Extreme weather exacerbates ozone pollution in the Pearl River Delta, China: role of natural processes
<p>Ozone (<span class="inline-formula">O<sub>3</sub></span>) pollution research and management in China have mainly focused on anthropogenic emissions, while the importance of natural processes is often overlooked. With the increasing frequency of extreme weat...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2024-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/24/1559/2024/acp-24-1559-2024.pdf |
| Summary: | <p>Ozone (<span class="inline-formula">O<sub>3</sub></span>) pollution research and management in China have mainly focused on anthropogenic emissions, while the importance of natural processes is often overlooked. With the increasing frequency of extreme weather events, the role of natural processes in exacerbating <span class="inline-formula">O<sub>3</sub></span> pollution is gaining attention. In September 2022, the Pearl River Delta (PRD) in southern China experienced an extended period (25 d) of regional <span class="inline-formula">O<sub>3</sub></span> exceedances and high temperatures (second highest over last 2 decades) due to extreme weather conditions influenced by the subtropical high and typhoon peripheries. Employing an integrated approach involving field measurements, machine learning and numerical model simulations, we investigated the impact of weather-induced natural processes on <span class="inline-formula">O<sub>3</sub></span> pollution by considering meteorological factors, natural emissions, chemistry pathways and atmospheric transport. The hot weather intensified the emission of biogenic volatile organic compounds (BVOCs) by <span class="inline-formula">∼10</span> %. Isoprene and biogenic formaldehyde accounted for 47 % of the in situ <span class="inline-formula">O<sub>3</sub></span> production, underscoring the predominant role of BVOC emissions in natural processes. The chemical pathway of isoprene contributing to <span class="inline-formula">O<sub>3</sub></span> formation was further explored, with <span class="inline-formula">O<sub>3</sub></span> production more attributable to the further degradation of early generation isoprene oxidation products (contributed 64.5 %) than the direct isoprene oxidation itself (contributed 35.5 %). Besides, it was found that the hot weather significantly promoted regional photochemical reactions, with meteorological factors contributing to an additional 10.8 ppb of <span class="inline-formula">O<sub>3</sub></span> levels compared to normal conditions. Temperature was identified as the dominant meteorological factor. Furthermore, the typhoon nearing landfall significantly enhanced the cross-regional transport of <span class="inline-formula">O<sub>3</sub></span> from northern to southern China through stratosphere–troposphere exchange (STE). The CAM-Chem model simulations revealed that the STE-induced <span class="inline-formula">O<sub>3</sub></span> on the PRD surface could reach a maximum of <span class="inline-formula">∼8</span> ppb, highlighting the non-negligible impact of STE. This study highlights the importance of natural processes exacerbated by extreme weather events in <span class="inline-formula">O<sub>3</sub></span> pollution and provides valuable insights into <span class="inline-formula">O<sub>3</sub></span> pollution control under global warming.</p> |
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| ISSN: | 1680-7316 1680-7324 |