Spatial distribution and sources of winter black carbon and brown carbon in six Chinese megacities

Qian Zhang; Zhenxing Shen; Tian Zhang; Shaofei Kong; Yali Lei; Qiyuan Wang; Jun Tao; Renjian Zhang; Peng Wei; Chong Wei; Song Cui; Tiantao Cheng; Steven Sai Hang Ho; Ziyi Li; Hongmei Xu; Junji Cao

doi:10.1016/j.scitotenv.2020.143075

Spatial distribution and sources of winter black carbon and brown carbon in six Chinese megacities

Sci Total Environ. 2021 Mar 25:762:143075. doi: 10.1016/j.scitotenv.2020.143075. Epub 2020 Oct 17.

Authors

Qian Zhang¹, Zhenxing Shen², Tian Zhang³, Shaofei Kong⁴, Yali Lei³, Qiyuan Wang⁵, Jun Tao⁶, Renjian Zhang⁷, Peng Wei⁸, Chong Wei⁹, Song Cui¹⁰, Tiantao Cheng¹¹, Steven Sai Hang Ho¹², Ziyi Li¹³, Hongmei Xu³, Junji Cao⁵

Affiliations

¹ Key Laboratory of Northwest Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an 710055, China; Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
² Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, China; Key Lab of Aerosol Chemistry & Physics, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China; International Joint Research Center for Persistent Toxic Substances (IJRC-PTS), School of Water Conservancy and Civil Engineering, Northeast Agricultural University, Harbin, China. Electronic address: zxshen@mail.xjtu.edu.cn.
³ Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
⁴ Department of Atmospheric Science, School of Environmental Sciences, China University of Geosciences, Wuhan 430074, China.
⁵ Key Lab of Aerosol Chemistry & Physics, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China.
⁶ South China Institute of Environmental Sciences, Ministry of Environmental Protection, Guangzhou, China.
⁷ Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
⁸ Division of Environment and Sustainability, The Hong Kong University of Science and Technology, Hong Kong, China.
⁹ Shanghai Carbon Data Research Center, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China.
¹⁰ International Joint Research Center for Persistent Toxic Substances (IJRC-PTS), School of Water Conservancy and Civil Engineering, Northeast Agricultural University, Harbin, China.
¹¹ School of Atmospheric Science, Fudan University, Shanghai, China.
¹² Division of Atmospheric Sciences, Desert Research Institute, Reno, NV 89512, United States.
¹³ Key Laboratory of Northwest Resource, Environment and Ecology, MOE, Xi'an University of Architecture and Technology, Xi'an 710055, China.

PMID: 33127135
DOI: 10.1016/j.scitotenv.2020.143075

Abstract

The light-absorbing carbonaceous aerosols, including black carbon (BC) and brown carbon (BrC), influenced heavily on aerosol environmental quality and the Earth's radiation. Here, a winter campaign to characterize BC and BrC in PM_2.5 was conducted simultaneously in six Chinese megacities (i.e., Harbin, Beijing, Xi'an, Shanghai, Wuhan, and Guangzhou) using continual aethalometers. The combinations of advanced aethalometer and generalized additive model (GAM) were used to precisely quantify the BC and BrC sources in these megacities. The averaged light-absorbing coefficients of BC (b_abs-BC) and BrC (b_abs-BrC) were 28.6 and 21.8 Mm^-1 in northern cities, they were 1.4 and 2.7 times higher than those in southern cities. The BrC dominated the total b_abs (>40%) in northern cities but low to 20% in southern cities. On the other hand, the BC fractions were high in the southern cities, with the contributions of 62.4-79.7%, whereas much lower values of 53.7-59.4% in the northern cities. Source apportionment showed that the combustion of liquid fuels (e.g., gasoline or diesel) was highly dominant to b_abs-BC (>80%) in Guangzhou and Wuhan. This was further supported by the high NO₂ loadings in the GAM model. Solid fuels (i.e., biomass or coal) contributed a substantial portion to total b_abs-BC in the other four cities where the high abundances of primary b_abs-BrC were observed. The diurnal trend showed the peaks of secondary-BrC (b_abs-BrC_S) and b_abs-BrC_S/ΔCO in the northern cities occurred at high relative humidity in nighttime, implying the secondary BrC formation was possibly related to aqueous reactions in winter. In contrast, in the southern cities of Shanghai and Guangzhou, the accumulation of vehicle emissions during the morning traffic rush hours lead the formation of secondary BrC through photochemical reactions. The results of this work can be applied for the development of more effective practices to control BC and BrC on regional scale.

Keywords: Black carbon; Brown carbon; Formation mechanism; GAM model; Light absorption; Source.