Combination Forms and Distribution Characteristics of Se in Daqing Longfeng Wetland Soils

In order to understand the amount,species and distribution of selenium(Se) in Daqing Longfeng wetland soil,the contents of Se were measured by a method of successive extraction,and the physical and chemical properties of soil that affects the deposition of Se were determined.The results showed that Se in Daqing Dragon wetland soil is of normal level,and Se contents showed obvious rules of variation in the vertical direction,varying between the 121~150 μg/kg.Among several kinds of Se forms,water-soluble Se,exchangeable Se and organic Se account for 1.5%~3.3%,3.6%~7.4%,24.0%~43.9% of the total Se,respectively,while unavailable Se including acid-soluble Se,sulphide Se and residual Se accounts for more than 50% of the total Se.Soil factors such as organic matter,soil pH and clay fraction play relatively important roles.However,due to the low proportion of effective Se and the high proportion of ineffective Se in soil,selenium is low in availability.It is the reason that people and living organisms in this region are insufficient in Se.