活性炭负载硫化纳米零价铁对胞外DNA在土壤-水界面的吸附行为与机制

Adsorption behaviour and mechanisms of extracellular DNA at soil-water interface by activated carbon loaded sulfidated nano-zero valent iron

抗生素抗性基因(Antibiotics Resistance Genes,ARGs)作为一类新型污染物,可通过垂直基因转移和水平基因转移在子代和非耐药菌中传播,使得传统的处理方法很难去除ARGs.ARGs在环境中以胞外DNA(Extracellular DNA,eDNA)形态存在,能够随生物活动和环境介质的迁移而传播到其他介质中,从而造成交叉污染.基于此,本研究以活性炭(Activated carbon,AC)为基底负载硫化纳米零价铁(Sulfidated nanoscale zero-valent iron,S-nZVI)制得活性炭负载硫化纳米零价铁(S-nZVI-AC),并以土壤-DNA-水为整体模拟土水界面,探究S-nZVI-AC对DNA的吸附行为与机制.结果表明,S-nZVI-AC对DNA的吸附量高达97.82 mg·g^(-1),其在棕壤-水和红壤-水体系中添加5%(W/W)就能够吸附47.53%和56.13%的DNA.S-nZVI-AC对DNA的吸附属于多层吸附,以表面吸附为主,并耦合了AC的微孔填充、π-π堆积、疏水作用和S-nZVI的静电作用,DNA上的磷酸基团(PO2-)是其主要吸附位点.S-nZVI-AC能够与土壤组分竞争吸附DNA,从而减少DNA在土壤-水体系中的迁移和转化.在土壤-水体系中,共存的重金属、阴离子、抗生素和有机农药对S-nZVI-AC的DNA吸附性能影响不大,其去除率仅下降了1.15%~5.83%.S-nZVI-AC在土壤-水体系中仍能保持铁碳结构,其表面的S-nZVI略有氧化并粘附了少量的土壤组分(石英、硅酸盐和有机质).本研究为实现eDNA在土壤-水体中的高效去除提供了一种实际可用、高效环保的方法,以期为阻控ARGs在环境中的赋存及传播提供新策略.

Antibiotic resistance genes(ARGs),as a new type of pollutants,can be transmitted by vertical and horizontal gene transfer to offspring and non-resistant bacteria,complicating their removal by traditional treatment methods.ARGs can exist in the environment in the form of extracellular DNA(eDNA),and spread to other media through biological activity and the migration of environmental media,causing cross-contamination.Accordingly,in this study,activated carbon(AC)was used as a substrate loaded with sulfidated nanoscale zero-valent iron(S-nZVI)to prepare activated carbon loaded with sulfidated nanoscale zero-valent iron(S-nZVI-AC);and the soil-water interface was simulated by using soil-DNA-water as a whole,the adsorption behaviour and mechanism of S-nZVI-AC on DNA were investigated.The adsorption capacity of SnZVI-AC for DNA was high up to 97.82 mg·g^(-1),and 47.53%and 56.13%of DNA could be removed by adding 5%(W/W)S-nZVI-AC in Inceptisol-water and Oxisol-water systems,respectively.The adsorption of DNA by S-nZVI-AC belongs to the multilayer adsorption,mainly surface adsorption,coupled with the micropore filling,theπ-πstacking,and the hydrophobic interaction of AC and the electrostatic interaction of S-nZVI.Phosphate groups(PO2-)on the DNA were the mainly adsorption sites.S-nZVI-AC can compete with soil components to adsorb DNA,thus reducing the migration and transformation of DNA in the soil-water system.In the soil-water systems,heavy metals,anions,antibiotics,and organic pesticides had little effect on the DNA adsorption performance of S-nZVI-AC,with a decrease of adsorption capacity by 1.15%~5.83%.S-nZVI-AC can still maintain the iron-carbon structure in the soil-water system,with the surface S-nZVI experiencing slightly oxidation and adhering to a small amount of soil components(quartz,silicate and organic matter).This study presents a practical,efficient and environmentally friendly method for the efficient removal of extracellular DNA in soil-water systems,aiming to provide a new strategy to mitigate the occurrence and spread of ARGs in the environment.