“…The second station is an urban background air quality station (hereafter BCN; 41 • 23′14.5"N 2 • 06′55.6″E; 68 m asl) located at the Institute of Environmental Assessment and Water Research (IDAEA-CSIC) in Barcelona. It is positioned adjacent to Diagonal Avenue, one of the city's main roads, and is flanked by a variety of commercial activities (Amato et al, 2009;Cusack et al, 2012;in 't Veld et al, 2023;in 't Veld et al, 2021;Pandolfi et al, 2016;Pandolfi et al, 2014;Pérez et al, 2008;Pey et al, 2009;Querol et al, 2014, Querol et al, 2004aRipoll et al, 2015). At both measurement sites, an aethalometer (Magee Scientific, USA, model AE33) was used to quantify the aerosol light absorption coefficient at seven different wavelengths (370, 470, 520, 590, 660, 880, and 950 nm) and the mass concentration of black carbon (BC) (Drinovec et al, 2015).…”