Application Of Element And Lead Isotope Tracing To The Migration Of Thallium In Soil From Yunfu Pyrite Mine

The toxicity of thallium for mammals is higher than other toxic elements (Cd, Cu, Pb, Cr) and the thallium contamination in soil was paid attention less for a long time, especially Tl was excluded from the environmental monitoring items in our country. Abundance of mineral containing Tl has been found in our country. With the exploitation and utilization resources containing thallium thallium can be released into soil,but the rule of migration and enrichment of thallium pollutants in soil were not found out clearly, which still needs research urgently.In this work, samples were collected from sulphur acid slags, soil under and outside the slag pile around pile site, background soil.Smelting slag and soil surrounding the sulfur acid plant were took as major research objects. Conclusions have gained through the detailed analysis including the soil and slag of physical and chemical characters, Tl trace element, Tl different phases and Pb isotope in soil. With the help of detailed handling of data and predecessors results, the primary results of this research as following:â‘ Soil under and outside the sulphuric acid slag had been polluted obvious under natural leaching and soil under the sulphuric acid slag was polluted more serious than that of the outside soil. Thallium pollutants were mainly concentrated in soils surface layer (0-16.5cm) and shown characteristics of contents rapidly decreasing along the uprights.â‘¡The sequentical extraction procedure indicated that thallium pollutants have high proportion of labile phases and are mainly in the Fe/Mn oxide fractions (Tl_Fe/MnOx). Organic (Tlorg) and exchangeable (Tlexc) fractions of Tl are the second fractions, the least is carbonate fractions (Tlcar). In the soil the migration capability of thallium in the exchangeable, carbonate and Fe/Mn oxide fractions is strong but organic and residual fractions of thallium have very weak migration capability relative. The exchangeable,carbonate and Fe/Mn oxide fractions are the mainly migration forms and organic and residual fractions show accumulation characters.?The migration capability of thallium pollutants in soil is affected by many factors. The first important factor is the pH condition, the proportion of Fe/Mn oxide and organic matter,granularity,CEC (Cation exchange capacity) are the second factors.?Sigificent linear correlation between the distribution of Tl and Pb is found in soil (0-10.5cm) surround slag pile which indicts Tl and Pb released from slag,then lead migrated with thallium inseparable. Lead isotope tracing implies the soil around the slag about 44cm was infected by Tl releasing from the acid slags and thallium pollutants in soil outside the slag pile migrated and diffused more quickly than that of soil under the slag.?The Geoaccumulation index (Igeo) and enrichment factor (EF) were used to evaluate Tl pollution in soil around the slag pile and the results showed Tl in soil outside the slag pile contaminated more serious than that of the under slag pile.The degree of Tl pollution decreased gradually with the depth of soil and the soil more than 10.5cm was affected very little or without by Tl pollutents.