MEASUREMENTS OF OZONE AND PEROXYACETYL NITRATE (PAN) IN MUNICH

Simultaneous measurements of ozone and-for the first time in Munich-of PAN were carried out at two sites in the urban area of Munich during two periods (16 June-15 September 1989 and 1 January-30 April 1990). M aximum mixing ratios reached 75 ppbv for ozone (10-min-average) and 5. 6 ppbv for PAN (20-min-value), respectively. Ozone showed more pronoun ced diurnal variations than PAN. In both cases they were related to di urnal variations of the global radiation and the mixing ratios of NOx. Regarding ozone linear correlation analysis with meteorological param eters revealed distinct dependencies, especially on UV radiation, wher eas the results for PAN reflected its more complicated formation. As f ar as dependencies on wind velocity are concerned, both ozone and PAN exhibited maximum mixing ratios in cases where the wind velocity was b elow 5 ms(-1). With increasing wind velocity both mixing ratios tended towards their natural background concentrations. Investigations conce rning the influence of the wind direction did not disclose any particu lar local effects, but rather a relationship to the general weather si tuations. On the whole, PAN could be considered as a more characterist ic indicator of smog conditions than ozone due to its low background c oncentrations and its thermal instability.