Impacts of transportation emissions on horizontal and vertical distributions of air pollutants in Shanghai: Insights from emission reduction in COVID-19 lockdown
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Résumé
Transportation is a major sector of anthropogenic emissions in urban areas and deteriorates air quality. The surface and vertical observational data were combined with the model results to reveal its impact on the horizontal and vertical variations of pollutants during the COVID-19 lockdown period. The evident reductions in ambient PM 2.5 (∼30%) and NO 2 (∼50%) concentrations but a ∼25% increase in O 3 concentration were observed at the transportation sites. On the vertical scale, a uniform decrease of ∼28% in PM 2.5 concentrations was observed within 600 m. However, the vertical profiles of NO 2 and O 3 exhibited increasing vertical variation rates with concentrations varying significantly within 400 m. Meanwhile, O x shared a similar pattern of vertical profile with O 3 , with a uniform increase (∼5%) within 600 m in the urban area. The WRF-CMAQ model reproduced the variations, and revealed that the reduction of transportation emissions was the key factor contributing to the increase of urban O 3 and O x due to the weakened NO titration effect. The simulated vertical profile of NO 2 was featured by a decreasing curve, while that of O 3 exhibited the opposite trend. We find that the transportation emissions impact vertical concentrations of NO 2 and O 3 within at most 400 m. The process analysis revealed that the vertical transport and horizontal transport from bay areas contributed to O 3 in the urban area, while chemical processes mainly consumed it. The reduction in transportation emissions weakened the consumption and resulted in O 3 accumulation during rush hours and at night. The variation of planetary boundary layer height also favored the rise of urban O 3 by promoting vertical transport at daytime and trapping it at night. The reduction in NO x emissions from the transportation enhanced O 3 pollution, suggesting that collaborative reductions in VOCs from multiple sectors should be conducted. This study also indicated that regional collaborations in emission reductions were necessary for comprehensive air pollution prevention. • Changes in air pollutant concentrations caused by lockdown differentiated evidently at transportation and industrial sites. • Vertical profiles of pollutants within 400 m height responded obviously to the reduction of transportation emissions. • Transportation emissions reduction and vertical transport are key factors of ozone accumulation near the surface.
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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) | 0,001 | 0,000 |
Scores machine (provisoires)
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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 découle