OZONE, SULFUR-DIOXIDE, CONDENSATION NUCLEI AND AEROSOL COMPOSITION OVER THE EASTERN PART OF THE NORTH-ATLANTIC BASIN

Surface concentrations of ozone, sulphur dioxide, condensation nuclei (CN) and aerosol composition were investigated during the internationa l marine expedition to the eastern part of the North Atlantic and Medi terranean sea (27 March-17 June 1991). Space-temporal distribution of the concentrations is discussed in connection with transport of pollut ed air from European continental sources to the oceanic atmosphere. Co rresponding episodes were identified using back trajectories of the ai r parcels and Rn-222 as a tracer of continental air. CN concentrations increased considerably during the periods of atmospheric transport fr om industrial regions, being the most sensitive indicator of anthropog enic pollution. The same is typical for excess sulfate while for SO2 a n anthropogenic input is relatively small. Particulate matter of pollu ted air is presented mainly by excess sulfate and ammonium ion with 30 -40% lack of chlorine as compared with the sea salt composition. Ozone concentrations up to 76.2 ppbv were registered over the Mediterranean sea in the air masses transported from Northern Italy and Southern Fr ance while the background level of O-3 for the North Atlantic is estim ated by the value 27 ppbv with standard deviation of 2 ppbv. The contr ibution of anthropogenic ozone into its concentration measured in the remote North Atlantic atmosphere was from 14 to 26 ppbv with maximum r eaching 42 ppbv. Rapid variations and high correlation between O-3, CN and Rn-222 values were observed in the vicinity of atmospheric fronts .