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、修复和预防来自矿山、工业场所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输特性，测量溶解成分的浓度和形态，鉴定初级和次级相以及微生物种群的特征。我们开发并应用反应溶质传输模型来帮助解释控制溶解成分释放和衰减的相互作用。我们最近实施了多收集器电感耦合质谱仪（MC-ICP-MS）技术来测量金属和类金属的同位素比率，包括Cr， Cu, Fe, Hg, Ni， Se和Zn。在动态流动系统中解释这些测量结果需要考虑输运和化学反应对同位素比率的影响。我们将同位素分馏纳入反应输运模型MIN3P，并描述了实验室色谱系统中S和Cr同位素的分馏。我们最近在同步加速器设备上进行了流式细胞实验，监测氧化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确定了反应机理、反应速率、反应过程和同位素分馏。在接下来的五年里，我将加快非传统同位素测量在地下水污染和修复研究中的应用研究。MC-ICP-MS稳定同位素比的测量受到一系列来自等压分子和类似质量和电荷的多原子分子的潜在干扰。通过将目标元素与溶液中的其他元素分离，以及测量干扰元素的其他同位素的浓度，可以克服许多这些干扰。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，需要进一步开发将这些测量应用于地下水污染地点的复杂溶液特征。此外，我们将采用技术来测定其他元素的同位素比率，包括Cd、Mo和Sb。将进行实验室批量实验，以评估在不同地球化学机制（包括吸附、沉淀、还原和氧化）下反应过程的渐进阶段同位素分馏的程度。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。在动态流动条件下，将进行色谱柱和流动池评估同位素分馏。这些实验将分离出单独的反应机制，包括吸附、沉淀和还原/氧化反应。将对进水和出水的水样以及沿柱长度收集的水样进行测量，以量化溶解成分的去除率和同位素比率的变化。选择流动通过细胞实验将监测使用同步加速器x射线吸收光谱测量氧化状态的变化，伴随同位素分数。我们在阿贡国家实验室的先进光源上获得了光束时间来完成这些实验。柱实验结果将使用包含同位素分馏的MIN3P反应输运模型进行解释。

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.