Light-absorbing aerosols (LAA), including black carbon (BC) and brown carbon (BrC), profoundly impact regional and global climate. Vehicle emission is an important source of LAA in urban areas, but real-world emission features of LAA from the urban vehicle fleet are not fully understood.
This study evaluates traffic-related BC and BrC emission factors (EFs) and their vehicular emission inventories via road tunnel measurements in a city, in 2017 and 2021. The distance-based and fuel-based EFs of BC for the mixed fleet were 1.05 ± 1.28 mg/km and 0.057 ± 0.057 g/kg, respectively, in 2021, with a dramatic decrease of 80% compared to those in 2017. The BC EFs for gasoline vehicles (GVs, including traditional gasoline and hybrid vehicles) and diesel vehicles (DVs) were 0.55 ± 0.065 mg/km and 10.5 ± 2.52 mg/km, respectively, in 2021. Compared to 2017, the BrC EFs also decreased significantly in 2021, by 10.8~53.6%.
Compared to 2017, the annual vehicular LAA emissions in the city have been significantly reduced in 2021 due to the reductions in EFs, by 69% for BC and 10% for BrC.
Our reduced EFs indicate the high effectiveness of air pollution mitigation and transport emission control strategies in reducing urban vehicular light-absorbing aerosol emissions. This reduction in BC and BrC emissions, as a result, have large implications for mitigating severe haze events and preventing global warming.
Our study will provide updated data for quantitative assessment of BC and BrC, and help us understand the real-world urban vehicular BC and BrC emission features in urban areas over recent years.
The results were published in the "Science of the Total Environment" under the title of "Tunnel measurements reveal significant reduction in traffic-related light-absorbing aerosol emissions in China" (http://doi.org/10.1016/j.scitotenv.2022.159212).
