Molecular compositions and sources of organic aerosols at a rural site on the Guanzhong Plain, Northwest China: The importance of biomass burning--颗粒学报PARTICUOLOGY

Liu, Y., Shen, M., Liu, H., Dai, W., Qi, W., Zhang, Y., . . . Li, J. (2024). Molecular compositions and sources of organic aerosols at a rural site on the Guanzhong Plain, Northwest China: The importance of biomass burning. Particuology, 89, 44-56. https://doi.org/10.1016/j.partic.2023.10.014

Molecular compositions and sources of organic aerosols at a rural site on the Guanzhong Plain, Northwest China: The importance of biomass burning

Yali Liu ^{a b}, Minxia Shen^a, Haijiao Liu ^{a b}, Wenting Dai ^a, Weining Qi ^a, Yifan Zhang ^{a b}, Lu Li^a, Yue Cao ^{a b}, Xin Wang ^a, Xiao Guo ^a, Yingkun Jiang ^{a b}, Jianjun Li ^{a c *}

a State Key Laboratory of Loess and Quaternary Geology, Key Lab of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China
b Xi'an Institute for Innovative Earth Environment Research, Xi'an 710061, China
c National Observation and Research Station of Regional Ecological Environment Change and Comprehensive Management in the Guanzhong Plain, Shaanxi, China

10.1016/j.partic.2023.10.014

Volume 89, June 2024, Pages 44-56

Received 20 September 2023, Revised 30 October 2023, Accepted 31 October 2023, Available online 14 November 2023, Version of Record 5 December 2023.

E-mail: lijj@ieecas.cn

Highlights

• Molecular composition and source of OA in rural area of Northwest China were analyzed.

• Photochemical formation of OPAHs, nitrophenols, and diacids in summer was stronger.

• Biomass burning was the major source of OA in the rural area, especially in winter.

• Increase of OA in haze event was caused by accumulation of POA, not SOA formation.

Abstract

The concentration of PM_2.5 has considerably reduced in recent years, but remains relatively high in China. In particular, the increasing contribution of organic compounds to PM_2.5 generates popular pressure for further reductions, resulting in an urgent need to study organic aerosol (OA). To investigate the molecular composition and source contribution of OA in the rural area of the Guanzhong Plain, Northwest China, PM_2.5 samples were collected during 3–23 August 2016 and 5–20 January 2017 and studied for more than 100 organic tracer compounds. The mean concentration of total measured organic compounds is 662 ± 296 ng/m³ in summer and 3258 ± 1925 ng/m³ in winter. Levoglucosan is the most abundant single compound found throughout the sampling period, which is a crucial tracer for biomass burning emissions, preliminary suggesting that biomass burning is an essential source of OA. In summer, organic compounds such as lipid compounds, sugar compounds, and polycyclic aromatic hydrocarbons (PAHs), more come from higher plants, wood burning, vehicle exhausts, plastic waste, and other direct emission sources. Oxygenated PAHs (OPAHs), nitrophenols, and phthalic acids more come from the atmosphere through the oxidation reaction of aromatic precursors, especially photochemical oxidation. However, in winter, most of the increases in concentrations of organic compounds are attributed to biomass burning. The analysis of a haze event (14–19 January 2017) during the winter sampling period shows that the increases in the concentration of organic compounds are unaccompanied by strong secondary formation under lower relative humidity (49.1% ± 13.5%). The main reason for the growth of OA in this haze event is the accumulation of primary OA (POA). The source apportionment by the positive matrix factorization (PMF) model shows that biomass burning (37.1%) is the primary source of OA in the rural regions of the Guanzhong Plain, especially in winter (40.6%). The contribution of secondary formation decreases from 26.0% in summer to 16.9% in winter, and the contribution of fossil fuel emissions is comparable across both seasons.

Graphical abstract

Keywords

Organic aerosol; Molecular composition; Seasonal variation; Source apportionment; Guanzhong Plain

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