Isotopic Tracing of Sources and Cycling of Hazardous Metal Mixtures

项目2摘要 在强心研究（SHS）中调查的美洲原住民社区显示砷（As）明显较高， 尿中的铀（U）和硒（Se）浓度相对于美国人口的平均水平。大部分 接触有害的金属混合物来自饮用的地下水，这些地下水通常被金属污染， 安全标准美国的部落土地往往与矿藏、铀矿和金属矿相吻合 含水层的污染。在北方平原，饮用水中铀和砷浓度升高反映了 这是由于含水层中自然发生的富集以及部落社区附近采矿的遗留问题。项目2 哥伦比亚大学北方平原超级基金研究计划将使用同位素 U和Se的组成，因为这些元素对含水层中的氧化还原变化敏感，以推断来源， 控制污染物暴露的过程。铀和硒的氧化还原化学控制着它们的水溶性 地下水中的浓度;氧化物种是移动的且有毒的，而还原物种是 不溶的溶解的U和Se的浓度受到多种过程的影响（例如，稀释，吸附， 分散），是地下水中氧化还原诱导的命运和循环的不良指标。因此， 地下水中溶解的U和Se及其浓度对于研究氧化还原诱导的 （im）动员、追踪吸收和人类接触。我们将使用U和Se同位素比值来表征 地下水中的氧化还原反应，获得关于反应进程的唯一机理信息。这些 数据将帮助我们确定本地和更远的来源，以及运输和循环过程中的金属， 在北/南达科他州SHS社区的地下水。此外，我们将开发同位素示踪剂， 环境暴露对人体中铀和硒循环的影响。具体目标是：（1）确定 地下水样品中U和Se同位素比值或“等截面”空间分布模式。这将使用 高分辨率数据和模型从项目1到目标威尔斯井内和周围的U，As和Se热点， 同位素特征我们还将确定这些热点周围的本地与远端污染源。 (2)确定地下水中天然存在的还原性U和Se去除水平， 根据U和Se同位素比值的时间演变，确定了潜在As释放的条件。我们将 表征U和Se的氧化还原转化以及多个地下水源（如果有）的潜在混合。 (3)使用同位素示踪剂确定人类暴露于环境污染。我们将开发一个 一种新的非侵入性方法来跟踪饮用水中U和Se的金属暴露。为此，我们将测量U 和硒同位素比率，以限制主要接触源和受影响的人口， 水等深线和项目3的观测数据。我们的研究结果将有助于评估暴露于 危险金属混合物、受污染含水层的监测和管理， 使用非侵入性诊断工具检测环境源。

Project 2 Summary Native American communities surveyed in the Strong Heart Study (SHS) show markedly higher arsenic (As), uranium (U) and selenium (Se) concentrations in urine relative to the average US population. Much of the exposure to hazardous metal mixtures comes from drinking groundwater contaminated with metals often above safety standards. Tribal lands in the US often coincide with mineral deposits, U mining, and metal(loid) contamination in aquifers. In the Northern Plains, elevated concentrations of U and As in drinking water reflect naturally occurring enrichment in aquifers, as well as the legacy of mining near tribal communities. Project 2 of the Columbia University Northern Plains Superfund Research Program (CUNP-SRP) will use isotopic compositions of U and Se, as these elements are sensitive to redox changes in the aquifer, to infer sources and processes controlling contaminant exposures. Redox chemistry of U and Se controls their aqueous concentrations in groundwater; the oxidized species are mobile and toxic whereas the reduced species are insoluble. Concentrations of dissolved U and Se are affected by multiple processes (e.g., dilution, adsorption, dispersion) and are poor indicators of redox-induced fate and cycling in groundwater. Thus, isotope ratios of dissolved U and Se in groundwater, in tandem with concentrations, are invaluable for studying redox-induced (im)mobilization, and tracing uptake and human exposure. We will use U and Se isotope ratios to characterize redox reactions in groundwater, acquiring unique mechanistic information about the reaction progress. These data will help us define local and more distal sources, and the transport and cycling processes of metals in groundwater within the SHS communities in North/South Dakota. Furthermore, we will develop isotopic tracers of U and Se cycling in humans impacted by environmental exposures. The specific aims are to: (1) Determine spatial distribution pattern of isotope ratios or “isoscapes” of U and Se in groundwater samples. This will use high-resolution data and models from Project 1 to target wells within and around U, As and Se hotspots for isotopic characterization. We will also identify local versus distal sources of contamination around these hotspots. (2) Determine the levels of naturally occurring reductive U and Se removal from groundwater and identify conditions for potential As release based on the temporal evolution of U and Se isotope ratios. We will characterize the redox transformation of U and Se and potential mixing of multiple groundwater sources (if any). (3) Determine human exposure from the environmental contamination using isotopic tracers. We will develop a novel non-invasive method to track metal exposure from U and Se in drinking water. For this, we will measure U and Se isotope ratios in urine to constrain primary exposure sources and affected populations by linking those to water isoscapes and the observational data from Project 3. Our results will help evaluate risk of exposure to hazardous metal mixtures, monitoring and management of contaminated aquifers, and linking exposures to environmental sources using a non-invasive diagnostic tool.