One year of aerosol chemical composition and source apportionment in Milan

European policy efforts to address air quality issues have led to significant reductions in pollutants over time. Despite this progress, the decrease is not homogeneous across all pollutants, as certain pollutants still exceed the thresholds set for air quality and health standards. The RI-URBANS project takes advantage of the expertise of the research infrastructures to carry out a coordinated experiment using state-of-the-art technologies in 13 European cities, where chemical composition has been studied throughout 2023. Its goal is to enhance the understanding and management of urban air quality providing a near real-time visualization and source apportionment online tool. This paper focuses on chemical characterization and source apportionment of organic aerosols, presenting data from the measurement campaign in Milan as part of the project. Innovative measurements of non-refractory aerosols using the ToF-ACSM mass spectrometer, along with black carbon concentration measurements derived from optical techniques (AE33, 7λ), enabled continuous monitoring of various emission sources with high temporal resolution. The coordinated analysis involved Positive Matrix Factorization (PMF) and the bi-linear model for black carbon source attribution application in each city, which were then compared with the project's new tool. Results provide insight into aerosol concentrations in the urban background of Milan throughout 2023, and an initial estimation of organic aerosol sources, highlighting significant seasonal variations. Detailed analysis will be deferred in forthcoming publications.