宁夏北部农耕地土壤中硒的质量含量及形态、价态分析

Analysis on Selenium Content,Form and Valence in Farmland Soil of Northern Ningxia

以宁夏北部富硒土壤为研究对象,分析耕作层土壤中硒的质量含量、赋存形态和价态.结果表明,宁夏北部农耕地富硒土壤呈大面积连片分布,土壤中硒的质量含量为0.02~1.80 mg/kg,平均值为0.26 mg/kg.土壤中7种形态硒的质量含量由大到小为残渣态、强有机结合态、腐殖酸结合态、水溶态、离子交换态、碳酸盐结合态、铁锰氧化物结合态,表现出高可利用态、潜在可利用态、低不可利用态的特征.土壤中水溶态和离子交换态硒分别以Se^(6+),Se^(4+)存在,不存在植物难以吸收的较低价态(Se,Se^(2-)).随着土壤pH值的增大,土壤中Se的总量呈降低趋势,在pH=8~9时硒的质量含量较高.

Taking the selenium-rich soil in northern Ningxia as the research object,the article analyzed the quality content,occurrence form and valence state of selenium in the cultivated-layer soil.The results showed that the selenium-rich soils in the agricultural land of northern Ningxia were distributed in large contiguous areas,and the mass content of soil Se ranged from 0.02 to 1.80 mg/kg with an average value of 0.26 mg/kg.The mass contents of the seven forms of Se in the soil were,from largest to smallest,residue state,strong organic bound state,humic acid bound state,water soluble state,ion exchange state,carbonate bound state,and iron-manganese oxide bound state,showing high availability and potential availability,and low non-availability.The water-soluble Se and ion-exchange Se in soil exist as Se^(4+) and Se^(6+) respectively without low valence Se(Se,Se^(2-)) which is difficult to be absorbed by plants.The total amount of Se in soil decreased and the content of Se reached higher at pH=8-9 with the increase of soil pH value.