Changes in Source-Specific Black Carbon Aerosol and the Induced Radiative Effects Due to the COVID-19 Lockdown

The impacts of anthropogenic emissions on the reduction of source-specific equivalent black carbon (eBC) aerosols and their direct radiative effects (DREs) were investigated during the lockdown of the coronavirus outbreak in a megacity of China in 2020. Five eBC sources were identified using a hybrid environmental receptor model. Results showed that biomass burning, traffic-related emissions, and coal combustion were the dominant contributors to eBC. The generalized additive model indicated that the reduction of traffic-related eBC during the lockdown was entirely attributed to the decrease of emissions. Decreased biomass-burning activities and favorable meteorological factors are both important drivers for the biomass-burning eBC reduction during the lockdown. A radiative transfer model showed that the DRE efficiency of eBC from biomass burning was the strongest, followed by coal combustion and traffic-related emissions. This study highlights that aggressive reduction in the consumption of residential solid fuels would be effective in achieving climate change mitigation.