Department of Chemistry, MSC03 2060, University of New Mexico, Albuquerque, New Mexico 87131, USA.
Environ Sci Process Impacts. 2017 Apr 19;19(4):605-621. doi: 10.1039/c6em00612d.
The mobility and accumulation of uranium (U) along the Rio Paguate, adjacent to the Jackpile Mine, in Laguna Pueblo, New Mexico was investigated using aqueous chemistry, electron microprobe, X-ray diffraction and spectroscopy analyses. Given that it is not common to identify elevated concentrations of U in surface water sources, the Rio Paguate is a unique site that concerns the Laguna Pueblo community. This study aims to better understand the solid chemistry of abandoned mine waste sediments from the Jackpile Mine and identify key hydrogeological and geochemical processes that affect the fate of U along the Rio Paguate. Solid analyses using X-ray fluorescence determined that sediments located in the Jackpile Mine contain ranges of 320 to 9200 mg kg U. The presence of coffinite, a U(iv)-bearing mineral, was identified by X-ray diffraction analyses in abandoned mine waste solids exposed to several decades of weathering and oxidation. The dissolution of these U-bearing minerals from abandoned mine wastes could contribute to U mobility during rain events. The U concentration in surface waters sampled closest to mine wastes are highest during the southwestern monsoon season. Samples collected from September 2014 to August 2016 showed higher U concentrations in surface water adjacent to the Jackpile Mine (35.3 to 772 μg L) compared with those at a wetland 4.5 kilometers downstream of the mine (5.77 to 110 μg L). Sediments co-located in the stream bed and bank along the reach between the mine and wetland had low U concentrations (range 1-5 mg kg) compared to concentrations in wetland sediments with higher organic matter (14-15%) and U concentrations (2-21 mg kg). Approximately 10% of the total U in wetland sediments was amenable to complexation with 1 mM sodium bicarbonate in batch experiments; a decrease of U concentration in solution was observed over time in these experiments likely due to re-association with sediments in the reactor. The findings from this study provide new insights about how hydrologic events may affect the reactivity of U present in mine waste solids exposed to surface oxidizing conditions, and the influence of organic-rich sediments on U accumulation in the Rio Paguate.
本研究采用水化学、电子探针、X 射线衍射和光谱分析等方法，调查了新墨西哥州拉古纳普韦布洛附近帕瓜特河（Rio Paguate）铀（U）的迁移和积累情况。帕瓜特河的地表水水源中 U 浓度升高并不常见，但它是一个独特的地点，引起了拉古纳普韦布洛社区的关注。本研究旨在更好地了解杰克派勒矿（Jackpile Mine）废弃矿山废物沉积物的固相化学性质，并确定影响帕瓜特河 U 命运的关键水文地质和地球化学过程。X 射线荧光的固相分析表明，位于杰克派勒矿的沉积物中 U 的含量范围为 320 至 9200mgkg。X 射线衍射分析表明，暴露于几十年风化和氧化作用的废弃矿山废物固体中存在钍石，一种含 U(iv)的矿物。这些含 U 矿物从废弃矿山废物中的溶解可能会导致 U 在降雨事件期间发生迁移。在最接近矿山废物的地表水中采样的 U 浓度在西南季风季节最高。2014 年 9 月至 2016 年 8 月采集的样品显示，杰克派勒矿附近的地表水中 U 浓度较高（35.3 至 772μg L），而距矿山 4.5 公里下游的湿地中的 U 浓度较低（5.77 至 110μg L）。与湿地沉积物中较高的有机质（14-15%）和 U 浓度（2-21mgkg）相比，位于河道床和岸边的沉积物中的 U 浓度较低（范围为 1-5mgkg）。在批实验中，湿地沉积物中约 10%的总 U 可与 1mM 碳酸氢钠络合；这些实验中溶液中的 U 浓度随时间推移而下降，这可能是由于在反应器中与沉积物重新结合所致。本研究的结果提供了新的见解，说明水文事件如何影响暴露于地表氧化条件下的矿山废物固相中 U 的反应性，以及富含有机质的沉积物对帕瓜特河 U 积累的影响。
