Chemical Composition and Size-Fractionated Origins of Aerosols over a Remote Coastal Site in Southern Taiwan

Abstract

In spring 2013 air samples were collected from a coastal site in the sparsely populated far south-west of Taiwan and analysed for ambient gases, inorganic salts, carboxylates, and saccharides. Concentration of ambient gases was in the order SO 2 > HCl > HNO 3 > NH 3 > HNO 2 . Day-night variation in concentrations indicated that photochemical conversion of HNO 2 to HNO 3 occurs during the day. PM 2.5 (16.16 ± 5.30 µg m -3 ) accounted for 61.1% of PM 10 mass concentrations. The main inorganic salts were SO 4 2-, NH 4 + , Na + , NO 3 -, and Cl -, collectively accounting for 48.8 ± 27.4% of the PM 2.5 . Cldepletion during the day was higher than during the night due to the presence of reactive photochemical products. The average Cl-depletion of PM 2.5 (53.1%) was markedly higher than that of PM 2.5-10 (26.0%), indicating that in PM 2.5 , a high amount of Cl -reacts with acidic gases to form HCl, which then escapes into the atmosphere. The carboxylate concentration in PM 2.5 was 0.50 ± 0.24 µg m -3 . It was found that low-molecular-weight carboxylates formed more readily in the open coastal region than in urban regions of southern Taiwan. Additionally, the daily mean ratio of Oxalate/non-seasalt SO 4 2-(6.15 ± 2.28%) in the coastal region was higher than that in the urban regions in southern Taiwan. The most prevalent saccharide in PM 2.5 was myo-inosital (333 ± 300 µg m -3 ), a type of soil fungus metabolite. Emissions of arabitol and mannitol, emitted through lichen and fungal activity, were markedly higher during the day. Only a trace amount (8.92 ± 16.92 µg m -3 ) of Levoglucosan (Levo), an indicator of biomass burning, was detected. The mean Levo/organic carbon ratio was 5.04 ± 8.72‰, suggesting that biomass burning contributed slightly to aerosols in the study area. An analysis of air mass backward trajectories showed that the products of biomass burning in Southeast Asia and southern China may be transported to the study area through long-range transport. This effect is more noticeable during the day when onshore breezes support the transport of particles sourced from the west of Taiwan.

Composition, Sources, and Distribution of PM2.5 Saccharides in a Coastal Urban Site of China

“…In contrast, saccharides from biological sources showed the highest level in April (the spring bloom season) on Jeju Island, and sucrose contributed to as high as 80% of the total saccharides [16]. Primary saccharides (sucrose, fructose, glucose) showed a unimodal distribution, with a dominant peak occurring in coarse-particles, while anhydrosaccharides were more likely to exist in fine particles [17]. Until now, studies on saccharides have mainly been focused on levoglucosan to evaluate the contribution of biomass burning on air pollution, but information related to the other saccharides, especially those from biological derivations, is still limited, and the characteristics of saccharides during periods of variable pollution levels are lacking.…”

Development of an Automated System (PPWD/PILS) for Studying PM2.5 Water-Soluble Ions and Precursor Gases: Field Measurements in Two Cities, Taiwan

“…Lung et al (2002) indicated that total ionic species accounted for 46.4% and 44.6% of PM 2.5 mass on dust events and non-dust-event days, respectively in Taipei. Recently, at a remote site in southern Taiwan, the concentrations of main inorganic salts, SO 4 2-, NH 4 + , Na + , NO 3 -, and Cl -, were also found to be high accounting for 48.8 ± 27.4% of the PM 2.5 (Tsai et al, 2015). Secondary aerosols , NH 4 + and NO 3 -) contributed approximately 50% and 60% of PM 2.5 mass in spring and winter respectively; but were responsible about 40% by mass in summer at Tainan, Taiwan (Lu et al, 2016).…”

High Loadings of Water-Soluble Oxalic Acid and Related Compounds in PM2.5 Aerosols in Eastern Central India: Influence of Biomass Burning and Photochemical Processing

“…Dicarboxylic acids and related polar compounds, including oxocarboxylic acids and α-dicarbonyls, are known to be ubiquitous in atmospheric aerosols and comprise a significant fraction of OAs (Kawamura and Yasui, 2005;Pavuluri et al, 2010;Tsai et al, 2015). They are directly released to the atmosphere from primary sources such as fossil fuel combustion and biomass burning (Kundu et al, 2010;Tsai et al, 2013;Cong et al, 2015).…”