239-7 Mass-Conserved Particle Tracking Method for Efficient Transport Simulation of PFAS

Session: Federal PFAS Remediation: Successes and Challenges

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PFAS compounds present unique challenges for transport and fate modeling. Understanding of their physical/chemical properties continues to evolve. Plumes can be large and span many orders of concentration magnitude, and several compounds have regulatory criteria in the low parts per trillion (PPT) range. When concentration drops over several orders of magnitude, numerical models with inadequately fine discretization tend to overpredict the extents of contamination due to numerical diffusion. This paper presents a new mass-conserved particle tracking algorithm for rapid assessment of PFAS transport for use within existing groundwater flow and transport models without incurring artificial spreading due to numerical diffusion. The algorithm was verified against an analytical solution over ten orders of magnitude and an existing model that had been used to optimize monitoring well locations for PFAS plume delineation. The existing model required grid refinement (discretization reduced from 250-foot grid size to 32-foot grid size) to achieve grid-independent results. The new particle tracking algorithm achieved similar transport model predictions without the need for discretization refinement.

Many legacy groundwater contamination sites have previously developed groundwater flow and transport models; some have employed optimization techniques for remedy optimization. Where PFAS is a new concern on legacy sites, mass-conserved particle tracking provides a means to readily use existing models for rapid assessment of PFAS transport and to apply optimization techniques for remedy design, performance, and transition from one technology to another or to long term monitoring.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5103

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