Sommersmog aus der Sicht der Atmosphärenchemie

Abstract

The objective of the Swiss resarch project POLLUMET (POLLUtion and METeorology) is to investigate the formation and transport of photooxidants over the Swiss Plateau and in the surrounding pre-Alpine valleys. Extensive meteorological and air chemistry measurements were obtained during three intensive field studies conducted in the month of July of the years 1990, 1991 and 1993. The study included ground-based measurements, observations from instrumented aircraft, measurements taken with radiosondes, radars and other surface and airborne instruments. The comprehensive database is aimed to provide the information needed for the application of photochemical models and their evaluation and refinement. In order to better understand the photochemical processes which control ozone formation over the Swiss Plateau, calculations with the Harvard Photochemical Model and the Harwell Photochemical Trajectory Model were conducted and compared with experimental data. Reduction scenarios performed with both models yield in one case a NOx-limited situation for rural areas, whereas the other model predicts a transition type situation. Hydrogen peroxide was used as an indicator to study the performance of the photochemical models. Combining measurements of ozone, NO2 and hydrogen peroxide indicates that ozone in rural areas might be reduced most effectively by NOx controls. The model results indicate, that in Switzerland emissions have to be reduced by a large amount to achieve a substantial reduction in peak values of surface ozone.