ESE Seminar - Bo Guo: "Fate and Transport of PFAS in Unsaturated Porous Media across Scales: Interfacial Partitioning, Thin Water Films, and Upscaling"

Abstract

Per- and polyfluoroalkyl substances (PFAS) are contaminants that have accumulated extensively in soils, which can act as long-term sources of groundwater contamination. Quantifying soil PFAS leaching is therefore critical for risk assessment, remediation, and regulatory decision-making. However, PFAS transport differs fundamentally from that of conventional contaminants because many PFAS are surfactants that adsorb at air–water and solid–water interfaces, leading to complex retention behavior and flow–transport coupling under variably saturated conditions.

I present a cross-scale framework for understanding and modeling PFAS fate and transport in soils and groundwater. I discuss the dominant processes controlling PFAS retention and migration, introduce a mechanistic mathematical model that incorporates PFAS-specific interfacial processes, and show how thin water films can uniquely control PFAS transport in unsaturated soils. This is followed by a multi-continuum, semi-analytical framework as a potential route for upscaling these processes and incorporating them into practical modeling tools. The goal is to connect interfacial physics across scales to improve predictions of long-term PFAS retention, leaching, and mass discharge to groundwater.

Bio

Dr. Bo Guo is an Associate Professor and University Distinguished Scholar at the University of Arizona. His research focuses on fluid flow and transport in porous media, with an emphasis on multiscale mathematical and computational modeling. He works on a range of environmental and energy problems, including contaminant transport in soils and groundwater, chemical weathering in the critical zone, shale oil and gas production, and geologic carbon storage. Bo earned his B.S. (with highest honor) from Tsinghua University and Ph.D. from Princeton University, and completed a two-year postdoc at Stanford University before joining the University of Arizona. He is the 2027 Henry Darcy Distinguished Lecturer, and a recipient of the AGU Hydrologic Sciences Early Career Award, NSF CAREER Award, and the Humboldt Research Fellowship for Experienced Researchers. He serves as an Editor of Hydrology and Earth System Sciences and an Associate Editor of Water Resources Research, and Advances in Water Resources.

Group Webpage https://guolab.arizona.edu/