Forms and Behavior of Selenium in Soil-Plant System.

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1. A method for the determination of selenium (Se) in environmental samples was developed by use of high-performance liquid chromatography with fluorescence detection. By this method, the total and soluble amounts of Se in soils could be determined with a high reproducibility and sensibility. Moreover, the proposed method could be applied to the fractional determination of Se in soil extracts.2. About 50 cultivated soils (Kameoka, Kyoto) were used for the determination of total and soluble Se in the soils. The average total Se content of plow layer soil was 0.288 ppm. Water-soluble and hot-water soluble Se were 8.9 and 20.4 ppb, which amounts to 3.1% and 7.2% of total Se. The correlations between total and these soluble Se were significantly high.3. A large proportion of the soluble Se in soils was found to be in an organic form by means of Sephadex G-25 gel-chromatography. The organic Se amounted to 69% of the Se extracted from the cultivated soils. In addition, it was considered that the organic Se was mainly contained as a form of amino acid in proteins, peptides.4. A behavior of trimethylselenonium ion (TMSe) which is an important urinary Se metabolite of animals was studied by adding TMSe to a soil. The added TMSe was found to be decomposed rapidly into gaseous Se compounds. From this result, it was considered that TMSe would hardly occur as organic Se in soils.5. Because soil Se easily dissolves in an alkaline solution, the form of alkali soluble Se was studied. Inorganic species have been considered to be the dominant forms of soil Se, but the result of the study has shown that greater part of soil Se occurs in organic forms.