Ozone depletion events occur not only in the stratosphere (the Antarctic "ozone hole"), but also near the Earth's surface at high latitudes in springtime. Although the mechanism for these boundary layer ozone losses is not completely understood, it is believed that they are caused by enhancements in reactive gas-phase bromine species, which may originate in sea-salt. Linnea Avallone participated in the Alert 2000 Polar Sunrise Experiment in Alert, Nunavut, Canada during April-May 2000 to study the causes of the sudden ozone loss phenomenon. The radical species chlorine oxide and bromine oxide (ClO, BrO) were measured using vacuum ultraviolet resonance fluorescence techniques that have been previously employed for stratospheric observations of the same molecules. The results from this study indicate that snow-covered surfaces near the Arctic Ocean are indeed sources of atmospheric bromine.
Members of Avallone's research group traveled to McMurdo Station, Antarctica in August-October 2002 to study halogen chemistry in a remote, unpolluted location. The results of this research were quite surprising: local pollution (from vehicles and the power plant) contributes significantly to changes in the ozone abundance, as do large storms travelling off the Antarctic continent. Further, the bromine chemistry seems to be unlike that seen in the Arctic. We are planning a second trip to Antarctica in fall 2004 to continue our research there, with a focus on understanding the impacts of local pollution and the snow/ice surface on ozone amounts.
