Measurements of trace substances in the Arctic troposphere as potential precursors and constituents of Arctic haze

During two measuring campaigns in early spring 1994 and 1995 (March/April) and one campaign in summer 1994, measurements of ozone, PAN, sulfur dioxide , nitric acid, and particulate nitrate, sulfate, and ammonium (only 1995) w ere recorded in the Arctic. Observations were made by aircraft at various s ites in the eastern and western Arctic. Ozone concentrations showed a stead y increase with altitude both in spring and summer. During five flights in springtime, low ozone events (LOEs) could be observed near the surface and up to altitudes of 2000 m. SO2 background concentrations, ranging from dete ction limit (0.5 nmol/m(3)) to 5 nmol/m(3), were observed during both sprin g and summer. Distinct maxima up to 55 nmol/m(3) in lower altitudes were on ly obtained in springtime. Concentrations of the organic nitrate PAN were w ithin a similar range as those of the inorganic nitrate HNO3 during spring campaigns. In contrast, concentrations of particulate nitrate were one half an order of magnitude lower. HNO3 concentrations increased significantly w ith altitude. Evidently, HNO3 was intruded from the stratosphere into the t roposphere. Sulfate concentrations ranged between 5 and 30 nmol/m(3); ammon ium concentrations were obtained within a range from 10 to 50 nmol/m(3).