Characterization of atmospheric trace gases and particulate matter in Hangzhou, China
The Yangtze River Delta (YRD) is one of the most densely populated regions in China with severe air quality issues that have not been fully understood. Thus, in this study, based on 1-year (2013) continuous measurement at a National Reference Climatological Station (NRCS, 30.22° N, 120.17° E; 41...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/1705/2018/acp-18-1705-2018.pdf |
| Summary: | The Yangtze River Delta (YRD) is one of the most densely populated regions in
China with severe air quality issues that have not been fully understood.
Thus, in this study, based on 1-year (2013) continuous measurement at a
National Reference Climatological Station (NRCS, 30.22° N,
120.17° E; 41.7 m a.s.l.) in the center of Hangzhou in the YRD, we
investigated the seasonal characteristics, interspecies relationships, and
the local emissions and the regional potential source contributions of trace
gases (including O<sub>3</sub>, NO<sub><i>x</i></sub>, NO<sub><i>y</i></sub>, SO<sub>2</sub>, and CO) and
particulate matter (PM<sub>2.5</sub> and PM<sub>10</sub>). Results revealed that severe
two-tier air pollution (photochemical and haze pollution) occurred in this
region, with frequent exceedances in O<sub>3</sub> (38 days) and PM<sub>2.5</sub>
(62 days). O<sub>3</sub> and PM<sub>2.5</sub> both exhibited distinct seasonal variations
with reversed patterns: O<sub>3</sub> reaching a maximum in warm seasons (May and
July) but PM<sub>2.5</sub> reaching a maximum in cold seasons (November to
January). The overall results from interspecies correlation indicated a
strong local photochemistry favoring the O<sub>3</sub> production under a volatile
organic compound (VOC)-limited regime, whereas it moved towards an optimum
O<sub>3</sub> production zone during warm seasons, accompanied by the formation of
secondary fine particulates under high O<sub>3</sub>. The emission maps of
PM<sub>2.5</sub>, CO, NO<sub><i>x</i></sub>, and SO<sub>2</sub> demonstrated that local emissions were
significant for these species on a seasonal scale. The contributions from the
regional transport among inland cities (Zhejiang, Jiangsu, Anhui, and Jiangxi
Province) on a seasonal scale were further confirmed to be crucial to air
pollution at the NRCS site by using backward trajectory simulations. Air
masses transported from the offshore areas of the Yellow Sea, East Sea, and
South Sea were also found to be highly relevant to the elevated O<sub>3</sub> at
the NRCS site through the analysis of potential source contribution function
(PSCF). Case studies of photochemical pollution (O<sub>3</sub>) and haze
(PM<sub>2.5</sub>) episodes both suggested the combined importance of local
atmospheric photochemistry and synoptic conditions during the accumulation
(related with anticyclones) and dilution process (related with cyclones).
Apart from supplementing a general picture of the air pollution state in the
city of Hangzhou in the YRD region, this study specifically elucidates the
role of local emission and regional transport, and it interprets the physical
and photochemical processes during haze and photochemical pollution episodes.
Moreover, this work suggests that cross-regional control measures are crucial
to improve air quality in the YRD region, and it further emphasizes the
importance of local thermally induced circulation for air quality. |
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| ISSN: | 1680-7316 1680-7324 |