SEASONAL AEROSOL CHEMISTRY AT DYE-3, GREENLAND

Aerosol trace element concentrations spanning an eleven month period at Dye 3, Greenland are presented. Sea salt input into the lower atmosphere of the ice sheet occurs predominantly in the winter months of December-February. These aerosols are the product of vigorous Arctic winter storms. Long range transport of crustal material from lower latitude arid regions to the Greenland Ice Sheet takes place predominantly during the spring. The onset of Arctic sunrise and associated weakening of the surface and upper level inversion over the ice sheet appear to be important factors resulting in higher crustal aerosol concentrations in the lower levels of the Greenland atmosphere during the month of April. A strong pulse of crustal aerosol (260 ng Al scm(-1)) was observed at Dye 3 on 14-15 April 1989. Meteorological evidence suggests that strong winds and deep convective activity injected dust high into the atmosphere over the Sahara desert region. This airmass then appears to have passed northward over western Europe where it mixed with anthropogenic aerosols and arrived in the Dye 3 region some 4-6 d hence. Elevated concentrations of anthropogenic aerosol species were also observed at the surface during the months of April and May. Long range transport of these aerosols appears to be important during the Arctic winter and spring, while enhanced downward mixing due to a weakening inversion results in elevated concentrations at the surface during April and May. An increase in scavenging due to persistent Arctic stratus and the northward migration of the Polar Front in the spring results in very low anthropogenic aerosol concentrations during the summer months. Particulate aerosol iodine and bromine concentrations also peak during the month of April at Dye 3. It has been suggested that this spring particulate halogen peak, which is observed throughout the Arctic, may be the result of photochemical aerosol production from biogenic organohalogen species. Regional meteorological phenomena as well as seasonal variations in source strength and long range transport appear to be important factors influencing aerosol concentrations in the surface atmosphere of the Greenland Ice Sheet.