Understanding and quantifying the retention and migration of per- and polyfluoroalkyl substances in the vadose zone

全氟和多氟烷基物质(PFAS)是最近在美国和其他国家的土壤和水域中发现的人造化学物质。它们的广泛使用和在环境中的持久性可能会导致美国数百万人接触到受全氟辛烷磺酸污染的饮用水。由于全氟辛烷磺酸对人类健康的影响，了解这些污染物如何在环境中移动并到达曝光点是很重要的。到目前为止，对全氟辛烷磺酸通过土壤向地下水的迁移了解甚少，也很难预测。了解它们是如何移动的，以及它们在土壤中停留的时间对清理和减少暴露至关重要。拟议的项目将结合实验和建模方法，研究控制全氟辛烷磺酸在土壤和地下水中移动的因素。该项目将生成数据和预测工具，为利益攸关方和决策者提供有价值的信息。该项目将通过支持STEM教育进一步造福社会，包括扩大代表性不足群体的参与，并向更广泛的社区宣传受PFAS污染的水构成的风险以及减少风险的干预潜力。越来越多的实地数据表明，土壤是PFAS对地下水的重要来源。然而，控制全氟辛烷磺酸在土壤中长期保留的主要机制仍然知之甚少。该项目将通过将新颖的实验和数学建模方法相结合来解决这一关键的知识差距。具体地说，该项目将1)在非饱和多孔介质中进行瞬变流动条件下的全氟辛烷磺酸运移研究；2)开发和使用最先进的数学模型，代表表面活性剂诱导的流动和全氟辛烷磺酸特有的运移过程，以确定控制全氟辛烷磺酸在土壤中的滞留和长期大量排放到地下水的关键因素。在该项目中开发的概念和计算工具预计将有助于为土壤中的全氟辛烷磺酸制定以科学为基础的州和联邦法规，并制定关于补救的议定书。研究结果将分发给当地一家自来水公司，以改善亚利桑那州图森市全氟辛烷磺酸污染问题的水资源管理和补救决策。此外，该项目将通过亚利桑那州科学、工程和数学学者计划培训亚利桑那大学STEM方面的未得到充分服务的本科生，并通过与弗兰德劳科学中心和行星馆合作，教育当地社区关于全氟辛烷磺酸污染。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Per- and polyfluoroalkyl substances (PFAS) are manmade chemicals that have recently been found in soils and waters all over the U.S. and other countries. Their widespread use and and persistence in the environment may result in exposure of millions of people in the U.S. to PFAS-contaminated drinking water. Because of the impacts of PFAS to human health, it is important to understand how these contaminants move in the environment and reach points of exposure. To date, the movement of PFAS through soil to groundwater is poorly understood and difficult to predict. Knowing how they move and how long they stay in soils is critical for cleanup and reducing exposure. The proposed project will integrate experimental and modeling approaches to study the factors that control the movement of PFAS in soils and groundwater. The project will generate data and predictive tools that can provide valuable information for stakeholders and decision makers. The project will further benefit society by supporting STEM education, including broadening of participation of underrepresented groups, and informing the broader community about the risks posed by PFAS-contaminated water and potential for intervention to mitigate risks.A growing body of field data demonstrates that soils serve as significant sources of PFAS to groundwater. However, the primary mechanisms that control the long-term retention of PFAS in soils remain poorly understood. This project will address this critical knowledge gap by combining novel experimental and mathematical modeling approaches. Specifically, the project will 1) conduct investigations of PFAS transport in unsaturated porous media under transient flow conditions; 2) develop and use state-of-the-art mathematical models that represent surfactant-induced flow and PFAS-specific transport processes to identify the critical factors that control the retention of PFAS in soils and the long-term mass discharge to groundwater. The conceptual and computational tools developed in this project are expected to contribute to the establishment of science-based state and federal regulations for PFAS in the soils and to develop protocols on remediation. The research findings will be disseminated to a local water utility to improve water resources management and remediation decisions for PFAS contamination problems in Tucson, Arizona. In addition, the project will train underserved undergraduates in STEM at the University of Arizona through the Arizona Science, Engineering and Math Scholars Program and educate the local community about PFAS contamination through by collaboration with the Flandrau Science Center & Planetarium.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.