| Summary: | 碩士 === 嘉南藥理科技大學 === 環境工程與科學系碩士班 === 93 === The water-soluble inorganic composition and low-molecular-weight dicarboxylic acids of PM2.5 (fine particle) and PM2.5-10 (coarse particle) in both daytime and nighttime were evaluated during both non-episodic period of 19 September to 20 October, 2004 and episode of 26-30 November, 2004. During both non-episodic and episodic periods, the size distribution of the water-soluble inorganic salts / dicarboxylic acids was studied, including those in the nanoaerosols of 5-100 nm.
To avoid the artifacts during each sampling period, the PM2.5 aerosol sampling was carried out after the gaseous pollutants were absorbed by annular denuder system (ADS). PM2.5 Aerosols collected on the Teflon filter (the first plate), but a part of PM2.5 NO3- was lost on the first filter. The lost NO3- species in PM2.5 aerosol was captured on the Nylon filter (the second plate) and was complete collected on the quartz filter of coating absorbent (the third plate). The percentage of PM2.5 NO3-on both Nylon and quartz filters displayed 10-13 % pf total aerosol NO3-. The percentage of total dicarboxylic acids in aerosol on both Nylon and quartz filters displayed 4.8-22.9 % of total dicarboxylic acids in aerosol.
During both episodic and non-episodic periods, the concentration of SO42- in both daytime and nighttime always exceeded contents of NO3- and NH4+ within both fine and coarse fractions. However, the increase of NO3-, presenting the traffic emission, was significant during the period of episode. The percentage contribution of dicarboxylic acids in both PM2.5 and PM10 was 0.8-1.0 % by mass. Oxalic acid was the biggest single dicarboxylic acids. It was followed by succinic acids and malonic acid. When the alkaline situation occurred, the existence of NH4+ induced the alkenes (malic acid and maleic acid) to be more stable. During the episode, the transformation percentage of dicarboxylic acids in both PM2.5 and PM10 increased significantly. The percent of oxalic acid in measured dicarboxylic acids raised from 69 % during non-episode to be 73-80 % during episode, indicating the more carbon-bonding dicarboxylic acids decomposed to be 2 carbon-bonding products, oxalic acid during the period of episode.
The dominant particle sizes of various inorganic salts including Na+, NH4+, K+, Mg2+, Ca2+, Cl-, NO3- and SO42- in aerosol appeared in both the droplet mode at 0.56-2.5 �慆 and the coarse mode at 3.1-6.2 �慆, respectively, during the non-episodic period. A small concentration peak of Aerosol NH4+ and SO42- appeared in the nuclei mode at 5-100 nm. Meanwhile, during the episode a significant concentration peak of various inorganic salts in aerosol increased in the nuclei mode at 5-100 nm. On the other hand, the concentration peak of low-molecular-weight dicarboxylic acids in aerosol appeared in both the droplet mode and the nuclei mode during the non-episodic period, but the significant concentration peak of dicarboxylic acids in aerosol existed in the nuclei mode, even at 5-18 nm, during the episode, indicating the concentration of primary dicarboxylic acids in aerosol has formatted more during the episode.
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