台北都會區近三年連續監測及事件日氣膠特性

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題名:	台北都會區近三年連續監測及事件日氣膠特性
作者:	王之群;Chen-Chun Wang
貢獻者:	環境工程研究所
關鍵詞:	氣膠連續監測特性;氣膠輻射作用力;氣膠污染事件;氣膠超級測站;Aerosol radiative forcing;Aerosol continuous monitoring;Aerosol supersite;Aerosol pollution event
日期:	2006-01-06
上傳時間:	2009-09-21 12:16:35 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	摘要大氣氣膠對環境的衝擊及人體健康的效應，已經引起重視，台灣第一座「氣膠超級測站」於2002年3月正式運轉，超級測站可連續監測PM2.5與PM10質量濃度、氣膠粒徑分布、PM2.5碳成分、PM2.5硫酸鹽、PM2.5硝酸鹽、散光係數、黑碳濃度(吸光係數)、氣膠總多環芳香烴以及氣象因子。本文彙整2002年3月至2005年2月三年的監測數據顯示PM2.5年平均質量濃度為31?33 μg m-3，主要化學成分為有機碳(3.4?8.2 μg m-3)、元素碳(2.5?4.1 μg m-3)、硫酸鹽(5.0?7.7 μg m-3)及硝酸鹽(1.3?3.6 μg m-3)。Hysplit模擬的逆溯氣流軌跡線可分成大陸沿岸傳輸、海洋傳輸及高壓迴流三類，其PM2.5分別為40 μg m-3、28 μg m-3及56 μg m-3。硫酸鹽平均鹽濃度在大陸沿岸傳輸及高壓迴流都為8 μg m-3左右，硝酸鹽平均濃度只有在高壓迴流有高值為6.1 μg m-3。發生高濃度事件日(PM2.5> 65μg m-3)以高壓迴流最多，共有63次。使用EC-tracer方法推估新莊地區二次有機碳濃度，加上以氯損失推估的二次無機氣膠，可推估出二次氣膠，另外，使用PM2.5/CO的比值計算一次氣膠也可推估出二次氣膠，後者推估的二次氣膠在O3 > 120 ppb時，平均濃度可達30 μg m-3。本文於2005年4月4日至2005年4月9日在超級測站進行為期6天的人工採樣，結果顯示氣膠粒徑分布中質量濃度及硝酸鹽有雙峰，其他離子都是單峰分布，主要的尖峰粒徑為0.56 μm或3.2 μm。大氣羰基類的分析顯示新莊地區以甲醛、乙醛及丙酮為主。甲醛、乙醛及丙酮平常日的濃度分別為4.4±2.0 μg m-3、9.8±8.3 μg m-3及16.5±10.0 μg m-3；事件日的濃度則分別為11.0±6.3 μg m-3、17.1±11.9 μg m-3及34.0±19.1 μg m-3。上班時段 (06:00?12:00) 的羰基類濃與當日日臭氧最大小時值有正相關，羰基類化合物與有機碳中的OC2關係較佳，且與粒徑越小氣膠的OC2關係更佳，顯示這些小粒徑的OC2來自於光化學反應。 Abstract The environmental impact and health effect of atmospheric aerosol has drawn a great attention. The first Taiwan aerosol supersite for continuous aerosol properties has been fully operated at Hsin-Chuang City in March 2002. Aerosol properties include PM2.5 and PM10 mass concentrations, size distribution, carbon content, sulfate, nitrate, light-scattering coefficient, black carbon, and polyaromatic hydrocarbons are monitored continuously. In addition, meteorological factors are collected collocatedly. The annual average of PM2.5 mass concentrations ranging from 31 to 33 μg m-3 are found based on data collected from March 2002 to February 2005 at aerosol supersite. Concentrations of major aerosol properties are 3.4-8.2 μg m-3 for organic carbon, 2.5-4.1 μg m-3 for elemental carbon, 5.0-7.7 μg m-3 for sulfate, and 1.3-3.6 μg m-3 for nitrate, respectively. Back trajectory analysis from Hysplit model shows air masses arriving at Hsin-Chuang site can be divided into from mainland China’s coastline transport, oceanic transport, and anticyclonic outflow during the stidy period. The PM2.5 mass concentrations for these three types of air mass are 40 μg m-3, 28 μg m-3, and 56 μg m-3, respectively. Sulfate average for air masses from mainland China’s coastline transport and anticyclonic outflow is around 8 μg m-3. In contrast, the highest nitrate is at 6.1 μg m-3, which occurred only under anticyclonic outflow. The statistic of high aerosol concentration event (PM2.5> 65μg m-3) shows anticyclonic outflow is the most frequent occurring type for the occurrence of 63. The estimation of senondary aerosol formation at Hsin-Chuang site is conducted by using EC-tracer method for calculating secondary organic carbon and chlorine loss for secondary inorganic aerosol. The estimation of secondary aerosol can also be calculated by using the ratio of PM2.5/CO for estimating primary aerosol. The secondary aerosol from the latter method can reach as high as 30 μg m-3 when O3 > 120 pp. In this study, an intensive aerosol collection for six days was conducted from April 4 to 9, 2005. The aerosol size-distribution analysis reveals that most aerosol water-soluble ions are unimodally distributed except for mass concentration and nitrate they are bimodally distributed. Peak aerosol diameter is either 0.56 μm for unimodal distribution or 0.56 and 3.2 μm for bimodal distribution. Aerosol carbonyl analysis shows major components at Hsin-Chuang site are formaldehyde, acetaldehyde, and acetone. Normal day concentrations for formaldehyde, acetaldehyde, and acetone are 4.4±2.0 μg m-3, 9.8±8.3 μg m-3, and 16.5±10.0 μg m-3, respectively. In contrast, event day concentrations for formaldehyde, acetaldehyde, and acetone are 11.0±6.3 μg m-3, 17.1±11.9 μg m-3, and 34.0±19.1 μg m-3, respectively. A positive correlation between aerosol carbonyl and daily maximum ozone concentration is found. Among carbon fractions, aerosol carbonyl has a better relationship with OC2 and is even better as aerosol diameter getting smaller. It suggests these small particles with OC2 composition are originated from photochemical reactions.
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