Effect of source variation on the size and mixing state of black carbon aerosol in urban Beijing from 2013 to 2019: Implication on light absorption

Yunfei Wu; Yunjie Xia; Chang Zhou; Ping Tian; Jun Tao; Ru-Jin Huang; Dantong Liu; Xin Wang; Xiangao Xia; Zhiwei Han; Renjian Zhang

doi:10.1016/j.envpol.2020.116089

Effect of source variation on the size and mixing state of black carbon aerosol in urban Beijing from 2013 to 2019: Implication on light absorption

Environ Pollut. 2021 Feb 1:270:116089. doi: 10.1016/j.envpol.2020.116089. Epub 2020 Nov 19.

Authors

Yunfei Wu¹, Yunjie Xia², Chang Zhou², Ping Tian³, Jun Tao⁴, Ru-Jin Huang⁵, Dantong Liu⁶, Xin Wang⁷, Xiangao Xia⁸, Zhiwei Han⁹, Renjian Zhang⁸

Affiliations

¹ Key Laboratory of Middle Atmosphere and Global Environment Observation (LAGEO), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. Electronic address: wuyf@mail.iap.ac.cn.
² Key Laboratory of Middle Atmosphere and Global Environment Observation (LAGEO), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; University of Chinese Academy of Sciences, Beijing 100049, China.
³ Beijing Weather Modification Office, Beijing 100089, China.
⁴ South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou 510530, China.
⁵ Key Laboratory of Aerosol Chemistry and Physics, State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China.
⁶ Department of Atmospheric Sciences, School of Earth Sciences, Zhejiang University, Hangzhou 310027, China.
⁷ Key Laboratory for Semi-Arid Climate Change of the Ministry of Education, Lanzhou University, Lanzhou 730000, China.
⁸ Key Laboratory of Middle Atmosphere and Global Environment Observation (LAGEO), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; Xianghe Observatory of Whole Atmosphere, Institute of Atmospheric Physics, Chinese Academy of Sciences, Xianghe 065400, China.
⁹ Key Laboratory of Regional Climate-Environment for Temperate East Asia (RCE-TEA), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.

PMID: 33246761
DOI: 10.1016/j.envpol.2020.116089

Abstract

Black carbon (BC) is the most important aerosol light-absorbing component, and its effect on radiation forcing is determined by its microphysical properties. In this study, two microphysical parameters of refractory BC (rBC), namely, size distribution and mixing state, in urban Beijing from 2013 to 2019 were investigated to understand the effects of source changes over the past years. The mass equivalent diameter of rBC (D_c) exhibited bimodal lognormal distributions in all seasons, with the major modes accounting for most (>85%) of the rBC masses. The mass median diameter (MMD) was obviously larger in winter (209 nm) than in summer (167 nm) likely due to the contribution of more rBC with larger D_c from solid fuel combustion and enhanced coagulation of rBC in polluted winter. More rBC particles were thickly coated in winter, with the number fraction of thickly coated rBC (f_coatBC) ranging within 29%-48% compared with that of 12%-14% in summer. However, no evidential increase in BC light-absorption capability was observed in winter. This finding was likely related to the lower absorption efficiency of larger rBC in winter, which partly offset the coating-induced light enhancement. Two stage of decreases in MMD and f_coatBC were observed, accompanied with a persistent decrease in rBC loading, thereby reflecting the discrepant effects of source control measures on rBC loading and physical properties. The control measures in the earlier stage before 2016 was more efficient to reduce the rBC loading but slightly influenced the microphysical properties of rBC. As of 2016, the reduction in rBC concentration slowed down because of its low atmospheric loading. However, rBC showed a more obvious decrease in its core size and became less coated. The decrease in f_coatBC may have weakened the BC absorption and accelerated the decrease in light absorption resulting from the reduction in rBC loading.

Keywords: Absorption capability; Black carbon; Mixing state; Size distribution; Source variation.

MeSH terms

Aerosols / analysis
Air Pollutants* / analysis
Beijing
Carbon / analysis
Environmental Monitoring

Substances

Aerosols
Air Pollutants
Carbon