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| Titel |
The roles of organics in New particle formation in the Megacity of Beijing, China |
| VerfasserIn |
Min Hu, Zhibin Wang, Zhijun Wu, Dingli Yue, Jun Zheng, Renyi Zhang, Michael Boy, Alfred Wiedensohler |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250084234
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| Zusammenfassung |
| The new particle formation (NPF) has been investigated in the high aerosol loading
environment of Beijing since March 2004. The occurrence frequency is comparable with less
aerosol loading environment, whereas the monthly or seasonal variations indicate location
dependency. Simultaneously measurements of gaseous precursors of H2SO4 vapor and
ammonia proved that the H2SO4-NH3-H2O ternary nucleation is an important mechanism for
Beijing NPF, which is mainly constrained by the concentrations of the gaseous sulfuric acid
and total particle surface area. The higher particle formation rates were observed on high
aerosol loading days, followed up NPF, then high organic matter observed by AMS,
which indicated the organic vapors should be involved in the new particle formation
process.
The roles of organics in the formation and growth of the NPF were focused on in the
case of summer 2008, Olympic Games period, the particle formation rates show
good correlations with sulfuric acid and organic vapors implying that both play
an important role in the atmospheric new particle formation. The best fit between
observed and modelled particle formation rates is achieved with the homogenous
nucleation theory of sulfuric acid (both homomolecularly and hetermolecularly) with
separate coefficients in J = KSA1[H2SO4]2 + KSA2[H2SO4][Org], in which
the contributions of the sulfuric acid and the organics involving terms have been
estimated as 43% and 57%, respectively. The growth of new particles contributed by
condensation and neutralization of sulfuric acid, coagulation as well as organic compounds
involved growth are discussed. The apparent growth rates vary from 3 to 11 nm h-1.
Condensation of sulfuric acid and its subsequent neutralization by ammonia and
coagulation contribute to the apparent particle growth on average 45±18% and 34±17%,
respectively. The 30% higher concentration of sulfate than organic compounds in particles
during the sulfur-rich NPF events but 20% lower concentration of sulfate during the
sulfur-poor type suggest that organic compounds are an important contributor to the
growth of the freshly nucleated particles, especially during the sulfur-poor cases. |
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