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| Titel |
Aerosol particle size distributions in the lower Fraser Valley: evidence for particle nucleation and growth |
| VerfasserIn |
M. Mozurkewich, T.-W. Chan, Y.-A. Aklilu, B. Verheggen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 4, no. 4 ; Nr. 4, no. 4 (2004-07-06), S.1047-1062 |
| Datensatznummer |
250001837
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| Publikation (Nr.) |
 copernicus.org/acp-4-1047-2004.pdf |
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| Zusammenfassung |
| Particle size distributions from 9 to 640nm diameter were measured at Eagle
Ridge in the lower Fraser Valley from 13 August to 1 September 2001 as part
of the Pacific 2001 Air Quality Study. The site was on top of a ridge, about
300m above the valley floor, in a predominantly agricultural area about 70km
ESE of Vancouver. To further characterize the particles, their
hygroscopic properties (affinity for water) were measured. The maximum of
the number distributions was generally between 40 and 100nm diameter, but
the number distribution was sometimes dominated by ultrafine particles with
diameters below 40nm. These ultrafine particles, which appeared to some
extent on all days, were frequently associated with elevated levels of CO
and NOx, as expected for fresh vehicular emissions. The appearance of
these fresh emissions was most pronounced when the growing mixed layer
reached the altitude of the site. In contrast, pronounced nucleation events
occurred on the five cleanest days; these resulted in particle number
concentrations as high as 5x104 particles cm-3 and growth
rates of 5 to 10nmhr-1. Nucleation appears to have been triggered
when the UV flux reached about 25Wm-2. The growth of these
newly formed particles was probably driven by
the photochemical oxidation of biogenic organic compounds. Dramatic growth
events were also observed on the afternoons of the more polluted days; these
produced an extremely narrow mode σ<0.3) at a diameter of about
40nm. Rainy days showed low number concentrations with the size
distributions shifted to small sizes. On one of these days there was
evidence of nucleation not far from the site; this may have been occurring
in the vicinity of the clouds. |
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