Thallium(Tl), an extremely toxic metal, is posing great hazards to water safety through anthropogenic activities (e.g., Pb-Zn smelter) and natural weathering in riverine systems. However, the relative contribution from each source remains obscure. This study investigated enrichment pattern of Tl and its isotopic compositions in sediment profiles from a recipient river, which was continuously collecting various Tl-bearing wastes discharged from a large Pb-Zn smelter in South China. Results show that high Tl content and ultra-fine particles (~ μm) of Tl-bearing mineral assemblages, probably derived from Pb-Zn smelting wastes, were ubiquitously observed in both of the depth profiles. In addition, the sediments generally yielded intermediate ε²⁰⁵Tl values of –3.76 ~ 1.01, which resembled those found in smelting wastes. A ternary mixing model was for the first time proposed for quantifying relative Tl contributions from each possible source. The calculation suggests that the smelter wastes are the major contributors, contributing approximately 80% of Tl contamination. All these results indicate that Tl isotope can be used as powerful proxies for quantitatively identifying potential different contributors in the environment. This is of critical importance to further implementation of pollution control and remediation strategy for the riverine systems in the near future.

铊 (Tl) 是一种剧毒金属，通过人为活动（例如铅锌冶炼厂）和河流系统中的自然风化对水安全构成极大危害。然而，每个来源的相对贡献仍然模糊不清。本研究调查了来自接收河流的沉积物剖面中 Tl 的富集模式及其同位素组成，该河流不断收集从华南一家大型 Pb-Zn 冶炼厂排放的各种含 Tl 废物。结果表明，在两个深度剖面中普遍观察到高 Tl 含量和含 Tl 矿物组合的超细颗粒 (~ μm)，可能来自 Pb-Zn 冶炼废料。此外，沉积物一般产生中间ε ²⁰⁵Tl 值为 –3.76 ~ 1.01，类似于在冶炼废料中发现的值。首次提出了一种三元混合模型，用于量化来自每个可能来源的相对 Tl 贡献。计算表明，冶炼厂废料是主要贡献者，约占 Tl 污染的 80%。所有这些结果表明，Tl 同位素可用作定量识别环境中潜在的不同贡献者的强大代理。这对于在不久的将来进一步实施河流系统的污染控制和修复战略至关重要。