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

保护地下水资源免受病原体和其他污染物的侵害，以及清除遗留污染物，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补救的从业人员无法预测其运输。 这项工作集成了表面的纳米级特性的测量与传输和建模实验中的孔隙尺度的理论框架，可用于更好地预测胶体的流动性。除了为研究人员开发建模工具和培训研究生外，所获得的知识将通过与初中和高中教师合作，参与非正式的社区活动以及在海外学习课程上合作向公众传播。所观察到的胶体在孔隙尺度上的传输行为可以通过在机械轨迹模拟中包含纳米级异质性来再现。 目前，这种表示是通过匹配传输实验凭经验确定的，但缺乏对已知纳米图案化表面的测试。拟议的项目将结合联合收割机的实验观察与纳米图案化的表面和机械轨迹模拟胶体相互作用，以解决知识差距（1）之间的关系离散表示的纳米级表面异质性和可测量的物理化学表面特性和（2）机制参数化的命运胶体超越孔隙规模。纳米图案表面将使用力-体积原子力显微镜进行表征。多晶粒微观模型实验，无论是在实验室和在硅/计算，将阐明孔尺度流动指进，近表面胶体的积累，消耗的快速连接的胶体亚群，并偏离预期的保留配置文件在不利的附件条件下之间的联系。结果将与国家的最先进的放大方法，以建立一致的理论模型来预测胶体运输过程中连续尺度。拟议的研究将：1）提高我们对地下水和其他不利环境中胶体输运的理论理解，以利于水资源保护和修复：2）为从业者和研究人员提供一套模拟工具; 3）通过关于颗粒输运和表面相互作用的短期课程加强研究生教育;和4）宣传更广泛的人群关于颗粒物在地下和地表水生系统中微量元素归宿和迁移中的作用。推广活动包括让初中和高中科学教师参与暑期实习，参与社区活动，如在图书馆和当地公园举办的“科学生活”和“科学星期日”，以及在厄瓜多尔合作举办海外学习班。该奖项反映了NSF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.