Geochemical Characteristics Of Selenium In Zoige

Selenium is one of rare dispersive elements, as micro-nutrientselement, which is necessary for the human and biological activities. Theresearch of chemical speciation and distribution characteristics ofselenium in natural mediums, and migration and transformation lawsamong mediums, has great significance in prevention and treatment ofselenium-lack endemic diseases (such as Kashin-Beck disease) andprotection of ecological environment. This thesis relies on the "sub-topic"Aba Eco-geochemical Survey (No.1212010913022) of China GeologicalSurvey Project Sichuan Province Kashin-Beck Disease WardGroundwater Investigation and Security of Water Supply Demonstration.Selenium element in Zoige region is selected as the research object. Thecontent of selenium in the various rocks, soils, water, plants, andchemical speciation of selenium were determined. Distributioncharacteristics and influencing factors of selenium were analyzed.Migration and transformation of selenium in terrestrial ecosystems werediscussed. This research provides a scientific basis for the etiologyinvestigation of Kashin-Beck disease in Zoige, and protection of theplateau swamp wetlands eco-environmental in the territory. The achievedresults are as follows.1. The research area belongs to a low-selenium environment. Overall,selenium content in soils in this region is extremely low and low,selenium content in rocks is lower than crustal abundance, and seleniumcontent in water is far lower than China major cities and the normaldrinking water, while in plants, it is between the level of deficiency andnormal grade. 2. The selenium content in research is necessarily related to thedegree of soil development and organic matter content in soil. With soildeveloping and maturing, the soil peat layer is gradually formed andthickened, and the organic matter content increases. Within a certainrange, selenium content rises with the increasing of the adsorptioncapacity of soil. When organic matter increases to a certain extent,selenium adsorption capacity of soil reaches saturated. Selenium isrelatively enriched in the topsoil in the process of soil formation. On thewhole, there is no significant correlation between the selenium contentand soil pH, Eh values. The total selenium content in the soil largelydetermines the content of the various species of selenium.3. The content of selenium in rocks with different lithologiccharacters is in the order as slate, clay stone, sandstone, limestone.Selenium content in rocks has no obvious correlation with that in topsoilsand deep soils.4. The content of selenium in different types of water bodies isfollowed as the order of swamp water, stream water, river water. Theorganic-rich peat swamp is conducive to the adsorption of selenium,while the streaming of river and stream goes against selenium enrichment.The geomorphology of the research area is favorable for exchange andmigration of elements between water and soil; selenium content in waterhas certain correlation to that in soil of the streaming region. The pH andEh values of water affects the selenium content of water body to a certainextent.5. According to plant species and its growing environment, seleniumcontent in different phytobiocoenoses is followed as Carex meyeriana,Kobresia tibetica, Carex muliensis, Psammophytes. To a certainextent, selenium content of soil influences the content of plants, butnot the decisive factor. The soil pH and Eh values are the decisive ones.In the migration and transformation process of selenium in the soil/plantsystem, species and content of selenium are controlled by soil, which affects the utilization of selenium to plants, and then determines theselenium content in plants.