Environmental And Biogeochemical Characteristics Of Selenium And Iodine Of Soilin Zhejiang Province

Selenium and iodine, two essential trace elements of human body, are vital to physiological health and life safety. The study about the geochemical characteristics of selenium and iodine in the natural medium, such as distribution characteristics and migration transformation rules, not only has a very important significance to the rational use of land resources advantage in areas where are rich in selenium and iodine, but also improves nutritional status that people lacking of selenium and iodine. In this paper, on the basis of predecessors’research, Se-enriched area in north of Zhejiang province and I-enriched area in east of Zhejiang province were chosen as the research objects, the contents of Se, I in the soil and the characteristics of space distribution were researched systematically.In this paper, the main research results obtained are as follows:the average selenium concentration in topsoil in the northern region of Zhejiang province is 0.344 mg·kg-1, which achieved selenium-rich level. And it shows that the selenium concentration has significant correlations with soil organic matter and the contents of sulfur, cadmium and mercury, but has nothing to do with the pH value. The measurement to content of different speciations of selenium shows that, organically-bonded state> humicacid-bonded State> residual state> carbonate-bonded state> ion exchange state> water soluble state> Fe-Mn oxides bonded state, the contents of the former three were much higher than the other four states and had a certain relationship to the soil physicochemical properties, respectively. Se concent in edible parts of vegetables met the selenium-rich standards. The average iodine concentration of topsoil in the eastern region of Zhejiang province is 19.35 mg·kg-1 which was much higher than that in southwestern area (1.65 mg·kg-1) and the average of Zhejiang province (1.95 mg·kg-1). The difference of iodine content in soil profiles was similar with that in the topsoils of two study areas, and the content of iodine was slightly higher than that in the surface soil, it has a certain law with the depth. Marine elements such as fluorine, chlorine, calcium, magnesium and iodine were significant positive correlation, so the main source of iodine in east of Zhejiang province was ocean and it must be connected with the local geological environment evolution, and in southwestern area, it might be the rock weathering. Finaly, affected by the soil medium, I contents in the edible part of vegetables grown in I-enriched area were much higher than that in iodine deficiency area. The results of this study provide basic data for the using of Se-enriched, I-enriched land resources and the ecological supplementation way of Se and I.