CAREER: Transport of perfluoroalkyl substances (PFAS) in partially and fully saturated porous media - evaluating the interactions of solution chemistry and organic matter quality

多聚和全氟烷基物质(PFAS)是人造化学品。全氟辛烷磺酸因其稳定性和其他有价值的化学性质而被用于各种产品。然而，PFAS的这种稳定性也使得PFAS难以在环境中生物降解。此外，它们的性质也对人类健康和环境构成威胁。据估计，超过600万美国人在供水中接触了全氟辛烷磺酸，全氟辛烷磺酸被认为是美国面临的最重要的环境污染问题之一。这一担忧源于一些研究表明，一些全氟辛烷磺酸可以进入并留在人体内，可能会导致癌症和其他健康问题。这一知识导致了许多努力，以处理水源，以消除发现后的全氟辛烷磺酸。抽取和处理地下水是这些常用的处理方法之一。虽然这种方法对一些污染物有效，但由于我们不完全了解PFAS与土壤中存在的天然有机物(NOM)之间的相互作用，因此很难预测PFAS在地下水中的迁移。这个职业项目的目标是通过调查NOM和PFAS的相互作用来解决这一知识差距。这将通过一系列具有良好特征的模型系统的实验来实现。了解这一过程将使我们能够改进地下水处理系统，以保护人类健康。这项工作将用于通过外联活动教育公众，以提高对PFAS挑战和解决这些关切的努力的认识。这些努力将提高国家的科学素养，同时教育公众关于重要的健康问题。这项职业提案的目标是确定全氟辛烷磺酸与土壤中有机物质相互作用的机制。这将使用一系列传统的和新颖的分析方法来评估有机物、阳离子和全氟辛烷磺酸如何通过一个框架相互作用，包括溶液相络合和在空气-水和固体-水界面上的积累。从这项研究中获得的机械论见解可以解释先前观察到的吸附分布和速率常数值的变化。拟议的工作将结合间歇式、静态柱和流通柱实验来评估PFAS从近地表来源通过包气带和饱和地下水的传输。一个理想的多孔介质系统将使用聚合物涂层微珠来创建，其中聚合物将被用作均匀的、定义明确的土壤有机质替代品。通过使用有机质替代品来阐明化学部分如何影响全氟辛烷磺酸与有机物的相互作用，将能够获得机械论上的见解。溶解有机物对全氟辛烷磺酸的络合作用和阳离子结合常数将基于尺寸排除层析中的共洗脱进行测定。采用液滴接触角和层叠多环静力柱相结合的方法评价气液界面蓄积量。最后，将利用高分辨率质谱仪对连续流出物进行分析，以量化流出物中的全氟辛烷磺酸浓度，从而完成全氟辛烷磺酸在直流柱中的传输。该项目包括多个部分的外展工作：1)教育活动将侧重于对初中生和高中生的外展，2)为不同学科的本科生提供研究机会，以及3)发展研究生的多学科思维。这些努力将通过提高科学素养和加强国家的STEM工作队伍来造福国家。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。

Poly and perfluoroalkyl substances (PFAS) are man-made chemicals. PFAS have been used in a variety of products due to their stability and other valuable chemical properties. However, PFAS this stability also makes PFAS difficult to biodegrade in the environment. In addition, their properties also pose a threat to human health and the environment. It is estimated that over six million Americans have been exposed to PFAS in the water supply, and PFAS is considered one of the most important issues in environmental contamination facing the Nation. This concern results from studies that have shown that some PFAS can enter and remain in the human body, potentially causing cancer and other health problems. This knowledge has led to many efforts to treat water sources to remove PFAS when discovered. Pumping and treatment of groundwater is one of these commonly used treatment approaches. While this approach has worked for some pollutants, the PFAS movement in groundwater is difficult to predict because we do not fully understand the interactions between PFAS and natural organic matter (NOM) present in soil. The goal of this CAREER project is to address this knowledge gap by investigating the interactions of NOM and PFAS. This will be achieved through a series of experiments with well characterized model systems. Understanding this process will allow us to improve groundwater treatment systems to protect human health. This work will be used to educate the public through outreach to increase awareness of PFAS challenges and efforts to address these concerns. These efforts will increase the scientific literacy of the Nation while educating the public on important health issues.The goal of this CAREER proposal is to identify the mechanisms of PFAS interactions with organic matter in soils. This will be achieved using a range of conventional and novel analytical approaches to assess how organic matter, cations, and PFAS interact through a framework including solution phase complexation and accumulation at air-water and solid-water interfaces. Mechanistic insights gained from this research could explain previously observed variability in sorption distributions and rate constant values. The proposed work will combine batch, static column, and flow-through column experiments to assess PFAS transport from a near surface sources through the vadose zone and saturated groundwater. An idealized porous media system will be created using polymer-coated beads, where the polymers will be employed as homogeneous well-defined soil organic matter proxies. Mechanistic insights will be enabled through the use of organic matter proxies to elucidate how chemical moieties affect PFAS-organic matter interactions. PFAS complexation by dissolved organic matter and cation binding constants will be determined based on co-elution in size exclusion chromatography. Air-water interfacial accumulation will be evaluated using droplet contact angle coupled with stacked multi-ring static columns operated in drainage and secondary imbibition modes. Finally, PFAS transport in flow-through columns will be completed using continuous effluent analysis by high resolution mass spectrometry to quantify PFAS concentrations in the column effluent. The project includes a multi-component outreach effort: 1) educational activities will focus on outreach to middle and high school students, 2) research opportunities for undergraduate students from a range of disciplines, and 3) development of multi-disciplinary thinking in graduate students. These efforts will benefit the Nation through increased scientific literacy and enhancement of the Nation’s STEM workforce.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.