台北都會區細懸浮微粒結合多環芳香烴的空間分佈與污染源解析

Abstract

人類暴露於多環芳香烴（PAHs）可能會對健康造成不良影響（如肺癌，DNA損傷，生殖毒理學和兒童發育影響等問題），其中多數研究顯示微粒相中細懸浮微粒內含有較多多環芳香烴物質，且細懸浮微粒容易穿透肺泡並損害人的健康。本研究執行的目的為利用24小時連續採集之樣本，量化細懸浮微粒(PM2.5)中多環芳香烴在不同垂直高度下的濃度差異，並推估吸入性暴露的潛在健康風險及評估大台北都會區多環芳香烴排放的汙染源貢獻。 本研究於2016年6月14日至2017年5月4日以台北都會區中的5棟建築高樓做為採樣點，於各大樓的低中高樓層同時進行空氣樣本採集，並將採集到的樣本通過方法優化過後的熱脫附氣相層析質譜儀(Thermal desorption gas chromatograph/mass spectrometer, TD-GC/MS)分析出31種PAHs物質，最後利用化學質量平衡模型（Chemical Mass Balance model, CMB model）解析出汙染源的貢獻狀況。 本研究中細懸浮微粒結合多環芳香烴的平均濃度(減去Naphthalene)為1.123 ± 0.869 (範圍為0.231至 5.551) ng/m3，最主要的濃度貢獻物質為Benzo[b+k+j]fluoranthene 和Benzo[ghi]perylene，其佔總PAH含量的19.73％和11.78％。而當量致癌濃度(ΣBaPeq）為0.075 ± 0.068 ng/m3，其遠低於世界衛生組織建立之最大風險允許水平(1ng/m3)，而測得之平均濃度和當量致癌濃度值均呈有隨著樓層高度下降的趨勢。 污染來源貢獻的結果顯示主要貢獻為交通相關的來源，其佔了54%；其次是燒香（13.3％），接著是道路灰塵（12.9％）、工業活動(10.92%)和烹飪行為(8.26%)。關於汙染源的垂直趨勢，汽車尾氣排放、柴油機尾氣排放、煞車行為加熱產生之微粒和道路揚塵貢獻濃度皆隨高度增加而降低。燒香及工業活動顯示沒有高度梯度趨勢，而烹飪行為造成的貢獻顯示出受到建築周圍環境影響的趨勢。這個結果有助於更好地界定PM2.5環境中的PAH趨勢和來源貢獻，並提供了台北都會區的暴露狀況信息，以利之後制定更有效的公共衛生保護政策。

Human exposure to polycyclic aromatic hydrocarbons (PAHs) may cause adverse health effects (e.g., lung cancer, DNA damage, reproductive toxicology and the child developmental effects), especially in fine particulate phase. The objectives of this study were using 24-hour continuous sampling results to (1) quantify PAHs concentration levels in PM2.5 (particles with an aerodynamic diameter less than 2.5μm) at various heights, (2) estimate the potential health risks associated with inhalation exposure, and (3) evaluate the contributions of compositions from emission sources in Taipei metropolis. The sampling campaigns were conducted at five buildings in Taipei metropolis from June 14 in 2016 to May 4 in 2017. Each set of sampling sites (low-, mid-, and high-level floors) was monitored simultaneously. A total of 31 PAHs were identified and quantified by an optimized analytical method of thermal desorption (TD) integrated to a gas chromatograph–mass spectrometer (GC/MS). Finally, Chemical Mass Balance (CMB) model was used for the source apportionments of pollutants. The average concentrations of PM2.5-bound PAHs (except Nap) were 1.123 ± 0.869 (ranged from 0.231 to 5.551) ng/m3. The predominant PAHs were Benzo[b]fluoranthene group and Benzo[ghi]perylene, constituting 19.73% and 11.78% of the total PAH contents. The average benzo[a]pyrene-equivalent toxicity (ΣBaPeq) was 0.075 ± 0.068 ng/m3, lower than the maximum permissible risk level of 1 ng/m3 (WHO). Moreover, both the average concentrations and ΣBaPeq values showed a decreased gradient from low-floor to high-floor. With regard to the results of source contributions, the major source was dominated by vehicle emission sources, accounting for 54.5%, followed by incense-burning activities (13.30%), road dust (12.94%), industrial activities (10.92%) and cooking (8.26%). About the vertical trend, the average source contributions from gasoline-powered vehicle exhaust, diesel-powered vehicle exhaust, brake lining particle and road dust decreased with heights. The incense burning and industrial activities did not show the difference by heights. However, the source of cooking reveled the trend which was influenced by the sampling environments. The results served to better define the trend of PM2.5 bound PAH and its source contributions in Taipei metropolis for developing a more effective policies to protect public health.