Contents, Species of Soil Selenium in Kashin-beck Disease-endemic Area, Ruoergai Wetland, Sichuan, China

This study studied that the amounts, species of Se in four kinds of soil (sandy soil, meadow soil, bog soil and peat soil) by a method of successive extraction in order to accumulate scientific data for preventing and curing the selenium response symptom of people and livestock in Ruoergai wetland. The results showed that the content range of Total Se (T-Se) in surface soil layer was 65-260 μg/kg in ten sampling sites and the low Se circumstance existed because of soil Se deficiency. Among several kinds of Se forms, Water soluble Se (W-Se), Exchangeable Se (E-Se) and Organic Se (O-Se) accounted for 1.12-3.08%, 2.91-6.03% and 10.28-45.6% of total Se respectively, unavailable Se including Acid soluble Se (A-Se), Sulfidic Se (S-Se) and Residual Se (R-Se) accounted for more than 60% of total Se. Of the soil O-Se, 57.84% (on average) was associated with the Humic Acid fraction (HA-Se) and 42.16% with the Fulvic Acid fraction (FA-Se), the range of C/Se in soil organic matter was 0.65×106-7.28×106 (on average 2.96×106) in surface soil layer. The soil organic matter was the most important factor affecting the content of soil T-Se and O-Se, the rich soil organic matter was helpful to the accumulation of soil T-Se and O-Se. It was clear that the lower utilization ratio of Se due to the low content of soil T-Se, the higher portion of O-Se and HA-Se were the possible reason for a deficiency of selenium in Kashin-Beck Disease-endemic area, Ruoergai wetland, Sichuan, China.