Continuous Monitoring of Atmospheric Halocarbons with a Dewater-Thermo Desorption Unit and GC-ECD: Insights from Industrial and Urban Environments
Notice bibliographique
Résumé
In the face of the complex composition of atmospheric pollutants, our laboratory has developed a Thermo Desorption Unit (TD) for capturing and concentrating trace-level volatile organic compounds (VOCs) in air samples. Because of the humid climate, we added a Dewater Unit (DW) before the TD to remove excess moisture from air samples while retaining polar and non-polar species to keep sample integrity. This setup has been successfully utilized in the past by connecting the DW-TD units with gas chromatography (GC) equipped with flame ionization detection (FID) and mass spectrometry (MS). While the data quality from GC-FID was extremely stable and robust, the drift and, thus, instability in MS is significant by comparison. In this research, we attempted to use electron capture detection (ECD) to test the stability of the DW-TD units by exploiting ECD’s high sensitivity, stability, and ease of operation. Another prominent advantage of ECD is that it only needs high-purity nitrogen gas as both the carrier and make-up gas. We exploited ECD's highly sensitive and selective properties to measure trace-level atmospheric chlorofluorocarbons (CFCs) and halocarbons to demonstrate the performance of the self-built DW-TD apparatuses. Since CFCs have extremely long atmospheric lifetimes and are well-mixed in the atmosphere due to the Montreal Protocol banning them from most applications, they exhibit certain background mixing levels during a relatively short period of time, e.g., weeks, with variability smaller than most GC’s analytical precisions. We then utilized this property to assess the stability of our homemade instrument. During the one-month continuous online analysis of DW-TD/GC-ECD at an industrial park known for semiconductor and electronics manufacturing, the mole fractions of CFC-12 was found to be 485.19±0.22 ppt (parts per trillion), with RSD (Relative Standard Deviations) = 0.06%. Although CFC-11, CFC-113, and CCl4 have long been phased out, abrupt rises in signal were still detected, suggesting emissions still existed in this industrial complex. By filtering out data with relatively stable mole fractions in between events, the RSD for CFC-11, CFC-113, and CCl4 was found to be 0.12%, 0.36%, and 0.30%, respectively. To further validate the high-value events observed in the industrial park, we conducted an additional one-month continuous online analysis of DW-TD/GC-ECD at a university campus in Taipei as a contrast of environment. This comparative study yielded stable background mole fractions for CFC-12, CFC-11, CFC-113, and CCl4, with RSD of 0.05%, 0.10%, 0.32%, and 0.29%, respectively. These results will be compared with the variability from AGAGE's online data using Medusa/GC-MS and the offline data of NOAA by GC-MS. The occurrence of the high-value events during the month-long measurements can be traced back to emission sources by utilizing backward trajectories to the potential sources for further investigation.
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 distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| 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 | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 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 tête enseignante, 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 ».