Counteractive effects of regional transport and emission control on the formation of fine particles: a case study during the Hangzhou G20 summit
<p>To evaluate the effect of temporary emission control measures on air quality during the 2016 G20 summit held in Hangzhou, China, an intensive field campaign was conducted with a focus on aerosol chemistry and gaseous precursors from 15 August to 12 September 2016. The concentrations of f...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-09-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/13581/2018/acp-18-13581-2018.pdf |
| Summary: | <p>To evaluate the effect of temporary emission control measures on air quality
during the 2016 G20 summit held in Hangzhou, China, an intensive field
campaign was conducted with a focus on aerosol chemistry and gaseous
precursors from 15 August to 12 September 2016. The concentrations of fine
particles were reduced during the intense emission control stages, with the
reduction of carbonaceous matter being mostly responsible for this observed
decrease. This, in turn, was mainly ascribed to the decrease of secondary
organic aerosols via the suppression of daytime peak secondary organic carbon
(SOC)formation. Although the regional joint control was enacted extending to the Yangtze River Delta
region, the effect of long-range transport on the air quality of Hangzhou was
ubiquitous. Unexpectedly high NO<sub><i>x</i></sub> concentrations were
observed during the control stage, when the strictest restriction on vehicles
was implemented, owing to contributions from upstream populous regions such
as Jiangsu and Shandong provinces. In addition, the continental outflow
traveling over the ocean triggered a short pollution episode on the first day
of the G20 summit, resulting in a significant enhancement of the
nitrogen/sulfur oxidation rates. In the wake of the summit, all air
pollutants evidently rebounded after the various control measures were
lifted. Overall, the fraction of secondary inorganic aerosols (SIA; in this
case sulfate, nitrate, and ammonium aerosols – SNA) in PM<sub>2.5</sub>
increased as relative humidity increased; however, the overall concentration
of PM<sub>2.5</sub> did not increase. Aerosol components that
had distinctly different sources and formation mechanisms, e.g.,
sulfate/nitrate and elemental carbon, exclusively showed strong correlations
during the regional/long-range transport episodes. The sulfate, nitrate, and
ammonium to elemental carbon (SNA∕EC) ratio, which was used as a proxy
for assessing the extent of secondary inorganic aerosol formation, was found
to be significantly enhanced under transport conditions from northern China.
This study highlighted that emission control strategies were beneficial for
curbing particulate pollution, in addition to the fact that
regional/long-range transport may offset local emission control effects to
some extent.</p> |
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| ISSN: | 1680-7316 1680-7324 |