Forms and transformations of selenium in soil.

1）建立了土壤中硒的定量形态分析方法，将土壤中的硒分为五种形态：腐殖酸中的有机硒、富里酸中的高分子量有机硒、无机硒（IV）、无机硒（VI）和低分子量有机硒（如硒氨基酸）。用该方法测定了几种土壤中的硒，发现有机硒占土壤总硒的50%以上。2）研究了培养和加热条件下土壤中硒的转化。淹水培养6周左右，土壤硒形态无明显的时间变化。在土壤加热条件下，随着加热温度的升高，土壤中有机硒减少，无机硒（IV）形成。在300 ℃以上加热，无机硒（IV）逐渐升华。3）建立了土壤中硒元素的选择性测定方法。在淹水条件下培养约3周的土壤中元素硒的形成被证实的方法。4）测定了冲绳县石垣岛、久米岛和宫古岛土壤中的全硒和可溶性硒含量。

1)A method for quantitative speciation of selenium (Se) in soil was developed and Se in soil was classified into five fractions : organic Se contained in humic acid, organic Se with high molecular weight in fulvic acid, inorganic Se(IV), inorganic Se(VI), and organic Se with low molecular weight such as selenoamino acids. Several soils were examined using this method, it was found that more than 50% of the total Se in the soils was in the forms of organic Se.2)Transformations of Se contained in soil by incubation and heating were studied. No remarkable temporal changes in the forms of soil Se were found by incubating soils under flooded condition for about 6 weeks. On heating soils, organic Se in the soil decreased and inorganic Se(IV) formed with increasing the heating temperature. The inorganic Se(IV) formed gradually sublimated with heating at temperature above 300 C.3)A method was developed for the selective determination of elemental Se in soil. Formation of elemental Se in the soil incubated in waterlogged condition for about 3 weeks was confirmed by the method. The elemental Se formed was estimated to be transformed from inorganic Se(IV) contained in the soil.4)Total and soluble Se contents in the soils collected at Ishigaki, Kume, and Miyako Islands of Okinawa prefecture were determined.