Long-term trends of black carbon levels, sources, and radiative effects from 2013 to 2022 in Beijing, China

Abstract Black carbon (BC), from incomplete combustion of biomass burning and fossil fuels, significantly impacts air pollution and climate. A long-term analysis of BC sources and radiative effects in key regions is essential for the development and refinement of more targeted air quality management strategies. However, there is a lack of sufficient studies addressing this issue. This study examines BC levels and sources from 2013 to 2022. Results show that air quality management measures lowered BC concentrations from 2.23 ± 1.94 μg m −3 in 2013 to 0.84 ± 0.71 μg m −3 in 2022. The most significant reductions in concentrations occurred during the heating season, which is attributed to the transition from coal-based energy to cleaner-burning gas. Significant reductions in BC were observed from both biomass burning and fossil fuels sources, with average annual reduction rates of 0.06 ± 0.01 μg m −3 yr −1 and 0.13 ± 0.03 μg m −3 yr −1 , respectively. BC levels were notably lowest in 2020 and 2021, primarily due to traffic control measures implemented during the COVID-19. This period offers a relevant scenario for examining BC trends under restricted traffic conditions. The relaxation of these measures in 2022 led to a subsequent rise in BC levels. To isolate the pandemic’s effect and accurately assess the effectiveness of air quality management measures, the direct radiative effect of BC was calculated for 2013 and 2019, showing a 80% reduction. This research provides essential evidence for understanding the long-term trends of BC in Beijing and its response to previous measures, supporting the development of more effective, targeted BC reduction strategies critical to sustaining long-term improvements in both air quality and climate outcomes.