| 摘要: | 都會地區細懸浮微粒(PM2.5)特性及來源對民眾健康影響和污染源管制相當重要。本文彙整2011年3月9日至2012年3月29日期間，在台灣北、中、南都會區三個空品監測站(新莊站、忠明站、小港站)進行共63次的PM2.5手動檢測質量及成分濃度，目的是藉由系統性收集PM2.5空間及時間變化，探討都會區PM2.5濃度受季節變化、不同檢測方法和儀器套件、不同天氣型態、潛在污染來源的影響，並研究大氣能見度和各種PM2.5成分及污染源的關係。研究結果發現，新莊站和忠明站PM2.5平均質量濃度都以春季最高，小港站則是以冬季濃度最高。依據天氣系統型態分析，新莊站和忠明站除了本地污染外，還受到亞洲大陸污染長程傳輸影響；南部地區由於受到亞洲大陸氣流傳輸影響較小，小港站主要應該是當地污染源排放加上環境對流擴散不佳的影響。在春、秋及冬季各站主要的成分都是SO42-，夏季則是有機碳(OC)濃度接近SO42-。夏季時，NO3-揮發比值最高，其餘揮發離子則較無季節性變化。整體觀測期間，三個監測站大多以R&P 2000 FRM (Federal Reference Method) 的PM2.5檢測濃度最低，空品站的自動監測濃度最高，R&P2300微粒成分採樣器則是介於兩者之間，且當質量濃度較高時，彼此間的差距也越大。其中，造成R&P2000與R&P2300檢測結果差異主要是受到R&P2300裝設蜂巢管影響。天氣型態(Chuang et al., 2008)對分析指出發生高壓迴流(HPPC)、高壓推擠(HPP)及鋒前暖區+弱南風(WAF+WSW)時，北部有高PM2.5質量濃度，北部在東北季風及西南季風期間濃度較低。中、南部則在HPPC、HPP及東北季風三種天氣類型較容易呈現高濃度PM2.5，並在WAF+WSW及西南季風期間有低濃度。利用PMF (Positive Matrix Factorization) (U.S. EPA, 2008)模式進行PM2.5污染源推估，三個監測站都解析出6個污染源，且都以Secondary nitrate and chloride的貢獻百分比最高，其次分別為Secondary sulfate、Gasoline emission、Soil dust、Diesel emission、Biomass burning。以PM2.5化學成分、污染來源和環境因子對大氣能見度進行多元迴歸分析，三個監測站PM2.5主要受到二次無機離子潮解的氣膠含水量，使大氣能見度降低。總結來說，台灣都會區PM2.5濃度隨著季節及不同天氣系統的改變而有所變化，PMF解析結果顯示交通排放對大氣PM2.5濃度有顯著貢獻，可提供給相關單位進行都市來源管制的評估；此外，PM2.5成分中的二次無機離子對都市能見度降低有重大影響。The characteristics and source contributions are very important in residents’ health effect and source control. This work compiles 63 samples of PM2.5 mass and speciations manually collected at three air quality monitoring stations (Xinzhuang, Chungming, and Siaogang) located in the metropolitan areas of northern, central, and southern Taiwan from March 9, 2011 to March 29, 2012. The aim of this work is studying seasonal variations of urban PM2.5, the effects of various measurement methods and instrumental units, different weather types, and potential source contributions on PM2.5. Moreover, the relationship of various PM2.5 speciations and sources with visibility is also investigated. The results show that the highest PM2.5 mass concentrations at the Xinzhuang and Chungming stations are occurred in spring, while that of the Siaogang station is in winter. For the weather patterns results, the sources of Xinzhuang and Chungming stations are contributed from local sources as well as long-range transport of Asian continent based on weather pattern analysis. In contrast, Siaogang station is affected locally plus poor ventilation in the environment. The major species is SO42- in almost all the stations and seasons except for the summer. Organic carbon concentration is very close to SO42- and highest vaporization proportion of NO3- is observed in summer while other volatile ions are without seasonal variations.For the whole observation study, the collected PM2.5 concentration is the lowest when using R&P 2000 FRM (Federal Reference Method), highest for referring to the data of air quality stations, and in the middle for the data from R&P2300 speciation sampler. In addition, the differences among sampling methods become wider when the collected concentrations are higher. The deviations between R&P2000 and R&P2300 are inferred to be affected by honeycomb denuders installed in the R&P 2300 sampler.High PM2.5 concentration was observed in the north for the weather patterns of High Pressure Peripheral Circulation (HPPC), High Pressure system Pushing (HPP), and Warm area Ahead of a cold Front coupling with Weak Southern Wind (WAF+WSW) based on the weather pattern analysis (Chuang et al., 2008). Lower PM2.5 concentration frequently occurred in the periods of Northeastern and Southwest monsoons. In contrast, high PM2.5 concentrations were normally appeared in HPPC, HPP, and Northeastern monsoon and low for WAF+WSW and Southwestern monsoon in the central and southern Taiwan. Six source types were resolved from PMF (U.S. EPA, 2008) (Positive Matrix Factorization) source apportionment for all three stations. Secondary nitrate and chloride contributed highest followed by Secondary sulfate, Gasoline emission, Soil dust, Diesel emission, and Biomass burning. Multiple regression analysis on atmospheric visibility using PM2.5 species, sources types, and environmental factors showed that visibility is mainly reduced by the water content deliquesced from secondary inorganic ions. In summary, Taiwan urban PM2.5 is varied by seasons and weather patterns. Traffic emissions contributed significantly to atmospheric PM2.5, which may help the authorities in urban pollution control and assessment. Moreover, secondary inorganic ions are significant in reducing urban visibility. |
