Light absorption enhancement of black carbon and its impact factors during winter in a megacity of the Sichuan Basin, China

Yuting Lan; Li Zhou; Song Liu; Ruilin Wan; Ning Wang; Dongyang Chen; Yi Li; Yan Jiang; Zhihan Rao; Wanting Jiang; Danlin Song; Qinwen Tan; Fumo Yang

doi:10.1016/j.scitotenv.2024.170374

Light absorption enhancement of black carbon and its impact factors during winter in a megacity of the Sichuan Basin, China

Sci Total Environ. 2024 Mar 25:918:170374. doi: 10.1016/j.scitotenv.2024.170374. Epub 2024 Feb 1.

Authors

Yuting Lan¹, Li Zhou², Song Liu¹, Ruilin Wan¹, Ning Wang¹, Dongyang Chen¹, Yi Li¹, Yan Jiang³, Zhihan Rao⁴, Wanting Jiang⁵, Danlin Song⁵, Qinwen Tan⁵, Fumo Yang¹

Affiliations

¹ College of Architecture and Environment, Sichuan University, Chengdu 610065, China; College of Carbon Neutrality Future Technology, Sichuan University, Chengdu 610065, China; Sichuan University Yibin Park, Yibin Institute of Industrial Technology, Yibin 644600, China.
² College of Architecture and Environment, Sichuan University, Chengdu 610065, China; College of Carbon Neutrality Future Technology, Sichuan University, Chengdu 610065, China; Sichuan University Yibin Park, Yibin Institute of Industrial Technology, Yibin 644600, China. Electronic address: lizhou@scu.edu.cn.
³ Sichuan Ecological Environment Monitoring Center, Chengdu 610091, China.
⁴ College of Architecture and Environment, Sichuan University, Chengdu 610065, China; College of Carbon Neutrality Future Technology, Sichuan University, Chengdu 610065, China; Sichuan University Yibin Park, Yibin Institute of Industrial Technology, Yibin 644600, China; Sichuan Ecological Environment Monitoring Center, Chengdu 610091, China.
⁵ Chengdu Academy of Environmental Sciences, Chengdu 610072, China.

PMID: 38307267
DOI: 10.1016/j.scitotenv.2024.170374

Abstract

Carbonaceous aerosols play a vital role in global climate patterns due to their potent light absorption capabilities. However, the light absorption enhancement effect (E_abs) of black carbon (BC) is still subject to great uncertainties due to factors such as the mixing state, coating material, and particle size distribution. In this study, fine particulate matter (PM_2.5) samples were collected in Chengdu, a megacity in the Sichuan Basin, during the winter of 2020 and 2021. The chemical components of PM_2.5 and the light absorption properties of BC were investigated. The results revealed that secondary inorganic aerosols and carbonaceous aerosols were the dominant components in PM_2.5. Additionally, the aerosol filter filtration-dissolution (AFD) treatment could improve the accuracy of measuring elemental carbon (EC) through thermal/optical analysis. During winter in Chengdu, the absorption enhancement values of BC ranged between 1.56 and 2.27, depending on the absorption wavelength and the mixing state of BC and non-BC materials. The presence of internally mixed BC and non-BC materials significantly contributed to E_abs, accounting for an average of 68 % at 405 nm and 100 % at 635 nm. The thickness of the BC coating influenced E_abs, displaying an increasing-then-decreasing trend. This trend was primarily attributed to the hygroscopic growth and dehydration shrinkage of particulate matter. Nitrate, as the major component of BC coating, played a crucial role in the lensing effect and exhibited fast growth during variation in E_abs. By combining the results from PMF, we identified the secondary formation and vehicle emission as the primary contributors to E_abs. Consequently, this study can provide valuable insights into the optical parameters, which are essential for assessing the environmental quality, improving regional atmospheric conditions, and formulating effective air pollution control strategies.

Keywords: Black carbon coating; Carbonaceous aerosols; Light absorption enhancement; Mixing state; PM(2.5); Sichuan basin.