Black carbon aerosols in China: Spatial-temporal variations and lessons from long-term atmospheric observations
Abstract. Using 13-year (2008–2020) continuous measurements of equivalent black carbon (eBC) in China, this study reports the spatial-temporal variations of eBC and its sources, including solid fuel (eBCsf) and liquid fuel combustion (eBClf). The results show that eBC and its sources exhibit spatial heterogeneity with higher concentrations in eastern and northern China compared to western and southern China. Seasonal variations of eBC and eBCsf generally show low values during summer and high values during winter in most stations. Long-term trends indicate that eBC and eBClf decreased most rapidly at urban stations while eBCsf declined faster at rural stations. Comparisons of eBC concentrations and trends between this study and other observations reveal higher eBC levels but lower reduction rates in China. Comparison between surface eBC observations and model simulations indicates models performed well in simulating spatial distribution but poorly in simulating inter-annual variations. Weather-normalized eBC concentrations were compared to several emission inventories, revealing higher correlations and suggesting that normalized eBC concentrations can be used to adjust emission estimates. Long-term observations of eBC and its sources show decreasing trends in China, primarily driven by emission reduction. Further analysis suggests that the reduction of eBC was mainly attributed to decreased emissions from solid fuel combustion in rural and baseline stations. This study provides insights for reducing uncertainties in black carbon emission inventories and improving model performance in simulating surface concentrations.