PIXE analysis of cascade impactor samples collected at the Kruger National Park, South Africa

Abstract Aerosol samples were collected in parallel with eight-stage cascade impactors (CIs) and stacked filter units (SFUs) in the Kruger National Park, South Africa, in September–October 1992. The collections took place at a regional “background” site and near prescribed savanna fires. The results obtained by PIXE analysis from the 41 parallel daily samples at the regional site were compared in terms of concentration ratios CI/SFU for the coarse and fine size fractions. The overall average ratio (average over all samples and various elements) was 0.77 ± 0.07 (based on 17 elements) for the coarse size fraction and 0.65 ± 0.07 (based on 14 elements) for the fine particle fraction. Possible explanations for these lower than 1 ratios are presented. From the CI data average elemental mass size distributions and mass median aerodynamic diameters (MMADs) were calculated for the regional site and for the near-fire collections. It was found that the MMADs for S, Cl, K, Zn, and Br were much lower near the fires than in the regional samples. Multivariate source apportionment was applied to the regional CI data set, and this was done separately for the coarse and the fine particle fraction. Biomass burning appeared to be the major source for the elements K, Zn, Br, and Rb in the fine size fraction.

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