- 學位論文
應用艙室技術於次級有機氣膠之特性評估
The Study of Secondary Organic Aerosol Using Controlled Environmental Chamber
摘要
本研究利用大型暴露艙模擬不同溫度(20℃、25℃、30℃)與相對濕度(RH 30%、50%、70%)的環境，探討室內低濃度臭氧（100ppb）與芳香劑內含之未飽和烯類化合物（600ppb）反應生成之次級有機氣膠的粒徑分佈與濃度。結果顯示次級有機氣膠形成初期，總粒數濃度可達1×106個／cm3，且多數微粒之粒徑介於50nm與 100nm之間，而後粒數濃度隨觀察時間增長而下降，但是微粒粒徑因膠結作用而增大，最終暴露艙內總微粒濃度維持於2×105個／cm3，約為背景濃度的二十倍。以往的相關研究指出次級有機氣膠的產生粒徑範圍為100nm以上，但於本實驗中可觀察其初期產生粒徑範圍介於50nm-100nm之間，甚至有粒徑低於50nm的次級有機氣膠產生。 實驗結果亦顯示次級有機氣膠之形成受溫度與濕度的影響；於溫度固定之狀況下，粒數濃度隨相對濕度的增加而降低，而相對濕度維持不變時，粒數濃度有隨溫度增加而減少之趨勢，然趨勢不若固定溫度狀況下顯著。此趨勢亦可見於超細微粒子（dp＜100nm）之形成，且此趨勢較前者明顯。此外，由具備影印機之辦公室採樣得知當室內場所通風狀況不良（ACH＜1）之環境更易累積細微粒子之粒數濃度，而當大量列印時環境內微粒濃度高過於零星列印，並且室內之微粒濃度易受室外空氣交換所影響。由於本研究量測之粒徑範圍小至100nm 以下，因此觀察到的總粒數濃度為文獻中其他於相同反應物濃度下產生之微粒的十倍以上。故室內次級有機氣膠對長時間處於室內場所人員的健康危害不容忽視。
並列摘要
This study is aimed to investigate the size distribution and concentration of the secondary organic aerosol resulting from the reaction between terpene (600 ppb), commonly found in air freshner, and ozone (100 ppb). The experiments were conducted in a controlled environmental chamber to simulate different combinations of temperature (20℃、25℃、30℃) and relative humidity (RH 30%、50%、70%). The results showed that the particle concentration could reach 1×106 particles/cm3 in the early stage of SOA formation and most particle sizes range between 50 nm ~ 100 nm. As observation continues, particle number concentration decreases while the particle size increases due to coagulation. The number concentration remained at 2×105 particles ／cm3, approximately twenty folds of background concentration. Previous studies pointed out that the sizes of SOA exceed 100 nm, while the current study found that SOAs in the initial stage range between 50nm to 100nm and some even smaller than 50nm. The results also indicated the formation of SOA is affected by temperature and relative humidity. When temperature is constant, the particle number concentration decreases with the increasing relative humidity, while the number concentration decreases with the increasing temperature under the condition of constant relative humidity. Same trend was found for ultrafine particles （dp＜100nm）. The results of air sampling from office with photocopier indicated that office environments with poor ventilation (air exchange per hour less than 1) accumulate greater concentration of fine particles. More particles were emitted during one episode of large volume of photocopying than many periodic photocopying. Moreover, the indoor particle concentration is affected easily by the outdoor environment. As the particle size observed in the current study are lower than 100 nm, the observed number concentration is approximately 10 times of those from the same reactants found in the literature. This study concluded that the health risk of occupants exposed to the indoor SOAs should not be overlooked.。