Applying the modified UV-activated TOP assay to complex matrices impacted by aqueous film-forming foams

Caitlin M Glover; Faezeh Pazoki; Gabriel Munoz; Sébastien Sauvé; Jinxia Liu

doi:10.1016/j.scitotenv.2024.171292

Applying the modified UV-activated TOP assay to complex matrices impacted by aqueous film-forming foams

Sci Total Environ. 2024 May 10:924:171292. doi: 10.1016/j.scitotenv.2024.171292. Epub 2024 Mar 2.

Authors

Caitlin M Glover¹, Faezeh Pazoki¹, Gabriel Munoz², Sébastien Sauvé², Jinxia Liu³

Affiliations

¹ Department of Civil Engineering, McGill University, Montréal, Quebec H3A 0C3, Canada.
² Département de chimie, Université de Montréal, Montréal, QC H2V 0B3, Canada.
³ Department of Civil Engineering, McGill University, Montréal, Quebec H3A 0C3, Canada. Electronic address: jinxia.liu@mcgill.ca.

PMID: 38432371
DOI: 10.1016/j.scitotenv.2024.171292

Abstract

Per- and polyfluoroalkyl substances (PFAS) are a large chemical family, and numerous chemical species can co-exist in environmental samples, especially those impacted by aqueous film-forming foams (AFFFs). Given the limited availability of chemical standards, capturing the total amount of PFAS is challenging. Thus, the total oxidizable precursor (TOP) assay has been developed to estimate the total amount of PFAS via the oxidative conversion of precursors into perfluorocarboxylic acids (PFCAs). This study aims to enhance the robustness of the TOP assay by replacing heat activation with UV activation. We evaluated the molar yields of known precursors in water in the presence of varying levels of Suwannee River natural organic matter (SRNOM) and in two soils. The impact of UV activation was also evaluated in two soils spiked with three well-characterized AFFFs, six AFFF-impacted field soils, and nine rinse samples of AFFF-impacted stainless-steel pipe. In the presence of 100 mg/L SNROM, 6:2 fluorotelomer sulfonate (FTS), 8:2 FTS, and N-ethyl perfluorooctane sulfonamidoacetic acid (N-EtFOSAA) in deionized water had good molar recovery as PFCAs (average of 102 ± 9.8 %); at 500 mg/L SNROM, the recovery significantly dropped to an average of 51 ± 19 %. In two soils (with 4 % and 8.8 % organic matter) with individual precursor spikes, the average molar recovery was 101 ± 9.4 %, except N-EtFOSAA, which had a reduced recovery in the soil with 8.8 % organic matter (OM). UV-activated assays outperformed heat-activated ones, especially in AFFF-impacted soils and pipe extract samples, with an average of 1.4-1.5× higher PFCA recovery. In almost all test samples, UV activation resulted in a notable shift towards longer PFCA chain lengths, particularly for samples with high OM content. The study confirmed the advantages of UV activation, including a significantly shortened exposure time (1 h vs. 6 h) and reduced matrix effects from OM due to the dual functions of UV in activating persulfate and photodegrading OM.

Keywords: Aqueous film-forming foams (AFFF); Per- and polyfluoroalkyl substances (PFAS); Photochemical degradation; Soil; Total oxidizable precursor assay (TOP); UV activation.