Arctic Air Chemistry Detailed

Earth scrubs pollutants from the atmosphere via oxidation chemistry, which at the poles is driven by halogens liberated from sea ice. Two studies aimed at understanding halogen atmospheric chemistry provide new details on the interactions of Arctic water, ice, and air. In one study, a team led by L. Gregory Huey of Georgia Tech describes first-ever measurements of atmospheric Cl₂ in Barrow, Alaska (Nat. Geosci. 2014, DOI: 10.1038/ngeo2046). The researchers note that light and O₃ are necessary for Cl₂ formation. Additionally, they find surprisingly high daytime Cl₂ concentrations given that sunlight also photolyzes Cl₂ to Cl•. The second study, by a group led by Christopher W. Moore of Nevada’s Desert Research Institute, documents how atmospheric O₃ and Hg(0) concentrations change in response to environmental conditions (Nature 2014, DOI: 10.1038/nature12924). When air moves over sea ice, O₃ and Hg(0) are depleted from near the ice’s surface. When air moves over open channels in the ice, however, convection mixes the air, drawing more O₃ and Hg(0) toward the water. Hg(0) is oxidized in the atmosphere to Hg(II), which is deposited out of air and could be converted to toxic compounds.