Response of atmospheric composition to COVID-19 lockdown measures during spring in the Paris region (France)
<p>Since early 2020, the COVID-19 pandemic has led to lockdowns at national scales. These lockdowns resulted in large cuts of atmospheric pollutant emissions, notably related to the vehicular traffic source, especially during spring 2020. As a result, air quality changed in manners that are st...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/21/17167/2021/acp-21-17167-2021.pdf |
| Summary: | <p>Since early 2020, the COVID-19 pandemic has led to
lockdowns at national scales. These lockdowns resulted in large cuts of
atmospheric pollutant emissions, notably related to the vehicular traffic
source, especially during spring 2020. As a result, air quality changed in
manners that are still currently under investigation. The robust
quantitative assessment of the impact of lockdown measures on ambient
concentrations is however hindered by weather variability. In order to
circumvent this difficulty, an innovative methodology has been developed.
The Analog Application for Air Quality (A<span class="inline-formula"><sup>3</sup></span>Q) method is based on the
comparison of each day of lockdown to a group of analog days having similar
meteorological conditions. The A<span class="inline-formula"><sup>3</sup></span>Q method has been successfully
evaluated and applied to a comprehensive in situ dataset of primary and
secondary pollutants obtained at the SIRTA observatory, a suburban
background site of the megacity of Paris (France). The overall slight decrease
of submicron particulate matter (PM<span class="inline-formula"><sub>1</sub></span>) concentrations (<span class="inline-formula">−14</span> %) compared to business-as-usual
conditions conceals contrasting behaviors. Primary traffic tracers
(NO<span class="inline-formula"><sub><i>x</i></sub></span> and traffic-related carbonaceous aerosols) dropped by 42 %–66 %
during the lockdown period. Further, the A<span class="inline-formula"><sup>3</sup></span>Q method enabled us to
characterize changes triggered by NO<span class="inline-formula"><sub><i>x</i></sub></span> decreases. Particulate nitrate
and secondary organic aerosols (SOAs), two of the main springtime aerosol
components in northwestern Europe, decreased by <span class="inline-formula">−45</span> % and <span class="inline-formula">−25</span> %,
respectively. A NO<span class="inline-formula"><sub><i>x</i></sub></span> relationship emphasizes the interest of NO<span class="inline-formula"><sub><i>x</i></sub></span>
mitigation policies at the regional (i.e., city) scale, although long-range
pollution advection sporadically overcompensated for regional decreases.
Variations of the oxidation state of SOA suggest discrepancies in SOA
formation processes. At the same time, the expected ozone increase
(<span class="inline-formula">+20</span> %) underlines the negative feedback of NO titration. These results
provide a quasi-comprehensive observation-based insight for mitigation
policies regarding air quality in future low-carbon urban areas.</p> |
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| ISSN: | 1680-7316 1680-7324 |