含铊资源利用中铊的同位素分馏及环境铊污染的源识别

Thallium (Tl) could exist as monovalent and trivalent state in natural environment and bears great potential to be vaporized. Dramatic environmental changes due to anthropogenic activites, such as industrial processes of smelting, oxidation-reduction reaction, could have significant impacts on the stable isotopic fractionation of Tl (203Tl/205Tl). The main purpose of this project is to identify the different "fingerprint" of Tl and its isotopic composition left by natural weathering and human activities, and to establish a source identification system of Tl pollution in a typical area. This area bears a mineralization zone of Tl-rich pyrite minerals and a factory utilizing the minerals to produce sulfuric acid. Firstly, the isotopic fractionation of Tl during production process of pyrite would be recognized by comparing Tl content and Tl isotopic composition of the original pyrite minerals and those of the pyrite slags, exhaust gas and effluent. Secondly, geochemical characterstics of Tl content and Tl isotopic composition would be comparatively studied in the Tl-rich soil from the pyrite mineralization zone and Tl-polluted soil from the pyrite slag disposing site, in order to uncover the relationship between the concentration and the isotopic fraction value of Tl. Finally, it would be combined with geochemical charactersitics of related element to establish a source tracing system for quantitative identification of Tl pollution in the studied soil. This study of identifying the differences between the "fingerprint" of Tl pollution by natural weathering and by human activities could provide a quantification method for pinpointing the contribution of different pollution sources. It would furnish the research on Tl environmental pollution with a brand-new theoretical framework in a systematic way with high scientific merits.

铊在自然界中有Tl+和Tl3+两种价态，具有较高挥发性。人类活动带来的环境剧变对铊稳定同位素组成（205Tl/203Tl）将产生明显影响，如工业中的高温冶炼、氧化-还原反应等过程。本项目拟对比研究典型含铊黄铁矿矿区原生黄铁矿及其利用过程各工序废渣、外排废气、废水中铊元素-同位素组成特征，结合相关元素地球化学的研究，了解铊在黄铁矿冶炼过程中的同位素分馏效应，识别铊元素-同位素组成在自然来源和人为活动来源不同的"指纹"特性。比较分析自然来源铊富集土壤（黄铁矿矿化区）和人为来源铊污染土壤（硫酸厂堆渣场）中铊元素-同位素组成的地球化学特征。研究不同端元铊同位素分馏值与铊含量的响应关系，并结合相关元素地球化学，建立定量解析土壤铊污染的源识别体系。本项目可望将相关研究从以往的定性向定量深化，为系统地研究环境Tl污染提供全新的思路，具有较高的科学理论研究价值。

铊在自然界中有Tl+和Tl3+两种价态，具有较高挥发性。人类活动带来的环境剧变对铊稳定同位素组成（205Tl/203Tl）将产生明显影响，如工业中的高温冶炼、氧化-还原反应等过程。本项目通过对比研究典型含铊黄铁矿矿区原生黄铁矿及其利用过程各工序废渣中铊、铅、锌、锶等重金属元素-同位素组成特征，结合相关元素地球化学的研究，了解铊在黄铁矿冶炼过程中的同位素分馏效应，识别铊、铅、锌、锶等重金属元素-同位素组成在自然来源和人为活动来源不同的“指纹”特性。与黄铁矿相比，Tl在各个废渣中表现出明显的分异特征。在沸腾炉渣、锅炉渣中ε205Tl明显低于旋风除尘渣和电除尘渣。结合Pb同位素分析，发现土壤/沉积物中20%~80%的铊来源于黄铁矿的开采利用。