Field studies of halogen activation and its relationship to tropospheric ozone depletion and mercury deposition

Simpson, W., Alvarez-Aviles, L., Hoenninger, G., Platt, U., Douglas, T., Sturm, M. and Domine, F. (2005) Field studies of halogen activation and its relationship to tropospheric ozone depletion and mercury deposition. Gordon Conference on Atrmospheric Chemistry, Big Sky Montana.

Halogen atoms and their oxides are potent atmospheric oxidizers that are active during polar springtime and may affect atmospheric chemistry in other regions and times of the year. An important source of these halogen radicals is halides, most often from sea salt, that are activated by heterogeneous chemistry. In this poster, we discuss field observations of halides in snow and halogen oxides in the gas phase in an attempt to understand halogen activation mechanistically. Recent studies have tried to implicate frost flowers, delicate and highly saline ice crystals that grow on re-freezing sea ice, in halogen activation. Therefore, we have investigated halogen activation both in immediate proximity to re-freezing cracks in the sea ice and hundreds of kilometers inland. Our findings indicate that frost flowers are not necessary for halogen activation and may simply be an effective source for sea-salt aerosol. During the polar springtime, reactive halogens deplete ozone in the boundary layer and oxidize gaseous elemental mercury to ionic mercury that deposits rapidly. We have also observed ozone and mercury (gaseous and in snow) and discuss the impact of halogen chemistry on these compounds.