Molecular characteristics of organic compositions in fresh and aged biomass burning aerosols

Jianjun Li; Jin Li; Gehui Wang; Ting Zhang; Wenting Dai; Kin Fai Ho; Qiyuan Wang; Yue Shao; Can Wu; Li Li

doi:10.1016/j.scitotenv.2020.140247

Molecular characteristics of organic compositions in fresh and aged biomass burning aerosols

Sci Total Environ. 2020 Nov 1:741:140247. doi: 10.1016/j.scitotenv.2020.140247. Epub 2020 Jun 16.

Authors

Jianjun Li¹, Jin Li², Gehui Wang³, Ting Zhang², Wenting Dai², Kin Fai Ho⁴, Qiyuan Wang², Yue Shao⁵, Can Wu⁶, Li Li²

Affiliations

¹ Key Lab of Aerosol Chemistry & Physics, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China. Electronic address: lijj@ieecas.cn.
² Key Lab of Aerosol Chemistry & Physics, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China.
³ Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai 200241, China; Institute of Eco-Chongming, 3663 N. Zhongshan Rd., Shanghai 200062, China. Electronic address: ghwang@geo.ecnu.edu.cn.
⁴ The Jockey Club School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China; Shenzhen Municipal Key Laboratory for Health Risk Analysis, Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China.
⁵ Chemical and Biological Engineering Department, University of Wisconsin-Madison, Madison, WI, USA.
⁶ Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai 200241, China; Institute of Eco-Chongming, 3663 N. Zhongshan Rd., Shanghai 200062, China.

PMID: 32585482
DOI: 10.1016/j.scitotenv.2020.140247

Abstract

Biomass burning (BB) is the most important source of primary organic aerosols (OA) in the atmosphere that has significant impact on local/regional air quality and human health. However, few studies paid attention to the evolution of molecular characteristics of BB OA in the atmospheric aging processes. In this study, both fresh and aged PM_2.5 aerosols from burning of rice, maize, and wheat straws were collected from a combined system of combustion chamber and oxidation flow reactor, and were analyzed for >100 organic species. The emission factors (EFs) of anhydrosugars and some fatty acids showed slight variations between fresh and aged samples, indicating that these compounds are relatively stable. However, the EFs of n-alkanes, fatty alcohols, and parent-PAHs decreased 8-57% from fresh to aged samples, suggesting that they can undergo further oxidation to form other organic materials in the atmosphere. Phthalic acids, nitrophenols and isoprene-derived products were mainly secondarily formed by aging processes. Thus their EFs increased by 2-23 times from fresh to aged samples. Levoglucosan was the most abundant individual organic tracer, and its EF varied slightly between fresh and aged samples, proving its indicative role on BB emission. Moreover, the ratio of vanillic acid to levoglucosan and p-hydroxybenzoic acid to levoglucosan increased 2-13 times from fresh to aged samples. Therefore they can be used to investigate the impact of aging processes on BB aerosols in the atmosphere. RO₂ + HO₂ pathway derived 2-methyltetrols (2-MTs) predominated the EFs of isoprene-derived products (SOA_i) in the fresh samples. However, RO₂ + NO pathway derived 2-methylglyceric acid (2-MGA) increased by >30 times and became comparable with 2-MTs in aged particles. The ratio of 2-MGA/2-MTs increased from 0.06-0.27 in fresh samples to 0.94-1.18 in aged samples, because the high loading of NO_x in BB smoke enhanced the formation of SOA_i through RO₂ + NO reactions.

Keywords: Atmospheric aging; Biomass burning; Molecular composition; Organic aerosol.

MeSH terms

Aerosols / analysis
Air Pollutants / analysis*
Atmosphere
Biomass
Environmental Monitoring
Particulate Matter / analysis

Substances

Aerosols
Air Pollutants
Particulate Matter