台灣大氣中PM2.5 污染濃度和汙染源的時空分布

臺灣細懸浮微粒的汙染狀況可透過分析臺灣空氣品質監測站的汙染與氣象資料、臺灣環保署的排放資料以及美國國家海洋暨大氣總署的多層氣流軌跡模式來進行評估。就臺灣而言，臺灣細懸浮微粒的汙染狀況在秋、冬與春季較夏季來的嚴重，而以台灣本島區分則是西部與中南部之汙染狀況較東部與北部來的嚴重。近年來，臺灣接近大陸之外島的細懸浮微粒狀況亦日趨惡化。從臺灣環保署76 個監測站的資料可發現，細懸浮微粒的年平均濃度從2005 年的35.92 μg/m³降至2014 年的24.99 μg/m³以及2015 年的21.82 μg/m³，而2013 年至2015 年間之降幅更明顯達到28.41 %。加嚴的車輛排放標準是臺灣細懸浮微粒汙染下降的一大主因尤其在都市更為明顯，以台北的萬華測站為例，細懸浮微粒濃度中位數在2006 年至2015 年間就下降到19.75 μg/m³。然而臺灣的中南部因為工廠與發電廠的排放使得其細懸浮微粒的汙染程度依舊偏高，以雲林縣的臺西站為例，細懸浮微粒濃度中位數在2006 年至2015 年間只下降到26.38μg/m³。另外在2012 年9 月高雄大林發電廠將兩座燃煤火力發電廠除役後發現，高雄市的林園測站之細懸浮微粒濃度從2012 年的39.3 μg/m3 降至2015 年的27.4 μg/m3 降幅達30.3 %。從多層氣流軌跡模式可知，臺西站的細懸浮微粒汙染主要是來自於台灣本土的工業源，而在秋、冬兩季時才會受到大陸長程傳輸的些微影響。本研究表示臺灣整體除中部地區尤其是雲林之外的細懸浮微粒濃度皆持續下降中，而臺灣中南部的細懸浮微粒主要是受到本土汙染源的影響以及些許的長程傳輸影響。

PM2.5 pollution in Taiwan can be evaluated by analyzing pollution and weather data from air quality monitoring stations and emission data from Taiwan EPA, and air mass tracking models of the National Oceanic and Atmospheric Administration (NOAA) HYSPLIT Model from the USA. PM2.5 pollution in Taiwan was high in fall, winter, and spring seasons and low in summer season. Island wide, PM2.5 pollution in Taiwan was high in west part and central and southern parts of Taiwan and relatively low in eastern and norther parts of Taiwan. PM2.5 pollution at offshore islands near China has deteriorated in recent years. Annual average of PM2.5 concentration at all 76 Taiwan-EPA monitoring stations was 35.92 μg/m³ in 2005 and declined to 24.99 μg/m³ in 2014, and 21.82 μg/m³ in 2015, with a sharp decrease of 28.41 % between 2013 and 2015. Increasing strict vehicular emission standards is the main reason of driving down the PM2.5 pollution in Taiwan, especially in cities, as exemplified by the median PM2.5 concentration at Wanhua station in Taipei being decreased to 19.75 μg/m3 from 2006 to 2015. But emissions from industries and power plants still keep relatively high PM2.5 pollution in central and southern Taiwan as exemplified by the median PM2.5 concentration at Taixi station in Yunlin County being decreased to 26.38 μg/m3 only from 2006 to 2015. Another example was the decrease of PM2.5 concentration at Linyuan station in Kaoshung City from 39.3 μg/m3 in 2012 to 27.4 μg/m3 in 2015 (30.3% decrease) since a nearby power plant (Dalin) retired two old coal-fired power plants in September 2012. The HYSPLIT model showed the majority of PM2.5 pollution in Taixi coming from domestic sources of nearby industrial complex and minor influenced by long-range transported pollution outside Taiwan in fall and winter seasons. It is concluded that overall PM2.5 concentration was decreasing except central Taiwan (Yunlin). Local sources contribute to most of the PM2.5 pollution in central and south Taiwan with additional contribution by long-range transport of pollution.