A 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, wher e concentrations are low, Since measurements will be made from an airplane, a time resolution of one hour is desirable. These conditions require effic ient sampling and analysis with low detection limits. To accomplish this, o ur sampler uses impaction, concentrating the aerosol deposit on a small are a. The impactor has 14 parallel sampling lines which are used sequentially to achieve the time resolution. The elemental analysis is done with Particl e-Induced X-ray Emission (PIXE), profiting from its high absolute sensitivi ty. The aerosol is expected to contain primarily sulphur (S) and emphasis i s placed on this element, however the multi-elemental nature of PIXE is of course used. Several substrates have been investigated regarding minimum de tection limits. Scanning Transmission Ion Microscopy (STIM) analysis has be en conducted on tno outdoor aerosol samples, rendering three-dimensional im ages and mass distribution profiles. The setup was tested at ground level w ith high time resolution (5 min). Results show that the detection capabilit ies are excellent. (C) 1999 Elsevier Science B.V.,All rights reserved.