含铊硫铁矿利用区河流沉积物中铊的迁移富集机制与来源示踪

In recent years, pollution incidents of highly toxic thallium (Tl) have occurred with unfortunate regularity in China. Our recent investigations have shown that there is a significant fractionation effect for the stable isotope composition of Tl during industrial processes utilizing pyrite minerals. The aim of this project is to further investigate the isotopic compositions of Tl in river sediments from typical point-sources and non-point-sources in the Yunfu City area, in the province of Western Guangdong using high-resolution MC-ICP-MS. The geochemical fractionation of Tl will b628e studied by sequential extraction, combined with related major and trace element composition to reveal the relationships between Tl fractionation and isotopic compostion. The characteristic isotopic variation of Tl in river sediments would be used to construct Tl isotopic fingerprints for typical point-source pollution. These fingerprints from different point-source pollution locations will be combined to determine systematic patterns of Tl isotopic variation in river sediments from non-point-source areas of pollution, and then to construct isotope mixing models to systematically analyze the sources, geochemical transfer pathways and quantify the contribution from each end-member for the source zones. This research will establish a quantitative tracing system for fingerprinting Tl pollution source and migration pathways in complex natural systems with multiple pollution sources. It will provide well founded scientific understanding of the serious issue of Tl pollution and result in better methods of prevention and control all over China.

剧毒重金属铊(Tl)污染事件近年在我国频频爆发。申请人近期研究表明云浮含Tl硫铁矿冶炼工业利用过程中Tl稳定同位素分馏效应十分显著。本项目拟利用高精度多接收等离子体质谱仪(MC-ICP-MS)进一步系统研究该硫铁矿工业利用区不同典型点源和复合污染区河流沉积物中Tl稳定同位素的组成特征，并利用分级提取技术厘清Tl的地球化学形态，结合Pb同位素和相关主微量元素地球化学的组成特征，查明不同Tl污染区各个环境端元中Tl的形态组成特征与Tl同位素组成变化之间的响应关系及其关键控制因素，提取Tl同位素的指纹特性。在此基础上，结合不同特征污染区Tl同位素变化特性，构建Tl同位素和Pb同位素的多元混合模型，建立系统解析复合Tl污染区河流沉积物中Tl污染来源和迁移转化的定量示踪体系，明确典型污染区Tl进入水体环境的关键通道和通量，为我国Tl污染防治提供科学可靠的理论依据和技术支撑。

铊(Tl)是一种剧毒重金属元素。近年来我国广东北江、陕西嘉陵江和湖南湘江等各大江河流域频频爆发水体铊污染事件，严重影响水源安全。近期研究表明，含铊硫化物矿产资源的开发利用是导致水体铊污染的重要来源之一。本项目在前期研究基础上，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，较系统研究了某典型露天硫铁矿工业利用区污染源样品以及不同点源和复合污染区河流沉积物中Tl稳定同位素的组成特征，并利用分级提取技术测定了样品中Tl等重金属的地球化学形态。结合不同特征污染区相关主微量元素地球化学的组成特征，以及X射线光电子能谱、X射线衍射和透射电子显微镜等分析表征测试技术，证实了利用铊同位素技术对沉积物进行源解析的可行性。由此构建了基于金属同位素组成的多元混合模型，建立了解析复合污染区河流沉积物中Tl来源和迁移转化的定量示踪体系。研究结果发现，河流沉积物中平均~80%的Tl污染来源于人为工业活动（尾矿端元和废水池底泥），且远离矿区10km处的下游沉积物仍有42%的Tl污染来源于人为活动。由此可见，铊同位素组成可作为甄别复杂环境基质中铊污染不同来源的示踪剂。该研究可为我国乃至全球Tl污染防治提供科学可靠的理论依据和技术支撑。