Occurrence and environmental fate of per- and polyfluoroalkyl substances (PFASs) at aqueous film-forming foams (AFFF)-impacted sites
Notice bibliographique
Résumé
Over the years, people have recognized that widely used per- and polyfluoroalkyl substances (PFAS) in industry and consumer products often appear as anthropogenic pollutants in the environment and biota. PFAS-containing aqueous film-forming forms (AFFFs) used for controlling class B fires constitute significant sources of PFAS pollution. The persistent, bioaccumulative and toxic properties of select PFAS call for a better understanding of the large chemical class in terms of their environmental behaviors and impact. In addition to anionic perfluoroalkyl acids (PFAAs), zwitterionic and cationic PFAS have been recognized as important constituents in AFFFs and at AFFF-impacted sites. However, assessing the environmental impact of AFFF deployment is challenging due to the large variety of PFAS species and complex chemistry. In particular, information on the appearance and abundance of zwitterionic and cationic PFAS is sparse, and the environmental behaviors of such compounds remain poorly understood. This thesis intends to fill such knowledge gaps.First, the PFAS profiles at four Canadian airports were characterized using a range of advanced analytical tools, which was the first study of its kind in Canada. Results showed that these airports were commonly impacted by more than one AFFF chemistry, while distinct PFAS profiles and loads indicate the influence of AFFF use history. In source zone areas, zwitterions and cations made a high contribution (34.5-85.5%) in surface soils but a low contribution (<20%) in groundwaters. The PFAS in source zone soils had limited horizontal transfer, while the vertical migration down soil columns occurred even in locations of low permeability. In the background soils where AFFF impact was insignificant, unidentified precursors made up high percentages, probably resulting from atmospheric deposition. The study provides improved methodology, new knowledge and a priority list of PFAS to support future PFAS monitoring and remediation efforts.Next, the biotransformation potential of zwitterionic polyfluoroalkyl compounds made via the historical electrochemical fluorination (ECF) process was investigated in aerobic soils. Two compounds with betaine head groups and two with tertiary amine groups were examined for the first time. The perfluoroalkyl sulfonamide betaine and tertiary amine were confirmed to be the precursors to perfluorooctane sulfonate (PFOS), while the amide betaine and tertiary amine were precursors to perfluorooctane carboxylate (PFOA). Comparing their transformation kinetics with four other previously reported ECF-zwitterions and cations indicates the great influence of structure, especially the nitrogen head groups, on the chemical persistence. Specifically, i) the ECF precursors with sulfonamide group have higher microbial stability than those with an amide group; ii) the ECF precursors containing quaternary ammonium or betaine groups have high stability in soils with DT50 in years or decades, while those with tertiary amine or amine oxide groups were less stable with DT50 of weeks or months. For the first time, this study establishes a preliminary structure-degradability relationship for ECF precursors
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».