Abstract High fluoride (F−) concentrations in groundwater are a recognized environmental health concern, and over 200 million people around the world routinely drink well water with F− concentrations that exceed safety guidelines. Groundwater in the Independence Basin of Central Mexico reaches F− concentrations of 15.5 mg L−1, which are over an order of magnitude greater than the World Health Organization limit of 1.5 mg L−1, but knowledge of sources and geochemical conditions responsible for releasing F− into solution is preliminary. The objectives of this work were to define F− hosts within a range of Independence Basin aquifer rock types and quantify chemical controls on F− release into solution. Solid-phase concentrations of F− in well-drill cuttings display no apparent depth dependence but are greatest within andesite, near-surface uncemented alluvium, and well-cemented Paleocene conglomerate samples, and they are least within volcanic glass, rhyolite, and ash matrix samples. Chemical extractions showed that large amounts of F− are bound with metal oxides/oxyhydroxides in all samples. Batch experiments examining F− release from aquifer materials under evolving groundwater conditions (i.e. increasing pH and specific conductance) revealed that F− may be released into solution with elevated pH but only slightly mobilized with increasing specific conductance. Therefore, declining aquifer water levels tapping into older, more mineralized groundwater (with high conductivity) in the Independence Basin may not have as great of an effect on F− release to solution than does evolving and increasing groundwater pH. Accordingly, the degree of rock weathering and pH of solution play the greatest roles in regulating the release of F− to groundwater, and results from this study may be used to better predict where F− groundwater contamination is most probable in aquifers around the world.

中文翻译：

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墨西哥独立盆地氟化物释放到地下水的地质来源和化学控制

摘要 地下水中的高氟 (F-) 浓度是公认的环境健康问题，全世界有超过 2 亿人经常饮用 F- 浓度超过安全指南的井水。墨西哥中部独立盆地的地下水达到 15.5 mg L-1 的 F− 浓度，这比世界卫生组织 1.5 mg L−1 的限制大一个数量级，但对排放源和地球化学条件的了解F-进入溶液是初步的。这项工作的目标是在独立盆地含水层岩石类型的范围内定义 F- 宿主，并量化对 F- 释放到溶液中的化学控制。钻井岩屑中 F− 的固相浓度没有明显的深度依赖性，但在安山岩中最大，近地表未胶结的冲积层和胶结良好的古新世砾岩样品，它们在火山玻璃、流纹岩和灰基质样品中最少。化学提取表明，在所有样品中，大量 F− 都与金属氧化物/羟基氧化物结合。在不断变化的地下水条件（即增加 pH 值和比电导率）下检查从含水层材料中释放 F- 的批量实验表明，F- 可能会在 pH 值升高时释放到溶液中，但随着比电导率的增加仅轻微移动。因此，在独立盆地利用更老、矿化程度更高的地下水（具有高电导率）的含水层水位下降对 F− 释放到溶液中的影响可能不如演变和增加地下水 pH 值的影响大。因此，