CHARACTERIZING SURFACE OZONE CONCENTRATIONS IN NORWAY

This paper focuses on characterizing the hourly ozone concentrations i n Norway in a form that is helpful for quantifying the potential for s urface ozone concentrations to affect vegetation. In general, the maxi mum hourly average concentrations experienced at the monitoring sites were below 0.10 ppm and, in most cases, sites experienced fewer than 5 % of their hourly average concentrations greater than or equal to 0.06 ppm. The lowest maximum hourly average concentrations occurred at the two remote Spitzbergen sites, Ny Alesund and Zeppelin (0.061 and 0.05 9 ppm, respectively). At the Nordmoen, Birkenes, Haukenes, and Valle s ites, the maximum hourly average concentrations were 0.091, 0.099, 0.1 15, 0.086 ppm, respectively. The infrequent occurrences of hourly aver age concentrations greater than or equal to 0.06 ppm were reflected in the absolute values of the exposure index that summed the hourly aver age concentrations greater than or equal to 0.06 ppm (SUM06). In most cases, values for the sigmoidally-weighted cumulative exposure index ( W126) were below 10 ppm-h however, the Jeloya and Drotningborg sites e xperienced values of 34.6 and 24.2 ppm-h, respectively. The cumulative exposure index that summed all the hourly average concentrations (SUM O) did not adequately focus on the important components of the ozone e xposure regime that appear to be responsible for affecting vegetation. For most of the sites, the long-term 7 h (0900-1559 h) and 12 h (0700 -1859 h) seasonal average concentrations were in the range of 0.030-0. 040 ppm. The magnitude of the long-term average concentrations was ass ociated more with the lack of low hourly average concentrations near m inimum detectable levels than with the occurrence of repeated high hou rly average concentrations. There was a large number of daily occurren ces when the maximum 8 h average concentration exceeded 0.03 ppm. For the two remote Spitzbergen sites, Ny Alesund and Zeppelin, 71 and 109 daily occurrences were registered, respectively. However, given the in terest on focusing on the occurrences of the higher hourly average con centrations, calculating the number of exceedences greater than 0.03 p pm for the daily maximum 8h average concentration may not be the most appropriate way to assess the potential for ozone concentrations to af fect vegetation.