Author(s)

Tuomas Laurila and Hannele Hakola

Abstract

Ozone Trends and Source Analysis of VOCs at the Finnish Background Stations A contribution to subproject TOR-2 Tuomas Laurila and Hannele Hakola Finnish Meteorological Institute, Air Quality Research, Sahaajankatu 20E, FIN-00810, Helsinki, Finland Introduction Both increasing and decreasing trends of the boundary layer ozone concentrations have been observed during recent years (Roemer, 1998). The increasing NOx emissions should result in increasing summer (photochemical production) but decreasing winter (NO titration) ozone concentrations in the regional scale. The changing trace gas composition of the background atmosphere may result in changes in ozone concentrations in a larger scale. The present background ozone concentrations (30-35 ppb) are very close to the concentrations considered harmful for sensitive vegetation (32.5 ppb as a 24 hour average, Ozone directive, 1992). The fi

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