||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.
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