Abstract
During September 1979, aerosol samples were collected at two coastal sites in the southern hemisphere: Cape Grim, Tasmania, in the southern temperate latitudes, and Townsville, Queensland, in the subtropical region. Cascade impactors and stacked filter units were used for sampling. The samples were analyzed for the light elements (6 < or = Z < or = 19) by proton elastic scattering analysis (PESA) and for the heavier elements (Z > or = 12) by PIXE. As anthropogenic and continental influences are essentially nonexistent along the track of airmasses for several days before they reach Cape Grim, this site is ideally suited for the study of purely marine airmasses. Sulfur at this site is dominated by seasalt, and the submicron sulfur particle mode universally encountered in the southern tropics and the northern hemisphere is almost not detectable here. It can be shown, however, that sulfur in excess of the amount accounted for by seasalt is present in all size fractions. Calcium appears enriched relative to seasalt on all particle sizes. Chlorine shows no net depletion; there may be chlorine enrichment on the intermediate particle sizes combined with losses on the largest and finest particles. Light element analysis of the submicron aerosol showed significant amounts of organic carbon ( approximately 0.3 mu g/m (super 3) ); black soot carbon was not visible in samples from Cape Grim during clean air conditions. Stoichiometric relationships between the light elements suggest that most of the nitrogen and sulfur are present in the form of ammonium sulfate. At Townsville, periods of strong continental influence alternated in the synoptic cycle with marine dominated airmasses. Evidence of biomass burning was present in the form of elevated concentrations of submicron potassium and of soot carbon. Chlorine is not depleted in the large particles. The submicron fraction shows evidence of chlorine loss, which is partially compensated by chloride gain on the smallest particles during the influence of biomass burning. Sulfur has a significant anthropogenic component even under marine conditions. Airmass origin and heavy metal abundance support long-range transport of sulfur and some heavy metals. At all times a strong submicron mode of sulfur was present at Townsville; stoichiometric calculations suggest that it exists in the form of neutral sulfates.