Optical Single-Particle Counters to Obtain the Spatial Inhomogeneity of Particulate Clouds
Titel:
Optical Single-Particle Counters to Obtain the Spatial Inhomogeneity of Particulate Clouds
Auteur:
Preining, Othmar
Verschenen in:
Aerosol science and technology
Paginering:
Jaargang 2 (1981) nr. 1 pagina's 79-90
Jaar:
1981-10-13
Inhoud:
Small aerosol systems, such as a laboratory test chamber, can be described sufficiently by average properties—total particle concentration, chemical composition, size distribution, and so on. Large systems, however, such as a section of the atmosphere, are inherently complex and inhomogeneous. The many causes of spatial inhomogeneities have hardly ever been adequately described, even though any nonlinear reaction depends strongly on such inhomogeneities. Optical single-particle counters can be used easily to find the fluctuations in concentration within an aerosol system by sampling the numbers of particles counted in consecutive time intervals of equal length or by measuring the distribution of time intervals between arriving particles and comparing the results with theoretical distributions. When sampling from a well-mixed cloud, a Poisson distribution is to be expected that can be analyzed using Poisson graph paper. If the aerosol is not well mixed, certain types of inhomogeneities can be associated with characteristic deviations from the Poisson distribution. The basic theoretical concepts are discussed, and some reulsts are presented of experiments using a Royco 225 aerosol particle counter and a TN-1705 pulse high analyzer to sample from an aerosol channel, room aerosols, traffic aerosols, and atmospheric aerosols.
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