Collaborative Research: Quantifying rare earth element transport in aquifers using field, laboratory, and numerical approaches

约翰松地下水是美国饮用水的主要来源，占世界淡水供应量的68%以上。因此，确保当前人口的地下水质量并保护其免受未来的污染是非常令人关切的。地下水的消耗会增加人体对特定重金属的负荷，地下水与埋藏的核废料的相互作用被认为是这些物质最有可能向环境释放的机制。了解含水层中重金属的地球化学对于开发准确的溶质运移模型至关重要，该模型可以用来预测重金属在含水层中随时间和不同环境条件下的去向和运移。我们试图量化稀土元素(REE)在真实含水层中沿地下水流动路径的浓度和行为，并建立这些重金属的地下水流动和迁移耦合模型。稀土元素之所以引起人们的兴趣，是因为它们有可能作为水-岩石反应的地球化学示踪剂，而且它们与超铀的化学相似之处使它们在研究含水层中的放射性污染物方面具有吸引力的天然类似物。我们的研究目标是：(1)阐明稀土元素在特征良好的含水层中沿地下水流动路径的地球化学行为，强调它们的浓度、分馏模式和形态。(2)建立一个针对每个含水层的稀土元素的表面和溶液联合络合模型，该模型也可以广泛应用于其他系统。(3)建立并实现了地下水系统中稀土元素流动与反应运移耦合模拟模型。为了实现这些目标，我们将在三年内实施一项综合的野外、实验室和数值模拟研究。我们将利用两个特征良好的含水层(即德克萨斯州的卡里佐·桑德和佛罗里达州的弗洛里丹含水层)作为该项目的实地部分。两者都是典型的饮用水含水层，代表着共同的、尽管组成不同的系统。研究中产生的数据将对“校准”含水层中稀土元素的反应运移模型至关重要，并将提高我们对反应性溶质运移的总体理解。

0126222Johannesson Groundwater is the principal source of drinking water in the United States, and represents over 68% of the world's fresh water supply. Therefore, assuring the quality of groundwater for current populations and protecting it from future contamination is of great concern. Groundwater consumption can increase the loading of specific heavy metals to our bodies, and interaction of groundwaters with buried nuclear wastes is considered the most likely release mechanism of these materials to the environment. Understanding the geochemistry of heavy metals in aquifers is critical to developing accurate solute transport models, which can be employed to predict the fate and transport of heavy metals in aquifers over time and under different environmental conditions. We seek to quantify rare earth elements (REE) concentrations and behavior along groundwater flow paths in real aquifers, and develop a coupled groundwater flow and transport model for these heavy metals. The REEs are of interest because of their potential as geochemical tracers of water-rock reactions, and because their chemical similarities to transuranics makes them attractive natural analogs for studying radioactive contaminants in aquifer. Our research objectives are: (1) To elucidate the geochemical behavior of REEs along groundwater flow paths in well characterized aquifers emphasizing their concentrations, fractionation patterns, and speciation.(2) To develop a combined surface and solution complexation model for the REEs that is specific to each aquifer, but can also be broadly applied to other systems. (3) To assemble and implement a coupled groundwater flow and reactive transport simulation model for REEs in groundwater systems. To accomplish these objectives, we will implement an integrated field, laboratory, and numerical modeling study over a period of three years. We will utilize two well characterized aquifers (i.e., Carrizo Sand, Texas; Floridan aquifer, Florida) for the field component of the project. Both are typical drinking water aquifers that represent common, albeit, compositionally different systems. The data generated in the study will be crucial for "calibrating" reactive transport models for REEs in aquifer, and will improve our general understanding of reactive solute transpor