Optical properties and radiative forcing of carbonaceous aerosols in a valley city under persistent high temperature

Chunyan Li; Bianhong Zhou; Junhui Zhang; Lihua Jiao; Kaijing Cheng; Long Chen; Yu Li; Yongqiang Li; Steven Sai Hang Ho; Zhongtao Wen

doi:10.1016/j.scitotenv.2024.172462

Optical properties and radiative forcing of carbonaceous aerosols in a valley city under persistent high temperature

Sci Total Environ. 2024 Jun 10:928:172462. doi: 10.1016/j.scitotenv.2024.172462. Epub 2024 Apr 12.

Authors

Affiliations

¹ College of Geography and Environment, Baoji University of Arts and Sciences, Shaanxi Key Laboratory of Disaster Monitoring and Mechanism Simulation, Baoji 721013, China.
² College of Geography and Environment, Baoji University of Arts and Sciences, Shaanxi Key Laboratory of Disaster Monitoring and Mechanism Simulation, Baoji 721013, China; State Key Laboratory of Loess and Quaternary Geology, Key Lab of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China. Electronic address: bhz620@163.com.
³ Division of Atmospheric Sciences, Desert Research Institute, Reno, NV 89512, United States.
⁴ Baoji Ecological Environment Science and Technology Service Center, Baoji 721000, China.

PMID: 38615761
DOI: 10.1016/j.scitotenv.2024.172462

Abstract

Carbonaceous aerosols were collected in the valley city of Baoji city in Northern China in August 2022. The light absorption characteristics and influencing factors of black carbon (BC) and brown carbon (BrC) were analyzed, and their radiative forcing was estimated. The results showed that the light absorption of secondary brown carbon [Abs_BrC,sec (370)] was 7.5 ± 2.4 Mm^-1, which was 2.5 times that of primary brown carbon [Abs_BrC,pri (370), 3.0 ± 1.2 Mm^-1]. During the study period, the absorption Ångström exponent (AAE) of aerosol was 1.6, indicating that there was obvious secondary aerosol formation or carbonaceous aerosol aging in the valley city of Baoji. Except for secondary BrC (BrC_sec), the light absorption coefficient (Abs) and mass absorption efficiency (MAE) of BC and primary BrC (BrC_pri) during the persistent high temperature period (PHT) were higher than those during the normal temperature period (NT) and the precipitation period (PP), which indicated that the light absorption capacity of black carbon and primary brown carbon increased, while the light absorption capacity of secondary brown carbon decreased under persistent high temperature period. Secondary aerosols sulfide (SO₄^2-), nitrate (NO₃^-) and secondary organic carbon (SOC) are important factors for promoting the light absorption enhancemen of BC and BrC_pri and photobleaching of BrC_sec during persistent high temperature period. The Principal Component Analysis-Multiple Linear Regression (PCA-MLR) model showed that traffic emissions was the most important source of pollution in Baoji City. Based on this, the secondary source accelerates the aging of BC and BrC, causing changes in light absorption. During PHT, the radiative forcing of BC and BrC_pri were enhanced, while the radiative forcing of BrC_sec was weakened, but the positive radiative forcing generated by them may aggravate the high-temperature disaster.

Keywords: Aerosol absorption; Carbonaceous aerosols; Extreme heat; Optical properties.