The drivers and health risks of unexpected surface ozone enhancements over the Sichuan Basin, China, in 2020
<p>Following a continuous increase in the surface ozone (<span class="inline-formula">O<sub>3</sub></span>) level from 2013 to 2019, the overall summertime <span class="inline-formula">O<sub>3</sub></span> concentrations acros...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-12-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/21/18589/2021/acp-21-18589-2021.pdf |
| Summary: | <p>Following a continuous increase in the surface ozone (<span class="inline-formula">O<sub>3</sub></span>) level from 2013 to
2019, the overall summertime <span class="inline-formula">O<sub>3</sub></span> concentrations across China showed a
significant reduction in 2020. In contrast to this overall reduction in
surface <span class="inline-formula">O<sub>3</sub></span> across China, unexpected surface <span class="inline-formula">O<sub>3</sub></span> enhancements of
10.2 <span class="inline-formula">±</span> 0.8 ppbv (23.4 %) were observed in May–June 2020 (relative to 2019)
over the Sichuan Basin (SCB), China. In this study, we use high-resolution
nested-grid GEOS-Chem simulation, the eXtreme Gradient Boosting (XGBoost)
machine learning method, and the exposure–response relationship to
determine the drivers and evaluate the health risks due to the unexpected
surface <span class="inline-formula">O<sub>3</sub></span> enhancements. We first use the XGBoost machine learning
method to correct the GEOS-Chem model–measurement <span class="inline-formula">O<sub>3</sub></span> discrepancy
over the SCB. The relative contributions of meteorology and anthropogenic
emission changes to the unexpected surface <span class="inline-formula">O<sub>3</sub></span> enhancements are then
quantified with a combination of GEOS-Chem and XGBoost models. In order to
assess the health risks caused by the unexpected <span class="inline-formula">O<sub>3</sub></span> enhancements over
the SCB, total premature mortalities are estimated. The results show
that changes in anthropogenic emissions caused a 0.9 <span class="inline-formula">±</span> 0.1 ppbv
<span class="inline-formula">O<sub>3</sub></span> reduction, whereas changes in meteorology caused an 11.1 <span class="inline-formula">±</span> 0.7 ppbv
<span class="inline-formula">O<sub>3</sub></span> increase in May–June 2020 relative to 2019. The meteorology-induced surface
<span class="inline-formula">O<sub>3</sub></span> increase is mainly attributed to an increase in temperature and decreases in precipitation, specific humidity, and cloud fractions over
the SCB and surrounding regions in May–June 2020 relative to 2019. These changes in
meteorology combined with the complex basin effect enhance biogenic
emissions of volatile organic compounds (<span class="inline-formula">VOCs</span>) and nitrogen oxides
(<span class="inline-formula">NO<sub><i>x</i></sub></span>), speed up <span class="inline-formula">O<sub>3</sub></span> chemical production, and inhibit the
ventilation of <span class="inline-formula">O<sub>3</sub></span> and its precursors; therefore, they account for the
surface <span class="inline-formula">O<sub>3</sub></span> enhancements over the SCB. The total premature mortality due
to the unexpected surface <span class="inline-formula">O<sub>3</sub></span> enhancements over the SCB has increased by
89.8 % in May–June 2020 relative to 2019.</p> |
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| ISSN: | 1680-7316 1680-7324 |