C-2-C-7 hydrocarbon concentrations in arctic snowpack interstitial air: Potential presence of active Br within the snowpack

samples of interstitial air from within the snow pack on an ice flee on the Arctic Ocean were collected during the April 1994 Polar Sunrise Experiment . The concentrations of C-2-C-7 hydrocarbons are reported for the first tim e in the snow pack interstitial air. Alkane concentrations tended to be hig her than concentrations in fr air samples above the snow but very similar t o winter measurements at various locations in the Arctic archipelago. Howev er, ethyne concentrations in both interstitial and free air were highly cor related with ozone mixing ratios, consistent with previous demonstrations o f the effects of Br atom chemistry. The analysis of total bromine within th e snow pack indicate an enrichment in total Br at the interface layer betwe en snow and free troposphere. The mixing ratios of some brominated compound s, such as CHBr3 and CHBr2Cl, are found to be higher in this top layer of s now relative to the boundary layer. Results were inconclusive due to the li mited number of samples, but suggest the possible presence of active bromin e in the snow pack and also that some differences exist between chemical re actions occurring in interstitial air compared to air in the boundary layer .