| 摘要: | 大氣氣膠的吸濕成長行為對於氣候、能見度、雲的形成扮演一個重要的角色，近幾年來，無機鹽類對於氣膠吸濕成長已有許多研究，但在有機物影響的研究仍然相當少。本文針對高山(鹿林山)、上風區(石門)、都會區(新莊)三個地區測站以GC-TCD系統量測方法(Chang and Lee, 2002；Lee and Chang,2002)進行大氣氣膠含水量實驗。石門與新莊測站採樣時間為2007年12月，正值受沙塵影響，鹿林山測站為2008年3月，正值受生質燃燒影響。 本文分析氣膠水溶性離子、有機碳、元素碳、水可溶有機碳(WSOC) 、並開發出HULIS (Humic like substances)分析方法。另外，以ISORROPIA模式模擬無機氣膠含水量，比較量測值與模擬值含水量的差異，並探討分析的氣膠化學成分對大氣氣膠含水量的影響。 實驗結果顯示，石門地區HULIS平均濃度為0.82 μg m-3，其來源為海水中浮游植物隨浪花飄向內陸時附著在蒸發的海鹽上；新莊地區平均濃度為0.65 μg m-3，其來源可能來自機動車輛排放的污染；鹿林山地區平均濃度為0.91 μg m-3，其來源應以生質燃燒排放長程傳輸為主。 石門/新莊/鹿林山氣膠含水量實測值減去模式推估值分別為-12.25 μg m-3、-5.58 μg m-3、0.67 μg m-3，表示在石門和新莊地區有機物抑制氣膠吸水，鹿林山地區的有機物則可加強氣膠吸水。本文另外發現隨著HULIS-C/WSOC 比例增加，發現氣膠有稍微提前潮解的現象。 在多元迴歸分析中，階段復迴歸納入NH4+和EC為顯著的預測因子，NH4+的選擇如同預期，可能是由於其代表硫酸鹽和硝酸鹽，但EC意外被選入，可能是由於硫酸鹽和硝酸鹽附著以EC為核心的氣膠上，但應該需要更多的數據來確認這個推論。本文得到的氣膠含水量的迴歸模式為Y (measured water content) = 9.741×EC + 3.667×NH4++5.592，R2=0.84。 絕對主成分分析中，第一因子代表為水溶性無機鹽類對於氣膠含水量的貢獻，其影響為正值。第二因子海鹽和第三因子HULIS對氣膠含水量影響為負值，本文認為是受到石門HULIS來源的經由海水浮游植物附著在蒸發的海鹽上飄向內陸所致，因為HULIS對含水量影響為負值，導致第二因子也抑制氣膠吸水。在總結上，本文認為氣膠含水量取決於無機鹽類的多寡，但有機物可能對於含水量有微量增加或抑制的影響，唯這個推論需要更多的數據來確認。 Hygroscopic growth of atmospheric aerosol particles plays an important role in climate forcing, visibility degradation, and cloud formation. In recent years many studies have conducted on the influence of inorganic salts to aerosol hygroscopic behavior but very few worked on the effects of organic components. This study collected atmospheric aerosols at mountain (Lulin), upwind area (Shimen), and urban area (Hsinchuang) and measured aerosol waster mass with a GC-TCD system (Chang and Lee, 2002；Lee and Chang, 2002). The sampling time period at Hsinchuang and Shimen was with the occurrence of a yellow-dust event in December 2007 and at Mt. Lulin during biomass burning transport in March 2008. In this study, water-soluble inorganic ions, organic carbon, elemental carbon, water-soluble organic carbon (WSOC) and humic like substances (HULIS) were measured. In addition, the ISORROPIA model was adopted to simulate aerosol water mass contributed from the inorganic salts for the comparison between the measured ones. The difference between measured and modeled aerosol water mass is discussed using the resolved aerosol chemical components. The results show average HULIS concentration at the Shimen site was 0.82 μg m-3 and was contributed from the phytoplankton in the sea water attached to the evaporated sea salt. The average HULIS concentration at Hsinchuang site was 0.65 μg m-3 with primary vehicle emission as its origin. Moreover, the Lulin site was averaged at 0.91 μg m-3 and was mainly contributed from long-range transport plume from biomass burning. The subtraction of modeled aerosol water mass from measured ones shows the differences at the Shimen, Hsinchuang, and Lulin site are -12.25 μg m-3, -5.58 μg m-3, and 0.67 μg m-3, respectively. It indicates organic components inhibit aerosol water uptake at the Shimen and Hsinchuang sites and enhance water uptake at the Lulin site. In addition, aerosol is found to deliquesce at low relative humidity range in accordance with the increase of HULIS-C/WSOC ratios. In the multiple regression analysis, stepwise regression selects NH4+ and EC as significant predictors. The choice of NH4+ is as expected because it represents the aerosol sulfate and nitrate. However, the selection of EC is out of expectation, which is probably due to the coating of sulfate and nitrate onto the associated aerosol EC core. This inference needs more data to verify. The resulted multiple regression function is Y (measured water content) = 9.741×EC + 3.667×NH4++5.592, R2=0.84. In the absolute principle component analysis for factors contributed to aerosol water mass, the first factor stands for positive contribution from water-soluble inorganic salts. In contrast, the second and the third factors represent negative contributions from sea salt and HULIS. The reason for this is probably due to the phytoplankton in the sea water attached to the evaporated sea salt. As the phytoplankton has a negative effect on aerosol water uptake so the sea salt in the contribution of aerosol water mass. In summary, aerosol water mass is dependent on the amount of inorganic salts; however, organic components might have a minor effect on enhancing or inhibiting water uptake. This inference certainly needs more data to verify. |
