Deconvolving light absorption properties and influencing factors of carbonaceous aerosol in Shanghai

Yi Zhou; Junwei Chen; Fan Fan; Yi Feng; Shunyao Wang; Qingyan Fu; Jialiang Feng

doi:10.1016/j.scitotenv.2022.156280

Deconvolving light absorption properties and influencing factors of carbonaceous aerosol in Shanghai

Sci Total Environ. 2022 Sep 15:839:156280. doi: 10.1016/j.scitotenv.2022.156280. Epub 2022 May 27.

Authors

Yi Zhou¹, Junwei Chen¹, Fan Fan¹, Yi Feng¹, Shunyao Wang¹, Qingyan Fu², Jialiang Feng³

Affiliations

¹ School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China.
² Shanghai Environmental Monitoring Center, Shanghai 200235, China.
³ School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China. Electronic address: fengjialiang@shu.edu.cn.

PMID: 35644399
DOI: 10.1016/j.scitotenv.2022.156280

Abstract

Black carbon (BC) and brown carbon (BrC) have intensive impacts on atmospheric visibility and global climate change. In this study, PM_2.5 samples were collected at Pudong (PD) and Qingpu (QP) of Shanghai in 2017, and characterized typical organic molecular tracers by gas chromatography-mass spectrometer. The light absorption (Abs) of carbonaceous aerosol and water-soluble organic matter was analyzed by a multi-wavelength thermal/optical carbon analyzer and a long-range ultraviolet-visible spectrophotometer. An improved two-component model integrated with both optical and chemical fingerprints of carbonaceous aerosol was applied to analyze the Abs of BC, water-soluble organic carbon (WSOC) and water-insoluble organic carbon (WISOC), with which the potential influencing factors including emission source and atmospheric aging were investigated. Results indicated that BrC contributed 19% at PD and 16% at QP of the total light absorption of the carbonaceous aerosol at 405 nm wavelength. Meanwhile, Abs_WSOC(405)/Abs_BrC(405) showed significant seasonal variations (27-50%) at both sites. Positive matrix factorization (PMF) analysis showed that vehicle emissions (60-61%) and biomass combustion (38-39%) were the major contributors to Abs_BC(405), while biomass burning (34-40%), nitrate-relevant secondary processes (22-23%), vehicle emissions (18-19%) and biogenic SOA (13-19%) were major contributors to Abs_WSOC(405). Hybrid combustion source (94-96%) had a predominant contribution to Abs_WISOC(405). Statistical analysis showed that biomass burning had a great impact on the enhancement of Abs_WISOC. Absorption Ångström exponent (AAE) and mass absorption efficiency (MAE) of each factor (source) using PMF analysis indicated that WSOC from combustion sources had higher AAE_WSOC(350_-₅₅₀₎ values (8.11 and 8.29 for coal and biomass burning, respectively) and MAE_WSOC(365) values (0.63-0.99) compared to other sources. Atmospheric aging process can lower the MAE_WSOC(365) value (0.24-0.52). Overall, our study facilitates a better understanding of the relationships among source, optical properties, and atmospheric transformation processes of the carbonaceous aerosols in Shanghai.

Keywords: Absorption Ångström exponent; Carbonaceous aerosol; Light absorption properties; Mass absorption efficiency; Source apportionment.

MeSH terms

Aerosols / analysis
Air Pollutants* / analysis
Carbon / analysis
China
Environmental Monitoring / methods
Particulate Matter* / analysis
Soot / analysis
Vehicle Emissions / analysis
Water / chemistry

Substances

Aerosols
Air Pollutants
Particulate Matter
Soot
Vehicle Emissions
Water
Carbon