Collaborative Research: The Effect of Dynamic Surface-Associated Phase Change on Environmental Mobility in Unsaturated Environments

俄克拉何马大学/新墨西哥州立大学自然和工程过程会导致非饱和区土壤的含水量随着时间的推移而显著变化。蒸发引起的水分含量的动态下降会导致污染物和其他孔隙水成分浓度的局部增加，从而导致污染物吸附增强和污染物沉淀的形成。由于吸附/解吸和沉淀/溶解过程往往具有很强的速率限制，动态含水量变化可能对无机和有机污染物的长期迁移率产生强烈影响，这些过程可能增加或减少长期迁移率。到目前为止，很少有定量信息可以用来模拟不饱和介质中的动态吸附或相变过程，或预测它们对污染物迁移的影响。这项工作的目的是量化水含量和成分的动态变化与发生的相应污染物相变之间的联系，重点是量化相变与地下流动性之间的最终联系。该项目最初将重点关注六种环境关注的独立化学污染物，四种有机化合物和两种无机化合物，所有这些都被选中表现出广泛的化学行为（吸附、形态形成、络合、固体形成），可能影响动态不饱和条件下的行为。工作将集中在三个紧密耦合的任务上，包括：1)动态不饱和实验；2)批量分析和光谱显微测量；3)结合动态地球化学/不饱和输运模型来解释前两项任务的结果，并综合和扩展实验工作的结果，以更好地理解和预测相变对污染物长期迁移的环境影响。所提出的工作的结果将提供必要的工具，以加强我们对自然和工程变化中含水量的污染物相变化的理解，并将为管理和修复不饱和区污染的增强决策过程提供所需的定量信息。由于降水和蒸发等自然过程，或者由于人类活动，土壤的含水量会随时间发生很大变化。这种含水量的变化会对有害无机物质（如金属和放射性化合物）以及有机物质（如药品、农药和碳氢化合物）的流动性产生巨大影响。该项目将提高我们预测土壤环境中有机和无机污染物随土壤含水量变化的能力。我们对土壤含水量和土壤中污染物流动性之间的联系的更好理解将有助于改进土壤修复技术的发展。

CBET-1336083/1336579Tohren C. Kibbey/Charalambos PapelisThe University of Oklahoma/New Mexico State UniversityNatural and engineered processes can cause the water content of soils in the unsaturated zone to vary significantly over time. Dynamic decreases in water content caused by evaporation can cause local increases in the concentrations of contaminants and other porewater constituents, which can drive enhanced contaminant sorption and the formation of contaminant precipitates. Because sorption/desorption and precipitation/dissolution processes tend to be strongly rate-limited, dynamic water content changes can have a strong influence on the long-term mobility of inorganic and organic contaminants, with these processes either increasing or decreasing long-term mobility. To date, little quantitative information is available that would allow realistic modeling of dynamic sorption or phase change processes in unsaturated media, or prediction of their impact on contaminant mobility. The objective of this work is to quantify the link between dynamic changes in water content and composition and the corresponding phase changes of contaminants that take place, with emphasis on quantifying the ultimate connection between phase changes and subsurface mobility. This project will initially focus on six separate chemical contaminants of environmental concern, four organic compounds and two inorganic compounds, all selected to exhibit a wide range of chemical behaviors (adsorption, speciation, complexation, solid formation) likely to influence behavior under dynamic unsaturated conditions. Work will be focused around three tightly-coupled tasks and will include 1) dynamic unsaturated experiments; 2) batch analyses and spectroscopic-microscopic measurements; and 3) coupled dynamic geochemical/unsaturated transport modeling to interpret the results of the first two tasks and to synthesize and expand the results of experimental work to better understand and predict environmental implications of phase change on long term contaminant mobility. The results of the proposed work will provide the tools needed to enhance our understanding of contaminant phase changes during natural and engineered changes in water content, and will provide quantitative information needed for enhanced decision making processes for managing and remediating contamination in the unsaturated zone.The water content of soils can vary substantially over time either because of natural processes, such as precipitation and evaporation, or because of human activities. This water content variability can have a dramatic effect on the mobility of hazardous inorganic substances, such as metals and radioactive compounds, as well as organic substances, such as pharmaceuticals, pesticides, and hydrocarbons. This project will enhance our ability to predict the movement of organic and inorganic contaminants in the soil environment as a function of soil water content. Our improved understanding of the link between soil water content and contaminant mobility in the soil will enable the development of improved soil remediation techniques.