T. Pakkanen

Atmospheric aerosol studies in southern Norway using size-fractonating smapling devices and nuclear analytical techniques

Atmospheric aerosol samples were collected during spring sampling campaigns in 1988 and 1989 at Birkenes and Nordmoen in southern Norway. The aerosol collectors used included stacked filter units (SFUs), a low volume sampler (referred to as ILVS), which consists of a filter preceded by three impaction stages, and an 11-stage Berner low-pressure impactor (LPI). All samples were analyzed for up to about 40 elements by INAA and PIXE. The resuls obtained from parallel samplings were intercompared in terms of ratios ILVS/SFU and LPI/SFU, whereby these ratios were calculated separately for the coarse and fine size fractions. For the ILVS/SFU parallel samplings, excellent agreement was observed between the results for the fine fraction, with the overall mean average ratio (based on 21 samples and 22 elements) being 0.99±0.10. For the coarse fraction, the overall mean ILVS/SFU ratio (based on 21 elements) was 0.75±0.13. This low result is explained by different upper-particle-size cut-offs of the two samplers. For the parallel samplings with LPI and SFU, the agreement was poorer, but still reasonable. The atmospheric concentrations observed at the two sites in the two campaigns and also the LPI size distributions for the various elements are discussed briefly.

Evaluation of the applicability of the MOUDI impactor for aerosol collections with subsequent multielement analysis by PIXE

Abstract The micro-orifice uniform deposit impactor (MOUDI) is an 8-stage impactor with cut-sizes down to 0.056 μm and which allegedly provides uniform aerosol deposits for the various stages. In the present study it was examined how uniform the aerosol deposits really are for each impaction plate and whether the uniformity is sufficient for a straightforward PIXE analysis. This was done by collecting several samples of ambient aerosol with the MOUDI and by determining the deposition pattern of various elements on the foils through a linear PIXE scan across each impaction foil. It was found that the deposits are far from uniform at the millimeter level for the stage numbers up to 6. Despite this, concentration data can easily be obtained by PIXE from such samples, provided that the analyzed area is carefully selected and appropriate correction factors for the nonuniformity are employed. Some size distribution data are presented. A comparison is also made of the size distribution data and detection limits that result from employing the MOUDI in combination with PIXE with those obtainable by PIXE analysis of some other types of cascade impactors.

Removal of atmospheric aerosols in the sub-arctic region

Abstract Airborne particulates have been collected with a virtual dichotomous impactor during March–April 1992 at Sevettijarvi in sub-arctic Finland. The samples have been analysed for trace element contents with Energy Dispersive X-Ray Fluorescence technique (EDXRF). Dry deposition fluxes of S, Ni, Cu, Zn and Pb have been estimated from knowledge of mass ratios between fine and coarse particles.