College of Ecology and Environment, Chengdu University of Technology, Chengdu 610059, China.
College of Ecology and Environment, Chengdu University of Technology, Chengdu 610059, China.
Sci Total Environ. 2022 Apr 15;817:152978. doi: 10.1016/j.scitotenv.2022.152978. Epub 2022 Jan 10.
Although enrichment of As and B has been extensively observed in major rivers within the Tibetan Plateau, the mechanisms regulating natural enrichment of As and B in the river basins remain poorly understood. To evaluate the hydrogeochemical controls on the As and B enrichment in the aqueous environment in the western Tibetan Plateau, samples of river waters, river sediments, and groundwater were collected within the Singe Tsangpo River basin. The results revealed significant enrichment of As and B in river water (up to 104 μg L for As and 3.2 mg/L for B), river sediment (up to 141 mg/kg for As and 79.4 mg/kg for B), and groundwater (up to 73 μg /L for As and 2.5 mg/L for B). Moreover, the decreases in the molar ratios from the Ca /(Na+K) in river water and the chemical index of alteration (CIA) in the sediments accompanied with the enrichment of heavier δO values along the river flow path suggested that, carbonate and silicate weathering were more substantial at the upper reaches, and the dissolution of evaporites was enhanced at the lower reaches. The As and B enrichment in the river waters primarily resulted from the discharge of geothermal springs, while the carbonate weathering has facilitated the B enrichment through providing HCO for the competitive adsorption with HBO or B(OH) . In addition, the recharge of surface water into groundwater resulted in elevated As and B concentrations in the alluvial aquifers at the lower reaches of the Singe Tsangpo River. The present study highlighted that variations in the weathering processes within the river basin could significantly contribute to the enrichment of As and B, which can improve our understanding of hydrogeochemical controls on the transport and enrichment of trace elements at the catchment scale worldwide.
尽管在青藏高原的主要河流中已经广泛观察到砷和硼的富集，但对控制流域内天然砷和硼富集的机制仍知之甚少。为了评估青藏高原西部水系环境中砷和硼富化的水文地球化学控制因素，在色林错流域内采集了河水、河沉积物和地下水样品。结果表明，河水（高达 104μg/L 的砷和 3.2mg/L 的硼）、河沉积物（高达 141mg/kg 的砷和 79.4mg/kg 的硼）和地下水中砷和硼均有明显的富集。此外，河水 Ca/(Na+K)摩尔比和沉积物化学蚀变指数（CIA）的降低，以及沿河流方向较重 δO 值的增加，表明碳酸盐和硅酸盐风化在河流上游更为显著，而在下游，蒸发岩的溶解作用得到了增强。河水砷和硼的富集主要是由温泉排放引起的，而碳酸盐风化通过为与 HBO 或 B(OH)竞争吸附提供 HCO，促进了 B 的富集。此外，地表水补给地下水导致色林错下游冲积含水层中砷和硼浓度升高。本研究强调了流域内风化过程的变化可能会显著促进砷和硼的富集，从而提高我们对流域尺度上痕量元素运移和富集的水文地球化学控制因素的认识。
