THESIS
2020
xv, 156 pages : color illustrations ; 30 cm
Abstract
Three groups of saccharides, primary sugars, sugar alcohols, and anhydrosugars, are ubiquitous
in the ambient atmosphere. They form part of fine aerosol (PM
2.5) mass, and constitute a
significant fraction of PM
2.5, water-soluble organic carbon (WSOC). Their water-solubility
render them active molecules contributing to aerosol’s role in affecting the climate system.
Anhydrosugars (e.g., levoglucosan) serve as unique molecular tracers tracking biomass burning
emissions while primary sugars and sugar alcohols are indicatives of biogenic sources. Despite
numerous studies on PM
2.5 source apportionment in the Pearl River Delta (PRD) region, studies
of long-term contribution changes by biomass burning and biogenic sources are non-existent.
This study aims to (1) analyze and compare the...[
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Three groups of saccharides, primary sugars, sugar alcohols, and anhydrosugars, are ubiquitous
in the ambient atmosphere. They form part of fine aerosol (PM
2.5) mass, and constitute a
significant fraction of PM
2.5, water-soluble organic carbon (WSOC). Their water-solubility
render them active molecules contributing to aerosol’s role in affecting the climate system.
Anhydrosugars (e.g., levoglucosan) serve as unique molecular tracers tracking biomass burning
emissions while primary sugars and sugar alcohols are indicatives of biogenic sources. Despite
numerous studies on PM
2.5 source apportionment in the Pearl River Delta (PRD) region, studies
of long-term contribution changes by biomass burning and biogenic sources are non-existent.
This study aims to (1) analyze and compare the decadal trends of biomass burning using
levoglucosan-tracer method and satellite data; and (2) to investigate contribution of biomass
burning and biogenic emission to PM
2.5 organic aerosol using receptor models incorporating
the saccharide source markers. In this work saccharide concentrations were quantified by
analyzing PM
2.5 filters collected at three sampling sites in the PRD region (Guangzhou, Nansha
and Tsuen Wan) from 2008 to 2017. Positive Matrix Factorization (PMF) analysis identifies
two sources for the saccharides, namely biomass burning and biogenic emission. The results
showed a clear seasonal trend of higher biomass burning contribution in winter due to crop
residue burning and residential heating for both levoglucosan tracer, in consistency with fire
spot data by satellite. Biomass burning tracers had no notable declining decadal trends among
three sites but slightly decreasing trends at Tsuen Wan and at Nansha in some years. Sugar
alcohols and primary sugars showed highest concentrations in fall due to vegetation
decomposition. Fungal spore contributions were calculated by using mannitol as the tracer and
exhibited the highest contribution in summer months for Tsuen Wan and Nansha but no
discernable seasonal variations in Guangzhou. They exhibited a rising trend at Tsuen Wan,
declining trend in Guangzhou while no notable trend at Nansha site.
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