| 摘要: | 在許多探討大氣基本物理特性、輻射作用、雲霧形成機制、區域性能見度、全球氣候變遷、氣膠化學組成與人體健康風險評估等研究中，發現大氣氣膠的含水量皆佔有不可忽略的影響程度。氣膠含水量在大氣氣膠的物理與化學特性研究領域中佔有相當重要的地位。近年來已有許多學者對無機氣膠的吸濕成長進行相當多研究，但在有機氣膠方面則是剛剛起步，再加上有機物質對於氣膠吸濕特性又有許多不確定的影響，所以在有機氣膠的吸濕特性方面仍需更多的研究及數據來說明其對氣膠含水量的影響。 本研究主要是以GC-TCD氣膠含水量分析儀（Lee and Chang, 2002; Chang and Lee, 2002）量測收集在濾紙上大氣常見有機四種二元酸（Oxalic acid、Succinic acid、Malonic acid及Glutaric acid）的含水量，且將量測的數據與文獻量測單顆粒氣膠含水量相比較。此外，亦藉由GC/MS分析技術，分析大氣中常見的有機二元酸的成分與含量。 就有機酸成分分析結果顯示：以新莊超級測站這個採樣點來說，大氣氣膠中有機酸的平均濃度：Oxalic acid=167±36ng/M3、Malonic acid=15±4ng/M3、Succinic acid=14±4ng/M3、Glutaric acid=4±1ng/M3，總二元有機酸佔質量濃度的百分比為0.56%±0.13%，佔總碳濃度的4.60%±1.23%，佔有機碳濃度的7.55%±1.84%。 就GC-TCD量測有機氣膠含水量來說：GC-TCD法顯示Oxalic acid及Succinic acid氣膠並無DRH與CRH，其AMC分別為1.26及1.00；Malonic acid氣膠DRH=70-75%，在潮解點相對濕度後，氣膠仍會隨著相對濕度再升高持續吸水；無CRH；Glutaric acid氣膠的DRH＝90％。 就溫度對有機氣膠含水量的影響來說：在增濕過程中，當溫度越高時，氣膠大量吸水點會發生在較低的相對濕度環境下；而在降濕過程中，氣膠的含水量在同一相對濕度環境下，卻會隨溫度增加而增加。 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. |
