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...[ Read more ]

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.