Effect of photooxidation on size distribution, light absorption, and molecular compositions of smoke particles from rice straw combustion

Ranran Zhao; Qixing Zhang; Xuezhe Xu; Wenjia Wang; Weixiong Zhao; Weijun Zhang; Yongming Zhang

doi:10.1016/j.envpol.2022.119950

Effect of photooxidation on size distribution, light absorption, and molecular compositions of smoke particles from rice straw combustion

Environ Pollut. 2022 Oct 15:311:119950. doi: 10.1016/j.envpol.2022.119950. Epub 2022 Aug 20.

Authors

Ranran Zhao¹, Qixing Zhang², Xuezhe Xu³, Wenjia Wang⁴, Weixiong Zhao³, Weijun Zhang⁵, Yongming Zhang⁴

Affiliations

¹ State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, 230026, Anhui, China; School of Chemistry and Chemical Engineering, Yancheng Institute of Technology, Yancheng, 224051, Jiangsu, China; School of Emergency Management and Safety Engineering, Yancheng Institute of Technology, Yancheng, 224051, Jiangsu, China.
² State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, 230026, Anhui, China. Electronic address: qixing@ustc.edu.cn.
³ Laboratory of Atmospheric Physico-Chemistry, Anhui Institute of Optics and Fine Mechanics, HFIPS, Chinese Academy of Sciences, Hefei, 230031, Anhui, China.
⁴ State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, 230026, Anhui, China.
⁵ Laboratory of Atmospheric Physico-Chemistry, Anhui Institute of Optics and Fine Mechanics, HFIPS, Chinese Academy of Sciences, Hefei, 230031, Anhui, China; University of Science and Technology of China, Hefei, 230026, Anhui, China.

PMID: 35998777
DOI: 10.1016/j.envpol.2022.119950

Abstract

Organic aerosol (OA) emitted from biomass burning (BB) impacts air quality and global radiation balance. However, the comprehensive characterization of OA remains poorly understood because of the complex evolutionary behavior of OA in atmospheric processes. In this work, smoke particles were generated from rice straw combustion. The effect of OH radicals photooxidation on size distribution, light absorption, and molecular compositions of smoke particles was systematically investigated. The results showed that the median diameters of smoke particles increased by a factor of approximately 1.2 after photooxidation. In the particle compositions, although both non-polar fractions (n-hexane-soluble organic carbon, HSOC) and polar fractions (water-soluble organic carbon, WSOC) underwent photobleaching after aging, the photobleaching properties of HSOC (1.87-2.19) was always higher than that of WSOC (1.52-1.33). Besides, the light-absorbing properties of HSOC were higher than that of WSOC, showing a factor of approximately 1.75 times for mass absorption efficiency at 365 nm (MAE₃₆₅). Consequently, the simple forcing efficiency (SFE) caused by absorption showed that HSOC has higher radiation effects than WSOC. After photooxidation, the concentration of 16 PAHs in HSOC fractions significantly decreased by 15.3%-72.5%. In WSOC fractions, the content of CHO, CHONS, and CHOS compounds decreased slightly, while the content of CHON compounds increased. Meantime, the variations in molecular properties supported the decrease in light absorption of WSOC fractions. These results reveal the aging behavior of smoke particles, then stress the importance of non-polar organic fractions in particles, providing new insights into understanding the atmospheric pollution caused by BB smoke particles.

Keywords: Biomass burning; Light absorption; Molecular composition; Non-polar and polar organic carbon; Photooxidation.

MeSH terms

Aerosols / analysis
Air Pollutants* / analysis
Biomass
Carbon / analysis
Environmental Monitoring / methods
Oryza*
Particulate Matter / analysis
Smoke

Substances

Aerosols
Air Pollutants
Particulate Matter
Smoke
Carbon