 |
| Titel |
Spatial and seasonal variability of PM2.5 acidity at two Chinese megacities: insights into the formation of secondary inorganic aerosols |
| VerfasserIn |
K. He, Q. Zhao, Y. Ma, F. Duan, F. Yang, Z. Shi, G. Chen |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 3 ; Nr. 12, no. 3 (2012-02-06), S.1377-1395 |
| Datensatznummer |
250010636
|
| Publikation (Nr.) |
 copernicus.org/acp-12-1377-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| Aerosol acidity is one of the most important parameters influencing
atmospheric chemistry and physics. Based on continuous field observations
from January 2005 to May 2006 and thermodynamic modeling, we investigated
the spatial and seasonal variations in PM2.5 acidity in two megacities
in China, Beijing and Chongqing. Spatially, PM2.5 was generally more
acidic in Chongqing than in Beijing, but a reverse spatial pattern was found
within the two cities, with more acidic PM2.5 at the urban site in
Beijing whereas the rural site in Chongqing. Ionic compositions of
PM2.5 revealed that it was the higher concentrations of NO3−
at the urban site in Beijing and the lower concentrations of Ca2+
within the rural site in Chongqing that made their PM2.5 more acidic.
Temporally, PM2.5 was more acidic in summer and fall than in winter,
while in the spring of 2006, the acidity of PM2.5 was higher in Beijing
but lower in Chongqing than that in 2005. These were attributed to the more
efficient formation of nitrate relative to sulfate as a result of the
influence of Asian desert dust in 2006 in Beijing and the greater wet
deposition of ammonium compared to sulfate and nitrate in 2005 in Chongqing.
Furthermore, simultaneous increase of PM2.5 acidity was observed from
spring to early summer of 2005 in both cities. This synoptic-scale evolution
of PM2.5 acidity was accompanied by the changes in air masses origins,
which were influenced by the movements of a subtropical high over the
northwestern Pacific in early summer. Finally, the correlations between
[NO3−]/[SO42−] and [NH4+]/[SO42−]
suggests that under conditions of high aerosol acidity, heterogeneous
reactions became one of the major pathways for the formation of nitrate at
both cities. These findings provided new insights in our understanding of
the spatial and temporal variations in aerosol acidity in Beijing and
Chongqing, as well as those reported in other cities in China. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|