The determination of HULIS in atmospheric aerosol and the investigation of the effects of the associated aerosol species on aerosol water mass

• Main Authors: Ya-Hsin Hou, 侯雅馨
• Other Authors: Chung-Te Lee
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/72096046641091585983

碩士 === 國立中央大學 === 環境工程研究所 === 96 === 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.