Study On The Limiting Factors Of Microbial Degradation Of Pollutants In Oil Contaminated Sites

There are many remediation methods for oil-contaminated soil,and microbial remediation has become a hot topic because of its low cost and no secondary pollution.Microbial remediation of petroleum contaminated soil has a good effect in the laboratory simulation stage,but when applied to the field,it has the problems of low degradation rate and long remediation time.At the same time,because of the need for production management,herbicides are used,and the salt in the oil field site pollutes the site.Because of this situation,taking salt and herbicide glyphosate as stress conditions and n-hexadecane and phenanthrene as target pollutants,the limiting factors of microbial degradation of characteristic pollutants in petroleum and petrochemical contaminated sites were explored.Taking the soil around a well site as the source of screening bacteria,the pollution-free soil in the campus was added with pollutants to simulate on-site remediation.The contents of n-hexadecane and phenanthrene in the soil were determined,and the cumulative degradation rate under various stress conditions was calculated;Soil organic matter,total nitrogen,total phosphorus,and p H were measured regularly to study the effects of stress conditions on soil physical and chemical properties;The number of bacteria and fungi in soil was measured regularly,and the changes of fungi and fungi under different stress conditions were studied;The activities of total dehydrogenase and catalase were measured regularly.16 S r RNA technology was used to determine the bacterial community structure on the 30 th and 120 th day,and the limiting factors of target pollutant degradation under various stress conditions were analyzed.Two strains L1 and L5 were selected from the soil around a well site.The 7-day degradation rate of n-hexadecane of L1 strain was 60.14%,and the L1 strain was identified as Ochrobactrum sp.by molecular biology method;the 7-day degradation rate of phenanthrene of L5 strain was 27.20%,and L5 strain was identified as Pseudomonas aeruginosa by molecular biology method.In the simulation experiment,n-hexadecane and phenanthrene were accumulated 120 days in non stress group(A1),low concentration Na Cl stress group(A2),high concentration Na Cl stress group(A3),low concentration herbicide glyphosate stress group(A4),high concentration herbicide glyphosate stress group(A5),low concentration Na Cl,herbicide glyphosate combined stress group(A6),high concentration Na Cl,herbicide glyphosate combined stress group(A7)The degradation rates were 94.92%,95.13%,75.57%,82.04%,87.18%,96.96%,65.07% and 87.33%,81.98%,66.31%,82.71%,88.58%,86.25%,58.45%,respectively.From the soil physical and chemical properties,the number of bacteria and fungi,and enzyme activity,the inhibition effect of high concentration salt stress was greater than that of herbicide glyphosate stress,and the inhibition effect of high concentration combined stress was the most obvious.In 16 S r RNA,the highest concentration salt stress group(A3,A7)had the lowest Chao1 abundance index,but from 30 d to 120 d,the Shannon diversity index had a little decrease,even higher than other groups at the end of the repair.The dominant phylum changed from Firmicutes,Actinobacteria,and Chloroflexi to Actinobacteria,Chloroflex I and Firmicutes at the level of phylum and genus respectively,and the dominant phylum changed from JG30＿KF＿CM45,Bacillales,and Bacillaceae become JG30＿KF＿CM45 、 Lysobacter 、Nocardioidaceae。 At 30 days,there was a negative correlation between Na Cl and p H,total phosphorus,and a positive correlation between p H and total phosphorus.Actinobacteria was positively correlated with Na Cl,p H,and TP.Chloroflxio,Proteobacteria,and Bacteroidetes were negatively correlated with Na Cl,p H,and TP.