PFAS Air Emissions and Groundwater Contamination Investigation Using Air Dispersion Modeling and Hydrogeology
Project Overview
This environmental forensic investigation evaluated the long-term impact of historical per- and polyfluoroalkyl substances (PFAS) emissions from a fluorochemical manufacturing facility on nearby public groundwater supply wells. The investigation integrated atmospheric emissions reconstruction, air dispersion modeling, environmental chemistry, hydrogeology, groundwater fate and transport, soil chemistry, environmental forensics, and quantitative exposure assessment to evaluate whether decades of airborne PFAS emissions resulted in measurable contamination of groundwater resources serving public drinking water systems. Multiple independent datasets, regulatory records, groundwater monitoring programs, hydrogeologic investigations, published scientific literature, and environmental sampling databases were synthesized to reconstruct historical contaminant releases and evaluate potential migration pathways from atmospheric emissions to groundwater supplies.
The investigation focused on historical emissions of perfluorooctanoic acid (PFOA), ammonium perfluorooctanoate (APFO), GenX (HFPO-DA), Nafion byproducts, and related PFAS compounds released during fluoropolymer manufacturing over multiple decades. Facility operating records, patent literature, emissions inventories, production histories, regulatory filings, and historical manufacturing information were evaluated to reconstruct changing production practices, emission controls, and source terms throughout the facility’s operational history. Particular emphasis was placed on understanding how historical air emissions evolved over time and how improvements in emission controls influenced long-term environmental releases.
A major component of the investigation involved integrating groundwater hydrogeology with air dispersion modeling to evaluate whether atmospheric deposition represented a plausible long-term source of PFAS contamination within public drinking water well capture zones. Hydrogeologic characterization included regional aquifer systems, groundwater flow patterns, source water protection areas, well construction information, aquifer characteristics, groundwater monitoring data, and soil properties governing PFAS transport. Air dispersion modeling using the EPA-approved AERMOD model reconstructed historical atmospheric deposition over multiple decades, while deposition analyses evaluated contaminant loading within individual groundwater well capture areas and source water protection zones. The integration of atmospheric transport with groundwater science provided a comprehensive evaluation of contaminant migration from air emissions to drinking water resources.
The investigation further incorporated extensive analysis of groundwater monitoring information obtained from multiple independent sources, including public water system monitoring, regulatory groundwater investigations, private well sampling programs, source water assessment data, and unregulated contaminant monitoring programs. Geographic information system (GIS) analyses integrated well construction records, groundwater flow information, analytical chemistry datasets, and regional well locations to evaluate spatial relationships between PFAS detections, groundwater protection areas, and historical emission sources. Independent comparison of multiple groundwater datasets strengthened the evaluation by providing complementary evidence regarding the extent and distribution of PFAS contamination within regional groundwater resources. The accompanying data integration maps illustrate the spatial relationship among well construction datasets, regulatory monitoring wells, and groundwater sampling locations used throughout the investigation.
The investigation was conducted using accepted principles of environmental chemistry, atmospheric dispersion modeling, hydrogeology, groundwater modeling, soil chemistry, contaminant fate and transport, environmental toxicology, GIS analysis, and quantitative human health risk assessment. Rather than relying upon any single environmental dataset, the evaluation synthesized emissions reconstruction, historical manufacturing records, hydrogeologic characterization, atmospheric deposition modeling, groundwater monitoring, regulatory investigations, soil chemistry, published scientific literature, and environmental sampling into a multidisciplinary weight-of-evidence assessment. This integrated environmental forensic methodology provides a scientifically robust framework for evaluating long-term PFAS contamination of drinking water resources resulting from historical industrial air emissions.
Chemicals of Concern
This investigation evaluated a broad suite of per- and polyfluoroalkyl substances (PFAS) associated with historical fluoropolymer manufacturing and the long-term environmental behavior of these highly persistent chemicals following atmospheric release. The principal chemicals of concern included perfluorooctanoic acid (PFOA), ammonium perfluorooctanoate (APFO), hexafluoropropylene oxide dimer acid (HFPO-DA or GenX), Nafion byproducts, and numerous additional fluorinated processing aids and polymerization compounds associated with fluoropolymer production. These chemicals were evaluated because of their environmental persistence, resistance to degradation, mobility in groundwater, potential for atmospheric transport, and documented human health concerns. The investigation integrated environmental chemistry, toxicology, hydrogeology, atmospheric science, and environmental fate and transport to evaluate their migration from industrial emissions into regional groundwater resources.
Perfluorooctanoic acid (PFOA) represented the principal contaminant evaluated during the investigation because it served for decades as a polymerization aid during fluoropolymer manufacturing and has become one of the most extensively studied PFAS compounds. The investigation reviewed historical production records, emissions inventories, manufacturing practices, patent literature, regulatory filings, and environmental monitoring data to reconstruct historical PFOA emissions over multiple decades. Toxicological evaluations considered the persistence, bioaccumulation potential, mobility, and recognized human health effects associated with long-term PFOA exposure, making PFOA the primary indicator compound for evaluating historical atmospheric deposition and groundwater contamination.
The investigation also evaluated ammonium perfluorooctanoate (APFO) because of its historical role as a fluoropolymer processing aid and its close relationship with PFOA production. Manufacturing records and environmental chemistry literature demonstrate that APFO was intentionally used during fluoropolymer production and may transform to PFOA under environmental conditions. Consequently, historical APFO emissions were reconstructed together with PFOA emissions to better characterize the cumulative atmospheric source term and subsequent environmental loading to soils and groundwater. Evaluation of both compounds provided a more complete understanding of historical PFAS releases associated with manufacturing operations.
The investigation further examined GenX (HFPO-DA) and Nafion byproducts, which became increasingly important following the industry’s transition away from PFOA-based processing aids. Although developed as replacement technologies, these compounds have demonstrated significant environmental persistence and have become contaminants of emerging concern. The investigation reviewed production history, regulatory investigations, analytical monitoring data, published scientific literature, and environmental occurrence studies to evaluate the distribution of these replacement PFAS compounds within groundwater, surface water, and surrounding environmental media. Evaluation of GenX and Nafion byproducts also provided important evidence regarding changes in manufacturing practices and evolving PFAS emission profiles through time.
An additional focus of the investigation involved evaluation of PFAS transformation products and the environmental processes governing long-term contaminant migration. Environmental chemistry assessments examined atmospheric transport, deposition, partitioning between air and aerosols, soil adsorption, porewater transport, groundwater migration, surface water interactions, and potential transformation pathways affecting PFAS compounds following release. Particular emphasis was placed on understanding how decades of atmospheric deposition could ultimately contribute to groundwater contamination through infiltration, recharge, and long-term subsurface transport. Integration of these environmental fate and transport processes provided a scientifically supported framework for evaluating historical contamination of public drinking water supplies.
Finally, the investigation recognized that long-term PFAS contamination results from the cumulative release, transport, deposition, and migration of multiple fluorinated compounds rather than any single chemical alone. Accordingly, the investigation integrated atmospheric emissions reconstruction, environmental chemistry, hydrogeology, groundwater science, soil chemistry, analytical chemistry, toxicology, regulatory investigations, and quantitative exposure assessment to evaluate the complete PFAS contamination pathway from industrial emissions to public drinking water wells. This multidisciplinary approach provides a scientifically reliable framework for evaluating complex environmental contamination involving persistent fluorinated compounds and demonstrates the importance of integrating multiple environmental disciplines when investigating long-term impacts on groundwater resources.
Methods
The investigation was conducted using accepted principles of hydrogeology, environmental chemistry, atmospheric dispersion modeling, contaminant fate and transport, soil chemistry, groundwater hydrology, geographic information systems (GIS), environmental toxicology, analytical chemistry, and quantitative human health risk assessment. Because PFAS contamination of public drinking water systems develops over extended periods through complex environmental transport mechanisms, the investigation integrated historical manufacturing records, emissions inventories, atmospheric deposition modeling, hydrogeologic investigations, groundwater monitoring data, regulatory reports, environmental sampling, published scientific literature, and engineering evaluations to reconstruct historical contaminant migration from industrial air emissions to regional groundwater resources. Rather than relying upon a single environmental dataset, the investigation employed a multidisciplinary weight-of-evidence approach that combined atmospheric science, hydrogeology, environmental chemistry, groundwater modeling, and analytical chemistry to evaluate long-term contaminant transport and potential impacts to public water supplies.
A major component of the investigation involved reconstruction of historical PFAS emissions associated with fluoropolymer manufacturing operations. Historical production records, emissions inventories, manufacturing process descriptions, engineering documentation, patent literature, regulatory filings, and facility operating histories were reviewed to characterize the quantity, timing, and composition of PFAS released over multiple decades. Particular emphasis was placed on evaluating historical changes in manufacturing practices, implementation of emission control technologies, transitions from legacy fluorinated processing aids to replacement compounds, and the resulting influence on long-term atmospheric emissions. These engineering and historical evaluations established the source terms required for subsequent atmospheric deposition modeling and groundwater transport analyses.
Atmospheric dispersion modeling represented a principal component of the investigation. Historical emissions were reconstructed using EPA-approved air dispersion modeling methodologies to estimate long-term airborne transport and atmospheric deposition of PFAS compounds across the surrounding region. Air modeling incorporated historical emission rates, source characteristics, meteorological observations, terrain, land use, atmospheric stability, and deposition parameters to estimate cumulative contaminant loading over multiple decades. Model results were evaluated spatially using Geographic Information Systems (GIS) to characterize PFAS deposition within public drinking water well capture zones, groundwater recharge areas, and source water protection areas. Integration of atmospheric transport with hydrogeologic mapping provided a comprehensive evaluation of the environmental pathway linking historical air emissions to groundwater contamination.
The investigation also incorporated detailed hydrogeologic characterization of the regional groundwater system. Hydrogeologic evaluations included regional aquifer properties, groundwater flow direction, hydraulic gradients, recharge characteristics, soil properties, groundwater well construction records, source water protection areas, and public water supply well capture zones. Groundwater monitoring results obtained from regulatory investigations, public water systems, private well sampling, and environmental investigations were integrated with hydrogeologic mapping to evaluate contaminant occurrence throughout the aquifer system. Geographic analyses further evaluated the spatial relationship between atmospheric deposition patterns, groundwater flow, and measured PFAS concentrations within regional drinking water wells.
Exposure assessment further integrated environmental monitoring data with contaminant fate and transport analyses. Analytical chemistry data obtained from groundwater monitoring programs, regulatory investigations, environmental sampling, and public drinking water systems were evaluated together with modeled atmospheric deposition, hydrogeologic conditions, and groundwater migration pathways to characterize long-term environmental exposure. The investigation evaluated multiple PFAS compounds using published analytical methods and compared environmental concentrations with applicable regulatory guidance and health-based criteria where appropriate. Integration of environmental monitoring with atmospheric deposition modeling substantially strengthened the evaluation by linking modeled environmental loading with independently measured groundwater concentrations.
Finally, the investigation employed accepted principles of uncertainty evaluation fundamental to environmental forensics and groundwater contamination investigations. Uncertainty associated with historical emission rates, manufacturing practices, atmospheric deposition, groundwater migration, analytical detection limits, hydrogeologic variability, and long-term environmental transport was addressed through integration of multiple independent datasets, historical engineering documentation, regulatory investigations, groundwater monitoring programs, atmospheric modeling, hydrogeologic characterization, and published scientific literature. Rather than relying upon isolated groundwater samples or individual modeling results, the investigation synthesized atmospheric science, hydrogeology, environmental chemistry, engineering analyses, analytical chemistry, and exposure assessment into a comprehensive weight-of-evidence framework. This multidisciplinary methodology provides a scientifically reliable basis for evaluating long-term PFAS contamination of groundwater resources while remaining consistent with accepted principles of environmental chemistry, hydrogeology, atmospheric dispersion modeling, contaminant fate and transport, environmental toxicology, and quantitative human health risk assessment.
Results
Review of the available engineering, hydrogeologic, analytical, and regulatory documentation demonstrated that evaluation of long-term PFAS contamination of public drinking water systems requires integration of atmospheric dispersion modeling, groundwater hydrogeology, environmental chemistry, analytical chemistry, contaminant fate and transport, geographic information systems (GIS), and quantitative human health risk assessment. Although individual groundwater monitoring events provide important information regarding contaminant occurrence at specific locations and times, no single environmental dataset independently characterizes the decades-long migration of PFAS from industrial air emissions through atmospheric deposition, soil infiltration, and groundwater transport. Accordingly, the investigation integrated multiple independent lines of scientific evidence to reconstruct historical PFAS releases, evaluate environmental migration pathways, characterize groundwater contamination, and assess potential impacts to public drinking water supplies using accepted principles of environmental forensics and hydrogeology. Collectively, these complementary sources of scientific information provided a comprehensive framework for evaluating complex PFAS contamination resulting from long-term industrial emissions.
One of the principal findings of the investigation was the strong agreement between historical manufacturing records, atmospheric dispersion modeling, hydrogeologic characterization, and groundwater monitoring regarding the environmental transport of PFAS from historical industrial emissions to regional drinking water resources. Historical facility records documented decades of fluoropolymer manufacturing involving PFOA, APFO, GenX, and related PFAS compounds, while atmospheric dispersion modeling reconstructed cumulative airborne deposition across surrounding groundwater recharge areas. Independent groundwater monitoring programs subsequently documented PFAS occurrence within public water supply wells, and hydrogeologic investigations demonstrated that groundwater flow patterns and recharge characteristics were consistent with the observed distribution of contamination. Independent agreement among engineering records, air modeling, groundwater monitoring, and hydrogeologic evaluations substantially strengthened confidence in the overall environmental reconstruction.
The investigation further demonstrated the importance of integrating atmospheric deposition with groundwater hydrogeology when evaluating long-term PFAS contamination. Air dispersion modeling estimated cumulative PFAS deposition across source water protection areas and groundwater recharge zones over multiple decades, while hydrogeologic analyses evaluated infiltration, recharge, groundwater flow direction, aquifer characteristics, and well capture zones governing contaminant migration following deposition. Geographic Information System (GIS) analyses further integrated modeled deposition patterns with groundwater monitoring locations, public water supply wells, and aquifer protection areas to evaluate spatial relationships between historical emissions and measured groundwater contamination. Evaluation of these interconnected environmental processes provided a substantially more scientifically representative assessment than evaluation of groundwater monitoring data alone.
Evaluation of groundwater monitoring information also demonstrated the value of integrating analytical chemistry with environmental transport modeling. Multiple independent groundwater monitoring programs, regulatory investigations, public water system sampling, and environmental investigations documented the occurrence of PFOA, GenX, and additional PFAS compounds within regional groundwater resources. Analytical chemistry results were compared with modeled atmospheric deposition, hydrogeologic conditions, groundwater migration pathways, and historical manufacturing records to evaluate the consistency between predicted contaminant loading and measured groundwater concentrations. Integration of analytical monitoring with environmental modeling therefore strengthened interpretation of groundwater data by providing multiple independent lines of scientific evidence supporting long-term contaminant migration from atmospheric emissions to drinking water supplies.
The investigation additionally demonstrated the importance of evaluating historical manufacturing practices and engineering controls when reconstructing environmental contamination. Historical production records documented changes in fluoropolymer manufacturing, implementation of emission control technologies, transition from legacy fluorinated processing aids to replacement compounds, and evolving emission profiles over time. Consideration of these historical engineering changes provided critical context for interpreting atmospheric emissions, groundwater monitoring results, and changing environmental contaminant distributions observed throughout the study area. Integration of engineering documentation with environmental chemistry and groundwater science therefore strengthened reconstruction of long-term PFAS release histories and environmental loading.
Another important finding involved the successful integration of atmospheric dispersion modeling, hydrogeology, groundwater science, environmental chemistry, analytical chemistry, geographic information systems, engineering evaluation, and quantitative human health risk assessment into a unified environmental forensic framework. No individual groundwater sample, hydrogeologic investigation, emissions inventory, or atmospheric model independently characterized the complexity of long-term PFAS contamination. However, when historical manufacturing records, atmospheric deposition modeling, groundwater monitoring, hydrogeologic characterization, GIS analyses, analytical chemistry, regulatory investigations, and environmental fate and transport evaluations were collectively reviewed, they provided a scientifically supported assessment of PFAS migration from industrial emissions to public drinking water resources. This multidisciplinary, weight-of-evidence approach represents a fundamental principle of modern environmental forensics and provides a technically reliable framework for evaluating complex groundwater contamination involving persistent fluorinated compounds and long-term industrial emissions.
Conclusions
The available scientific and technical documentation provides a comprehensive foundation for evaluating long-term PFAS contamination of groundwater resources using accepted principles of environmental chemistry, atmospheric dispersion modeling, hydrogeology, contaminant fate and transport, groundwater science, soil chemistry, analytical chemistry, environmental toxicology, and quantitative human health risk assessment. Although PFAS contamination develops through complex environmental processes occurring over decades, the integration of historical manufacturing records, emissions reconstruction, atmospheric deposition modeling, groundwater monitoring, hydrogeologic characterization, engineering evaluations, and regulatory investigations provides a scientifically reliable framework for characterizing contaminant migration from industrial air emissions to public drinking water supplies. This multidisciplinary approach allows environmental contamination to be evaluated using methodologies that are consistent with accepted scientific practice and widely recognized within the hydrogeologic, environmental engineering, and environmental health professions.
The investigation demonstrated that evaluation of long-term PFAS contamination is most scientifically reliable when atmospheric dispersion modeling, groundwater hydrogeology, environmental chemistry, analytical chemistry, contaminant fate and transport, engineering analyses, and regulatory science are considered collectively rather than independently. This weight-of-evidence approach reduces uncertainty by integrating complementary sources of scientific information and provides a technically supported basis for evaluating historical emissions, atmospheric deposition, groundwater migration, contaminant persistence, and potential human exposure. Independent agreement among manufacturing records, atmospheric modeling, groundwater monitoring, hydrogeologic investigations, and analytical chemistry substantially strengthens confidence in the overall scientific assessment while recognizing the complexity of evaluating persistent environmental contaminants over multiple decades.
The investigation further demonstrated the importance of evaluating PFAS contamination within the broader context of regional hydrogeology, groundwater recharge, atmospheric deposition, soil chemistry, aquifer characteristics, well capture zones, and long-term contaminant migration. PFAS released to the atmosphere may undergo atmospheric transport and deposition before infiltrating soils, entering groundwater recharge areas, and migrating through aquifer systems supplying public drinking water wells. Comprehensive investigations integrating atmospheric science, hydrogeology, groundwater modeling, environmental chemistry, soil science, and analytical chemistry therefore provide a more technically accurate understanding of groundwater contamination than evaluations based solely upon individual groundwater samples or isolated monitoring events. Consideration of these multiple environmental processes is essential for developing scientifically defensible evaluations of PFAS migration and long-term impacts to drinking water resources.
The investigation also demonstrated the value of integrating historical emissions reconstruction with atmospheric deposition modeling and groundwater monitoring. Historical manufacturing records and engineering documentation established the magnitude and timing of PFAS emissions, while EPA-approved atmospheric dispersion modeling estimated cumulative deposition across groundwater recharge areas and public water supply well capture zones. Independent groundwater monitoring programs subsequently documented PFAS occurrence within regional aquifers, providing objective analytical measurements that complemented modeled environmental loading. Integration of engineering analyses, atmospheric science, hydrogeology, and analytical chemistry therefore provided a substantially more comprehensive evaluation of long-term environmental contamination than reliance upon environmental monitoring or modeling alone.
More broadly, this investigation demonstrates how modern environmental consulting integrates air dispersion modeling, hydrogeology, groundwater science, environmental chemistry, contaminant fate and transport, analytical chemistry, geographic information systems (GIS), environmental toxicology, and quantitative human health risk assessment to evaluate complex PFAS contamination investigations. These multidisciplinary evaluations provide scientifically supported assessments of environmental contamination while remaining grounded in accepted hydrogeologic principles, atmospheric science, peer-reviewed scientific literature, engineering analyses, environmental monitoring, and objective technical evaluation. By combining historical emissions reconstruction, atmospheric deposition modeling, groundwater characterization, analytical chemistry, exposure assessment, and environmental forensics, comprehensive investigations are able to develop reliable assessments of long-term PFAS contamination that are consistent with recognized scientific practice and contemporary environmental health methodologies.
This investigation was conducted under the direction of Dr. Paul Rosenfeld, an environmental scientist, hydrogeologist, air dispersion modeler, environmental forensic expert, and exposure assessment specialist with more than twenty-five years of experience evaluating PFAS contamination, groundwater quality, atmospheric dispersion modeling, environmental chemistry, contaminant fate and transport, hydrogeology, drinking water investigations, soil chemistry, environmental toxicology, and quantitative human health risk assessment. Throughout his career, Dr. Rosenfeld has conducted investigations involving PFAS, chlorinated solvents, petroleum hydrocarbons, volatile organic compounds, metals, pesticides, radionuclides, combustion byproducts, and numerous other environmental contaminants affecting groundwater resources, public drinking water systems, industrial facilities, residential communities, and occupational environments. His professional experience includes historical emissions reconstruction, groundwater contamination investigations, hydrogeologic characterization, atmospheric deposition modeling, environmental site investigations, regulatory review, contaminant fate and transport analysis, and expert witness testimony involving complex environmental contamination, toxic tort litigation, and drinking water exposure investigations.
References
Agency for Toxic Substances and Disease Registry (ATSDR). (2024). Toxicological Profile for Perfluoroalkyls (PFAS).
Interstate Technology & Regulatory Council (ITRC). (2026). PFAS Technical and Regulatory Guidance Document.
National Academies of Sciences, Engineering, and Medicine. (2022). Guidance on PFAS Exposure, Environmental Transport, and Human Health.
U.S. Environmental Protection Agency (EPA). (2024). Guidelines on Significant New Use Rules and PFAS Manufacturing.
U.S. Environmental Protection Agency (EPA). (2024). Integrated Risk Information System (IRIS): Perfluorooctanoic Acid (PFOA).
U.S. Environmental Protection Agency (EPA). (2024). National Primary Drinking Water Regulations for PFAS.
U.S. Environmental Protection Agency (EPA). (2024). AERMOD Implementation Guide.
U.S. Environmental Protection Agency (EPA). (2024). Guidelines on Air Quality Models (40 CFR Part 51, Appendix W).
U.S. Geological Survey (USGS). (2024). Groundwater Hydrology and Aquifer Characterization.
North Carolina Department of Environmental Quality (NCDEQ). PFAS Investigation Program.