High sensitivity elemental analysis methodology for upper tropospheric aerosol

In this study, a sampling and analysis tool for aerosol particles has been developed. Its purpose is to characterize upper tropospheric aerosols, where concentrations are low. Since measurements will be made from an airplane, a time resolution of one hour is desirable. These conditions require efficient sampling and analysis with low detection limits. To accomplish this, our sampler uses impaction, concentrating the aerosol deposit on a small area. The impactor has 14 parallel sampling lines which are used sequentially to achieve the time resolution. The elemental analysis is done with Particle-Induced X-ray Emission (PIXE), profiting from its high absolute sensitivity. The aerosol is expected to contains primarily sulphur (S) and emphasis is placed on this element, however the multi-elemental nature of PIXE is of course used. Several substrates have been investigated regarding minimum detection limits. Scanning Transmission Ion Macroscopy (STIM) analysis has been conducted on two outdoor aerosol samples, rendering three-dimensional images and mass distribution profiles. The setup was tested at ground level with high time resolution (5 min). Results show that the detection capabilities are excellent.