The distribution of soil selenium in Shouning County of Fujian Province and its influencing factors

Based on multi-purpose regional geochemical survey in Shouning County of Fujian Province, the authors found the characteristics of selenium distribution and enrichment and the correlation between selenium and pH as well as other elements. The results show that the selenium content in surface soil is from 0.13 mg/kg to 0.92 mg/kg, with the average value of 0.35 mg/kg. The total selenium content in deep soil is from 0.14 mg/kg to 0.54 mg/kg, with the average value of 0.29 mg/kg. The selenium content in the soil developed in late Yanshanian normal granite is the highest, with an average value of 0.39 mg/kg, followed by the soil developed in 4^th member of the Nanyuan Formation and the upper part of the Xiaoxi Formation. The selenium content of different soil types shows that the content of yellow soil is higher than that of red soil, and that of red soil is higher than that of paddy soil. The surface soil generally belongs to selenium-rich and selenium-sufficient soil, the area of selenium-rich soil contains 405.04km², accounting for 28.24%. The selenium content in the surface soil demonstrates an apparent feature of enrichment relative to the content in the deep soil, with the strong enrichment area basically consistent with the area of selenium-rich soil with the potential of developing selenium-rich agricultural products. The correlation analysis indicates that the selenium content in soil has a significant positive correlation with organic carbon, aluminum oxide, total iron oxide and manganese, and has a negative correlation significantly with pH, indicating that soil physical and chemical properties, iron and manganese oxides in the soil play important roles in the geochemical behaviors of selenium.