Gejiu Tin Polymetallic Deposit Arsenic Contamination Geochemical Studies

With the deepening of mining depth and smelting capacity and the environmental awareness of the public, it has been acknowledged that numerous mine tailings are characterized by environmental pollution under the environmental degradation. The tin-exploitation history of the Gejiu Tin-polymetallic Mine in Yunnan province dates back to 200 years ago. Not only being famous for its tin mines, but also rich in 27 associated useful compositions. After beneficiation, these compositions are into tailings dams. There are altogether 31 tailing dams in Gejiu, accumulating 190 million tons of tailings and 390 thousand tons of tin. For such a huge volume of potential contamination, it is essential for contamination transmission to ecological environment. For tailings dams in Gejiu area, Using multiple methods of artificial heavy minerals analysis, major elements testing, X-ray powder diffractometry and trace elements testing etc., has comprehensive studied characteristics of the chemical components, the mineral components, contents and occurrence of valuable elements etc.; Discussing the characteristics of contamination transmission along the chain of rock(ore)- concentrator-water-tailings-soil-plant; these study have reached the following conclusions:(1) The modes of occurrence of arsenic in Gejiu Sn-bearing Polymetal Ore Deposit are:Occurrence of arsenic in ore minerals are arsenopyrite, arsenic-huinickel oxide ore mineral of arsenic in arsenic calcium copperscorodite, arsenic lead and arsenic in copper vanadium ore of lead, arsenic in tailings by arsenopyrite, realgar Exist. Arsenopyrite is the main area of arsenic occurrence, pyrrhotiti, pyrite, and chalcopyreite, tetrahedrite tin and associated minerals of natural arsenic inbismuth.(2)This study area is acidic tailings-oxidizing environment, the tailingsof arsenic and heavy metals easily oxidized to form some of the most toxic As (â…¢).(3)The need to strengthen the monitoring of the tailings, in order to avoid serious environmental geological disasters. Section through the tailings samples for analysis after the results indicate:the metalsulfide in the air because the oxygen content and temperature of chemical weathering will occur, so the different seasons anddifferent climates and its oxidation and decomposition are closely related. And in the chemical weathering, lead to increased acidity of the end of the water, in this case, chalcopyrite; pyrite andarsenopyrite in the iron into Fe3+,Fe3+will increase theoxidation and decomposition of metal sulfides. So once the tailings surrounding physical and chemical (pH, conductivity, temperature) conditions have changed on the surroundingecological Transformation will cause serious damage.(4) Arsenic contamination of Gejjiu Tin-bearing Polymental ore Deposit transmission path are:According to the Aresenci contamination of Gejiu Tin-bearing Polymental ore Deposit transmission path are:According to the Arsenopyrite oxidation releases arsenic to As(â…¢) in water-based oxide.As(â…¢) is beneficial to plant uptake of arsenic, the arsenic contamination in this area can be absorbed into the soil through the plant-vegetation system. As shown, the tailings through the oxidation of arsenopyritein the release of arsenic as As (â…¢), the forms of arsenic into thewater and soil, and then absorbed by plants.