| With the widespread use of plastic film,soil in China has been contaminated to varying degrees with phthalates(PAEs).The main influencing factors of plastic film on the accumulation of PAEs in soil include film thickness,film color,treatment method,film type,etc.These factors are still unclear about the changes in PAEs released into the soil after the use of plastic film.In view of soil PAEs pollution,microbial remediation is considered to be the most effective method to degrade soil PAEs.However,the specific PAEs bioremediation technology remains at the level of degradation effect,while the impact of exogenous microorganisms on soil microbial community in the remediation process is still unclear.Therefore,this study takes farmland soil as the research object.Firstly,outdoor experiments were conducted to study the effects of different types of plastic film and treatment methods on soil PAEs accumulation.Based on this,typical Dibutyl phthalate(DBP)contaminated soil was selected as the test contaminated soil,and indoor control experiments were conducted to optimize the degradation conditions of DBP contaminated soil by Acinetobacter baumannii DP-2.Finally,a simulated DBP contaminated soil remediation experiment was conducted,Analyze the degradation effect of microbial Acinetobacter baumannii DP-2 addition on DBP contaminated soil and the impact of soil microbial activity.The main research findings were as follows:(1)The effects of plastic film types and treatment methods on the accumulation of PAEs in soil were elucidated.It was found that the main types of PAEs in soil were DBP and Di-2-ethylhexyl phthalate(DEHP),while the molecular weights of other PAEs were relatively small.As the thickness of the plastic film increases,the content of PAEs released into the soil increases,ranging from 2.62 to 3.86 mg/kg.The content of PAEs released by black film into the soil was significantly higher than that of white film,increasing by approximately 0.25-0.94 mg/kg.The content of PAEs released by plastic film through plowing and landfill into the soil is higher.(2)The optimal conditions for the degradation of DBP contaminated soil by Acinetobacter baumannii DP-2 were optimized:relative moisture content of 60%,inoculation amount of 10%,carbon source of glucose,and addition amount of NaCl solution of 2.5 mL.On the basis of single factor experiments,the response surface methodology was applied to determine the optimal degradation conditions for the degrading bacterium DP-2.The relative moisture content was 54.38%,the inoculation amount was 14.32%,and the NaCl solution was 2.0 mL.The theoretical value of the degradation rate predicted by the model was 69.27%,while the actual measured value was 65.81%,which was in good agreement with the predicted value.(3)Clarified the remediation effect of Acinetobacter baumannii DP-2 applied in soil.The degradation rates of 20 mg/kg and 50 mg/kg DBP in the unsterilized soil treatment group were higher than those in the sterilization treatment group.The degradation rate of DBP in the experimental group with the addition of degradation bacteria DP-2 was significantly higher than that in the blank group(P<0.05).The degradation rates of DP-2 on DBP contaminated soil with concentrations of 20 mg/kg and 50 mg/kg within 30 days were 78.92%and 71.42%,respectively.(4)The microorganisms that play a key degradation role in the remediation process of DBP contaminated soil are Acinetobacter genus,Bacillus genus,etc.Acinetobacter baumannii DP-2 can reduce the diversity of bacteria and fungi in soil with different concentrations of DBP.The addition of the degrading bacterium DP-2 introduced the exogenous microorganism Acinetobacter,which had the highest relative abundance in the community,accounting for 44.28%.It had a synergistic effect with indigenous microorganisms such as Bacillus,Arthrobacter,and Bacillus in the bacterial genus.But it has antagonism with Ascomycota,Penicillium,Verticillium nigrum and other fungi,affecting the growth of fungi.At the same time,high concentration of DBP pollution in soil can inhibit the growth rate of Acinetobacter.In summary,this study elucidated the impact of different plastic films on the accumulation of PAEs in soil through outdoor experiments,and identified the main pollutants of PAEs released by plastic films into the soil;The conditions for the degradation of DBP contaminated soil by Acinetobacter baumannii DP-2 were optimized,and the remediation experiment of DBP contaminated soil was simulated.This provides a theoretical basis for objectively evaluating the accumulation of PAEs in soil and effectively implementing PAEs contaminated soil remediation. |
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