Source apportionment of black carbon using an advanced Aethalometer model in a typical industrial city of China

Black carbon (BC) aerosol can lead to adverse health effects and drive climate change; therefore, the characteristic research and identification of BC sources are essential for lowering emissions. In this study, equivalent black carbon (eBC) measurement was performed using a seven-wavelength Aethalometer (AE33) at an urban site in a typical industrial city (Zibo) of Northern China for the first time. The monitoring was performed from February 2021 to January 2022. The mass absorption cross-section (MAC) of AE33 was optimised using the online elemental carbon (EC) data, and eBC was corrected using the MAC. The corrected annual BC concentration was 1.72 ± 1.18 µg/m³. The diurnal variation of BC depicted a bimodal distribution. Furthermore, the BC concentration on weekends was 18 % lower than on weekdays. The diurnal variation and weekend effect reflect the critical contributions of traffic emission to BC concentration. The source apportionment of BC was calculated by a constraining Aethalometer model, which restricted the Ångström exponent using the online potassium ions. The results revealed that BC was not significantly affected by biomass burning (BC_bb) in Zibo. The relative contribution of BC_bb was higher in winter than in other seasons. The daily morning peak of BC was primarily influenced by traffic sources, whereas the contribution of biomass burning increased after 17:00 in the evening peak. Our findings suggest that it is more important to control fossil fuel sources for BC emission reduction in Zibo, while it is necessary to strengthen the control of biomass combustion sources in winter.