| Oil is an essential energy substance for the current social development.However,with the increasing demand for oil,the large-scale exploitation and processing of petroleum have caused a series of problems such as oil leakage,especially in the oil field and its surrounding soil where petroleum pollution is the most serious.This study carried out indoor simulated pollution tests(For 20 weeks)under aerobic and anaerobic conditions on soil from Nanyang,Yanchang and Shengli oil fields,and different crude oil pollution concentrations were set.Nalkanes and polycyclic aromatic hydrocarbons(PAHs)were used as research objects to explore the changing rules of petroleum hydrocarbon components,and high-throughput sequencing technology was used to explore the changing characteristics of microbial community structure in the process of petroleum degradation,so as to reveal the relationship between petroleum hydrocarbon degradation and microbial community structure in different polluted soils under aerobic and anaerobic conditions,providing theoretical basis for microbial remediation of crude oil contaminated soils.The main conclusions are as follows:(1)Compared with sterilized soil,the degradation rate of n-alkanes in non-sterilized soil is faster,and microorganisms play a role in degradation.As the main component of nalkanes,middle carbon alkanes(C21-C30)showed stronger degradation in soil.Aerobic conditions are conducive to the degradation of n-alkanes.The highest degradation rates are95.9% and 96.2% in Yanchang soil under 1% and 2% concentration,respectively,and 98.1%in Nanyang soil under 3% concentration.Compared with aerobic conditions,anaerobic conditions are not favorable to the degradation of n-alkanes.The aerobic degradation rate is16.9%-55.0% higher than that of anaerobic at 1% concentration,40.0%-60.2% higher than that of anaerobic at 2% concentration,and 42.7%-61.0% higher than that of anaerobic degradation at 3% concentration.After 20 weeks of degradation,the aerobic and anaerobic degradation rates of n-alkanes in soil with different pollution concentrations were significantly correlated with nitrate nitrogen,sand and total nitrogen.(2)Compared with sterilized soil,the degradation rate of PAHs in non-sterilized soil is faster,and microorganisms play a role in degradation.Tricyclic aromatic hydrocarbons(acenaphthene,acenaphthene,fluorene,anthracene and phenanthrene),as the main components of PAHs,showed stronger degradation in soil.Aerobic conditions are conducive to the degradation of PAHs.The highest degradation rates of PAHs were 70.4% and 68.1% in Shengli soil at 1% and 2% concentration,respectively,and 74.1% in Yanchang soil at 3%concentration.Compared with aerobic conditions,anaerobic conditions are not favorable to the degradation of PAHs.The aerobic degradation rate is 16.9%-64.1% higher than that of anaerobic at 1% concentration,33.0%-45.7% higher than that of anaerobic at 2%concentration,and 6.1%-52.9% higher than that of anaerobic degradation at 3% concentration.After 20 weeks of degradation,the relationship between PAHs degradation rate and physicochemical properties in soil with different pollution concentrations was significantly different under aerobic and anaerobic conditions,and the physicochemical factors played a major role in the soil were different.(3)At the phylum level,Proteobacteria and Actinobacteriota dominate the bacterial abundance in soil samples from different regions,while Ascomycota dominates the fungal abundance at the phylum level.After 20 weeks of degradation,the abundance of Proteobacteria and Ascomycota increased under aerobic conditions,but decreased under anaerobic conditions.The OTUs number and α-diversity index of soil bacteria and fungi decreased under aerobic conditions,while the OTUs number and α-diversity index of soil bacteria and fungi increased and decreased under anaerobic conditions.The bacterial and fungal community structure of soil aerobic and anaerobic samples in different areas was significantly different,and the dominant bacteria genera were different.Under aerobic conditions,the degradation changes of n-alkanes in soil were greatly correlated with the bacterial communities of Acidobacteriota,Gemmatimonadota,Myxococcota and the fungal communities of Basidiomycota and Rozellomycota,and only the bacterial communities of Acidobacteriota and Myxococcota played the main role under anaerobic conditions.The degradation bacteria groups of PAHs were similar under aerobic and anaerobic conditions,and the main groups were Bacteroidota of bacteria and Mortierellomycota of fungi.In summary,this study found that the degradation of petroleum hydrocarbon components in soil under aerobic conditions is better than that under anaerobic conditions.There are great differences in the structure and diversity of bacterial community between aerobic and anaerobic soil samples.Under aerobic conditions,Gemmatimonadota,Basidiomycota,Rozellomycota and other microbial groups had strong degradation effects on petroleum hydrocarbon components.These conclusions provide theoretical support for microbial remediation of oil-contaminated soil. |
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