Preliminary results of ambient measurements with a multistage impactor

Abstract

Ambient air measurements were conducted with an eight-stage Sierra impactor in Dusseldorf and Duisburg, Germany. In addition to gravimetric routine measurements in both cities with the aid of a High Volume Sampler PM10, dust particles were collected on nucleopore filters and analyzed for chemical compounds on the eight impactor stages with a scanning electron microscope equipped with an energy dispersive x-ray spectrometer and an image analysis unit. Polydisperse glass beads and glass fibers were used in calibrating the multistage cascade impactor. Collection efficiency curves are presented together with computed values for the glass dusts. Comparative measurements in Dusseldorf and Duisburg revealed differences from city to city due to their respective industrial character. The filter loading on impactor stages 1 and 2 was too low to be evaluated. Furthermore, the excessive deposition of droplets on the last stage prevented evaluation. Due to the industrial character of Duisburg, the gravimetric dust concentration was about 80 μg/m3 air and thus twice that of Dusseldorf. The concentration of metals (Fe, Zn, Mn, Pb) was higher in Duisburg; organic compounds were excessive in Dusseldorf.