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Exploring the regional-scale atmospheric fate and transport of per- and polyfluoroalkyl substances (PFAS)
Citation:
D'Ambro, E., H. Pye, C. Allen, K. Talgo, L. Reynolds, K. Brehme, R. Gilliam, AND B. Murphy. Exploring the regional-scale atmospheric fate and transport of per- and polyfluoroalkyl substances (PFAS). American Geophysical Union, San Francisco, California, December 09 - 13, 2019.
Impact/Purpose:
There is emerging evidence that air emissions of PFAS pollutants from production and processing sites can lead to ecosystem enhancements far downwind. We quantify the magnitude of downwind deposition and airborne concentrations of one PFAS compound. We do this by leveraging the bottom-up science present in the regional-scale chemical transport model CMAQ (Community Multiscale Air Quality). This scientific poster demonstrates the evaluation of these estimates with deposition measurements made near a case study facility.
Description:
Per- and polyfluoroalkyl substances (PFAS) are a class of man-made substances whose emissions to air may contribute significantly, via transport and deposition, to elevated concentrations in surface water, ground water, and private well water in the vicinity of large point sources. Air emissions inventory and air quality modeling techniques can be used to quantify the importance of this exposure pathway. We begin by analyzing a case study facility, Chemours Inc. outside Fayetteville, North Carolina, with a goal of determining the current level and composition of PFAS emitted from the plant. We identify priority PFAS compounds for air modeling based on availability of measured observations as well as intrinsic properties like volatility, expected emission rates, and atmospheric reactivity, which we estimate with structure-activity relationships. For chemically reactive compounds, we postulate likely degradation mechanisms based on known gas-phase organic chemistry. After synthesizing this data, we update and apply the Community Multiscale Air Quality model (CMAQ) version 5.3 to model PFAS emissions and transport at fine scale (1 km) near the Fayetteville, NC Chemours facility. PFAS-specific tracers, properties, and chemistry are added to CMAQ to capture the dynamic transformations and removal processes that affect the extent of atmospheric transport of these pollutants. We evaluate model performance against deposition and ambient air sampling and quantify the model uncertainty with these measurements. Finally, we compare our new understanding of PFAS emissions from Chemours Inc. to the information available in the National Emissions Inventory (NEI) in order to guide further development of air emission inventories to better capture nationwide PFAS manufacturing-related releases.