Tucson Chapter

Join us to hear talks from two U of A hydrology students, Mardy Nadel on Determining site-specific soil screening levels for PFAS at an airport source area and Ben West on Determining site-specific soil screening levels for PFAS at an airport source area.

Date: June 16th

Time: 6:00-7:30pm

Location: Montgomery & Associates, 1550 E Prince Rd 

Cost: $5 for members, $10 for nonmembers, free for student members
Please register online in advance.
If joining on Zoom, the presentation will start at 6:30pm.

About: Marcy Nadel

Marcy Nadel is a Hydrology and Environmental Science PhD student at the University of Arizona. Her research in the Brusseau Contaminant Transport Laboratory focuses on field-scale per- and polyfluoroalkyl substances (PFAS) soil retention, leaching, and transport processes in unsaturated soils. Prior to graduate school she worked in PFAS delineation and remediation as a Senior Geologist for Shannon & Wilson, Inc.

Abstract:

Soils impacted by aqueous film-forming foam (AFFF) use at military and civilian airports are a major, ongoing source of per- and polyfluoroalkyl substances (PFAS) in the environment. This study determines site-specific soil screening levels (SSLs) for three PFAS using field and laboratory data from an AFFF source area at U.S. Air Force installation. We apply multiple PFAS-specific approaches: a one-dimensional analytical solution transport model, modified U.S. Environmental Protection Agency (EPA) dilution-attenuation factor (DAF) equation, and field-measured soil and porewater concentrations. The modeling effort is supported by high-resolution soil characterization, including measurements of physical, hydraulic, and geochemical properties. Such SSLs are used to quantify the risk of PFAS leaching to groundwater, which often results in human and environmental exposures. Our PFAS-specific approaches reflect the complexity of PFAS partitioning and vadose zone transport, an area of active research. Differences among the SSLs generated for each PFAS by the different approaches highlight the dominant processes controlling soil retention and mass discharge at this site.

About: Ben West

Ben is a PhD student with Dr. Laura Condon at the University of Arizona. He is interested in using mathematical and computational modeling to better understand how societies interact with their surrounding environments, as well as how our infrastructure may respond to changes in the environment.

Abstract:

Droughts have had a growing impact on both natural resources and human infrastructure. In a changing climate drought duration and intensity are both expected to change, and the past 40 years have already shown an unusually large number of droughts of extreme intensity and duration. However, the connections between drought severity and drought recovery are not well understood. This is only further complicated by the fact human operations can influence drought evolution and impacts through a complex system of trade-offs. Our understanding of the trade-offs in water management decision-making and watershed dynamics is extremely limited because most models of human operations make critical simplifications in their representation of the surrounding environment.  Here, we use ParFlow, a fully integrated physical hydrology model, to examine watershed storage and streamflow dynamics during drought with varying levels of water management. ParFlow is well suited for this purpose as it directly represents the vadose zone and its role groundwater-surface water interactions that are crucial to the full picture of watershed dynamics. With ParFlow, we model several idealized watersheds under various drought conditions. Drought conditions are simulated for a baseline scenario (with no human operations), and with different groundwater pumping strategies. By comparing these simulations, we gain important insights into the role of drought duration on recovery as well as the impacts of water management decision-making. We are also able to look at how changed antecedent conditions, either from natural causes such as preceding dry or wet years, or anthropogenic causes such as groundwater depletion due to long term pumping, change drought evolution and recovery. This work could help design drought mitigation strategies that enhance water resource sustainability in an era of increasing drought intensity.