A summer time series of particulate carbon in the air and snow at Summit, Greenland

Abstract

Carbonaceous particulate matter is ubiquitous in the lower atmosphere, produced by natural and anthropogenic sources and transported to distant regions, including the pristine and climate-sensitive Greenland Ice Sheet. During the summer of 2006, ambient particulate carbonaceous compounds were characterized on the Greenland Ice Sheet, including the measurement of particulate organic (OC) and elemental (EC) carbon, particulate water-soluble organic carbon (WSOC), particulate absorption coefficient (σ ap), and particle size-resolved number concentration (PM 0.1-1.0). Additionally, parallel ∼50-day time series of water-soluble organic carbon (WSOC), water-insoluble organic carbon (WIOC), and elemental carbon (EC) were quantified at time increments of 4-24 h in the surface snow. Measurement of atmospheric particulate carbon found WSOC (average of 52 ng m -3) to constitute a major fraction of particulate OC (average of 56 ng m -3), suggesting that atmospheric organic compounds reaching the Greenland Ice Sheet in summer are highly oxidized. Atmospheric EC (average of 7 ng m -3) was well-correlated with σ ap (r = 0.95) and the calculated mass-absorption cross-section (average of 24 m 2 g -1) appears to be similar to that measured using identical techniques in an urban environment in the United States. Comparing surface snow to atmospheric particulate matter concentrations, it appears the snow has a much higher OC (WSOC+WIOC) to EC ratio (205:1) than air (10:1), suggesting that snow is additionally influenced by water-soluble gas-phase compounds. Finally, the higher-frequency (every 4-6 h) sampling of snow-phase WSOC revealed significant loss (40-54%) of related organic compounds in surface snow within 8 h of wet deposition. Copyright 2007 by the American Geophysical Union.