Bromine, Iodine and Mercury on the East Antarctic plateau: preliminary results from sampling along a traverse.

Sunlit snow is photochemically active and plays a key role in the exchange of gas phase species between the cryosphere and the atmosphere. Bromine (Br), Iodine (I) and Mercury (Hg) can be photoactivated by the UV radiation and released from the snowpack into the atmosphere. Mercury is a heavy toxic metal very labile in the snowpack where it can be photoreduced back to elemental Hg (Hg(0)) and exchanged with the atmosphere. Similarly, iodine can undergo photochemical activation in surface snow and be remitted in the atmosphere where it has a role in new particle formation. Bromine is involved in the polar mercury cycle (Atmospheric mercury depletion events) as well as contributing to the polar tropospheric ozone cycle causing the so-called Ozone depletion events. However, it seems to be more stable after deposition into the snowpack. Here we present measurements of bromine, iodine and mercury performed by ICP-MS, on bulk and surface snow samples taken over a 600 km traverse in East Antarctica (East Antarctic International Ice Sheet Traverse, EAIIST 2019). The samples give us deposition records of the last season and the last few years for the surface and bulk samples, respectively. The analyses show a decrease of concentrations toward the inland except for the sites characterised by a strong snow metamorphosis caused mainly by the wind friction. Future studies will investigate the possible link between the concentration profile and the variation of the solar radiation reaching the Antarctic Plateau during spring caused by the ozone hole formation.