Issue 12, 2021

Surface-water/groundwater boundaries affect seasonal PFAS concentrations and PFAA precursor transformations

Abstract

Elevated concentrations of per- and polyfluoroalkyl substances (PFAS) in drinking-water supplies are a major concern for human health. It is therefore essential to understand factors that affect PFAS concentrations in surface water and groundwater and the transformation of perfluoroalkyl acid (PFAA) precursors that degrade into terminal compounds. Surface-water/groundwater exchange can occur along the flow path downgradient from PFAS point sources and biogeochemical conditions can change rapidly at these exchange boundaries. Here, we investigate the influence of surface-water/groundwater boundaries on PFAS transport and transformation. To do this, we conducted an extensive field-based analysis of PFAS concentrations in water and sediment from a flow-through lake fed by contaminated groundwater and its downgradient surface-water/groundwater boundary (defined as ≤100 cm below the lake bottom). PFAA precursors comprised 45 ± 4.6% of PFAS (PFAA precursors + 18 targeted PFAA) in the predominantly oxic lake impacted by a former fire-training area and historical wastewater discharges. In shallow porewater downgradient from the lake, this percentage decreased significantly to 25 ± 11%. PFAA precursor concentrations decreased by 85% between the lake and 84–100 cm below the lake bottom. PFAA concentrations increased significantly within the surface-water/groundwater boundary and in downgradient groundwater during the winter months despite lower stable concentrations in the lake water source. These results suggest that natural biogeochemical fluctuations associated with surface-water/groundwater boundaries may lead to PFAA precursor loss and seasonal variations in PFAA concentrations. Results of this work highlight the importance of dynamic biogeochemical conditions along the hydrological flow path from PFAS point sources to potentially affected drinking water supplies.

Graphical abstract: Surface-water/groundwater boundaries affect seasonal PFAS concentrations and PFAA precursor transformations

Supplementary files

Article information

Article type
Paper
Submitted
08 Aug. 2021
Accepted
23 Okt. 2021
First published
15 Nov. 2021
This article is Open Access
Creative Commons BY-NC license

Environ. Sci.: Processes Impacts, 2021,23, 1893-1905

Surface-water/groundwater boundaries affect seasonal PFAS concentrations and PFAA precursor transformations

A. K. Tokranov, D. R. LeBlanc, H. M. Pickard, B. J. Ruyle, L. B. Barber, R. B. Hull, E. M. Sunderland and C. D. Vecitis, Environ. Sci.: Processes Impacts, 2021, 23, 1893 DOI: 10.1039/D1EM00329A

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