Abstract Many sedimentary aquifers across the globe are contaminated with As, a known toxicant and carcinogen, thereby making millions of people vulnerable to a health hazard. Although the source of As enrichment is being linked to the provenance of the sediments (i.e. hard rocks), there are limited studies of groundwater As enrichment in hard rock areas. In this study, we collected the groundwater samples from complex hard rock aquifer system across the Himalayan collision zone in Upper Indus River Basin (UIRB) to understand the source and to evaluate the hydrogeochemical processes responsible for groundwater As mobilization. The study suggests that groundwater As enrichment comes from volcanic rocks and ophiolitic melange. Such, As contaminated aquifers are widely used for groundwater exploitation for drinking and other purposes in Ladakh (UIRB). The results indicated that As enrichment occurs with an increase in temperature and depth. The results also indicated that the groundwater in Ladakh is described by multiple hydrochemical facies with pH circum-neutral to alkaline in nature. Higher pH, Fe2+ and Mn and lower ORP, NO3−, and SO42− in groundwater are found to be associated with high As groundwater indicating metal oxides/hydroxides under reducing conditions are predominantly controlling the groundwater As mobilization.

中文翻译：

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拉达克上印度河流域 (UIRB) 高海拔基岩含水层中的地质地下水砷

摘要 全球许多沉积含水层都被砷污染，砷是一种已知的有毒物质和致癌物质，从而使数百万人容易受到健康危害。尽管 As 富集的来源与沉积物（即硬岩）的来源有关，但对硬岩地区地下水 As 富集的研究有限。在这项研究中，我们从上印度河流域 (UIRB) 喜马拉雅碰撞带的复杂硬岩含水层系统中收集地下水样本，以了解来源并评估负责地下水流动的水文地球化学过程。该研究表明，地下水 As 富集来自火山岩和蛇绿混杂岩。例如，受污染的含水层在拉达克 (UIRB) 被广泛用于饮用水和其他用途的地下水开采。结果表明，随着温度和深度的增加，As富集发生。结果还表明，拉达克的地下水由多种水化学相描述，pH 值在中性至碱性之间。发现地下水中较高的 pH、Fe2+ 和 Mn 以及较低的 ORP、NO3- 和 SO42- 与高砷地下水有关，这表明还原条件下的金属氧化物/氢氧化物主要控制地下水的 As 流动。