Atmospheric water-soluble organic carbon measurements at Summit, Greenland

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 (WSOCG) and particle (WSOCP) phases were made during the 2006 summer season at Summit, Greenland. These samples represent the first direct, simultaneous measurements of both WSOCG and WSOCP at Summit. From early June to early July, WSOCG and WSOCP concentrations at 150 cm above the snow averaged 667 and 194 ng C m−3, respectively. This value for WSOCG 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 WSOCG. Firn air measurements of WSOCG 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 WSOCG and increases in WSOCP, likely resulting from temperature-dependent gas-to-particle partitioning, as these episodes occurred during the coldest part of the early morning.