ABSTRACT
Selenium (Se) is of great environmental and geochemical concern as an essential trace element for humans and a powerful proxy for paleo-ocean. The study on Se speciation is critically important for understanding the mobility, bioavailability, and toxicity of Se in soils. Soil samples were collected from Enshi prefecture of Hubei Province, a typical seleniferous area well known for human Se poisoning in the early 1960s in China. Se K-edge X-ray absorption fine structure spectra was obtained at beamline 1W1B at the Beijing Synchrotron Radiation Facility, Institute of High Energy Physics. The XANES results showed that dominant organic Se and lesser Se(IV) were present in seleniferous agricultural soils from Enshi, and the proportion of organic Se was significantly decreased in the order of paddy soils > uncultivated soils > upland soils. Furthermore, the distribution and speciation of Se in the soil from mine tailings was remarkably different from those for tellurium, another element in Group 16 of the periodic table.
