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Presentation Slides

“Baseline Data Acquisition and Numerical Modeling to Evaluate the Fate and Transport of PFAS within the Vadose Zone” by Dr. Jeff Silva (ER18-1389)

This project evaluates the significance of PFAS transport mechanisms in the vadose zone, develops mathematical relationships to parameterize these mechanisms, and incorporates these equations within the well-known HYD0oRUS unsaturated flow and transport simulator. Laboratory experiments were performed to provide data to validate PFAS-specific modifications made. Mechanisms investigated included air-water interfacial adsorption (AWIA), multi-component competitive effects on AWIA, impacts of surface-tension reduction on PFAS transport, and kinetic processes related to AWIA. Additionally, a PFAS transport dataset collected from a well characterized field site is being used to evaluate the model performance at the field-scale. Completion of the project will facilitate a robust numerical simulator that can support future DoD site investigations and remediation efforts.

“PFAS-LEACH—A Comprehensive Decision Support Platform for Predicting PFAS Leaching in Source Zones” by Dr. Bo Guo (ER21-5041)

This project has developed and demonstrated PFAS-LEACH—an advanced, comprehensive decision support platform for predicting PFAS leaching in source zones. PFAS-LEACH accounts for the various PFAS-specific fate and transport processes in soil and groundwater and has the capability to quantify source attenuation, spatial mass distribution, and long-term mass discharge from the vadose zone to groundwater at PFAS-impacted sites. It includes four tiers of models spanning from a full-process 3D numerical simulator to analytical solutions implemented in Excel to simple dilution-attenuation calculations. The presentation will describe the specific processes represented in each of the model Tiers and will illustrate, with specific examples, how the different model Tiers can be used to answer practical questions such as characterizing source strengths and derivation of soil screening levels.

Speaker Biographies

Dr. Jeff Silva is a hydrogeologist that has worked in the fields of environmental remediation, consulting, and research for over 25 years. He has served as a principal or co-principal investigator on projects funded by SERDP, ESTCP, the Air Force Civil Engineer Center and the Department of Energy. At GSI North America, Inc., Dr. Silva has been working his most recently SERDP-funded work. His areas of expertise include groundwater and surface water hydrology, geochemistry, transport and fate processes in environmental systems, site investigation/characterization, DNAPL/LNAPL investigations, quantitative hydrogeology, tracer applications in subsurface investigations, and groundwater remediation technology evaluation and design. His current professional focus centers on modeling transport processes in the vadose zone with specific attention to PFAS. He received his doctoral degree in civil an environmental engineering from the Colorado School of Mines in Golden, CO.

Dr. Bo Guo is an Associate Professor in the Department of Hydrology and Atmospheric Sciences at the University of Arizona. His research focuses on the fundamental physics and mathematical modeling of fluid flow and transport in permeable geological materials, motivated by environmental and energy problems including fate and transport of PFAS in soil and groundwater, shale gas/oil production, and geological carbon storage. Dr. Guo holds a B.S. in Hydraulic Engineering from Tsinghua University and a Ph.D. in Civil and Environmental Engineering from Princeton University. Prior to joining the University of Arizona, Dr. Guo was a postdoc in the Department of Energy Science and Engineering at Stanford University. Bo was the chair of the 25th Computational Methods in Water Resources (CMWR) international conference and currently serves as the chair of the AGU Groundwater Technical Committee and an associate editor of Water Resources Research and Journal of Hydrology.