Abstract Rio Tarapaya, a major tributary of the upper Rio Pilcomayo and a crucial water resource in the arid Southeastern Bolivian highlands, has been impacted by in-stream mine tailings and acid rock drainage over the past five centuries, from historic and ongoing mining at Cerro Rico de Potosi. Identification of the effects of in-stream mine tailings on the waters of Rio Tarapaya is essential to better understand the dynamics of these complex systems and propose successful management strategies. A study was performed on river waters and sediments at six sites in a reach of Rio Tarapaya, beginning at the city limits of Potosi and ending just after the confluence with Rio Cayara, a relatively unimpaired river 7.3 km downstream. Concentrations of dissolved metals (such as Fe, Al, Mn, and As) in the Ca–Mg–HCO3–SO4 dominated stream were generally orders of magnitude greater than Bolivian receiving water body criteria and United Nations Food and Agriculture Organization irrigation and livestock drinking water guidelines. Variability of Ca and Mg in water and sediment was controlled by dissolution of gypsum, dolomite and calcite, which was supported by Spearman correlation coefficients. The primary ionic products of in-stream sulfide mineral weathering (SO42−, Fe, Al, Mn, Zn and As), are the dominant ions of stream water and sediment leachate. Results are consistent with PHREEQC modeling of minerals such as gibbsite, melanterite, goethite, calcite and dolomite. In general, the reactivity of bed material increased and stream water quality decreased with increasing distance from Potosi. Metals and metalloids are spiraling downstream via seasonally driven particle transport, sulfide weathering, and salt dissolution coupled with biotic interactions. The reactivity of the millions of tonnes of in-stream tailings in Rio Tarapaya and persistence of contemporary illicit tailings discharges indicates that the upper Rio Pilcomayo will remain severely degraded for the foreseeable future unless substantial remediation is undertaken.

中文翻译：

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河内尾矿对玻利维亚波托西州皮尔科马约河源头支流的水质影响

摘要 Rio Tarapaya 是 Rio Pilcomayo 上游的主要支流，也是玻利维亚东南部干旱高地的重要水资源，在过去的五个世纪中，由于 Cerro 的历史性和持续性采矿而受到尾矿和酸性岩排水的影响。里科·德·波托西。识别河内尾矿对 Rio Tarapaya 水域的影响对于更好地了解这些复杂系统的动态并提出成功的管理策略至关重要。对 Rio Tarapaya 河段的六个地点的河水和沉积物进行了研究，从波托西的城市边界开始，在与 Rio Cayara 汇合后结束，Rio Cayara 是下游 7.3 公里处相对未受损害的河流。溶解金属（如 Fe、Al、Mn、和 As) 在 Ca-Mg-HCO3-SO4 主导的河流中，通常比玻利维亚接收水体标准和联合国粮食及农业组织灌溉和牲畜饮用水指南大几个数量级。水和沉积物中 Ca 和 Mg 的变化受石膏、白云石和方解石的溶解控制，这得到 Spearman 相关系数的支持。流中硫化物矿物风化的主要离子产物（SO42−、Fe、Al、Mn、Zn 和 As）是流水和沉积物渗滤液的主要离子。结果与矿物的 PHREEQC 模型一致，例如三水铝石、墨脱石、针铁矿、方解石和白云石。总的来说，随着与波托西距离的增加，床层物质的反应性增加，溪流水质下降。通过季节性驱动的粒子传输、硫化物风化和盐溶解以及生物相互作用，金属和类金属正在向下游呈螺旋式上升。Rio Tarapaya 数百万吨尾矿的反应性和当代非法尾矿排放的持续存在表明，除非采取实质性补救措施，否则在可预见的未来，Rio Pilcomayo 上游将继续严重退化。