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Organic acids in aerosols Earth's atmosphere are ubiquitous and they have been extensively studied across urban, rural and polar environments. However, little is known about their properties, transport, source and seasonal variations in the Svalbard Archipelago. Here, we present the annual trend of organic acids in the aerosol collected at Ny-Ålesund and consider their size-distributions to infer their possible sources and relative contributions. A series of carboxylic acids were detected with a predominance of C2-oxalic acid. Pinic acid and cis-pinonic acid were studied in order to better understand the oxidative and gas-to-particle processes occurred in the Arctic atmosphere. Since the water-soluble organic fraction is mainly composed by organic acids and ions, we investigated how the seasonal variation leads to different atmospheric transport mechanisms, focusing on the chemical variations between the polar night and boreal summer. Using major ions, levoglucosan and MSA, the Positive Matrix Factorization (PMF) identified five different possible sources: a) sea spray; b) marine primary production; c) biomass burning; d) sea ice related process and e) secondary products. Unlabelled Image • A year-round record of organic acids was studied in Arctic aerosols. • The study investigates sources and seasonal trend of particulate organic acids. • The study provides an overview of the change of sources throughout the seasons. • PMF defines five sources for low molecular weight organic acids. [ABSTRACT FROM AUTHOR]

The chemical composition of atmospheric aerosol collected at the Col Margherita Atmospheric Observatory (46° 22ˈ 0.059ˈˈ N, 11° 47ˈ 30.911ˈˈ E, 2543 m a.s.l.) was investigated during spring and summer 2018. This is the first study of this area and should lead to a better understanding of the aerosol chemical composition in the Southern slope of the Eastern Italian Alps, with the aim of proposing this high altitude site as a background station. Aerosol samples were analyzed to determine several water soluble components (Cl−, Br−, I−, NO 3 −, SO 4 2−, K+, Mg2+, Na+, NH 4 +, Ca2+), organic acids (methanesulfonic acid and C 2 –C 7 carboxylic acids), monosaccharides, alcohol-sugars, levoglucosan and its isomers, sucrose, phenolic compounds, free L- and D-amino acids and photo-oxidation products of α-pinene (cis-pinonic acid and pinic acid). The majority of the mass concentration is explained by ionic species, but the other investigated compounds allow us to study other processes or identify the potential sources. Carboxylic acids and photochemical products of α-pinene were used to study photochemical or oxidative processes. Biomass burning input was evaluated using two specific classes of biomarkers: anhydrosugars and phenolic compounds, while biogenic inputs were studied using sugars and free amino acids. None of these water soluble organic compounds have been properly investigated previously in alpine sites because their concentrations in aerosol are very low. • Chemical composition of aerosol collected at Col Margherita Atmospheric Observatory. • First investigation of water soluble organic compounds in alpine sites. • Col Margherita Atmospheric Observatory as background site in the Eastern Italian Alps. [ABSTRACT FROM AUTHOR]