Abstract. The evolution of fine aerosol (PM1) species as well the contribution potential sources to total organic (OA) at an urban background site in Barcelona, western Mediterranean basin (WMB) was investigated. For this purpose, a quadrupole chemical speciation monitor (Q-ACSM) deployed acquire real-time measurements for two 1-year periods: May 2014–May 2015 (period A) and September 2017–Octo...