Measurements on the distribution of trace substances in the Arctic troposphere

During the ‘Arctic Haze’ measuring campaign in March–April 1994 and the ‘Merisec’ measuring campaign in June 1994 the horizontal and vertical variations of 03−, SO2−, PAN-, HNO3−, nitrate- and sulfate-concentrations were measured. Eight representative measuring flights are presented. The aircraft observations showed that ozone depletion is occurring beyond the Arctic inversion layer during April and June. Ozone concentrations generally increased significantly with altitude. NO values were always below the detection limit. HNO3 was accumulated on impregnated filters instead of commonly used nylon filters. Only impregnated cellulose filters exhibit high collection efficiencies at low contents of atmospheric water vapor. For measuring SO2 a sensitive filter technique was applied. The mixing ratio of S02 seldom exceeded the value of 200 pptv in April 1994 (150 pptv in June 1994). The concentrations showed no continuous vertical gradient, but often a layered structure.