Microbial Degradation Of Polycyclic Aromatic Sulfur Heterocycles In Contaminated Soils

The PASHs(Polycyclic Aromatic Sulfur Heterocycles)are toxic,biodegradable organics,and more carcinogenicity and bioaccumulation than the PAHs(polycyclic aromatic heterocycles).When the soil is contaminated by this kind of hardly-decomposed organic compound,its structure will be destroyed,its physical and chemical properties will be changed.Crops and plants around will also be affected,resulting in Poor harvests.What’s more,this will threaten our health,even our lives.The alkyl-substituted benzothiophene and alkyl-substituted dibenzothiophene are the mainly sulfocompound in diesel,which accounts for over 60 percent of the total mass fraction of sulfur.And they also considered as one of the main pollutions of PASHs,both the industry and academia has paid much attention on searching better ways to improve the microbial degradation method to deal with the PASHs.The result in this study may help reduce the pollution of PASHs in soil and provide a theoretical basis and technical support for insitu bioremediation.In this study,we simulate the soil remediation experiment on the FCC diesel contaminated soil to find strains with superior ability of degradation,and optimized soil pollution degradation scheme.In our previous work,we found that the Pseudomonas sp.LKY-5 has a good performance of degradation on PAHs,such as the thiophene and dibenzothiophene,we called it the ‘selected strain’ and used the enrichment culture and shake cultivation to increase it.Then,we collected some soil samples contaminated by petroleum from the Shengli Oilfield in the city of Dongying.The basic physical and chemical property analysis is done based on those samples,we also investigated the types of indigenous strains and their contents.We also took some FCC LCO from the Qingdao oil refinery of Sinopec,GC-MS analysis of the diesel fractions,and they were treated as the soil pollutant in later experiments.In the last,we used the single factor experiment method in the flowerpot experiment to screen for the significant factors that influenced the degradation rate of PAHs.By controlling the variables,we studied the degradation of PASHs under multi-factor and the relationship between the bacterial strains(both the ‘selected strain’ and the ‘indigenous strains’)and the degradation of PASHs.The experimental results show that the temperature is 30 degrees Celsius,the concentration of pollutants is 7g/L,the initial degradation bacteria is 21%,the nutrient ratio of C:N:P is 100:10:1,the water content is 20%,the dosage of bentonite is 7%,the maximum desulfurization rate can be 78.96%.