2007年9月底，位於臺灣東北深澳火力發電廠停止運轉。火力發電廠是主要空氣汙染的點排放源之一，根據環保署TEDS8.1版資料庫(以2010年為基準年)，臺灣東北部硫氧化物最主要的排放源是協和火力發電廠。因此深澳發電廠關廠後，當地汙染源排放的減少對空氣品質改變的情形，值得分析與討論。 硫氧化物濃度下降的因素有三：風場改變、降水增加與當地硫氧化物濃度排放減少。選擇臺灣東北部環保署空氣品質監測站電廠關廠前後五年八方位風向比例，相關係數達0.8以上，中央氣象局人工測站更達到0.9以上，說明電廠關廠前後的風場環境變化不大。2002至2012年期間臺灣東北部地區降水時數上升趨勢顯著，電廠關廠後各測站秋、冬兩季降水量增加，春季降水量減少。電廠關廠後各測站乾日比例減少，尤其以秋季最明顯，但春季在電廠關廠後，多數測站的乾日比例增加。SO2關廠後乾日濃度值小於關廠前濕日濃度值，表示電廠關廠後SO2濃度的下降，降水量對汙染物的移除機制絕非主要因素，因此可以確定基隆地區SO2濃度下降一定與當地汙染物排放濃度減少有關。SO2 10%濃度極大值以協和發電廠為主，1%濃度極大值在深澳發電廠關廠前，深澳與協和發電廠影響程度各半。電廠關廠後五年東風分量SO2濃度下降最多，西北風分量下降最少，由此即可區別深澳與協和發電廠對大氣環境的影響。 透過HYSPLIT前推軌跡模擬2005年至2010年深澳與協和火力發電廠的排放路徑，並探討前推軌跡對各環保署空氣品質監測站的影響。2005至2010年大環境風場改變不大，9月至隔年4月主要風場為東北風，5至8月為西南風；SO2高濃度軌跡在2007年10月起出現頻率突然減少，與大環境風場無關而與深澳發電廠關廠後排放量消失有關。 ;Shenao thermal power plant, located in the northeast of Taiwan near Keelung city, had been stopped operating in the end of September, 2007. Thermal power plant is the main source of the air pollution. According to Taiwan’s EPA TEDS8.1 database (2010 baseline year), Xiehe thermal power plant is the main source of the sulfer oxides in the northeast of Taiwan. The changes of the air quality after Shenao power closing is worth to analyze and discuss. There are three factors of the decrease of the concentration of sulfer oxides: the changes of the wind field, the increase of the precipitation and the local emissions decreased of the concentration of sulfer oxides. The coeficion of the ratios of the eight wind directions before and after the five year of the Shenao power plant closing reachs 0.8 while using EPA’s air quality monitoring station (AQS) in the northeast of the Taiwan, 0.9 using CWB’s manual weather station. The wind field environment was not change clearly because of the high coeficion. During 2002-2012, the trend of the precipitation hour raise in the northeast of Taiwan. After Shenao power plant closing, the accumulate precipitation gain in fall and winter and decrease in spring for most of the weather station. The precipitation is not the main machenism of the concentration decreased SO2 of after Shenao power plant because the mean concentration of SO2 in dry day after Shenao power plant closing is lower than that in wet day before Shenao power plant closing. We make sure the concentration decreased of SO2 is highly related to the local emission decreased. Most of the numbers of 10% of the maximum concentration of SO2 are related to Xiehe power plant. Before Shenao power plant closing, Shenao and Xiehe power plant is the main source of SO2 for 1% of the maximum concentration stastitic. Between Oct 2007 and Sep 2012, the east wind part of the concentration of SO2 decreased most, and the northwest wind part decreased least. We can distinguish the impacts of the atmospheric environment between Shenao and Xiehe power plant. We use HYSPLIT to simulate the forward trajectories of Shenao and Xiehe power plant emission between 2005 and 2010 and discuss the influence of the EPA’s AQS. Northeast wind is the main wind field from September to April, and southwest wind is the main wind field form May to August. The large scale of the wind field changes less between 2005 and 2010. The frequency of the trajectory of the high concentration of SO2 decreased evidently in October 2007. It is related to the emission loss of Shenao power plant and is not related to the wind field change.
