Ozone troposphérique en Suisse

As with other European countries, considerably higher ozone concentration are measured in Switzerland than would occur naturally. At the measuring stations of the national survey network for air pollutants (NABEL), especially in years with favourable meteorological conditions for the formation of photochemical oxidants, the following values have been found : yearly average values of up to 70 µg/m³, monthly average values of up to 100µg/m³, and maximum 1-hourly average values towards 250 µg/m³. Ozone peak concentrations occurred during distinct episodes in the hot season. The episodes extended mainly over the whole country and were measured at all stations at almost the same time, though with different concentrations. The highest peak concentrations occurred in the Swiss plateau between the Jura and the Alps. In comparison higher mean concentrations over the year and over the vegetation period were found in the Lower Alps and Alps. The Air Quality Standards in the Swiss Ordinance on Air Pollution Control (maximum 1 hourly-average 120 µg/m³) and the similar guidelines for air quality established by international specialized organization such as the World Health Organization and the ECE-expert groups “Effect of Pollutants” have often and sometimes considerably been exceeded during the hot season.