Contribution of black carbon and desert dust to aerosol absorption in the atmosphere of the Eastern Arabian Peninsula

• Published in: Atmospheric environment (1994) 2024-05, Vol.324, p.120427, Article 120427
• Main Authors: Mahfouz, Mohamed M.K., Skok, Gregor, Sciare, Jean, Pikridas, Michael, Alfarra, M. Rami, Moosakutty, Shamjad, Alfoldy, Balint, Ivančič, Matic, Rigler, Martin, Gregorič, Asta, Podlipec, Rok, Lohmann, Svenja, Hlawacek, Gregor, Heller, Rene, Tutsak, Ersin, Močnik, Griša
• Format: Article
• Language: English
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2024.120427

Discriminating the absorption coefficients of aerosol mineral dust and black carbon (BC) in different aerosol size fractions is a challenge because of BC's large mass absorption cross-section compared to dust. Ambient aerosol wavelength dependent absorption coefficients (babs) in supermicron and submicron size fractions were determined with a high time resolution. The measurements were performed simultaneously using identical systems at an urban and a regional background site in Qatar. At each site, measurements were taken by co-located Aethalometers, one with a virtual impactor (VI) and the other with a PM1 cyclone to respectively collect super-micron-enhanced and submicron fractions. The combined measurement of aerosol absorption and scattering coefficients enabled the particles to be classified based on their optical properties' wavelength dependence. The classification reveals the presence of BC internally/externally mixed with different aerosols. Helium ion microscopy images provided information concerning the extent of mineral dust in the submicron fraction. The determination of absorption coefficients during dust storms and non-dust periods was used to establish the absorption Ångström exponent for dust and BC. Non-parametric wind regression, potential source contribution function and back-trajectory analysis reveal major regional sources of desert dust associated with north-westerly winds and a minor local dust contribution. In contrast, major BC sources found locally were associated with south-westerly winds with a smaller contribution made by offshore emissions transported by north-easterly and easterly winds. The use of a pair of Aethalometers with VI and PM1 inlets separates contributions of BC and dust to the aerosol absorption coefficient. The text discusses a study focused on discriminating between aerosol mineral dust and BC absorption coefficients in various aerosol size fractions. The key highlights from the text are as follows:•Collocated sites measurements: Measurements were conducted simultaneously at both an urban and a regional background site in Qatar using identical systems. Collocated Aethalometers were used, one with a virtual impactor and the other with a PM1 cyclone, to collect supermicron-enhanced and submicron aerosol fractions, respectively.•Classification based on Optical Properties: The combination of aerosol absorption and scattering coefficient measurements allowed for the classification of particles based on the wavelen