In the Main Ethiopian Rift (MER) area, rural populations often use water that exceeds the World Health Organization thresholds for fluoride (F^–) and arsenic (As), two elements that are hazardous for human health. In this study, twenty-nine water samples were collected from lakes and hot and cold springs in southern MER to investigate source(s) and health-risk of the F^– and As contamination. According to major ion and trace element analyses, only cold spring water is safe for consumption, whereas hot spring water is the most contaminated. Leaching tests performed with the MER rhyolitic volcanic rocks and their weathered products (fluvio-lacustrine sediments) demonstrate that the main cause of the F^– and As release is geogenic, i.e., not related to anthropogenic activities. The weathering of volcanic glass and minerals (apatites, clays, hydro-oxides) by CO₂-bearing alkaline water induces the mobilisation of F^– and As from solid to liquid phase. This process is particularly fast, when fluvio-lacustrine sediments are involved, and can be further enhanced by hot groundwater leaching. This study, investigating the distribution, sources, and mechanisms of F^– and As release in MER water, could be of interest also for other sectors of the East African Rift and other similar volcano-tectonic settings.

中文翻译：

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埃塞俄比亚主要裂谷水域中氟化物和砷的起源

在埃塞俄比亚的主要裂谷（MER）地区，农村居民经常使用的水超过了世界卫生组织的氟化物（F ^–）和砷（As）的阈值，这是对人体健康有害的两个元素。在这项研究中，29个水样，从湖泊和冷热泉收集在南部MER调查源（S）和在F的健康风险^-和As污染。根据主要的离子和痕量元素分析，只有冷泉水可以安全饮用，而温泉水是污染最严重的。浸出与MER流纹质火山岩及其风化产物（河湖相沉积）进行的测试表明，F的主要原因^-由于释放是地源的，即与人为活动无关。火山玻璃和矿物质（磷灰石，粘土，氢氧化物）通过CO风化₂荷瘤碱性水诱导F的动员^-液相和如从固体。当涉及河流湖泊沉积物时，此过程特别快，并且可以通过热水地下水淋洗进一步增强。这项研究调查了分布，来源和F的机制^-而作为释放MER水，可能是兴趣也东非大裂谷和其他类似的火山构造设置的其他部门。