||Growth Laws for the Formation of Secondary Ambient Aerosols: Implications for Chemical Conversion Mechanisms.
McMurry, P. H. ;
Wilson, J. C. ;
||Minnesota Univ., Minneapolis. Particle Technology Lab.;Environmental Sciences Research Lab., Research Triangle Park, NC.
Particle size distribution ;
Air pollution ;
Test chambers ;
Field tests ;
Laboratory equipment ;
Chemical reaction mechanisms ;
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The evolution of aerosol size distributions growing by gas-to-particle conversion has been observed recently in field and laboratory studies. A technique for extracting particle diameter growth rates from such data is presented. The functional dependence of these growth rates on particle diameter (i.e. the growth law) is then examined to infer clues about possible chemical mechanisms of gas-to-particle conversion. The data are consistent with the conclusion that droplet phase (heterogeneous) reactions were important in the Great Smoky Mountains where relative humidities were high (r.h. greater than 75%), while gas phase reactions were the predominant mechanism in smog chamber experiments (r.h. about 35%).