SEASONAL AEROSOL CHEMISTRY AT DYE-3, GREENLAND

Aerosol trace element concentrations spanning an eleven month period a t Dye 3, Greenland are presented. Sea salt input into the lower atmosp here of the ice sheet occurs predominantly in the winter months of Dec ember-February. These aerosols are the product of vigorous Arctic wint er storms. Long range transport of crustal material from lower latitud e arid regions to the Greenland Ice Sheet takes place predominantly du ring 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 concentration s 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 obser ved at Dye 3 on 14-15 April 1989. Meteorological evidence suggests tha t strong winds and deep convective activity injected dust high into th e atmosphere over the Sahara desert region. This airmass then appears to have passed northward over western Europe where it mixed with anthr opogenic aerosols and arrived in the Dye 3 region some 4-6 d hence. El evated concentrations of anthropogenic aerosol species were also obser ved at the surface during the months of April and May. Long range tran sport of these aerosols appears to be important during the Arctic wint er and spring, while enhanced downward mixing due to a weakening inver sion results in elevated concentrations at the surface during April an d May. An increase in scavenging due to persistent Arctic stratus and the northward migration of the Polar Front in the spring results in ve ry 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 p articulate halogen peak, which is observed throughout the Arctic, may be the result of photochemical aerosol production from biogenic organo halogen species. Regional meteorological phenomena as well as seasonal variations in source strength and long range transport appear to be i mportant factors influencing aerosol concentrations in the surface atm osphere of the Greenland Ice Sheet.