【摘要】 通过红黄泥和紫潮泥两种土壤淹水培养和硒的价态测定结果表明 :在 45 0mV培养下 ,外加Se(Ⅵ )第 1天有 5 7 2 %仍保持Se(Ⅵ ) ,2 3 4%还原为有机Se ,培养过程中Se(Ⅵ )呈稳定态 ,有机Se则氧化成Se(Ⅵ ) ,反应为准一级动力学方程 ;在 175mV培养下 ,外加Se(Ⅵ )第 1天有 81 8%还原为有机Se ,8 9%为Se(Ⅵ ) ,培养过程中有机Se呈稳定态 ,Se(Ⅵ )则还原为Se(Ⅳ ) ,反应符合动力学一级方程 .土壤中Se(Ⅵ ) Se(Ⅳ )体系氧化还原反应的临界电位为 71 4mV— 2 0 6 1mV(pH7 0 ) ,土壤pH上升 1个单位 ,电位相应降低 40 1mV .Se(Ⅵ ) Se(Ⅳ )体系在土壤氧化还原顺序中的反应次序居锰体系之后 ,与铁体系平行更多还原

【Abstract】 Two soils, red soil and alluvial soil, with added Se were flooded for 24 days, samples were taken at various time intervals and analyzed the Se species.The Results showed that under higher redox potential ( E h=450?mV), 57 2% of the added Se (Ⅵ) remained un\|changed, and 23 4% converted to organic form at the first day. Then the organic Se was oxidized into Se(Ⅵ),which followed pseudo first order kinetics. Under lower redox potential ( E h=175?mV), 81 8% of the added Se(Ⅵ) converted to stable organic Se, and only 8 9% remained Se (Ⅵ) at the first day; then Se (Ⅵ) was reduced to Se(Ⅳ) which followed first order kinetics. The critical redox potential of Se(Ⅵ)/ Se(Ⅳ) varied from 71 4 ?mV to 206 1 ?mV. Redox potential decreased 40 1 ?mV with every unit increase in pH. The reduction of Se(Ⅵ) to Se(Ⅳ) followed the reduction of MnO 2, and paralleled that of Fe(Ⅲ)更多还原