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Limited monitoring data are available regarding the occurrence of emerging per- and polyfluoroalkyl substances (PFAS) in drinking water. Here, we validated an analytical procedure for 42 PFAS with individual detection limits of 0.001-0.082 ng/L. We also evaluated how different sample pH conditions, dechlorinating agents, and storage holding times might affect method performance. PFAS were analyzed in tap water samples collected at a large spatial scale in Quebec, Canada, covering 376 municipalities within 17 administrative regions. Target and nontarget screening revealed the presence of 31 and 23 compounds, respectively, representing 24 homolog classes. Overall, 99.3% of the tap water samples were positive for at least one PFAS, and the ƩPFAS ranged from below detection limits to 108 ng/L (95th percentile: 13 ng/L). On average, ƩPFAS was 12 times higher in tap water produced from surface water than groundwater; however, 6 of the top 10 contaminated locations were groundwater-based. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) had high detection rates (88% and 80%, respectively). PFOS (median: 0.15 ng/L; max: 13 ng/L) and PFOA (median: 0.27 ng/L; max: 8.1 ng/L) remained much lower than current Health Canada guidelines but higher than USEPA's interim updated health advisories. Short-chain (C3-C6) perfluoroalkyl sulfonamides were also recurrent, especially the C4 homolog (FBSA: detection rate of 50%). The 6:2 fluorotelomer sulfonyl propanoamido dimethyl ethyl sulfonate (6:2 FTSO2PrAd-DiMeEtS) was locally detected at ∼15 ng/L and recurred in 8% of our samples. Multiple PFAS that are most likely to originate from aqueous film-forming foams were also reported for the first time in tap water, including X:3 and X:1:2 fluorotelomer betaines, hydroxylated X:2 fluorotelomer sulfonates, N-trimethylammoniopropyl perfluoroalkane sulfonamides (TAmPr-FHxSA and TAmPr-FOSA), and N-sulfopropyl dimethylammoniopropyl perfluoroalkane sulfonamidopropyl sulfonates (N-SPAmP-FPeSAPS and N-SPAmP-FHxSAPS)., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:, (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Reproducible analytical procedures and rigorous quality control are imperative for an accurate monitoring of cyanobacterial toxins in environmental water samples. In this study, the short-term and long-term storage stability of diverse cyanotoxins (anatoxins, cylindrospermopsin, anabaenopeptins, and 12 microcystins) was evaluated in water samples, under different scenarios. Transport controls were performed at three monitoring sites in spiked ultrapure water and lake water to investigate short-term stability issues. Medium-term storage stability was evaluated for up to 14-28 days in ultrapure water, chlorine-treated drinking water (amended with reductant), and surface water (filtered and unfiltered) stored at different temperatures (20 °C, 4 °C, and -20 °C). Substantial decreases of cylindrospermopsin and anabaenopeptins were observed in tap water (20 °C) and unfiltered surface water (20 °C or 4 °C). Regardless of matrix type, cyanotoxin recoveries generally remained within an 80-120% range when the water samples were kept frozen. After a prolonged storage duration of 365 days at -20 °C, most cyanotoxins experienced decreases in the range of 10-20%. The notable exception was for the tryptophan-containing MC-LW and MC-WR, with more substantial variations (30% to 50% decrease) and conversion to N-formylkynurenine analogs. Reanalysis of field-collected surface waters after long-term storage at -20 °C also indicated significantly decreasing trends of cyanotoxins (between 6% and 23% decrease). In view of the above, short sample hold times should be favored as recommended in EPA methods., (Copyright © 2020. Published by Elsevier B.V.)

The herbicide atrazine remains in use in Canada, the United States, and several other countries, while being banned since 2003 in the European Union. A comprehensive quality survey of atrazine (ATZ) and one of its metabolites, desethylatrazine (DEA), was conducted in 2015-2018 in drinking water available to consumers in Quebec, Canada. Temporal variations of ATZ and DEA were monitored in tap water from the Montreal area for 18 consecutive months (Temporal survey 2015-2016). Within this time window, the sum of ATZ and DEA in tap water samples (n = 450) varied from 40 to 250 ng L -1 (median: 98 ng L -1 ). ATZ was systematically detected (100%), with a concentration range of 30-195 ng L -1 (median: 49 ng L -1 ) while DEA was in the range of 10-187 ng L -1 (median: 36 ng L -1 ). Maximum ATZ concentrations remained about 25× lower than the Canadian drinking water quality guideline (5000 ng L -1 ), but 48% of the samples were above that of the European Union (100 ng L -1 ) regarding the sum of ATZ and DEA. Trends of ATZ and DEA in drinking water were also examined across southwestern Quebec (Spatial survey 2017-2018). The sum of the two triazines in this second set of samples varied from below the method detection limit (for 33 out of the 52 surveyed municipalities) to 104 ng L -1 . Apart from Montreal, locations in the southern shore of the St. Lawrence showed generally higher levels of atrazine and DEA. The highest concentrations clustered in the Montérégie region, along the St. Lawrence River (e.g., Brossard, Longueuil, Saint-Constant) and/or downstream from agricultural areas. The ATZ concentrations are suggested to have decreased compared to previous surveys, which is consistent with the decrease in the sales of active ingredients in Ontario (upstream sources) and Quebec., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In the last decade or so, concerns have arisen with respect to the widespread occurrence of perfluoroalkyl acids (PFAAs) in the environment, food, drinking water, and humans. In this study, the occurrence and levels of a large range of perfluoroalkyl and polyfluoroalkyl substances (PFASs) were investigated in drinking water (bottled and tap water samples) from various locations around the world. Automated off-line solid phase extraction followed by ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry was used to analyze PFASs of various chain lengths and functional groups. In total, 29 target and 104 suspect-target PFASs were screened in drinking water samples (n=97) from Canada and other countries (Burkina Faso, Chile, Ivory Coast, France, Japan, Mexico, Norway, and the USA) in 2015-2016. Out of the 29 PFASs quantitatively analyzed, perfluorocarboxylates (PFCAs: C 4/14 ), perfluoroalkane sulfonates (PFSAs: C 4 , C 6 , C 8 ), and perfluoroalkyl acid precursors (e.g., 5:3 fluorotelomer carboxylate (5:3 FTCA)) were recurrently detected in drinking water samples (concentration range: -1 ). Tap water samples from Canada showed noteworthy differences depending on their source; for instance, ∑ 29 PFASwas significantly greater in those produced from the Great Lakes/St. Lawrence River ecosystem than those produced from other types of sources (14 versus 5.3ngL -1 , respectively). A suspect-target screening approach indicated that other perfluoroalkane sulfonamides (FBSA, FHxSA), perfluoroethyl cyclohexane sulfonate (PFECHS), ultrashort chain (C 2 -C 3 ) PFSAs (PFEtS, PFPrS), and two additional PFSAs (PFPeS (C 5 ) and PFHpS (C 7 )) were repeatedly present in tap water samples (concentration ranges: -1 ). To the authors' best knowledge, this constitutes the first observation of a cyclic perfluoroalkane sulfonate (PFECHS) and C 4 -C 6 perfluoroalkane sulfonamides (FBSA, FHxSA) in drinking water. According to the newly updated US EPA health advisory for PFOS and PFOA (70ngL -1 ), the drinking water samples collected in the present monitoring would not pose a health risk to consumers as regards PFAA levels., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Adsorption of mixtures of cyanotoxins onto sediment as a dominant mechanism in the elimination of cyanotoxins from the aqueous phase has not been extensively investigated. The aim of this study was to investigate adsorption and desorption behavior of six microcystins including microcystin (MC)-LR, RR, YR, LY, LW and LF and cylindrospermopsin (CYN) on natural sediment. Freundlich and Langmuir isotherms could be fitted for MC-LR, RR, YR and CYN. Sorption kinetics showed immediate rapid adsorption for all cyanotoxins: CYN, MCLW and MCLF were adsorbed 72.6%, 56.7% and 55.3% respectively within 2 h. Results of desorption experiments demonstrated that less than 9% of cyanotoxins desorbed from sediment within 96 h. Adsorption of cyanotoxins onto three fractionated sediments particles, clay-silt (<75 μm), find sand (75-315 μm) and coarse sand (315-2000 μm) demonstrated that adsorption capacity of coarse sand fraction for all the tested cyanotoxins was less than 4% of the clay-silt fraction. Results of this study revealed that there is a potential for cyanotoxins to accumulate in the sediments of lakes, as well as in drinking water treatment plants. Monitoring programs must consider cyanotoxins in the particulate phase to avoid largely underestimating toxin concentrations following their release from blooms., (Copyright © 2015 Elsevier Ltd. All rights reserved.)