Source apportionment and diurnal variability of autumn-time black carbon in a coastal city of Salé, Morocco

Black carbon BC assessment is a new topic of low importance in scientific research in Morocco. The following study aims to understand the temporal variation BC concentrations, their correlation with the meteorological variables, and to estimate the contribution of fossil fuel and biomass combustion to BC and nitrogen dioxide (NO2) during the 2020 autumn season. For this purpose and during seven weeks, in-situ measurements of equivalent black carbon (eBC) and NO2 were conducted simultaneously at an urban background monitoring site in Sale, Morocco. Contribution of fossil fuel (BCff) and biomass burning (BCwb) to eBC was apportioned based on the spectral dependence of the absorption of BC. The average eBC concentration observed was 1.9 ± 1.5 µg/m3. It was found that eBC and NO2 are strongly correlated (r=0.6) and typically emitted from local sources within Sale city. Fossil fuel combustion, mainly from road transport, is the largest contributor to ambient eBC and NO2 concentrations. However, wood combustion makes a significant contribution to the observed eBC of around 28%. The relationship between meteorological variables and BC levels was not significate and likely don’t contribute to daily variations.