initial concentration below 1000mg/L in solution,and the degradation efficiency of toluene was significantly higher than that of benzene(p<0.01).Their products were phenoland benzylalcohol respectively.(3)The degradation efficiency of strain FB1 on benzene and toluene were significantly increased with biochar amendment(p<0.01),and were positively correlated with the OD600 value of the strain FB1 solution(p<0.01).These results indicated that biochar amendment might accelerate microbial growth and thus increase the degradation of benzene and toluene.(4)The decrease of concentrations of benzene and toluene in biochar amendment soil could be explained by the facts that the biochar can adsorb benzene and toluene in soil,and that the biochar amendment can promote the biodegradation of benzene and toluene in soil.