The enrichment of As in the western Qinghai–Tibet Plateau and its surrounding basins has been widely reported. However, the spatial distribution of arsenic content in the Surface’s Critical Zone (SCZ) of the Shiquan River Basin in the western Qinghai–Tibet Plateau is poorly understood, as is the mechanisms through which water–rock interactions and surface water-groundwater interactions influence arsenic enrichment and migration. In this study, the contents of arsenic and other chemical components in surface water, groundwater, sediment, soil, and rock in the Shiquan River Basin were analyzed to investigate the hydrogeochemical process of arsenic migration. The results indicate that the concentration ratios of HCO3–/(Na++K+), Ca2+/(Na++K+), Na+/(Na++Ca2+) and δ18O in the surface water of the Shiquan River Basin vary along the runoff path. Carbonate and silicate weathering dominate the middle and upper reaches, while evaporite dissolution gradually increases in the lower reaches. Arsenic is enriched in rocks, soil, surface water, and groundwater in the SCZ, with slightly higher concentrations found in the surface water, sediment, and soil in the middle reaches than in the upper and lower reaches. This spatial distribution suggested that the hydrogeochemical processes along the runoff path controlled the distribution of As in the basin. Water–rock interactions and hot spring discharge of arsenic-bearing minerals contributed to its enrichment in the basin, while adsorption by riverbed sediment led to the gradual decay of dissolved arsenic. The underlying aquifer (alluvial-diluvial layer) recharged by surface water is the main source of high arsenic concentration in groundwater. The findings of this study can serve as a reference for studying arsenic in similar high-arsenic basins worldwide.

中文翻译：

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青藏高原西部十泉河流域地表临界带砷富集与运移的水文地球化学过程


青藏高原西部及其周围流域的砷富集已被广泛报道。然而，人们对青藏高原西部十泉河流域地表临界区 （SCZ） 中砷含量的空间分布知之甚少，水-岩石相互作用和地表水-地下水相互作用影响砷富集和迁移的机制也知之甚少。本研究对十泉河流域地表水、地下水、沉积物、土壤和岩石中砷等化学成分的含量进行了分析，研究了砷迁移的水文地球化学过程。结果表明：石泉河流域表层水中HCO3–/（Na++K+）、Ca2+/（Na++K+）、Na+/（Na++Ca2+）和δ18O的浓度比沿径流路径变化。碳酸盐和硅酸盐风化作用在中上游占主导地位，而蒸发岩溶解在下游逐渐增加。SCZ 的岩石、土壤、地表水和地下水中富含砷，中游地表水、沉积物和土壤中的浓度略高于上下游。这种空间分布表明，沿径流路径的水文地球化学过程控制了流域中 As 的分布。水岩相互作用和含砷矿物的温泉排放促进了其在流域内的富集，而河床沉积物的吸附导致溶解的砷逐渐腐烂。由地表水补给的底层含水层（冲积-稀释层）是地下水中砷浓度高的主要来源。 本研究结果可作为研究全球类似高砷盆地中砷的参考。