Endemia effects and impacts of geological background onsoil elements distribution and effects of endemic diseasein the Three Gorges Reservoir District
三峡库区地质背景对土壤元素 分布的影响及地方病效应

Based on testing results of top-soils in the Three Gorges Reservoir District, distribution characteristics of element contents in soils were discussed by different types of parent rocks, such as mudstone and limestone. It can be concluded that, in the Three Gorges Reservoir District, the soils in the limestone areas are abundant in most of the elements, such as As,Br,B,Sb,C,F,I,Li,Mo,CaO and so on,which are more than twice the contents in soils rooting in mudstone areas. On the other hand, the soils in the mudstone districts are poor in most of the elements. Only several elements, such as Ba,P,Sr,Na2O, SiO2, are higher in contents than those in soils of limestone areas. The difference in elements distribution characteristics is closely related with the distribution of endemic fluorosis and Keshan disease in the Three Gorges Reservoir District. Endemic fluorosis mainly occurs in areas where soil content of fluorine is higher, which is the outcome of limestoneweathering and soil-forming process. And Keshan disease mainly happens in the lower-selenium soils areas, which is the result of mudstone-weathering and soil-forming process. Geological environmental conditions are responsible for the incidence of the endemic diseases in these areas. The research results can provide important reference to rational allocation of agriculture and rational planning of rural-urban areas in the Three Gorge Reservoir District.