Col Margherita Observatory: A background site in the Eastern Italian Alps for investigating the chemical composition of atmospheric aerosols

The chemical composition of atmospheric aerosol collected at the Col Margherita Atmospheric Observatory (46 degrees 22' 0.059" N, 11 degrees 47' 30.911" 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-, NO3-, SO2-, K+, Mg2+, Na+, NH4+, 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 a-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 a-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.