施锰对土壤锰氧化物形成及镉固定的影响

Effects of Manganese Application on the Formation of Manganese Oxides and Cadmium Fixation in Soil

为了探明外源Mn(Ⅱ)对稻田土壤锰氧化物形成及水稻(Oryza sativa L.)累积镉的影响,文采用土壤盆栽试验方法,以硫酸锰形式添加外源锰,锰水平分别设置为:0 mg·kg-1土(CK),100 mg·kg-1土(Mn100),400 mg·kg-1土(Mn400)和800mg·kg-1土(Mn800)4个处理。通过分析土壤中锰氧化物含量、不同形态镉及其含量、根表铁锰膜中镉含量以及水稻镉含量的变化,研究了施锰对土壤锰氧化物形成及其固定镉的效应。结果表明:施锰显著增加了土壤各形态锰氧化物含量并能降低土壤中镉的有效性,在成熟期,Mn800处理土壤可交换态镉降低了7.4%,无定形铁锰氧化物结合态镉含量增加了13.2%,土壤胶体中镉含量增加了29.4%。施锰显著增加了根表铁锰膜的铁、锰含量,显著减少了铁锰膜对镉的吸附,在分蘖期,Mn400和Mn800处理铁锰膜的铁含量分别增加了95.8%和113.6%,Mn100、Mn400和Mn800处理铁锰膜的锰含量分别增加了186.2%、1093.1%、1362.1%,Mn800处理铁锰膜的镉含量减少了70.3%。施锰(Mn100,Mn400,Mn800)可有效降低水稻镉含量,地上部分镉含量分别降低了51.9%、56.1%、68.4%,籽粒镉含量分别降低了26.7%、31.0%、27.1%。皮尔逊相关分析显示,土壤中不同锰氧化物含量均与根表铁锰膜镉含量、水稻地上部镉含量呈极显著负相关。上述结果表明施锰促进了土壤锰氧化物的形成及其对镉的固定,从而降低了土壤中镉的有效性和根表铁锰膜镉含量,减少了水稻对镉的吸收。该研究可为探明土壤中锰、镉的环境行为及其相互关系,指导重金属污染土壤治理与作物安全生产提供依据。

To investigate the impact of exogenous Mn(Ⅱ) on the formation of manganese oxide in paddy soil and cadmium accumulation in rice, the soil pot experiment method was used in this paper. Exogenous manganese was added in the form of manganese sulfate, and the manganese levels were set to 0 mg·kg-1 soil(CK), 100 mg·kg-1 soil(Mn100), 400 mg·kg-1 soil(Mn400) and 800 mg·kg-1 soil(Mn800) for treatment to study the effect of applying manganese on the formation of manganese oxide in the soil and its fixation to cadmium by analyzing the changes in the content of manganese oxide, different forms and contents of cadmium in the soil, the cadmium content in iron-manganese plaque on root surface and the cadmium content in rice. The result showed that the application of manganese led to the significant increase in the content of manganese oxide of various forms in the soil and could effectively reduce the validity of cadmium in the soil. At the maturity stage, after the treatment with Mn800, the exchangeable cadmium in the soil is reduced by 7.4%, the cadmium content in the bound amorphous iron-manganese oxide was increased by 13.2%, and the cadmium content in soil colloid was increased by 29.4%. After the application of manganese, the content of iron and manganese in ironmanganese plaque on the root surface was increased significantly, and the adsorption of cadmium by the iron-manganese plaque was reduced significantly. At the tillering stage, the iron content in the iron-manganese plaque was increased by 95.8% and 113.6% respectively after treated with Mn400 and Mn800, the manganese content in the iron-manganese plaque was increased by 186.2%, 1093.1% and 1362.1% respectively after treated with Mn100, Mn400 and Mn800, and the cadmium content in the iron-manganese plaque was reduced by 70.3% after treated with Mn800. The application of manganese(Mn100, Mn400 and Mn800) can effectively reduce the cadmium content in rice. The cadmium content in the overground part was reduced by 51.9%, 56.1% and 68.4% respectively, and the content of grain cadmium was reduced by 26.7%, 31.0% and 27.1% respectively. Pearson’s correlation analysis showed that different contents of manganese oxide in the soil were negatively correlated with the cadmium content in iron-manganese plaque on the root surface, and the cadmium content in the overground part. It indicated that the application of manganese promoted the formation of manganese oxides in the soil and its fixation to cadmium, thereby reducing the validity of cadmium in soil and the cadmium content in iron-manganese plaque on the root surface, and reducing the absorption of cadmium by rice. This study can provide a basis for exploring the environmental behaviors of manganese and cadmium in the soil and their interrelationships, and guiding the treatment of soil contaminated by heavy metals and the safe production of crops.