“…Regarding the latter, several studies conducted in EU cities have shown that total particle number concentrations can vary as high as a factor of roughly 9 within the same city (Birmili et al, 2013;Buonanno et al, 2011;Mejía et al, 2008;Mishra et al, 2012). Localized spatial variations in urban aerosol PSDs and number concentrations are due in part to the nature of local emission sources near the measurement site and meteorological conditions, including wind speed and direction, temperature, and relative humidity (Baxla et al, 2009;Birmili et al, 2001;Charron and Harrison, 2003;Kaul et al, 2011;Nieto et al, 1994;Rose et al, 2010;Stanier et al, 2004;Swietlicki et al, 2008;Väkevä et al, 2000;Wehner and Wiedensohler, 2003;Weingartner et al, 1997;Yu et al, 2018). Physiochemical processes that can transform an aerosol population over space and time are also very important, such as particle growth due to coagulation and condensation, particle shrinkage due to evaporation, reactive uptake, and wet and dry deposition (Gaston et al, 2014;Limbeck et al, 2003;Lin et al, 2011;Moise and Rudich, 2002;Salma et al, 2011;Tang et al, 2010;Zhu et al, 2002a, b).…”