THE INFLUENCE OF THE ORIGIN, SEASON AND TIME OF THE DAY ON THE DISTRIBUTION OF INDIVIDUAL NMHC MEASURED AT RORVIK, SWEDEN

Tropospheric ozone research (TOR) is a subproject of EUROTRAC, the joint European environmental project studying the impact of human activities on the troposphere over Europe. Rorvik, located on the Swedish west coast (57-degrees 23' N; 11 degrees-55' E, sea level), was established as a TOR station in 1989. Data from measurements of nine C2-C5 hydrocarbons and ozone, performed every 4 h during the period February 1989 to October 1990, are presented. The measured concentrations were very scattered, but all the NMHC showed a seasonal variation with high concentrations during winter and low during summer. In addition, the results indicate a seasonal variation in the NMHC profile, i.e. the relative concentrations of individual hydrocarbons. The ozone concentration was on the whole anti-correlated to the NMHC concentration. A diurnal variation was found when a multifactor analysis of variance was applied to the data. The origin of the hydrocarbons in terms of transport sectors was classified using back trajectories. The highest concentrations were obtained in air masses originating from Continental Europe and southern England. The main part of the estimated NMHC burden at Rorvik during the period was due to emissions in other countries.