Concentrations and characteristics of selenium in soil samples from Dashan Region, a selenium-enriched area in China

In order to clarify the total selenium (Se) content and species of Se in the soils of Dashan Region, a typical Se-enriched area in China, 69 soil samples with different land-use purposes were collected, and the concentrations of total Se, water-soluble Se, exchangeable Se, acid-soluble Se, organic-bound Se and residual Se and the physical and chemical properties of these soils were investigated. The total Se content ranged between 0.31 and 7.65mgkg(-1) (dry weight). The concentrations of water-soluble, exchangeable, acid-soluble, organic-bound and residual forms of Se were 7.71-26.8gkg(-1), 24.7-93.3gkg(-1), 112-1430gkg(-1), 26-765gkg(-1) and 1300-5330gkg(-1), respectively. The concentrations of total Se were positively correlated with the contents of clay and soil organic matter, but were negatively correlated with pH values. The contents of bioavailable Se, which consists of water-soluble Se and exchangeable Se, were negatively correlated with the contents of soil organic matter, but positively correlated with pH values. The results suggest that pH value and the content of organic matter are key factors that regulate the bioavailability of Se in soils of Dashan Region.