Enhanced 2,4-dichlorophenol degradation by remodeling of crude soil microbial community structure using carbon-based immobilized microorganisms

In recent years, immobilized microbial remediation technology has attracted more and more attention, but highefficiency and low-cost microbial preparations are still very rare. Therefore, PEG-nZVI/GAC composite carrier material was prepared by liquid phase reduction method. A strain of Bacillus marisflavi capable of degrading chlorophenols was immobilized on the above composite carrier material by adsorption method to prepare granular activated carbon supported polyethylene glycol modified nano-zero-valent iron immobilized microorganism (PEG-nZVI/GAC@B). Soil remediation experiments were designed to explore the remediation effect of 2,4-DCP and its impact on soil physicochemical properties and microbial community structure. The results showed that in 119 days, PEG-nZVI/GAC@B could remove 96.30 % of 2,4-DCP in the soil. Soil dissolved organic matter was also consumed or absorbed during the remediation process, and the change trend of soil microbial number and soil enzyme activity was similar, reaching a peak between 21 and 28 days of remediation. Among them, the number of bacteria in the PEG-nZVI/GAC@B group reached a maximum of 3.30x106 CFU/g soil on the 28th day. The results of high-throughput sequencing showed that the original Pseudomonas and Proteobacteria in the soil had certain adaptability to 2,4-DCP, and the PEG-nZVI/GAC@B group had high Shannon index and Pielou's evenness index, indicating that it could improve soil microbial diversity and restore soil microbial homogeneity. The species distribution of PEG-nZVI/GAC@B group was more concentrated in Bacillus, which protected Bacillus marisflavi from adverse natural conditions. As an excellent 2,4-DCP contaminated soil remediation material, PEG-nZVI/GAC@B is expected to solve the problem of 2,4-DCP soil pollution.