低分子量有機酸廣泛存在於城市、農村、森林、極地、對流層與海洋大氣中，成為大氣環境中有機氣膠微粒的重要組成之一，其來源為人為和生物排放碳氫化合物及其光化降解產物所導致。由於吸濕和大氣氣膠雲凝結核活性(active cloud condensation nuclei，CCN)的特性，吸收和散射太陽輻射，改變全球熱平衡，進而影響降雨及氣候。然而目前國內外對於大氣氣膠中有機酸的光化產物形成與損失的相關研究甚少。本計畫將分兩年進行，第一年計畫將低分子量有機酸液態氣膠控制在不同光源及生成條件下進行光化反應，藉由離子層析(IC)測定低分子量有機酸濃度，及FTIR 與拉曼光譜快速測定官能基的互補關係，即時監測光化反應進行之物種變化，探討有機酸的光化機制，模擬陽光照射的白天光化轉換機制與無光源的晚上物種存在差異性與CO2 產生排放率。第二年計畫將進一步探究光化期間有機酸物種轉變及大氣低分子量有機酸液滴氣膠老化過程和光化轉化率與影響光化反應的控制因子，模擬在海洋飛沫主要組成與純水環境中，低分子量有機酸光化反應差異，以探討海洋飛沫對低分子量有機酸氣膠微粒在經海洋傳遞之長程傳輸的光化反應過程所扮演的角色。 Low molecular weight carboxylic acids (LMWCA) exist ubiquitous in the urban, rural, forest, the Arctic, troposphere and marine atmosphere, being important composition of atmospheric aerosol organic particulate matter. They are thought to have several sources mainly including anthropogenic and biogenic emissions hydrocarbon and degradation of photochemical production. Due to hygroscopicity and cloud condensation nuclei (CCN) activities of atmospheric aerosols influence precipitation and climate, changing the global thermal equilibrium by absorbing and scattering solar radiation. Nevertheless the related researches about photochemical production formation and loss of atmospheric aerosol carboxylic acids are still poorly in the world. Hence, this two-year research will be carried out. During the first year, the photochemical reaction of droplet-phase LMWCA in the various light sources and controlled conditions will be explored to study photochemical mechanism of carboxylic acids and to compare simulated transformation mechanisms of LMWCA and production rates of CO2 between daytime and nighttime. Using ion chromatograph (IC) to quantify LMWCA concentration and Raman spectroscopy to complement FTIR spectroscopy limits allow the detection of many functional groups quickly. We discriminate the transformation carboxylic acids species and monitor the real-time progress of photochemical reaction. During the second year, we further explore the chemical aging processes of LMWCA in atmospheric aerosol, photochemical transformation rates and control factor. We study the photochemical reaction of LMWCA with marine spray, compared to that with deionized water environment, to understand the important roles of complicated marine spray components on the photochemical reaction of LMWCA aerosol during long-range transport.
