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List of Abstracts 42during POLARCAT (airborne lidar observations, CALIOP vertical profiles…) and particle dispersion model(FLEXPART) initialized by ECMWF are conducted to retrieve the critical processes responsible of thehorizontal and vertical transport. This turns out to be also a first step to calculate the radiative fluxes of theaerosol plumes in the Arctic region.P-Interfaces.5 ID:4315 15:35Comparison of Snow-pit and Atmospheric Concentrations of Sulphate, Nitrate, MSA and BlackCarbon in the High ArcticSangeeta Sharma 1 , Desiree Toom-Sauntry 1 , James Zheng 2 , Joseph McConnell 3 , Richard Leaitch 11 Environment Canada, 4905 Dufferin Street, Toronto, Ontario M3H 5T4 Canada2 ESS, Natural Resources Canada, Ottawa, Canada3 Desert Research Institute, Reno, NevadaContact: sangeeta.sharma@ec.gc.caIce-cores and snow-pits hold a wealth of historical information on the composition of the atmosphericaerosol that has deposited to the snow surface. A comparison between the aerosol measurements in theatmosphere and the snow-pit can provide knowledge about rates of aerosol deposition and potentiallyprovide information on historical concentrations in the atmosphere. We have a unique data-set of major ionand black carbon concentrations in snow-pit samples collected at Mt. Oxford ice-cap by Natural ResourcesCanada (Northern Ellesmere Island, 82°11’N, 73°02’W, 1782 m above sea level) and in the atmosphere atAlert (about 150 km northeast of Mt. Oxford, 230 m above sea level). Alert is a WMO-GAW measurementstation operated by Environment Canada since 1979 for the atmospheric aerosol measurements. It isestimated that snow-pit samples at the depth of 10.4 m correspond to the atmospheric deposition from 1979.A preliminary comparison of the snow-pit concentrations of sulphate, nitrate, methane-sulphonic acid(MSA) and black carbon with measurements of the same aerosol quantities in the air at Alert from 1980 to2009 will be shown. Despite the difference in elevation between the two sites, vertical profiles in Arctic hazefrom several studies (AGASPII, 1986; ISDAC, 2008) suggest that differences in the mean aerosolconcentrations at both elevations are insufficient to explain the differences between the atmospheric andsnow-pit measurements. If that is true, then the atmospheric aerosol concentration may not be a dominantfactor for determining the level of aerosol deposition in this region. Net deposition rates will also bedetermined for sulphate, nitrate, MSA and black carbon.P-Interfaces.6 ID:4277 15:35Nitrogen oxides in the firn air at Summit, Greenland: an interannual comparison.Claudia Toro 1 , Richard Honrath 1 , Louisa Kramer 1 , Detlev Helmig 2 , Brie Ann Van Dam 2 , Brian Seok 2 ,Laurens Ganzeveld 3 , Paul V. Doskey 11 Michigan Technological University, Houghton, MI, USA2 Institute of Alpine and Arctic Research, University of Colorado, Boulder, CO, USA3 Wageningen University, NetherlandsContact: catoro@mtu.eduPrevious studies have shown that the sunlit polar snowpack is an active reactor, where previously depositedchemical species can undergo photochemical processes that subsequently result in an efflux of trace gases tothe overlying atmosphere, altering its oxidative capacity. Among these species, nitrate has been widelyrecognized as the substrate for nitrogen oxides (NOx) fluxes observed at a number of different remote polarsites, as well in mid-latitude snow-covered environments. However, the extent and the impact of thesecryosphere-atmosphere interactions on tropospheric chemistry cannot yet be adequately quantified due toscarcity of long-term field measurements. Such measurements are prerequisite to the development ofiCACGP-IGAC 2010 12 July, 2010