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

0126222约翰内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污染是非常值得关注的问题。地下水的消耗会增加特定重金属对我们身体的负荷，地下水与掩埋的核废料的相互作用被认为是这些物质向环境释放的最有可能的机制。了解含水层中重金属的地球化学特征对于建立准确的溶质运移模型至关重要，该模型可用于预测含水层中重金属随时间和不同环境条件下的命运和运移。我们试图量化稀土元素（REE）在实际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耦合地下水流动和运输模型。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反应的地球化学示踪剂，而且它们与超铀元素的化学相似性使它们成为研究含水层放射性污染物的有吸引力的天然类似物。我们的研究目标是：(1)阐明稀土元素沿地下水流动路径的地球化学行为，强调其浓度、分异模式和形态。(2)建立针对各含水层，但也可广泛应用于其他体系的稀土元素表面和溶液复合络合模型。(3)构建并实现地下水系统中稀土元素的地下水流动与反应输运耦合模拟模型。为了实现这些目标，我们将在三年的时间里实施一个综合的现场、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Carrizo Sand和佛罗里达州的Floridan含水层）作为项目的现场组成部分。两者都是典型的饮用水含水层，代表了共同的，尽管在组成上不同的系统。研究中产生的数据对于“校准”含水层中稀土元素的反应输运模型至关重要，并将提高我们对反应溶质输运的总体理解

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