CHEMICAL SIGNATURES OF THE LOS-ANGELES AEROSOL (D(P)LESS-THAN-3.5-MU-M)

The frequency distributions of the chemical components of the Los Ange les aerosol measured over a 1-year period are approximately lognormal. For nonreactive aerosol components, the geometric standard deviation (GSD) is nearly constant at 1.85 +/- 0.14, even for components from di fferent source types. The GSD of CO is lower than those of the nonreac tive aerosol species, which, in turn, tend to be lower than those of t he reactive aerosol species. A possible explanation is offered based o n the equation for mean square fluctuating compositions in a turbulent fluid. An apparent bimodal frequency distribution for sulfates probab ly corresponds to the two differing reaction pathways by which gas-to- particle conversion occurs. The composition of the aerosol correspondi ng to the most probable total aerosol mass concentration is reported. This composition differs from the simple average chemical composition, and may be more appropriate for certain applications.