| Summary: | 碩士 === 國立中央大學 === 環境工程研究所 === 92 === Water content of atmospheric aerosols is related to atmospheric radiation, cloud and mist formation, visibility, local climate change, chemical and physical properties of aerosols, and human health assessment. As the results, the measurements of water content of aerosols become increasingly important in aerosol science research. Resently, many scholars have invested the hygroscopic characteristic of inorganic aerosols. However, few researches focused on similar topics of the organic aerosols. Because the hygroscopicity of organic aerosols is uncertain for now, it needs more scientific datas to realize the relationship between atmospheric moisture and hygroscopicity of organic aerosols related to water content within them.
In this research, a thermal conductivity detector (GC-TCD, Lee and Chang, 2002; Chang and Lee, 2002) was used to measure water content of four organic acids (Oxalic acid, Succinic acid, Malonic acid and Glutaric acid). The results of oxalic acid and succinic acid showed no DRH(Deliquescence Relative Humidity) and CRH(Crystallization Relative Humidity). AMC(Aerosol Mass Change) of oxalic acid and succinic acid indicated 1.26 and 1.00, respectively. The DRH of Malonic acid is at 70-75%. Water content of malonic acid increased with increasing relative humidity above DRH. However, malonic acid shows that CRH doesn’t exist. Glutaric acid reveals its DRH at 90%.
Applying GC/MS, the quantities of dicarboxylic acids were measured in associated with atmospheric aerosols. Air-borne particulate samples at Hsin-Chuang supersite from 19th September to 28th September. The average concentrations of oxalic acid, malonic acid, succnic acid and glutaric acid were 167±36 ng/M3, 15±4 ng/M3, 14±4 ng/M3, 4±1 ng/M3, respectively. The average percentage to four dicarboxylic acids was about 0.56%±0.13%. That total dicarboxylic acid mass concentration occupied 4.60%±1.23% and 7.55%±1.84% of total carbon and organic carbon concentrations.
The sensitivity of water content of organic aerosols was also influenced by temperature. During the experiments of increasing humidity, DRH of organic aerosols occurred at lower RH for higher temperatures. Contrastly, water content of organic aerosols increased with increasing temperature under the same humidity during the process of decreasing humidity.
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