Chemical composition of atmospheric aerosol at Ny Alesund (Svalbard Islands): a focus on Elemental and Organic Carbon and organic acids

The Arctic is experiencing substantial climatic changes since the past decades and the atmospheric aerosol plays a key role in the current climatic changes, influencing the energy budget of the surface and lowermost atmosphere. In particular, during polar sunrise, the Arctic troposphere is a unique chemical reactor, due to emissions both from human activity in the mid/high latitude areas and from natural sources in the Arctic Ocean; moreover, light-induced chemical reactions cause changes in atmospheric composition. The coupled effect of meteorological patterns and extreme variations in solar irradiance starting in spring makes difficult to unravel the factors of the production and removal of many environmentally relevant chemical compounds. Hence, daily PM10 and size-segregated (by 4-stage impactor) aerosol samples were continuously collected at Gruvebadet station (Ny Alesund, Svalbard Islands, 78.9°N, 11.9°E) during the spring-summer period (March-September) along five consecutive years (2010-2014) and were analysed for ion, metal and EC/OC (Elemental/Organic carbon) content. Here we focus on the EC and OC fraction of the aerosol and on selected organic anions (oxalate, acetate, propionate, formate, glycolate and pyruvate), because of their importance in the absorption of solar radiation (EC) and their sensitivity to oxidation processes and to the dynamic atmospheric production/consumption triggered and/or mediated by solar radiation (organic compounds). Most of the determined organic anions show very low concentration in all the years, with the exception of oxalate, which is always dominant among the organic anions. The temporal trends of the measured compounds is studied in comparison both with the broad band UV solar irradiance data in order to evaluate the effect of the photochemistry on the studied compounds. Moreover, correlations among different chemical markers are studied, together with backtrajectory analysis, so to spot the long-range transport events delivering these compounds together with pollutants from the anthropized areas of the Northern hemisphere. For instance, in particular periods, significant correlation between nitrate and organic acids are found, whose nature is still to be ascertained and which could be related to common photochemical production processes. Besides, the similarity in the spring pattern of sulphate and oxalate hints at a common anthropogenic source of the latter in this period and requires further investigation