The Role of Phase-state for Deposition of Per- and Polyfluoroalkyl Substances (PFAS)

EMMA D'AMBRO, Benjamin Murphy, Jesse Bash, Havala Pye, U.S. Environmental Protection Agency

     Abstract Number: 575
     Working Group: Aerosol Sources and Constituents of Emerging Importance and Their Impacts across Spatial Scales

Abstract
Per- and polyfluoroalkyl substances (PFAS) are a class of man-made compounds whose emissions to air may contribute, via transport and deposition, to concentrations in surface water, ground water, and private well water in the vicinity of large point sources. Air quality modeling techniques can be used to quantify air concentrations and deposition fluxes to help parse the role of exposure pathways such as direct inhalation and ingestion via contaminated water. We apply the Community Multiscale Air Quality model (CMAQ) version 5.3.2 to a case study in Eastern North Carolina to model the PFAS emissions and transport at fine scale (1 km) from the Chemours Inc. Fayetteville-Works. The 23 PFAS with the largest emissions by mass are identified and added explicitly to CMAQ, along with an aggregate “other PFAS” species to represent the balance of the emissions. An updated deposition parameterization (Surface Tiled Aerosol and Gaseous Exchange, STAGE) is utilized along with estimated chemical properties for each species to simulate the deposition flux to specific, sub-grid land surface types. Thus, the updated model (CMAQ-PFAS) captures the dynamic transformations and removal processes that affect the extent of atmospheric transport of PFAS. Herein, we test the sensitivity of our results, primarily the predicted air concentrations and deposition rates, to the level of detail in our speciated emissions inputs. We find that the chemical specificity is important for accurate physicochemical properties which determine phase state and thus deposition rates of PFAS. We provide recommendations for future chemical transport modeling studies of PFAS.

Disclaimer: The views expressed in this presentation are those of the authors and do not necessarily reflect the views or policies of the U.S. EPA.