Elucidating the origins of ultrafine particles in a major city using long-term datasets: Evidence of a new midday process
Notice bibliographique
Résumé
Ultrafine particles (UFPs) are both directly emitted from human activities and produced through atmospheric processes. The origins of ultrafine particles were explored in an urban area by analyzing 6 to 520 nm particle size data collected from 2006 to 2021 near a busy roadway in downtown Toronto, Canada. Days were classified into five categories: Strong Nucleation, Midday Pollution, Traffic Pollution, Baseline, and Mixed. Strong Nucleation days, which comprised about 6% of the days, showed long nucleation events (¿ 3 hr) with an average particle number concentration of 3.1±0.1 × 1 0 4 #/ cm 3 around noon (10 am to 2 pm). Midday Pollution days also exhibited higher particle concentrations around noon with an average of 3.3±0.06 × 1 0 4 #/ cm 3 . The higher number concentrations on these days appeared to arise from locally emitted UFP and be associated with enhanced production of UFP within vehicle exhaust plumes. The Traffic Pollution days showed morning traffic emissions, with no midday rise. The average total UFP concentration around the morning rush hour (6 am to 9 am) on these days was 2.1±0.2 × 1 0 4 #/ cm 3 . About 27% of the days had lower particle number concentrations (daily average: 1.2±0.2 × 1 0 4 #/ cm 3 ) throughout the day. The number concentrations were lower on these “Baseline days” and the influence of traffic emissions was also lower but still observable in the diurnal pattern. Lastly, Mixed days were the days that showed higher than Baseline concentrations of UFP around the morning rush hour (2.0±0.06 × 1 0 4 #/ cm 3 ) or midday (2.3±0.1 × 1 0 4 #/ cm 3 ); UFP on these days came from a mix of traffic pollution, nucleation event, or a midday process, with no one of these sources clearly dominant. These days could not be categorized into any of these categories with confidence. Analysis of the organic and inorganic speciation, trace elements, and traffic-related air pollutants suggested that the UFP on Midday Pollution days came from vehicle emissions enhanced by reactions within their exhaust plumes. Moreover, the time series analysis of these categories showed that the frequency of Midday Pollution days has decreased over the years with the number of Baseline days correspondingly increasing. Meteorological analysis showed that Midday and Traffic Pollution days happened more often in winter while Strong Nucleation days were more frequent in summer. This study has shown that higher midday UFP concentrations do not arise only due to nucleation events and that a previously unrecognized Midday Pollution process can be a large contributor. • Particle size distribution was collected in an urban area from 2006 to 2021. • Based on particle size distribution days were classified into five categories. • A previously unrecognized ”Midday Pollution” process was observed after classifying. • Noon UFP levels on Midday Pollution days were like those on Strong Nucleation days. • UFP on Midday Pollution days had larger spikes associated with vehicle exhaust.
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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 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 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 ».