土壤中二氧化锰对As(Ⅲ)的氧化及其意义

EFFECT OF BIRNESSITE (δ-MnO_2) ON OXIDATION OF ARSENITE IN SOILS

研究了土壤中δ-MnO_2对三价砷的氧化动力学及其在农业生产上的意义。结果表明,氧化动力学符合假一级速率方程,且土壤中氧化铁、氧化铝和碳酸钙与δ-MnO_2的包蔽能改变氧化反应速率;砷污染水稻田的排水搁田能显著减轻水稻砷害。

For all δ-MnO2 samples, uncoated and coated with Al, Fe oxides and GaCO3, the depletion of As (Ⅲ) by the samples followed 'pseudo' first-order kinetics. The extent of masking of the electron-accepting sites on the δ-MnO2 for converting As(Ⅲ) to As(V) varied with the kind and amount of coating, The amount of As (Ⅲ) and As (V) sorbed by the MnO2 coated with Al and Fe oxides increased markedly while that of the MnO2 coated with CaCO3 decreased.The field experiment showed that furrowing and draining in the paddy soil could increase soil redox potential greatly and lower the total H2O-As and As(Ⅲ) in the soil markedly and make rice plant grow better, with the result that grain yield was higher by 22% and arsenic content in brown rice was lower by 24%. So it is convenient and inexpensive to eliminate or alleviate arsenic toxicity by furrowing and draining.