Atmospheric Black Carbon over Qatar: Seasonal Variability and Source Apportionment

The earth’s atmosphere contains minute particles suspended within it. These atmospheric particles influence the earth's radiation budget through their ability to absorb and scatter radiation. Black carbon (BC) is a type of carbonaceous particle, characterized by highly absorbing solar radiation. Unlike sulfate and sea-salt aerosols, black carbon causes positive radiative forcing due to its absorbing nature. With the accumulation of greenhouse gases in the atmosphere, the average global temperature increased by 1.09°C (IPCC, 2021), between 1850-1900 and the last decade. Since black carbon is one of the major light-absorbing components of aerosol, there is a need to assess BC concentration, their origin, and the contribution of both human-induced combustion and biomass burning emissions to BC levels. In this study, four-year measurements of aerosol absorption at seven wavelengths were investigated in order to determine the daily and seasonal behavior of black carbon and contribution of fossil fuel (FF) and biomass burning (BB) emissions to total BC mass concentration in a suburban area located north of Doha. The highest concentrations of BC were observed during the winter and the lowest values during the summer. The absorption coefficient (Babs) at 470 nm (950 nm) showed large daily variability, ranging from 7 (3) to 187 (95) Mm-1. The mean Babs at 470 nm and 950 nm for the full period were 55± 29 Mm -1 and 25 ± 13 Mm -1, respectively. Fossil fuel emissions were found to be the major source of BC levels. Nonetheless, the influence of biomass burning should not be disregarded. Future studies must be done to fully identify the enhanced absorption in shorter wavelengths.