Per- and polyfluoroalkyl substances (PFAS) are extensively used in urban environments and are, thus, found in urban stormwater. However, the relevance of stormwater as a pathway for PFAS to urban streams is largely unknown. This study evaluated the impact of urban stormwater runoff on PFAS concentrations and spatial distribution in three urban streams affected by stormwater discharges from separate sewer systems. River water was sampled during dry (DW) and wet weather (WW) upstream, immediately downstream, and further downstream of three urbanized areas with separate sewer systems and with and without point sources (i.e. waste water treatment plant, airports). Water samples were analyzed for 34 targeted PFAS compounds and sediment samples for 35 targeted PFAS and 30 PFAS compounds using a total oxidizable precursor assay. The sum of the quantified PFAS concentrations ranged from the reporting limit (RL) to 84.7 ng/L during DW and increased as the streams were affected by WW discharges (0.87 to 102.3 ng/L). The highest PFAS concentrations were found downstream of urban areas and/or point sources (i.e. airports) during WW, indicating a clear contribution from stormwater discharges. A consistent PFAS contribution from the WWTP was observed under both DW and WW conditions. During WW events, concentrations of perfluorooctanesulfonic acid (PFOS) and total PFAS (PFOA equivalents) exceeded the annual average environmental quality standards, which are an established limit of 0.65 ng/L for PFOS and a proposed limit of 4.4 ng/L for total PFAS. Notably, except for the legacy PFAS, PFOS and perfluorooctanoic acid (PFOA), the most frequently quantified PFAS during DW were short-chain. For WW, long-chain perfluorocarboxylic acids (PFCAs) and a precursor, 6:2 Fluorotelomer sulfonic acid (6:2 FTS), were more frequently quantified, suggesting stormwater is a source of these longer-chain and particle-associated PFAS. The detection of unregulated fluorotelomer sulfonates (FTSs) such as 6:2 and 8:2 FTS during WW suggests a need for regulatory action, as these compounds can degrade into more stable PFAS. In sediment, higher concentrations, and a greater variety of PFAS were found at sites with known point sources i.e. airports. Long-chain PFCAs (C7–C13), perfluoroalkyl sulfonates (PFSAs) (C6), and precursors (i.e. N-Ethyl perfluorooctane sulfonamidoacetic acid), were more prevalent in sediments than in the water. Notably, PFOS concentrations in sediment exceeded the lowest Predicted No-Effect Concentration (PNEC) across sites, posing a potential long-term environmental risk, though current PNECs for other PFAS may underestimate such risks. The findings of the study highlight urban stormwater as a source of PFAS to urban streams indicating the need to minimize PFAS sources in the urban environment and to effectively treat stormwater to protect receiving water bodies.

This study investigated how urban stormwater runoff, known to contain various chemical substances, alters pollutant concentrations in the receiving water bodies. Samples were collected under dry and wet weather conditions at 4 sampling stations along the Fyrisån, a river that passes along the city of Uppsala, Sweden. Samples were analyzed for 80 organic substances, 19 metals (total and dissolved phase), and conventional physicochemical parameters. 19 of 80 organic substances were qualified above the limit of quantification (LOQ) in at least one sampling event. The most detected substance family was poly-fluoroalkyl substances (PFAS). The concentrations of detected organic substances and metals increased in wet weather conditions. Organic substance and metal concentrations showed similar spatial variation with higher concentrations measured at sampling locations close to urbanized areas.

Cette étude a examiné comment le ruissellement des eaux pluviales urbaines, connues pour contenir diverses substances chimiques, modifie les concentrations de polluants dans les masses d'eau réceptrices. Des échantillons ont été collectés dans des conditions de temps sec et humide dans 4 stations d'échantillonnage le long de la Fyrisån, une rivière qui passe le long de la ville d'Uppsala, en Suède. Les échantillons ont été analysés pour 80 substances organiques, 19 métaux (phase totale et dissoute), et des paramètres physico-chimiques conventionnels. 19 des 80 substances organiques ont été qualifiées au-dessus de la limite de quantification (LOQ) à au moins un des événements d'échantillonnage. La famille de substances la plus détectée était les substances polyfluoroalkyles (PFAS). Les concentrations des substances organiques et des métaux détectés ont augmenté par temps humide. Les concentrations de substances organiques et de métaux présentaient une variation spatiale similaire, les concentrations les plus élevées étant mesurées aux points d'échantillonnage proches des zones urbanisées.