Collaborative Research: Predicting Colloid Distribution in Subsurface Granular Media by Resolving Nanoscale Heterogeneity and Continuum-Scale Flow Field Topologic Impacts

保护地下水资源不受病原体和其他污染物的侵害，以及清理遗留污染，需要有能力预测地下水系统中污染物的流动性。在环境条件下，与介质表面的相互作用可能导致一些被称为胶体的非常小的颗粒移动的距离远远超过预期，使地下水资源保护和修复的从业者没有可行的方法来预测它们的运输。这项工作将纳米尺度表面特征的测量与孔隙尺度理论框架内的传输和建模实验相结合，可以用来更好地预测胶体的迁移性。除了为研究人员开发建模工具和培训研究生外，所获得的知识还将通过与初中和高中教师合作、参加非正式的社区活动以及合作开设“海外学习”课程向公众传播。观察到的胶体在孔隙尺度上的输运行为可以通过在机械轨迹模拟中包含纳米尺度的非均质来重现。目前，这种表征是通过匹配输运实验来确定的，但缺乏对已知纳米图案表面的测试。拟议的项目将结合胶体与纳米图案表面相互作用的实验观察和机械轨迹模拟，以解决以下方面的知识空白：(1)纳米尺度表面非均质性的离散表示与可测量的物理化学表面特征之间的关系；(2)孔隙尺度以外胶体命运的机械参数化。纳米图案表面将使用力-体积原子力显微镜进行表征。在实验室和计算机/计算机中进行的多颗粒微模型实验将阐明孔隙尺度流动指移、近表面胶体的积累、快速附着的胶体亚群的耗损以及在不利的附着条件下偏离预期的保留剖面之间的联系。结果将与最先进的升级方法相结合，以建立一致的理论模型来预测连续尺度上的胶体输运过程。提出的研究将：1)提高我们对地下水和其他不利环境中胶体迁移的理论认识，有利于水资源的保护和修复；2)为从业者和研究人员提供一套模拟工具；3)通过粒子输运和表面相互作用的短期课程加强研究生教育；4)向更广泛的人群介绍颗粒在地下和地表水生系统中微量元素的命运和运输中的作用。拓展活动包括让初中和高中科学教师参加暑期实习，参加在图书馆和当地公园举办的“活着的科学”和“星期天的科学”等社区活动，以及在厄瓜多尔合作举办“出国学习”课程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Protection of groundwater resources from pathogens and other contaminants, as well as cleanup of legacy contamination, requires the ability to predict the mobility of contaminants in groundwater systems. Under environmental conditions, interactions with media surfaces may lead some very small particles known as colloids to move far greater distances than expected, leaving practitioners of groundwater resource protection and remediation without a viable way to predict their transport. This work integrates measurements of nanoscale characteristics of surfaces with transport and modeling experiments within a pore-scale theoretical framework that can be used to better predict the mobility of colloids. In addition to developing modeling tools for researchers and training graduate students, the knowledge gained will be disseminated to the general public by working with middle and high school teachers, participating of informal community-level events, and collaborating on Learning Abroad classes. The observed transport behavior of colloids at the pore scale may be reproduced through inclusion of nanoscale heterogeneity in mechanistic trajectory simulations. Currently such representation is determined empirically via match to transport experiments but lacks testing on known nano-patterned surfaces. The proposed project will combine experimental observations of colloid interaction with nano-patterned surfaces and mechanistic trajectory simulations to address knowledge gaps on (1) relationships between discrete representations of nanoscale surface heterogeneities and measurable physicochemical surface characteristics and (2) mechanistic parameterization of the fate of colloids beyond the pore scale. Nano-pattern surfaces will be characterized using force-volume atomic force microscopy. Multi-grain micromodel experiments, both in the laboratory and in silico/computational, will elucidate links between pore scale flow fingering, accumulation of near surface colloids, depletion of a fast-attaching subpopulation of colloids, and deviation from expected retention profiles under unfavorable attachment conditions. Results will be integrated with state-of-the-art upscaling approaches to build consistent theoretical models to predict colloid transport processes at continuum scales. The proposed research will: 1) improve our theoretical understanding of colloid transport in groundwater and other unfavorable contexts to the benefit of water resource protection and remediation: 2) provide a suite of simulation tools for practitioners and researchers; 3) enhance graduate student education through short courses regarding particle transport and surface interaction; and 4) outreach a broader population regarding the role of particulates in trace element fate and transport in subsurface and surface aquatic systems. Outreach include engaging middle and high school science teachers during summer internships, participation in community-level events, such as Science Alive and Science Sunday, held at libraries and local parks, and collaboration on Learning Abroad classes in Ecuador.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.