School of Geographic Sciences, Hunan Normal University, Changsha 410081, People's Republic of China; Key Laboratory of Environmental Heavy-Metal Contamination and Ecological Remediation, Hunan Normal University, Changsha 410081, People's Republic of China.
School of Geographic Sciences, Hunan Normal University, Changsha 410081, People's Republic of China; Key Laboratory of Environmental Heavy-Metal Contamination and Ecological Remediation, Hunan Normal University, Changsha 410081, People's Republic of China.
Sci Total Environ. 2022 Jul 10;829:154394. doi: 10.1016/j.scitotenv.2022.154394. Epub 2022 Mar 8.
This paper reports Pb isotopes in different fractions following the three step BCR and 1 M HCl extractions on river sediments from lower reaches of the Xiangjiang river in China, and highlights the importance of Pb isotopes in heavy metal contamination assessment. Lead concentrations and Pb isotopes in bulk sediments and sediment fractions (leachates and residues) from the river were analysed using ICP-MS techniques. Results showed that sediments were highly enriched with Pb with enrichment factors >5.5, while Pb in sediments was dominated by reducible and residual Pb fractions, residing mainly in Fe-oxide and silicate minerals. Pb isotopes in sediments was characterized by radiogenic Pb produced from the decay of uranium and thorium with Pb/Pb ratios of 1.1744 for less radiogenic Pb and 1.1816 for more radiogenic Pb. The leachates and residues from BCR extraction generally had similar Pb isotope compositions, of which the Pb/Pb ratios were 1.1798 ± 0.002 and 1.1844 ± 0.008 respectively. Differentiation of Pb isotopes between BCR leachates and residues was insignificant. However, differentiation between leachates and residues using 1 M HCl extraction was significant, as shown by average Pb/Pb ratios of 1.1746 ± 0.005 and 1.1858 ± 0.008 for leachates and residues respectively. Pb isotopic tracing suggests that Pb in sediments from Zhuzhou section arose from the mixing of anthropogenic Pb from coal combustion (39%) and mining-smelting for Pb-Zn ores (58%); while Pb in sediments from Xiangtan, Changsha and Xiangyin sections arose from the mixing of anthropogenic Pb from mining-smelting for Pb-Zn ores (54%), and lithologically inherited Pb from granite weathering (35%) with a small amount of contribution from coal combustion (10%). The present study suggests that the BCR extraction scheme was not appropriate for ecological risk assessment of heavy metal contamination in mining-impacted (ore-Pb dominated) river sediments.
本研究报告了湘江下游河流沉积物经三步 BCR 和 1 M HCl 提取后的不同组分中的 Pb 同位素，并强调了 Pb 同位素在重金属污染评估中的重要性。采用 ICP-MS 技术分析了河流沉积物中总沉积物和沉积物各组分（浸出液和残渣）中的 Pb 浓度和 Pb 同位素。结果表明，沉积物中 Pb 高度富集，富集因子>5.5，而沉积物中的 Pb 主要以可还原和残留 Pb 为主，主要存在于铁氧化物和硅酸盐矿物中。沉积物中的 Pb 同位素特征为铀和钍衰变产生的放射性 Pb，放射性较低的 Pb 的 Pb/Pb 比值为 1.1744，放射性较高的 Pb 的 Pb/Pb 比值为 1.1816。BCR 提取的浸出液和残渣的 Pb 同位素组成一般相似，其 Pb/Pb 比值分别为 1.1798±0.002 和 1.1844±0.008。BCR 浸出液和残渣之间的 Pb 同位素没有明显差异。然而，使用 1 M HCl 提取的浸出液和残渣之间的 Pb 同位素存在显著差异，浸出液和残渣的平均 Pb/Pb 比值分别为 1.1746±0.005 和 1.1858±0.008。Pb 同位素示踪表明，株洲段沉积物中的 Pb 来自燃煤（39%）和铅锌矿开采冶炼（58%）的人为 Pb 的混合；而湘潭、长沙和湘阴段沉积物中的 Pb 则来自铅锌矿开采冶炼（54%）的人为 Pb 和花岗岩风化（35%）的岩性继承 Pb 的混合，以及少量燃煤（10%）的贡献。本研究表明，BCR 提取方案不适用于受采矿影响（以矿石-Pb 为主）的河流沉积物中重金属污染的生态风险评估。
