Groundwater flowpath characteristics drive variability in per- and polyfluoroalkyl substances (PFAS) loading across a stream-wetland system

Journal Article · Fri Jan 24 00:00:00 EST 2025 · Science of The Total Environment

DOI:https://doi.org/10.1016/j.scitotenv.2025.178533· OSTI ID:2586444

Rey, David M. ^[1]; Briggs, Martin A. ^[2]; Tokranov, Andrea K. ^[3]; Lind, Hayley G. ^[3]; Scordato, Patrick T. ^[3]; Iery, Ramona Darlington ^[4]; Moore, Henry E. ^[5]; Slater, Lee D. ^[6]; LeBlanc, Denis R. ^[3]

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1. US Geological Survey, Lakewood, CO (United States). Hydrologic Remote Sensing Branch
2. US Geological Survey, Storrs, CT (United States). Hydrologic Remote Sensing Branch
3. US Geological Survey, Northborough, MA (United States). New England Water Science Center
4. Naval Facilities Engineering and Expeditionary Warfare Center (NAVFAC EXWC), Columbus, OH (United States)
5. Rutgers University, Newark, NJ (United States)
6. Rutgers University, Newark, NJ (United States); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

Groundwater dependent ecosystems in areas with industrial and military land use are at risk of direct exposure to a wide range of contaminants, including PFAS chemicals. Glaciated terrain often has mixed high and low permeability sediments coupled with groundwater flow-through lake features. These hydrogeologic attributes create highly complex ‘source to seep’ dynamics that make spatiotemporal contaminant transport patterns difficult to predict. We investigated one such system in detail using a suite of heat-tracing and chemical methods. Numerous (n=57) preferential groundwater discharge zones (vertical flux rates ranging 0.2 to 3.2 m/d) were identified across the upper Quashnet River stream-wetland system in Mashpee, MA, USA, adjacent to an Air Force Base with several known PFAS source areas. Surface-water and groundwater samples were collected and analyzed (n=145) for precursors and terminal PFAS compounds between March and September 2022. Samples were collected at identified seeps along the Quashnet River (n=59), from wells upgradient from the stream-wetland system (n= 44), from contributing flow-through kettle lakes (n=8), and at multiple locations along the Quashnet River (n=34). Samples from seeps and wells had measured PFAS concentrations ranging from non-detect to approximate 3,500 ng/L (mean= 1,650 ng/L), and a range of deuterium excess values (3.2 to 15.9 per mil) indicative of varying degrees of groundwater-lake interaction prior to emergence at the discharge zones. Groundwater-lake interaction along flowpaths that sourced the sampled seeps was farther supported by significant correlations (p < 0.01) between deuterium excess and %PFAS precursors, and between %PFAS precursors and multiple terminal PFAS compounds (e.g., PFPeS, PFBS, PFHxS). However, some sampled seeps contributing groundwater to the stream-wetland system had much higher total PFAS concentrations (>1000 ng/L) than the upgradient kettle lakes, despite showing lake (evaporative) isotopic signatures, indicating the potential for groundwater flowpath convergence at wetland discharge zones and the influence of lakebed PFAS precursor reactions. PFAS compounds and water isotopic composition at sampled multilevel groundwater wells, rivers, lakes, and seeps suggest that a complex mixture of source groundwater and flowpath characteristics are responsible for diverse observed PFAS mixtures at preferential discharge zones across the stream-wetland system. Further, total PFAS loading patterns to the Quashnet River via groundwater discharge remained remarkably similar from winter to summer to fall conditions, despite a regional dry period in late summer 2022 with the upper river channel completely drying. This work addresses gaps in the existing PFAS literature by demonstrating the importance of subsurface fate and transport on PFAS compound concentrations in controlling contaminant mass loading in preferential groundwater discharge zones and presents a transferrable field toolkit for efficient characterization of spatially preferential PFAS transport dynamics.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE; USGS
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 2586444
• Report Number(s): PNNL-SA--201022
• Journal Information: Science of The Total Environment, Journal Name: Science of The Total Environment Vol. 964; ISSN 0048-9697
• Publisher: Elsevier BV
• Country of Publication: United States
• Language: English

Related Subjects

Contaminant transport
Groundwater-surface water interactions
Mass loading
PFAS