Environmental behaviors of selenium in soil of typical selenosis area, China

Daba Mountain area is one of the two endemic selenosis areas in China, which may relate with the environmental behaviors of selenium (Se) in soil. This study focuses on the concentraion and distribution of Se and its relationships with some other elements in natural soil in the area. The average concentration of Se in Daba Mountain soils was 14.3 times higher than the value cited for natural soil background worldwide, suggesting that soils in the region were contaminated by the element. The finding was confirmed by Müller geoaccumulation index assessment with 22% slightly polluted, 15% moderately polluted, 11% highly to very highly polluted and 8% moderately polluted to highly polluted. Soil Se is generally enriched in topsoil, and its distribution is extremely uneven and significantly site-specific. However, the concentrations of Se in soils have significant positive correlation with them in corresponding parent materials (r = 0.995, P < 0.01). Besides of Se, the concentrations of elements, such as Ca, Sr, V, Cu, Zn, Ni, Mg, Co, and Fe are also obviously abnormal compared with their background values of Chinese soil. Selenium behaviors in the region were controlled by multifactors: in addition to the parent material, pedogenic processes, biologic processes, and element geochemical behaviors also impacted the concentration and distribution of selenium in soil.