Emission characteristics and influencing mechanisms of PAHs and EC from the combustion of three components (cellulose, hemicellulose, lignin) of biomasses

Junhan Wang; Hongxing Jiang; Yingjun Chen; Yong Han; Junjie Cai; Yu Peng; Yanli Feng

doi:10.1016/j.scitotenv.2022.160359

Emission characteristics and influencing mechanisms of PAHs and EC from the combustion of three components (cellulose, hemicellulose, lignin) of biomasses

Sci Total Environ. 2023 Feb 10;859(Pt 2):160359. doi: 10.1016/j.scitotenv.2022.160359. Epub 2022 Nov 21.

Authors

Junhan Wang¹, Hongxing Jiang¹, Yingjun Chen², Yong Han¹, Junjie Cai¹, Yu Peng³, Yanli Feng⁴

Affiliations

¹ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China.
² Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China. Electronic address: yjchenfd@fudan.edu.cn.
³ Institute of Environmental Pollution and Health, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China.
⁴ Institute of Environmental Pollution and Health, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China. Electronic address: fengyanli@shu.edu.cn.

PMID: 36423835
DOI: 10.1016/j.scitotenv.2022.160359

Abstract

Biomass burning is an important source of polycyclic aromatic hydrocarbons (PAHs) and elemental carbon (EC), but the formation mechanisms are still unclear. Cellulose, hemicellulose, and lignin are the three major components of biomass. In this study, the three-components extracted from three typical biomass raw materials were used for laboratory combustion experiments, to investigate the differences in the emission factors and chemical compositions of PAHs and EC. The average emission factors of the 16 kinds of PAHs were showing as lignin (135 ± 180 mg/kg) > cellulose (97.8 ± 124 mg/kg) > hemicellulose (48.9 ± 65.2 mg/kg), and the average emission factors of EC presented in the descending order of cellulose (1.65 ± 3.02 g/kg), lignin (1.30 ± 1.04 g/kg), and hemicellulose (0.450 ± 0.480 g/kg), respectively. The proportion of naphthalene emitted from cellulose and hemicellulose combustion is higher, while fluoranthene and pyrene accounted significantly higher proportion for lignin. Moreover, the influence of ignition temperature and oxygen content on the emission characteristics of PAHs and EC were also discussed. The influence of ignition temperature on the emission of EC and PAHs is more significant compared to oxygen content, because it obviously promoted the PAHs and EC formations through resonance-stabilized hydrocarbon-radical chain reaction (RSR) pathway. However, correlation analysis combined with cluster analysis showed that the RSR-pathway probably had different effects on PAH growth for the three-components, as the indene-involved RSR-pathway were mainly related to 4-6 ring PAHs for cellulose and lignin (except fluoranthene and pyrene), but 2-4 ring PAHs for hemicellulose. We also found that the fitted results according to the proportion of three-components were significantly higher than the measured values of raw materials for indene, medium-molecular-weight PAHs, and soot-EC. These results presented the different formation pathways for medium-molecular-weight PAHs and the two EC components emitted by biomass combustion, which are worthy of further studies in exploring the generation mechanisms of PAHs and EC.

Keywords: Elemental carbon; Formation pathway; Indene; Polycyclic aromatic hydrocarbons; RSR pathway; Three components.

MeSH terms

Carbon / chemistry
Cellulose
Lignin
Oxygen / analysis
Polycyclic Aromatic Hydrocarbons* / analysis

Substances

Polycyclic Aromatic Hydrocarbons
Lignin
pyrene
Cellulose
Carbon
Oxygen