Abstract:

Selenium is one of the most important trace elements for human and animal, which also has a bright application future. The research of geochemical distribution and bioavailability controlling factors of soil selenium has important significance. In this paper, characteristics and influencing factors of soil selenium content all over the Hainan Island covering the range of 27,426 km² were summarized. The results showed that the selenium full and selenium rich soil was up to 69.98% of the study area and topsoil selenium content to a certain extent inherited into the soil parent rock (or deep soil), but the difference among soil parent rock formation generated enrichment or dilution of soil selenium content. Further studies have shown that the selenium content in soil has a significant positive correlation with organic carbon, aluminum oxide, total iron oxide, manganese, and the CIA, indicating that the clay minerals, organic carbon, iron and manganese oxides in the soil and weathering and leaching extent were playing important roles in the geochemical behaviors of selenium, while these indicators were important parameters to affect the bioavailability of soil selenium. The bioavailability of soil selenium reduced with increasing content of soil organic carbon, clay, CEC and other indicators. In the study area, when the soil pH is higher than 6.5, the soil selenium content is lower. While the soil pH is lower than 6.5, the soil selenium content increase with the pH decreasing. As the soil pH is 5.5 to 7.5, the bioavailability of soil selenium is relatively higher. Therefore, developing selenium rich agricultural products not only is based on the total level of Se in the soil but also the range of content of the soil pH, TOC, CEC, clay and other indicators should be considered.

Key words: soil selenium content, bioavailability, geochemical characteristic, influencing factor, Hainan Island