| Since the 1980s,China’s vegetable industry has made great progress.Protectedcultivation has become a main way of vegetable production and an important way for farmers to increase production and income.In the process of protected cultivation,problems such as pesticide residue pollution caused by excessive pesticide application,unreasonable mix-upand misuse have gradually become prominent,seriously affecting the quality and safety of protected vegetables.In particular,neonicotinoid insecticides such as imidacloprid andacetamiprid are widely used in protected vegetable planting and have high detection rate in soil.In recent years,biochar as a soil conditioner has been used more and more to repair contaminated soil,and the remediation efficiency can be improved by physical modification of biochar or combined chemical remediation technology.Based on this,the novel biochar（BC-nZVI）was prepared by loading nano zero-valent iron,and the adsorption anddegradation properties of the novel biochar,biochar（BC）,biochar combined with sodium persulfate（BC-PS）on imidacloprid and acetamiprid were compared,and the relatedmechanism was preliminarily discussed.The remediation effect of new biochar oncontaminated soil was studied through soil-water suspension and pot experiment,and the interaction between new biochar and soil microorganisms was further explored through the changes of soil microbial activity.This study provides new materials and theoretical basis for remediation of pesticide contaminated soil in protected vegetable fields.The specific research results are as follows:（1）Preparation of BC-nZVI and Study on Adsorption and Degradation Performance.（1）Preparation of BC-nZVI.nZVI and BC-nZVI with carbon-iron ratios of 3:1 and 5:1were successfully prepared by liquid phase reduction method.Through scanning electronmicroscope,nZVI can be successfully loaded on BC surface.（2）Determination of BC-nZVI dosage and carbon-iron ratio.The results showed that BC-nZVI with carbon-iron ratio of 3:1 added 0.2g·L-1 had better adsorption and degradation performance than BC-nZVI with carbon-iron ratio of 5:1.The adsorption rate and degradation rate of imidacloprid（acetamiprid）were greatly improved compared with BC.Compared with BC,the adsorption rate and degradation rate of imidacloprid（acetamiprid）by BC-PS werealso greatly improved.（3）Verification of adsorption performance of BC-nZVI.The adsorption performance of BC-nZVI was further verified by isothermal adsorption experiments.The results showed that BC-nZVI had better removal effect on imidacloprid and acetamiprid than BC.（4）Study on degradation mechanism of BC-nZVI.The results showed that BC had persistent free radicals and contains hydroxyl,carboxyl and other functional groups,which could play a certain role in redox.BC-nZVI had not only hydroxyl,carboxyl and otherfunctional groups of BC,but also nZVI which could carry out redox,thus greatly enhancing the degradation ability of BC-nZVI.In addition,the existence of sulfate radical and hydroxyl radical in BC-PS system,in which hydroxyl radical was dominant.（2）Study on soil application performance of BC-nZVI.（1）Through the soil-water suspension experiment,it was found that BC-nZVI and BC-PS could remove pesticides better,and the removal rate of imidacloprid（acetamiprid）by BC-nZVI was significantly higher than that by BC.（2）Through tomato pot experiment,it was found that BC-nZVI was better than BC in removing imidacloprid from tomato leaves and soil.The addition amount（0.1%）of BC-nZVI in this experiment was higher in removing imidacloprid from tomato leaves and soil than the control group in 30 days,which further verified the feasibility of the application of the new biochar.（3）Through the microbial carbon source utilization experiment,it was found that the addition of BC-nZVI at the dosage of 0.1%in this experiment could promote the microbialactivity and increase the types and quantity of microorganisms,which indicated that BC-nZVI could promote the microbial degradation of pesticides by promoting the microbial activity,and BC-nZVI had little effect on soil toxicity,thus being suitable for farmland soil remediation. |
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