Molecular characterization of organic aerosols in urban and forested areas of Paris using high resolution mass spectrometry

Abstract. In order to study aerosols in environment influenced by anthropogenic and biogenic emissions to variable extents, PM₁ samples were collected during the summer 2022 in the greater Paris area (ACROSS campaign, Atmospheric Chemistry Of the Suburban Forest, June 14 to July 25) at two locations that represent the urban Paris and the suburban forested area. They were analyzed using high resolution mass spectrometry (HRMS) together with total carbon (TC) by a thermo-optical method. Both sites are compared here to explore differences in aerosol composition from urban and forested environments. The TC analysis shows similar organic carbon (OC) concentrations at both sites (3.2 ± 1.8 µg m^-3 for Paris and 2.9 ± 1.5 µg m^-3 for Rambouillet), and higher elemental carbon (EC) values in the urban area. Both OC and EC concentrations did not show significant variations for daytime and nighttime conditions. This work highlights the influence of anthropogenic inputs into the chemical composition of urban and forested areas, derived into the presence of CHO and CHON compounds but also the detection of two sulfur-containing compounds (C₅H₁₂SO₇ and C₁₀H₁₇NSO₇), which could be tentatively assigned as organosulfates. A smaller number of aromatic compounds were observed for clean periods, that better represent the local biogenic and anthropogenic contributions in Rambouillet and Paris, respectively.