“…(1)) was generated by using average contributions (Table S1 in the Supporting Information) that were available in the literature (Zheng et al, 2002;Lee et al, 2003;Kim et al, 2005;Marmur et al, 2005;Alastuey et al, 2006;Hopke et al, 2006;Kulkarni et al, 2007;Song et al, 2008;Yuan et al, 2009;Chan et al, 2011;Guo et al, 2011). Next, hourly fluctuations were added by assuming random variability and a lognormal distribution (Lingwall and Christensen, 2007) for each source, except for vehicle exhaust. Time series data of carbon monoxide (a classic tracer for traffic) collected at an air quality monitoring station in an urban area were used to approximate the diurnal and weekly vehicle exhaust variations.…”