Bioremediation Of Petroleum Hydrocarbon Contaminated Soil By Biochar Immobilized Microorganisms

Soil pollution is serious in oilfield exploitation areas in China,among which petroleum hydrocarbon is the main pollutant.Petroleum hydrocarbon damages soil ecological environment and threatens human health,which has attracted extensive attention of researchers.Bioremediation technology has advantages in remediation of petroleum hydrocarbon-contaminated soil due to its strong practicability and no secondary pollution.Biochar immobilized microorganism technology,in its unique way and method,provides microorganism with good protection in the soil.By improving the adaptability of microorganisms in the soil,the remediation effect of petroleum hydrocarbon-contaminated soil can be improved.Using biochar from agricultural waste for soil remediation can effectively promote the comprehensive utilization of agricultural resources.Three types of biochars were fabricated from maize（Zea mays）straw,reed（Phragmites australis）straw and pine（Pinus armandi）needles.The productivity,ash,and pH of these biochars were analyzed.The biochar properties were characterized by BET（Brunauer Emmett Teller）,energy dispersive spectroscopy,scanning electron microscope and FTIR（Fourier Transform Infrared Spectroscopy）.The removal rates of total petroleum hydrocarbons,and the components were compared through 40 days remediation.The results showed that the structure and physicochemical properties of biochars were significantly influenced by biomass material.Biochar of pine needles was layered,and maize straw biochar showed a pore-shaped profile but was covered with debris in pores.The BET of reed straw biochar was 93.47 m²?g^-1,with clear pore structure and depth.After 40days remediation,the removal rates of total petroleum hydrocarbon and the components showed that reed straw biochar>corn straw biochar>pine needle biochar>natural removal.The effect of biochar on the removal of petroleum hydrocarbon was obvious.Removal rates of each component were saturated hydrocarbon>aromatic hydrocarbon>non-hydrocarbon.The remediation effect of reed biochar and reed biochar immobilized microorganisms on petroleum hydrocarbon pollutants in soil was compared through a 40-day remediation experiment.The results showed that the removal rate of total petroleum hydrocarbons in the immobilized treatment group was 55.01%,which was nearly 10%higher than that in the biochar treatment group.High throughput sequencing technology was used to analyze the effects of biochar and biochar immobilized microorganisms on microbial diversity in petroleum hydrocarbon-contaminated soil.It was found that the addition of biochar could effectively increase the abundance of bacteria and fungi in soil.However,the contaminated soil treated with immobilized microorganisms by biochar was more likely to produce dominant microflora,including Proteobacteria,Basidiomycetes.The immobilized microorganism of biochar had great influence on the microbial diversity in petroleum hydrocarbon contaminated soil.The effects of microbial inoculation and particle size on the removal efficiency of petroleum hydrocarbon pollutants in biochar immobilized microbial remediation were compared.The results showed that 1 cm segment reed biochar immobilized microorganism had better removal efficiency of petroleum hydrocarbons in soil,and the removal rate of total petroleum hydrocarbons was the highest（62.59%）with the inoculation amount of 3%.At the end of the remediation experiment,the activity of four enzymes was the highest in the 1 cm segment biochar immobilized microorganism treatment group,that is,the growth and metabolism of microorganisms in the treatment group were strong,which was the optimal treatment.