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

Abstract

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.

Measuring the Emission Changes and Meteorological Dependence of Source‐Specific BC Aerosol Using Factor Analysis Coupled With Machine Learning

“…Vehicular emissions is a major source of OC and NO 2 (Bi et al., 2019; B. S. Liu et al., 2022; H. K. Liu et al., 2022; Zotter et al., 2017). The percentage of light absorption showed an increasing trend from 370 to 880 nm (Figure 3), which is consistent with previous reports (H. K. Liu et al., 2021, 2022; Yuan et al., 2022). The estimated AAE for VE was 1.08 (Figure S3 in Supporting Information ), which fitted the range of VE characteristic values (0.8–1.2) (Blanco‐Donado et al., 2022; Briggs & Long, 2016).…”

Source Apportionment of Elemental Carbon in Different Seasons in Hebei, China

“…The last factor was characterized by high loadings of As (43%) and Pb (30%). According to previous studies, high loadings of As and Pb are found in coal combustion (Tan et al, 2017;Liu et al, 2021). Thus, this factor was recognized as resulting from coal combustion which contributed 35% of EC.…”

“…Five sources of EC were identified by PMF during wintertime shown in Figure 4. The first factor was characterized by high loadings of Ca 2+ (86%), Si (48%), and Ti (43%), widely recognized as associated with mineral dust (Tao et al, 2017;Liu et al, 2021). This factor barely contributed to EC during winter.…”

“…The 14C method can provide a good level of accuracy in the results, but limitations, such as high cost and a minimum sample loading required for analysis, hinder its promotion. Another method uses mathematical models such as the Aethalometer (AE) model and a receptor model to apportion BC into its various sources based on its optical features and chemical composition (Rajesh and Ramachandran, 2017;Wang et al, 2020;Liu et al, 2021). Compared with the 14C method, mathematical models are not restricted by sample loadings because online data are also applicable.…”

Contributions of Traffic and Industrial Emission Reductions to the Air Quality Improvement after the Lockdown of Wuhan and Neighboring Cities Due to COVID-19

“…The lockdown of Wuhan and surrounding cities provided an unintended experimental condition under which to investigate the influences of emissions from different sectors, e.g., traffic and industry, by completely or partially removed emissions. A few studies showed that the air pollution level declined during the lockdown period [25][26][27][28][29][30]. The air pollution reduction can be visualized from measurements by the China National Environmental Monitoring Network [31].…”