Particle analysis of an urban aerosol using high spatial resolution techniques

A single-particle scintillation counter-analyser mounted in a light aircraft has been used to obtain information on the Na and K content of the particulates in the atmosphere of Sydney, Australia. A spatial resolution of 1 km is obtained along a 250-km flight path. Total mass loadings and loadings as a function of particle size for Na and K agree with published data for filter samples collected on the ground. Na/K ratios for individual plumes indicate soil dust and combustion are the principal contributors to urban haze detected by this method. The large sea-salt contribution is readily identified and significant sources of non-marine Na exist, particularly in the smaller size ranges. The results suggest that sea-salt contribution to the Na measured in coastal city aerosols may be overestimated.