| Biochar has the characteristics of large specific surface area and abundant pore structure,and can be used as a cheap and efficient environmental adsorbent,which can be applied to the remediation of PAHs contaminated soil.In this study,rice straw was used as raw material,and biochar was prepared by oxygen-free pyrolysis of tube furnace at 300 °C,500 °C and 700 °C.On this basis,the effects of pyrolysis temperature on bio-vaporization elements and functional group composition were studied.At the same time,phenanthrene(PHE)in persistent organic pollutant Polycyclic aromatic hydrocarbons(PAHs)was used as research object,and microbial immobilization technology was adopted.PAHs-degrading bacteria(Achromobacter sp.LH-1)was immobilized on biochar to prepare PAHs degrading bacteria,and the research on the bioreme diation of PHE-contaminated soil by biochar and degrading bacteria was carried out.The high-throughput microbial classification and sequencing technology was used to analyze the soil microbial species richness and community structure during the remediatio n process.At the same time,the whole genome sequencing technology was used to quantitatively analyze all the DNA information in the soil environmental samples,focusing on biochar and The effect of PAHs degrading bacteria on the expression of key enzyme genes in the cycle of C,N,P and S elements in contaminated soil,and explore the influence of the use of biochar on the cyclic metabolism of nutrients in soil,and then reveal the application of biochar The impact on the soil ecological environment.The main findings are as follows:The effects of the structural properties of biochar prepared at different temperatures and the adsorption capacity of PAHs were investigated.It was found that with the increase of pyrolysis temperature,the yield of biochar decreased gradually,the ash content increased gradually,and the polar functional groups gradually.The reduction and aromatization degree are gradually enhanced,resulting in more pore structure;at the same time,the biochar prepared at three temperature s has different adsorption capacity for PHE,and the biochar is pyrolyzed at 300 ?,500 ? and 700 ?.The PHE adsorption rates reached 76.3%,91.2% and 76.3%,respectively.It indicates that the biochar prepared at 500 °C has the strongest adsorption capacity for PHE,and it is suitable as a adsorbent for the repair test of PHE contaminated soil.The simulated pot experiment of applying biochar to non-contaminated soil found that after application of biochar,the contents of total nitrogen,total phosphorus,total potassium and organic matter in the soil increased,and the activities of invertase,phosphatase and urease increased.The soil water content and soil p H were increased,indicating that biochar improved the physical and chemical properties of the soil and enhanced soil nutrients.The results showed that the PHE degradation rate of PHE-contaminated soil treated with biochar was 85.4%,and the PHE decomposition rate of PHE-contaminated soil treated with PAHs degrading bacteria was 93.4%.Soil organic matter,total nitrogen,total phosphorus and total the potassium content increased,and the phosphatase and sucrase activities increased.It indicated that biochar and PAHs degrading bacteria had good repairing effect on PHE contaminated soil.The high-throughput sequencing technology was used to investigate the changes of microbial community structure in PHE-contaminated soil treated with biochar and PAHs degrading bacteria.It was found that adding biochar to soil could increase the abundance of soil microbial quantity.According to the analysis of microbial community structure,proteobacteria and acidobacteria are the dominant bacteria in the soil.The richness of the western species is close to 50% of the soil's overall door richness.The soil microbial community was analyzed at the genus level,and it was found that biochar and PAHs degrading bacteria had significant effects on the microbial community structure in the contaminated soil.The addition of biochar made Subdivision3 genera incertae sedis sp.?Ohtaekwangia sp.?Lysobacter sp.recovered to the level of non-polluted soil,and a higher abundance of Achromobacter sp.was detected in the treatment group of the bacterial liquid treatment group and the treatment group of the microbial agent.This genus is an additional genus contained in the microbial agent,indicating that Achromobacter sp.in the polycyclic aromatic hydrocarbon degrading bacterium can stably exist in the soil and actively degrade the polycyclic aromatic hydrocarbons in the soil.Through the whole genome sequencing technology,the biochar and PAHs degrading bacteria were used to control the PHE-contaminated soil,and the functional genes of microbial enzymes in the process of soil carbon,nitrogen,phosphorus and sulfur were involved.The results showed that biochar treatment significantly changed the abundance of regulatory genes involved in key carbon,nitrogen,phosphorus and sulfur cycling processes.In the study of the carbon cycle enzyme gene,it was found that the addition of biochar reduced the gene abundance of carbonase in the Calvin cycle and enhanced the degradation enzymes such as starch,cellulose,hemicellulose and pectin during carbon degradation.This indicates that biochar can decompose structurally complex fi ber materials into easily exploitable carbon compounds while promoting the soil,and promote the conversion and migration of refractory organics in the soil,which plays an important role in promoting carbon cycle.In turn,the biogeochemical cycle of carbon is accelerated.In the study of nitrogen cycle enzyme gene,it was found that the addition of biochar reduced the key enzyme abundance during nitrogen fixation and the abundance of key enzymes in nitrification;increased the nitrite reductase gene abundance during denitrification.However,the abundance of the nitric oxide reductase and nitrous oxide reductase genes is reduced.Biochar reduces the abundance of enzyme genes associated with soil nitrogen fixation,resulting in a decrease in the amount of a mmonia produced by microbial activity in the soil.Biochar has a large amount of nitrate,and the gene abundance of nitrate reductase in the soil is reduced,which increases the content of nitrate in the soil.The gene abundance of nitric oxide reductase is reduced,which can effectively reduce the greenhouse.The emission of gaseous N2 O protects the ecological environment.In the study of the phosphorus cycle enzyme gene,it was found that biochar had little effect on the gene abundance of key enzymes in the PHE-contaminated soil phosphorus cycle,indicating that biochar had little effect on the soil phosphorus cycle;It was found that the addition of biochar increased the abundance of sulfur oxidase in the process of soil sulfur oxidation,reduced the abundance of related enzyme genes in the sulfur reduction process,increased the content of oxidized sulfur in the soil,and reduced the reduced state.Sulfur content.PAHs degrading microbial agents significantly change the abundance of regulatory genes involved in key carbon,nitrogen,phosphorus and sulfur cycling processes.In the study of the carbon cycle enzyme gene?It was found that the addition of PAHs degrading bacteria to the soil increased the gene abundance of soil carbonase,increased the carbon content in the soil,and increased the key enzymes in the carbon degradation process.The gene abundance accelerates the biogeochemical cycle of carbon in the soil;In the study of the nitrogen cycle enzyme gene,it is found that the addition of the microbial agent will reduce the abundance of key enzyme genes in the nitrogen fixation process and enhance the key enzymes of nitrification.Gene abundance,reducing the nitrate abundance gene abundance during denitrification;In the study of the sulfur cycle enzyme gene,it was found that the PAHs degrading bacteria had little effect on the sulfur cycle gene and could not change the sulfur cycle in the soil.In the study of the sulfur cycle enzyme gene,it was found that the microbial agent can increase the abundance of sulfur oxidase in the process of soil sulfur oxidation and reduce the abundance of related enzyme genes in the sulfur reduction process,indicating that the metabolism of sulfur may gradually increase the sulfate in the soil.And the content of sulfite.In summary,it is speculated that the addition of PAHs degrading microbial agents may increase the carbon content in the soil that is easily utilized by plants and microorganisms,and the ammonia content in the soil is reduced,and the nitr ate content is decreased.The content of sulfate and sulfite is increased. |
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