The atmospheric oxidizing capacity in China – Part 2: Sensitivity to emissions of primary pollutants
<p>Despite substantial reductions in anthropogenic emissions, ozone (O<span class="inline-formula"><sub>3</sub></span>) pollution remains a severe environmental problem in urban China. These reductions affect ozone formation by altering levels of O<span cla...
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| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2024-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/24/12943/2024/acp-24-12943-2024.pdf |
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| Summary: | <p>Despite substantial reductions in anthropogenic emissions, ozone (O<span class="inline-formula"><sub>3</sub></span>) pollution remains a severe environmental problem in urban China. These reductions affect ozone formation by altering levels of O<span class="inline-formula"><sub>3</sub></span> precursors, intermediates, and the oxidation capacity of the atmosphere. However, the underlying mechanisms driving O<span class="inline-formula"><sub>3</sub></span> changes are still not fully understood. Here, we employ a regional chemical transport model to quantify ozone changes due to a specified emission reduction (50 %) for winter and summer conditions in 2018. Our results indicate that reductions in nitrogen oxide (NO<span class="inline-formula"><sub><i>x</i></sub></span>) emissions increase surface O<span class="inline-formula"><sub>3</sub></span> concentrations by 15 %–33 % on average across China in winter and by up to 17 % in volatile organic compound (VOC)-limited areas during summer. These ozone increases are associated with a reduced NO<span class="inline-formula"><sub><i>x</i></sub></span> titration effect and higher levels of OH radicals. Reducing NO<span class="inline-formula"><sub><i>x</i></sub></span> emissions significantly decreases the concentration of particulate nitrate, which enhances ozone formation through increased HO<span class="inline-formula"><sub>2</sub></span> radical levels due to reduced aerosol uptake and diminished aerosol extinction. Additionally, an enhanced atmospheric oxidative capacity, driven by larger contributions from the photolysis of oxidized VOCs (OVOCs) and OH-related reactions, also favors urban ozone formation. With additional reductions in anthropogenic VOC emissions, increases in summertime ozone (VOC-limited areas) can be offset by reduced production of radicals from VOC oxidations. To effectively mitigate ozone pollution, a simultaneous reduction in the emission of NO<span class="inline-formula"><sub><i>x</i></sub></span> and specific VOC species should be applied, especially regarding alkenes, aromatics, and unsaturated OVOCs, including methanol and ethanol.</p> |
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| ISSN: | 1680-7316 1680-7324 |