Prediction and Remediation Strategies for Groundwater Contaminated by Dissolved Metals

我的研究计划的长期目标是开发改进的技术，用于预测、补救和预防来自矿场、工业场址和其他污染源的地下水污染。我的研究包括确定地下水流动系统的物理和溶质运移特征，测量溶解成分的浓度和形态，识别初级和次级相，以及微生物种群的特征。我们开发和应用反应溶质传输模型，以帮助解释控制溶解成分释放和衰减的相互作用。*我们最近采用了多收集电感耦合质谱仪(MC-ICPMS)技术来测量金属和类金属的同位素比率，包括铬、铜、铁、汞、镍、硒和锌。在动态流动系统中解释这些测量需要考虑运输和化学反应对同位素比率的影响。我们在反应输运模型MIN3P中加入了同位素分馏，并描述了S和铬同位素在实验室柱系统中的分馏。我们最近在同步加速器设施中进行了流通式电池实验，监测氧化状态的变化和相应的同位素比率的变化。这种方法以前所未有的详细程度提供了反应机理、反应速率、反应进度和同位素分馏的确定。*在接下来的五年里，我将加快研究非传统同位素测量在地下水污染和修复研究中的应用。MC-ICPMS对稳定同位素比值的测定受到同压分子和多原子分子相似质量和电荷的一系列潜在干扰的影响。其中许多干扰可以通过将目标元素与溶液中的其他元素分离，以及通过测量干扰元素的其他同位素的浓度来克服。我们已经开发了在含有低浓度总溶解固体(TDS)的溶液中进行同位素测量的程序，但需要进一步开发，以将这些测量应用于地下水污染地点特有的复杂溶液。此外，我们将实施其他元素的同位素比率测定技术，包括Cd、Mo和Sb。*将进行实验室批量实验，以评估在不同的地球化学制度下，包括吸附、沉淀、还原和氧化的反应进展阶段的同位素分馏程度。这些实验的测量结果将使用地球化学模型进行解释，并与理论计算进行比较。*将进行色谱柱和流通池，以评估在动态流动条件下的同位素分馏。这些实验将分离出单独的反应机理，包括吸附、沉淀和还原/氧化反应。将对进水口和出水口的水样以及沿柱子长度收集的水样进行测量，以量化溶解成分的去除速度和同位素比率的变化。将使用同步加速器X射线吸收光谱来监测选定的流通式电池实验，以测量伴随着同位素部分的氧化状态的变化。我们已经在阿贡国家实验室的高级光源上获得了光束时间，以完成这些实验。柱实验结果将使用反应传输模型MIN3P进行解释，该模型包含了同位素分馏。

The long-term goal of my research program is to develop improved techniques for the prediction, remediation and prevention of groundwater contamination derived from mine sites, industrial sites and other sources of contamination. My research includes determination of the physical and solute transport characteristics of groundwater flow systems, measurements of the concentration and speciation of dissolved constituents, identification of primary and secondary phases and characterization of microbiological populations. We develop and apply reactive solute transport models to assist in interpretation of the interactions that control the release and attenuation of dissolved constituents.* We have recently implemented multicollector inductively coupled mass spectrometer (MC-ICP-MS) techniques to measure the isotopic ratios of metals and metalloids, including Cr, Cu, Fe, Hg, Ni, Se and Zn. Interpretation of these measurements in dynamic flow systems requires consideration of the effects of transport and chemical reactions on isotope ratios. We have incorporated isotope fractionation into the reactive transport model MIN3P, and described fractionation of S, and Cr isotopes in laboratory column systems. We have recently conducted flow-through cell experiments at synchrotron facilities monitoring changes in oxidation state and corresponding changes in isotope ratios. This approach provides determinations of the reaction mechanism, reaction rate, reaction progress and isotope fractionation at an unprecedented level of detail. * Over the next five years I wlll accelerate my research on the application of non-traditional isotope measurements to studies of groundwater contamination and remediation. Measurements of stable isotope ratios by MC-ICP-MS are affected by a series of potential interferences from isobaric molecules and polyatomic molecules similar mass and charge. Many of these interferences can be overcome by separation of the target element from other elements in the solution, and by measurements of the concentrations of other isotopes of the interfering elements. We have developed procedures for isotope measurements within solutions containing low concentrations of total dissolved solids (TDS), additional development is required to apply these measurements to the complex solutions characteristic of sites of groundwater contamination. In addition, we will implement techniques for determination of isotope ratios of additional elements, including Cd, Mo and Sb. * Laboratory batch experiments will be conducted to assess the extent of isotope fractionation at progressive stages of reaction progress under differing geochemical regimes, including adsorption, precipitation, reduction and oxidation. The measurements from these experiments will be interpreted using geochemical models and compared to theoretical calculations. * Column and flow-through cell will be conducted to assess isotope fractionation under dynamic flow conditions. These experiments will isolate individual reaction mechanisms, including adsorption, precipitation and reduction/oxidation reactions. Measurements will be made on the influent and effluent water samples and on water samples collected along the length of the column to quantify the rate of removal of dissolved constituents and the changes in isotope ratio. Select flow-through cell experiments will be monitored using synchrotron X-ray absorption spectroscopy to measure changes in oxidation state that accompany isotopic fraction. We have obtained beam time at the Advanced Photo Source at the Argonne National Laboratory to complete these experiments. Column experiment results will be interpreted with using the reactive transport model MIN3P, which incorporates isotope fractionation.