Atmospheric water-soluble organic carbon measurements at Summit, Greenland

Abstract

The recently discovered active photochemistry in the surface layers of polar snow may complicate the interpretation of organic compounds found in ice cores. In order to better understand the transformation and cycling of organic species in Arctic surface snow, measurements of water-soluble organic carbon (WSOC) in the gas (WSOC G) and particle (WSOC P) phases were made during the 2006 summer season at Summit, Greenland. These samples represent the first direct, simultaneous measurements of both WSOC G and WSOC P at Summit. From early June to early July, WSOC G and WSOC P concentrations at 150 cm above the snow averaged 667 and 194 ng C m −3, respectively. This value for WSOC G is very similar in magnitude to the sum of acetic and formic acid gas concentrations measured during previous summers at Summit, suggesting that these two monocarboxylic acids constitute a significant fraction of the mass of measured WSOC G. Firn air measurements of WSOC G revealed concentrations within the snowpack nearly an order of magnitude greater than those in the air just above the snow. During one period, four out of five consecutive nights showed concurrent decreases in WSOC G and increases in WSOC P, likely resulting from temperature-dependent gas-to-particle partitioning, as these episodes occurred during the coldest part of the early morning.