典型铅锌冶炼过程中铊同位素分馏特性及环境示踪意义

Thallium (Tl) pollution has been increasingly explosive in our country these years due to extensive exploration and utilization of Tl-bearing minerals. This research proposal would focus on a typical Pb-Zn smelting factory involved Tl discharge and some nearby sediment profiles receiving Tl pollution in the North River Basin, Guangdong Province, with high-precision measurement of Tl isotopic composition using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) as the key technique, combined with geochemical speciation analysis. The aims are (1) to study stable isotopic fractionation of Tl under extreme environmental conditions during different production processes of Pb-Zn smelting; (2) to extract environmental geochemical "fingerprint" of Tl isotopic composition and special trace element composition, by comparing geochemical characterstics of Tl concentration and isotopic composition between different discharge end-members and sediment profiles, and construct a quantitative tracing technique for identifying relative contributions arising from natural weathering and anthropogenic source,respectively; and (3) to calculate deposition rate and accumulation flux of Tl pollution from different sources coupled with sediment dating technique, thereby gaining a comprehensive understanding of Tl temporal-spatial variability and evolution in the Tl pollution hot-spot area at the North River Basin. The findings of this research would not only enrich a further understanding of Tl environmental geochemistry and Tl isotopic fractionation mechanism, but also provide reliable advanced technique supports and effective scientific theory evidence for establishing a prevention and compensation rationale for Tl pollution, which has high scientific merits and practical significances.

含铊矿产资源长期过度的开发利用导致近年我国环境铊污染呈高发态势。本项目拟以广东北江流域典型涉铊铅锌冶炼厂和附近河流沉积物剖面为研究对象，利用多接收道等离子体质谱仪(MC-ICP-MS)的铊同位素高精度测试技术，并结合铊环境地球化学形态的分析，揭示铅锌冶炼各不同生产过程极端环境条件下铊同位素分馏效应，对比研究冶炼厂不同排放端元和沉积物剖面中铊元素-同位素组成的环境地球化学特征，提取铊同位素和特征微量元素环境地球化学特效指纹指标，判定北江铊污染的自然来源和人为来源，构建定量示踪沉积物铊污染源识别的方法体系；结合沉积物剖面的年代学研究，计算不同来源的铊在水环境中的沉积速率和累积通量，全面认识北江典型污染区域铊的时空演变规律。本项目不仅丰富并深化对铊环境地球循环和铊同位素地球化学的认识，还可为建立铊污染防治和补偿机制提供科学有效的理论依据和可靠的先进技术支撑，具有重要的科学理论研究价值和实践意义。

含铊矿产资源长期过度的开发利用导致近年我国环境铊污染呈高发态势。本项目以广东北江流域典型涉铊铅锌冶炼厂和附近河流沉积物剖面为研究对象，利用等离子体质谱仪(ICP-MS)研究铊等微量元素地球化学，并结合铊等重金属环境地球化学形态的分析，查明沉积物中铊等重金属污染分布特征，判别沉积物中铊等重金属异常富集的形成机制。在此基础上，利用多接收道等离子体质谱仪(MC-ICP-MS)的铊同位素高精度测试技术，揭示了铅锌冶炼生产过程中铊同位素分馏效应。与铅锌矿原料相比，通过高温冶炼焙烧后，铊同位素发生了一定程度的分馏效应，导致Tl同位素在不同工序废渣中表现出明显的分异特征。其中，在固相残渣中Tl同位素组成明显偏重；而由大气沉降形成的电除尘渣，脱硫废水形成的污酸底泥和除尘废水沉淀形成的石灰中和渣中Tl同位素组成明显偏轻。通过进一步对比研究冶炼厂排放端元和沉积物剖面中铊元素-同位素组成的环境地球化学特征提取了铊同位素地球化学特效指纹指标，利用同位素二元混合模型计算得出，铅锌冶炼厂排出的污酸底泥废弃物对河流沉积物中Tl的贡献率范围为16.0 % - 87.9 %，平均值为59.6±16.9%。这一结果定量地证实了Pb-Zn冶炼活动对所研究沉积物剖面中Tl污染的巨大人为影响。污染不仅局限于表层，而且还延伸到深部沉积物。同时也进一步证实了即使在复杂的水环境条件下，铊同位素仍可以作为追踪深度剖面沉积物中重金属铊污染源的有力环境指标。本项目不仅丰富并深化对铊环境地球循环和铊同位素地球化学的认识，还可为建立铊污染防治和补偿机制提供科学有效的理论依据和可靠的先进技术支撑，具有重要的科学理论研究价值和实践意义。