Source Apportionment of Black Carbon from Fossil Fuel and Biomass Burning at an Urban Site in North Africa (Kenitra, Morocco)

Abstract

Abstract In an urban area of Kenitra, Morocco, the apportionment of black carbon (BC) sources into fossil fuel (BCff) and biomass burning (BCwb) using the Aethalometer model has been conducted. This study investigates the temporal trends of BCff and BCwb contributions to the total BC concentrations. The analysis unveils distinct diurnal, weekly, and seasonal patterns in BCff and BCwb concentrations, providing insights into the origins and dynamics of BC pollution. Source apportionment results revealed that the relative contribution of fossil fuels to total black carbon concentrations was more pronounced during winter and summer. In contrast, the contribution of biomass burning exhibited variability across different seasons. Fossil fuel has higher seasonal contributions (ranging from 90.1% in winter to 93.8% in autumn) than biomass burning (ranging from 6.2% in autumn to 9.9% in winter) to the total BC concentrations. This seasonal variation highlights the complex interplay between meteorological conditions and emission sources. Diurnally, BCff peaks during traffic rush hours (human-induced morning and evening homecoming traffic), while biomass-burning-derived BC (BCwb) peaks at nighttime, particularly in winter, reaching values as high as 13% of total BC concentration. Nighttime BC concentration, on average, surpasses daytime levels, suggesting the stronger influence of meteorological conditions than emissions. These variations in BCff and BCwb levels provide compelling evidence of their local origins, primarily from vehicle emissions, socioeconomic activities, and industry-related combustion in the study area. This study underscores also a significant link between biomass and fossil fuel-derived black carbon emissions, with their levels being affected by meteorological conditions such as wind, temperature, and pressure. Lastly, these findings underline the critical importance of considering temporal variations in BC pollution in the development of effective air quality management strategies.

Keywords

• Black carbon
• Source apportionment
• Fossil fuel
• Biomass burning
• Temporal variation