Fate and Transport of Metal-Based Nanoparticles in the Subsurface

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。尽管在过去的十年中纳米技术发展迅速，但我们目前对纳米材料在环境中的命运和运输的了解仍然相当有限。例如，目前尚不清楚大多数工程纳米材料将如何与土壤基质相互作用，它们的运输是否可以使用经典的颗粒过滤理论建模为胶体颗粒，或者不饱和条件如何影响纳米颗粒在自然土壤中的运输、保留和持久。尽管研究碳纳米材料在环境中的行为已经付出了一些努力，但关注金属基纳米材料运输的研究数量非常有限，金属基纳米材料是一类特别重要的纳米材料，因为它们具有潜在的毒性，并且在个人护理产品中广泛使用。因此，本文拟重点研究三种具有代表性的金属基纳米材料；纳米银（Ag）、纳米二氧化钛（TiO2）和纳米氧化锰（MnOx）。该研究计划旨在将详细的实验室实验与数学模型相结合，以阐明控制石英砂和自然土壤中金属基纳米颗粒的命运和运输的机制。为了实现这一目标，本研究围绕四个具体任务进行，(1)表征金属基纳米颗粒悬浮物和土壤性质，(2)测量水饱和条件下金属基纳米颗粒的运输和保留，(3)测量不饱和条件下金属基纳米颗粒的运输，以及(4)建立和验证预测金属基纳米颗粒在地下系统中的运输和持久性的数学模型。研究计划中特别新颖的方面包括考虑含有TiO2的防晒霜和化妆品中常用的表面涂层和乳化剂，以及使用力体积显微镜对沉积在沙粒表面的纳米颗粒进行成像。从每个任务中收集的信息将被整合起来，以推进我们对多孔介质中金属基纳米颗粒传输机制的基本理解，最终目标是开发一个数值模拟器，该模拟器可用于根据已知输入参数预测工程纳米颗粒在地下的传输行为。拟议研究的智力价值在于两个对纳米技术安全和可持续发展至关重要的领域；(1)推进了我们对金属基纳米材料在多孔介质中的命运和传输的基本理解；(b)开发和验证了可用于模拟纳米颗粒在地下传输的数学模型。这项工作中提出的实验研究和数学建模的独特耦合为纳米材料在不饱和和饱和多孔介质中的行为的概念模型提供了严格的验证，并将最终发展能够预测纳米材料在自然系统中可能遇到的一系列条件下的命运和运输的数值模拟器。我们预计，在这项工作中开发的实验参数和数学模型可以用于预测其他纳米材料（例如，亚铁烷）在地下系统中的命运和运输。纳米颗粒在多孔介质中保留的基本知识也可用于模拟过滤技术处理含有纳米颗粒的饮用水或废水的性能。该项目的一个重要组成部分将是将教育倡议纳入研究人员的研究和教学活动，目的是将获得的知识的影响扩大到期刊出版物和会议报告的传统框架之外。为了达到这个目标，我们将采取以下措施：(a)让本科生进行综合实验和数学建模研究；(b)发展互动式多媒体教学工具；以及(c)招收女性和少数族裔学生。教学材料，包括教程，说明性案例研究和建模工具，将在一个专门的网站上发布，以便学生和教师都可以探索控制金属基纳米粒子在陆地环境中的命运和运输的过程。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).0854136Pennell Despite the rapid development of nanotechnologies over the past decade, our current understanding of nanomaterial fate and transport in the environment remains quite limited. For example, it is not known how most engineered nanomaterials will interact with soil matrices, whether or not their transport can be modeled as colloidal particles using classic particle filtration theory, or how unsaturated conditions impact nanoparticle transport, retention and persistence in natural soils. Although some effort has been devoted to investigate the behavior of carbonaceous nanomaterials in the environment, a very limited number of studies have focused on the transport of metal-based nanoparticles, a particularly important class of nanomaterials because of their potential toxicity and widespread use in personal care products. For this reason, the proposed research will focus on three representative metal-based nanomaterials; nano-silver (Ag), nano-titanium dioxide (TiO2), and nano-manganese oxide(s) (MnOx). The research program is designed to couple detailed laboratory experimentation with mathematical modeling to elucidate mechanisms governing the fate and transport of metal-based nanoparticles in quartz sands and natural soils. To achieve this goal, the research is structured around four specific tasks, (1) characterization of metal-based nanoparticle suspensions and soil properties, (2) measure the transport and retention of metal-based nanoparticle under water saturated conditions, (3) measure the transport of metal-based nanoparticle under unsaturated conditions, and (4) develop and validate mathematical models for the prediction of metal-based nanoparticle transport and persistence in subsurface systems. Particularly novel aspects of the research plan include the consideration of surface coatings and emulsifying agents commonly used in sunscreens and cosmetic products containing TiO2 and the use of force-volume microscopy to image nanoparticles deposited on sand grain surfaces. Information gathered from each task will be integrated to advance our fundamental understanding of the mechanisms governing metal-based nanoparticle transport in porous media, with the ultimate goal of developing a numerical simulator that can be used to predict the transport behavior of engineered nanoparticles in the subsurface based on known input parameters. The intellectual merit of the proposed research lies in two areas critical to the safe and sustainable development of nanotechnologies; (1) advancement of our fundamental understanding of metal-based nanomaterial fate and transport in porous media and (b) development and validation of mathematical models that can be used to simulate nanoparticle transport in the subsurface. The unique coupling of experimental studies and mathematical modeling proposed in this work provides for rigorous validation of conceptual models of nanomaterial behavior in unsaturated and saturated porous media, and will culminate in the development of numerical simulator capable of predicting nanomaterial fate and transport over a range of conditions that might be encountered in natural systems. We anticipate that the experimental parameters and mathematical models developed in this work can be adapted to predict the fate and transport of other nanomaterials (e.g., ferroxane) in subsurface systems. The fundamental knowledge of nanoparticle retention in porous media can also be used to model the performance of filtration technologies for treatment of drinking or waste water containing nanoparticles.An essential component of the project will be the incorporation of education initiatives into the research and instructional activities of the investigators, with the goal of extending the impact of acquired knowledge beyond the traditional framework of journal publications and conference presentations. This goal will be achieved through the following initiatives: (a) the inclusion of undergraduate students conducting integrated experimental and mathematical modeling research, (b) the development of interactive, multi-media instructional tools, and (c) recruitment of female and underrepresented minority students. The instructional materials, consisting of tutorials, illustrative case studies and modeling tools, will be released on a dedicated web site so that students and instructors alike can explore processes that govern the fate and transport of metal-based nanoparticles in terrestrial environments.