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Distribution and budget of reactive nitrogen compounds (NOy) in polar regions: atmospheric effects and air-snow interactions (NITRAS)
IADC_id: 23
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Call year: 2015
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Observations on atmospheric chemistry of reactive nitrogen (NOy = NOx + HNO3 + particulate nitrate + PAN + etc.) in the global atmosphere are limited , in particular, in the polar regions due to uncertainties surrounding the NOy distribution and budget as they are transported into the polar sites and the mechanism for the conversion between NOx and NOy. The NOy in polar regions have received attention due to discoveries of NOx and HONO production from nitrate (NO3-) in snow surfaces, sufficient to alter the global OHx (HO+HO2), NOx and O3 budgets in the overlying atmosphere. Hence, knowledge of the natural background concentration and main sources of NOy is pivotal in determining their influence and the impact of human activity on the atmospheric photochemistry and on ecosystems in polar environments.rnThus, while the release of nitrogen species from snow surface has been investigated, little is known about the sources of snow NO3- and the air-snow interaction and deposition of NOy. The current understanding of this process is the absorption of NOy by snow surfaces determining the presence and reduction of nitrate (NO3-) in a surface phase. Inorganic NO3- species, as HNO3, as a neutral salt (NH4NO3), or as fixed sea salt, are likely the predominant precursors of snow NO3-. Previous studies indicate that HNO3 is not the only source of snow NO3- because it is lost from the snow surface due to its volatilization, in apparent contradiction to laboratory studies showing irreversible uptake of HNO3 on ice surfaces. NO3- particles could be also important sources of snow NO3- due to their more efficient deposition. These particles can be formed from the sea salt promoting the conversion of gas phase nitrate to the aerosol phase. However, other NOy species can be deposited and converted to NO3- in snow. Measurements performed during the “Alert 2000” campaign highlighted that the dominant source for snow NO3- was wet deposition during snowfall (Ianniello et al., 2002). Recently, the microbial activity within the snow has been proposed to produce nitrogen monoxide (NO), HONO and HNO3 (Amoroso et al., 2010). In addition, detailed sampling of surface snow during winter and springtime at Ny-Ålesund demonstrated that NO3- dry deposition is the predominant process determining NO3- concentrations during precipitation-free periods and prevails over any NO3- postdeposition losses via photolysis and HNO3 evaporation within (Björkman et al., 2014). Besides, climate change such as changes in UV radiation, in concentrations of pollutants, in snow cover, and in temperature could affect the extent of these depositional and air-snow processes. The goals of this project proposal are: to determine the atmospheric concentrations, the partitioning and the budget of NOy; to quantify the direction and magnitude of NOy fluxes at the snow-atmosphere interface; to identify chemical processes that control the NOy transport, conversion and deposition in the snow; and, then, to investigate about the atmospheric sources of snow NO3- and the links with climate changes. These investigations will comprise appropriate studies on chemical and physical snow properties; on the lifetimes and loss processes and photolysis rates for NOy; and desorption coefficients and reactivity for NOy in relation to the snow surface. The chemical and physical properties of the atmosphere (solar radiation, temperature, and the concentration of pollutants) and snow (temperature, hardness, density, reflectance, specific surface area, size and shape of snow grains, penetration of UV radiation, snow accumulation rate, pH, and ionic strength) can affect the magnitude of these post-depositional processes. Furthermore, in this research activity we will introduce and will test for the first time a portable in-situ Nitrogen Oxide Monitor on Climate Change Tower in order to perform automatic and continuous measurements of nitrogen oxides over year. For comparison and evaluation of this sensor, parallel automatic NOx analyzers will be used near the sampling site.rnReferences:rnAmoroso, A., Dominè, F., Esposito, G., Morin, S., Savarino, J., Nardino, M., Montagnoli, M., Bonneville, M., Clement, J.-C., Ianniello, A. and Beine, H.J. (2010) Environ. Sci. Technol. 44, 714–719.rnBjorkman, M.P., Vega, C.P., Kuhnel, R., Spataro, F., Ianniello, A., Esposito, G., Kaiser, J., Marca, A., Hodson, A., Isaksson, E., and Roberts, T.J. (2014) J. Geophys. Res. Atmos. 119, 12,953-12,976.rnIanniello, A., Beine, H.J., Sparapani, R., Di Bari, F., Allegrini, I. and Fuentes, J. (2002) Atmos. Environ.36, 5299–5309.
National/International Cooperation:
As an international collaboration partner, ESSO-National Centre for Antarctic and Ocean Research, Earth System Science Organization, Ministry of Earth Sciences (India) will be involved to contribute to air-snow interaction processes and nitrogen fluxes. These collaboration and related activities will be established in early March 2015. As a national collaboration partner, Arabba Avalanche Centre (ARPAV) will be involved to contribute to physical snow studies.
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