BLANCO-ALEGRE, C., CALVO, A.I., ALVES, C., FIALHO, P., NUNES, T., GOMES, J., CASTRO, A., ODUBER, F., COZ, E., FRAILE, R. (2020) - Aethalometer measurements in a road tunnel: a step forward in the characterization of black carbon emissions from traffic. Science of the Total Environment, STOTEN-D-19-11914, doi: 10.1016/j.scitotenv.2019.135483.​

​A sampling campaign was conducted in the Liberdade Avenue tunnel (Braga, Portugal) during a week (with 56,000 vehicles) to monitor black carbon (eBC-equivalent black carbon) by means of an Aethalometer AE-31, and gaseous pollutants (CO₂, CO, NO_x). Inside the tunnel, the mean eBC mass concentration was 21 ± 10 μg m⁻³, reaching a maximum hourly value of 49.0 μg m⁻³. An hourly and weekday-weekend study was carried out. Regarding the Absorption Ångström exponent (AAE), a mean value of 0.97 ± 0.10 was obtained, for a source of practically pure traffic. There was a positive significant correlation between eBC and the number of light vehicles (r = 0.47; p < 0.001) and between eBC and the gaseous emissions: CO (r = 0.67; p < 0.001), CO₂ (r = 0.71; p < 0.001), NO (r = 0.63; p < 0.001) and NO₂ (r = 0.70; p < 0.001). The mean black carbon emission factors (EF_BC) inside the tunnel were 0.31 ± 0.08 g (kg fuel)⁻¹ and 0.11 ± 0.08 mg veh⁻¹ km⁻¹, similar to those found in other studies for gasoline and diesel vehicles in road tunnels.