Machine Learning Modeling Reveals Divergent Air Pollutant Responses to Stringent Emission Controls in the Yangtze River Delta Region
Ozone (O<sub>3</sub>) and fine particulate matter (PM<sub>2.5</sub>) are critical atmospheric pollutants whose complex chemical coupling presents significant challenges for multi-pollutant control strategies. This study investigated the spatiotemporal variations and driving m...
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| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-06-01
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| Series: | Atmosphere |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2073-4433/16/6/710 |
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| Summary: | Ozone (O<sub>3</sub>) and fine particulate matter (PM<sub>2.5</sub>) are critical atmospheric pollutants whose complex chemical coupling presents significant challenges for multi-pollutant control strategies. This study investigated the spatiotemporal variations and driving mechanisms of O<sub>3</sub> and PM<sub>2.5</sub> in Jiaxing, China, during different COVID-19 lockdown periods from November 2019 to January 2024. Using high-resolution monitoring data, random forest modeling, and HYSPLIT backward trajectory analysis, we quantified the relative contributions of anthropogenic emissions, meteorological conditions, and regional transport to the formation and variation of O<sub>3</sub> and PM<sub>2.5</sub> concentrations. The results revealed a distinct inverse relationship between O<sub>3</sub> and PM<sub>2.5</sub>, with meteorologically normalized PM<sub>2.5</sub> decreasing significantly (−5.0 μg/m<sup>3</sup> compared to the pre-lockdown baseline of 0.6 μg/m<sup>3</sup>), while O<sub>3</sub> increased substantially (15.2 μg/m<sup>3</sup> compared to the baseline of 5.3 μg/m<sup>3</sup>). Partial dependency analysis revealed that PM<sub>2.5</sub>-O<sub>3</sub> relationships evolved from linear to non-linear patterns across lockdown periods, while NO<sub>2</sub>-O<sub>3</sub> interactions indicated shifts from VOC-limited to NO<sub>x</sub>-limited regimes. Regional transport patterns exhibited significant temporal variations, with source regions shifting from predominantly northern areas pre-lockdown to more diverse directional contributions afterward. Notably, the partial lockdown period demonstrated the most balanced pollution control outcomes, maintaining reduced PM<sub>2.5</sub> levels while avoiding O<sub>3</sub> increases. These findings provide critical insights for developing targeted multi-pollutant control strategies in the Yangtze River Delta region and similar urban environments. |
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| ISSN: | 2073-4433 |