According to Fig. 6,which presents the contribution of PAHs by number
of rings, it is possible to observe that the contribution of the 2 and 3
rings PAHs was ~80% of ΣPAH throughout the years. Taking into account the PAHs species suggested as markers of certain sources, it appears
that the prevalence of lower molecular weight compounds in ambient
air samples can be essentially related to road traffic, more
specifically with vehicles with diesel engines (Khalili et al., 1995;
Miguel et al., 1998). Cement industries were also related to the 3 rings
PAHs (Aci, Acp and Ant)