Long-term spatiotemporal distribution characterization of atmospheric black carbon MERRA-2 concentration over China

Black carbon (BC), a component of atmospheric aerosols, strongly adsorbs solar radiation, thereby influencing atmospheric stability and air quality. In this study, the spatiotemporal distribution, historical trends, and influencing factors of BC concentration in China from 1980 to 2020 have been investigated using MERRA-2 (Modern-era Retrospective Analysis for Research and Applications, Vision2) reanalysis dataset, population distribution, and industrial statistics data. The annual total MERRA-2 BC concentration in China (averaging 1.08 μg/m³ over the study period) exhibited three distinct phases: slow growth (1980–1999, 0.02 μg/m³/year), rapid growth (2000–2007, 0.61 μg/m³/year), and gradual decline (2008–2020, -0.014 μg/m³/year). The BC concentration was consistently higher in autumn and winter than in spring and summer, being lowest in July (9.6 μg/m³) and highest in December (14 μg/m³). Spatially, the annual average BC concentration from 1980 to 2020 followed the order: central Yangtze River region (3.14 μg/m³) > eastern coastal region (2.72 μg/m³) > northeastern region (1.40 μg/m³) > western riverine region (0.69 μg/m³) > northwestern frontier region (0.31 μg/m³). High BC-concentration areas, mainly in the central and eastern regions, correlate with regions of vigorous human activities and high industrialization levels, confirming that human activity markedly influences BC pollution. Since 2013, the implementation of emission control strategies and adjustments in the energy structure in China had led to a significant decline in BC concentration. By revealing the spatiotemporal distribution and trends of BC concentration in China, this study provides valuable scientific insights for atmospheric science, environmental protection, and air pollution.