TEMPORAL VARIATION IN AEROSOL COMPOSITION AT SUMMIT, GREENLAND, SUMMER 1989

At a high altitude site at Summit, Greenland, aerosol sulfur, chlorine , and potassium were found to occur mainly during sporadic high concen tration episodes, lasting less than 24 h, over a much lower background level. Particle size resolved time sequence sampling was performed by automated two-stage streaker and high sensitivity elemental analysis by proton induced X-ray emission, PIXE, with a detection limit of 9 ng m(-3). In a series of 165 4-h samples during one summer month in 1989 , peak concentrations in the fine <2 mu m diameter fraction were somet imes coincident and sometimes not, indicating different degrees of ass ociation of these elements in air masses passing over the site. Most o f the S, Cl, and K was measured during the short high concentration ep isodes. This finding could not have been made by using a long time ave rage sampling strategy.