The carbonaceous content (OC and EC) of PMx samples
was analysed by a thermal–optical transmission technique
developed by the University of Aveiro (Pio et al., 2011). The
PM2.5–10 samples were decarbonated with HCl fumes, previously
to OC/EC analysis. Two 9 mm diameter filter punches, in
the case of the PM2.5 samples, or strips representing 1/20 of the
total area, for other size fractions, were used in each analytical
run. The system comprises a quartz tube with two heating
zones, a pulsed laser and a nondispersive infrared (NDIR) CO2
analyser. The filter strips or punches are placed vertically inside