Sources of high PM2.5 concentrations in Milan, Northern Italy: Molecular marker data and CMB modelling

► High PM2.5 concentrations determine harmful health effects. ► Information on the impacting sources are needed for PM2.5 reduction strategies. ► Source apportionment for PM2.5 in the polluted Northern Italy was performed by CMB. ► Local and diffuse sources were estimated. ► The relevance of secondary aerosol in summer and winter is discussed.