Flux measurements from in-snow production of molecular halogens in Barrow, Alaska

Wednesday, 17 December 2014
Kyle D Custard1, Angela R. W. Raso1, Paul B Shepson2, Kerri Pratt3 and Ralf M Staebler4, (1)Purdue University, West Lafayette, IN, United States, (2)Purdue Univ, West Lafayette, IN, United States, (3)University of Michigan Ann Arbor, Department of Chemistry and Department of Earth & Environmental Sciences, Ann Arbor, MI, United States, (4)Environment Canada Toronto, Toronto, ON, Canada
Molecular halogens have been shown to influence the oxidation capacity of the Arctic boundary layer. However, their sources are not completely understood. Here we report observations of molecular Br2 and Cl2 production within the Arctic tundra snowpack in the presence of solar radiation and ozone. In-snow experiments were conducted in the tundra snowpack of Barrow, Alaska during January and February of 2014. During these experiments snowpack interstitial air was sampled while periodically irradiated by solar simulating lights. Upon irradiation, Cl2 and Br2 were produced, with the release being enhanced by the addition of ozone, for both molecular halogens. Flux measurements of Br2 and Cl2 from the tundra snowpack were also conducted, via the gradient flux method. Fluxes ranging from 6.9x107 to 1.4x109 and 1.6x107 and 2.5x109 molecules∙cm2∙s-1 were observed for Br2 and Cl2, respectively. These fluxes, however, represent those from the snowpack, and in relatively low ambient light conditions, and so will likely represent lower limits to what apply during ozone depletion events later in the spring.