 |
| Titel |
Chemical composition and mass size distribution of PM1 at an elevated site in central east China |
| VerfasserIn |
Y. M. Zhang, X. Y. Zhang, J. Y. Sun, G. Y. Hu, X. J. Shen, Y. Q. Wang, T. T. Wang, D. Z. Wang, Y. Zhao |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 22 ; Nr. 14, no. 22 (2014-11-20), S.12237-12249 |
| Datensatznummer |
250119177
|
| Publikation (Nr.) |
 copernicus.org/acp-14-12237-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| Size-resolved aerosol chemical compositions were measured continuously for
1.5 years from June 2010 to January 2012 with an aerosol mass spectrometer
(AMS) to characterize the mass and size distributions (MSDs) of major
chemical components in submicron particles (approximately PM1) at
Mountain Tai (Mt. Tai), an elevated site in central east China. The annual
mean mass concentrations of organic, sulfate, nitrate, ammonium, and chloride
were 11.2, 9.2, 7.2, 5.8, and 0.95 μg m−3, respectively,
which are much higher than those at most mountain sites in the USA and
Europe, but lower than those at the nearby surface rural sites in China. A
clear seasonality was observed for all major components throughout the study,
with low concentration in fall and high in summer, and is believed to be
caused by seasonal variations in planetary boundary layer (PBL) height, near
surface pollutant concentrations and regional transport processes. Air masses
were classified into categories impacted by PBL, lower free troposphere
(LFT), new particle formation (NPF), in-cloud processes, and polluted
aerosols. Organics dominated the PM1 mass during the NPF episodes, while
sulfate contributed most to PM1 in cloud events. The average MSDs of
particles between 30 and 1000 nm during the entire study for organics,
sulfate, nitrate, and ammonium were approximately log-normal with mass median
diameters (MMDs) of 539, 585, 542, and 545 nm, respectively. These values
are slightly larger than those observed at ground sites within the North
China Plain (NCP), likely due to the relative aged and well-mixed aerosol
masses at Mt. Tai. There were no obvious differences in MMDs during the PBL,
LFT, in-cloud and polluted episodes, but smaller MMDs, especially for
organics, were observed during the NPF events. During the PBL, NPF, and
polluted episodes, organics accounted for major proportions at smaller modes,
and reached 70% at 100–200 nm particles in the polluted events. In
cloud episodes, inorganics contributed 70% to the whole size range
dominated by sulfate, which contributed 40% to small particles
(100–200 nm), while organics occupied 20%, indicating that sulfate is
a critical chemical component in cloud formation. Seven clusters of air
masses were classified based on 72 h back-trajectory analysis. The majority
of the regionally dispersed aerosols were found to be contributed from short
distance mixed aerosols, mostly originated from the south with organics and
sulfate as major components. Air masses from long range transport always
brought clean and dry aerosols which resulted in low concentrations at Mt.
Tai. AMS-PMF (positive matrix factorization) was employed to resolve the
subtype of organics. Oxygenic organics aerosols (OAs) occupied 49, 56, 51,
and 41% of OAs in the four seasons respectively, demonstrating that most
OA were oxidized in summer due to strong photochemical reactions. Biomass
burning OAs (BBOAs) accounted for 34% of OA in summer, mainly from field
burning of agriculture residues, and coal combustion OAs (CCOAs) accounted
for 22% of OA in winter from heating. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|