AIRBORNE MEASUREMENTS OF ATMOSPHERIC AEROSOL-PARTICLES AND TRACE GASES DURING PHOTOSMOG EPISODES OVER THE SWISS PLATEAU AND THE SOUTHERN PRE-ALPINE REGION

The concentration of atmospheric aerosol particles, primary and second ary trace gases as well as meteorological parameters were obtained fro m aircraft measurements in July 1993 over the Swiss Plateau and the So uthern Pre-Alpine Region as part of the POLLUMET (POLLUtion and METeor ology) study. On sunny afternoons, the spatial distribution of particl es in the size range 0.12-3.12 mu m showed a good agreement with those of secondary pollutants O-3 and NOz (= NOy - NO2 - NO; NOy: total odd nitrogen) in the well mixed planetary boundary layer but poor correla tion with the distributions of primary pollutants NO2 and CO. The resu lts indicate that under conditions of high air pollution and strong ph otochemical activity the aerosol particles mainly grow by means of sec ondary processes (heterogeneous nucleation) into the diameter range 0. 12-1.5 mu m. On the other hand, the distribution of the CN particle co ncentration (0.01-3 mu m) was similar to the NO2 concentration indicat ing that CN mainly consisted of primary particles. (C) 1998 Elsevier S cience Ltd. All rights reserved/