2D Finite-difference Simulation of Transport of Post-wildfire PFAS Contamination

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4. 2D Finite-difference Simulation of Transport of Post-wildfire PFAS Contamination

The frequency and size of wildfire events have increased significantly. Every year, approximately 650 million acres of forests are burned by wildfires. These events not only directly affect the physical, chemical, and biogeochemical properties of the soil and surface materials through the heating and combustion process but also indirectly through changes in vegetation and soil erosion. Moreover, the way humans respond to wildfires can also have an impact on the environment. For instance, the use of aqueous film-forming foams (AFFFs) is an effective method to suppress fires, but they contain per- and polyfluoroalkyl substances (PFAS) that are toxic and persistent in the soil environment. Hence, there is a growing need to understand the behaviour of PFAS in the environment, as they are becoming increasingly prevalent due to their use in fire-fighting foams. In addition to adsorption to soil particles, PFAS have a tendency to adhere to the interface between air and water in the soil, which complicates their presence and transport in unsaturated soils. The air-water interface can significantly increase the retention of PFAS during its transport. In this paper, a two-dimensional (2D) numerical model was developed to simulate the transport of PFAS by incorporating advection-dispersion and taking into account the impact of adsorption on the air-water interface and soil solid phase. This study shows that though advection is generally the dominant factor in PFAS transport in saturated systems, the presence of adsorption onto air-water interfaces in the soil can significantly affect transport rates and become dominant in unsaturated cases.

9th International Congress on Environmental Geotechnics (ICEG2023)

Human-Induced and Natural Disaster Mitigation