钝化剂对土壤镉铅有效性和微生物群落多样性影响

为研究海泡石和生物炭两种钝化剂对镉铅复合污染土壤修复效果及微生物群落功能多样性的影响,以南京某蔬菜地土壤为研究对象,采用盆栽试验方法,研究海泡石和生物炭单施及配施条件下,土壤理化性质、土壤微生物群落功能多样性、土壤Cd、Pb有效态含量的变化以及萝卜和小白菜两种作物对Cd、Pb富集的影响。结果表明:海泡石和生物炭单施、混施均显著促进土壤Cd、Pb由酸溶态向残渣态转化,降低Cd、Pb生物有效性。其中,2.5%海泡石处理Cd、Pb有效态含量降幅最大,与对照相比,种植萝卜和小白菜的土壤Cd、Pb含量分别降低71.88%～75.44%和81.21%～84.52%。生物炭对土壤微生物活性影响显著,2.5%生物炭处理微生物对碳源利用能力最强,但微生物群落功能多样性未显著增加。添加海泡石和生物炭均减轻了萝卜和小白菜可食部位对Cd、Pb的富集,2.5%海泡石和1.25%海泡石与1.25%生物炭配施处理,萝卜可食部位Cd和Pb含量均满足《食品安全国家标准》(GB 2762—2017),但小白菜可食部位Pb含量超出安全标准。研究表明,从土壤环境质量和作物安全角度考虑,一般采取海泡石和生物炭配施进行重金属Cd-Pb复合污染土壤的修复,而且在中度Cd-Pb污染的菜地土壤中优先考虑种植萝卜类蔬菜。

Effects of passivating agents on the availability of Cd and Pb and functional diversity of the microbial community in contaminated soils

The effects of sepiolite and biochar on the remediation of soil contaminated with cadmium and lead and the functional diversity of soil microbial community were studied. A pot experiment was conducted to investigate the effect of single and combined application of sepiolite and biochar on Cd-Pb contaminated soil samples collected from vegetable bases in Nanjing. Changes in soil physiochemical properties, functional diversity of soil microbial community, availability of soil Cd and Pb, and accumulation of Cd and Pb in radish(Raphanus sativus L.)and pakchoi(Brassica chinensis L.)were estimated. The results indicated that application of passivating agents could effectively promote the transformation of Cd and Pb from acid soluble to residual forms, and decrease the contents of available Cd and Pb in the tested soil. The largest degree of reduction for Cd and Pb contents was observed in the treatment with 2.5% sepiolite. Compared with the control treatment, the contents of soil available Cd and Pb decreased by 71.88%~75.44% and 81.21%~84.52% with radish and pakchoi, respectively. Biochar had a significant effect on soil microbial activity, and microorganisms exhibited the strongest ability of carbon source utilization upon treatment with 2.5% biochar. However, there was no significant increase in the functional diversity of soil microbial community. Application of sepiolite and biochar reduced the enrichment of Cd and Pb in edible parts of radish and pakchoi. The contents of Cd and Pb in edible parts of radish met the limit set by the National Food Safety Standard of the People''s Republic of China(GB 2762-2017)upon treatment with 2.5% sepiolite and 1.25% sepiolite combined with 1.25% biochar. However, the content of Pb in the edible part of pakchoi exceeded the food safety standards. From the perspective of soil quality and crop safety, our results suggest that the combination of sepiolite and biochar is effective for the remediation of Cd-Pb contaminated soil, and root vegetables such as radish could be grown in soil contaminated with moderate amounts of Cd-Pb.