Chemical composition, structures, and light absorption of N-containing aromatic compounds emitted from burning wood and charcoal in household cookstoves

• Published in: Atmospheric chemistry and physics Vol. 20; no. 22; pp. 14077 - 14090
• Main Authors: Xie, Mingjie, Zhao, Zhenzhen, Holder, Amara L, Hays, Michael D, Chen, Xi, Shen, Guofeng, Jetter, James J, Champion, Wyatt M, Wang, Qin'geng
• Format: Journal Article
• Language: English
• Published: Germany Copernicus GmbH 20-11-2020; Copernicus Publications
• Subjects: Absorption; Aerosol particles; Aerosols; Air pollution; Analytical methods; Aromatic compounds; Burning; Carbon; Charcoal; Chemical composition; Chromatography; Coal; Combustion; Downstream effects; Electromagnetic absorption; Emissions; Fossil fuels; Fuels; Hardwoods; Households; Identification; Light; Light absorption; Liquid chromatography; Mass ratios; Mass spectrometry; Mass spectroscopy; Membrane filters; Membranes; Molecular weight; Optical properties; Organic matter; Particulate emissions; Particulate matter; Polytetrafluoroethylene; Quartz; Spectroscopy; Suspended particulate matter; Vapor phases; VOCs; Volatile organic compounds; United States > US; China
• ISSN: 1680-7316; 1680-7324; 1680-7324
• DOI: 10.5194/acp-20-14077-2020

N-containing aromatic compounds (NACs) are an important group of light-absorbing molecules in the atmosphere. They are often observed in combustion emissions, but their chemical formulas and structural characteristics remain uncertain. In this study, red oak wood and charcoal fuels were burned in cookstoves using the standard water boiling test (WBT) procedure. Submicron aerosol particles in the cookstove emissions were collected using quartz (Q
) and polytetrafluoroethylene (PTFE) filter membranes positioned in parallel. A back-up quartz filter (Q
) was also installed downstream of the PTFE filter to evaluate the effect of sampling artifact on NACs measurements. Liquid chromatography-mass spectroscopy (LC-MS) techniques identified seventeen NAC chemical formulas in the cookstove emissions. The average concentrations of total NACs in Q
samples (0.37 ± 0.31 - 1.79 ± 0.77 μg m
) were greater than 50% of those observed in the Q
samples (0.51 ± 0.43 - 3.91 ± 2.06 μg m
), and the Q
to Q
mass ratios of individual NACs had a range of 0.02 - 2.71, indicating that the identified NACs might have substantial fractions remaining in the gas-phase. In comparison to other sources, cookstove emissions from red oak or charcoal fuels did not exhibit unique NAC structural features, but had distinct NACs composition. However, before identifying NACs sources by combining their structural and compositional information, the gas-particle partitioning behaviors of NACs should be further investigated. The average contributions of total NACs to the light absorption of organic matter at λ = 365 nm (1.10 - 2.57%) in Q
and Q
samples (10.7 - 21.0%) are up to 10 times larger than their mass contributions (Q
0.31 - 1.01%, Q
1.08 - 3.31%), so the identified NACs are mostly strong light absorbers. To explain more sample extracts absorption, future research is needed to understand the chemical and optical properties of high molecular weight (e.g., MW > 500 Da) entities in particulate matter.