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Impact and growth phenomena observed with sub-micrometer atmospheric aerosol particles collected on polished silicon at low coverage.
Atmos. Environ. 36, 3963-3971 (2002)
The processes occurring during the initial stages of size-selected sampling of atmospheric aerosol matter were explored by means of high-resolution scanning electron microscopy and energy dispersive X-ray spectrometry. The final four stages of a Berner impactor served to collect particles with aerodynamic diameters between 60 nm and I mum on polished silicon substrates at sampling times between 10s and 16 min. In the single-particle impact regime (fractional coverage below 5%), most of the particles produced circular black tracks, of which 15 to 30% contained cores of carbonaceous nanoparticles. At a fractional coverage above about 10%, initially generated deposits became increasingly active as centres of preferred aerosol collection. As a result, the number of black spots remained almost constant, but the area per spot increased rapidly. At this stage of fractional coverage, structured aerosol matter became visible within large black areas of random shape. The deposits showed clear evidence for the onset of phase separation between carbon nanoparticles and material rich in sulphur, probably a mixture of alkaline and alkaline earth sulphates. After some time of sample storage in air the low-coverage sulphate matter tended to attain a fractal pattern. At a fractional coverage of several hundred per cent, large amorphous or crystalline objects had grown, but 30% or more of the nominal impact area still did not contain any aerosol matter. Moreover, carbon nanoparticles were found to be phase separated from the newly grown, very uniform aerosol material. The observations imply that sub-micrometer aerosol matter collected in impactors has lost memory of the original particle morphology.
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Publication type
Article: Journal article
Document type
Scientific Article
Keywords
Impactor; Aerosol particles; Scanning electron microscopy; Carbon nanoparticles; Sulphate; Phase separation
Language
english
Publication Year
2002
HGF-reported in Year
0
ISSN (print) / ISBN
1352-2310
e-ISSN
1873-2844
Journal
Atmospheric Environment
Quellenangaben
Volume: 36,
Issue: 24,
Pages: 3963-3971
Publisher
Elsevier
Reviewing status
Peer reviewed
Institute(s)
Institute of Radiation Protection (ISS)
POF-Topic(s)
30504 - Mechanisms of Genetic and Environmental Influences on Health and Disease
Research field(s)
Radiation Sciences
PSP Element(s)
G-501100-006
Erfassungsdatum
2002-11-13