Mathematical Modeling and Analysis of Competitive Adsorption of Multi-component PFAS and Reactive Transport of PFAA Precursors in the Vadose Zone

Abstract

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals widely used in industrial and consumer products for their unique resistance to water, oil, temperature, and chemical reactions. However, their persistence in the environment and potential for bioaccumulation pose significant risks to human health and ecosystems. The challenges and motivations for this dissertation arise from the need to fully address PFAS leaching and retention, which previous work has struggled with due to the complex mechanisms and dynamics of contaminant transport in the vadose zone. Additionally, the critical changes in flow regimes and surface tension modifications, caused by the multi-component adsorption of PFAS, present significant difficulties. Lastly, there is a crucial need to investigate the reaction transport phenomena of PFAS, specifically the transformation from degraded PFAA precursors, to better understand their environmental impact and develop effective remediation strategies. This dissertation consists of two studies xxx findings from two comprehensive studies to enhance the understanding of PFAS behavior in the vadose zone, a critical subsurface region influencing groundwater contamination. The first study develops a multi-component mathematical model to quantify the transport and retention of PFAS mixtures, highlighting the impact of competitive adsorption in varied soil types over long periods. The second study develops a detailed model to simulate the transformation and degradation of PFAS precursors, incorporating environmental and physicochemical factors to elucidate their long-term environmental impacts. Both studies employ advanced numerical modeling, combined with literature experimental data, to provide a robust framework for predicting PFAS transport and transformation. The findings emphasize the significant role of the vadose zone in retaining PFAS and the PFAAs precursors, the influence of soil properties and co-contaminants on PFAS behavior, and the necessity for site-specific remediation strategies. This dissertation research provides critical insights into developing effective remediation techniques, informing regulatory policies, mitigating the long-term impacts of PFAS contamination, and ultimately contributing to the protection of soil and groundwater resources.