Selenium Speciation Analysis and Its Transformation and Enrichment in Soils of Fuzhou City

Selenium speciation in soil and rock samples taken from Fuzhou City was investigated in this work. The results showed a significantly positive correlation between species and total amount of selenium in topsoil. The residue species of selenium occupied 28.77% of total selenium, the species of strong bound in organic compounds and the species of humic acid bound approximately accounted for 57.44% of total amount of selenium in topsoil. Meanwhile, the selenium abundance between top soil and sub-soil also displayed a significant positive correlation. Selenium abundance in topsoil increased with the acidity increase but no obvious increase with the increase of content of organic substances. While selenium abundance in deep soil insignificantly varied with the change of pH value but significantly influenced by organic substance content. Moreover, the abundance of selenium dramatically deviated from the samples with different materials except the types of rocks, which decreased in the order of topsoil＞deepsoil＞rock. The results suggested that the process of selenium adsorption in soil organic substance and clay mineral caused selenium enrichment in topsoil in the process of rock weathering and soil development. This paper has proposed a method to estimate speciation concentration of selenium according to the total selenium and established a formula to calculate available selenium content with given data of selenium abundance and speciation in soils. And a suggestion that only selenium species of organic bound, residue, ion exchangeable and total amount of selenium be considered in soil selenium assessment has put forward.