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Title 細懸浮微粒(PM2.5)調查技術開發
Abstract 本計畫針對移動污染源的質量濃度與分徑調查方法進行探討，分別在效能測試系統與機車引擎動力計系統對儀器與量測方法進行驗正。在效能測試系統中，對實驗使用的PM2.5 cyclone、Diluter做效能測試，並以SMPS、APS在奈米與微米的粒徑分佈範圍，對EEPS、ELPI、MOUDI與濾紙採樣做量測的效能比對。測試結果顯示PM2.5 cyclone、Diluter符合預期的需求；三台儀器其比對結果相近，但因偵測範圍與功能性考量，計畫中選擇ELPI與PM2.5 cyclone濾紙採樣作為量測儀器。在機車引擎動力系統中，ELPI與PM2.5 cyclone濾紙採樣被使用於量測稀釋10倍後的引擎排氣中粒狀污染物，在不同轉速條件下分別就數目濃度、體積濃度與質量濃度進行量測，同時也一併量測溫濕度與Opacity。實驗結果顯示，在引擎轉速2000 rpm時的微粒數目濃度約1.5×107 #/cm3、質量濃度約15~20 mg/m3，並有隨著轉速增加而減少之趨勢，其中PM2.5約佔總質量濃度的90~95%。結果中發現ELPI所測得的體積濃度與質量濃度並無相關性，其可能為微粒帶電與成分組成造成的影響有關，造成大粒徑微粒範圍量測值的誤判。同時Opacity在量測上也受到濕度與排氣壓力的影響，其量測值得正確性仍需再作探討。依本研究結果建議，機車引擎排氣中粒狀物的量測，可以ELPI量測數目濃度，並搭配濾紙分徑採樣量測質量濃度，採樣時應依排氣條件進行稀釋，以符合儀器偵測極限與避免水氣過飽和凝結。
EngTitle Development of fine particle (PM2.5) measurement technology
EngAbstract This study aimed to characterize the aerosol emission from motorcycle engine, and to explore the feasibility and necessity of adopting the PM2.5 size-selective sampling convention. A dynamometer was used to control a four-stroke motorcycle engine to generate stable exhaust aerosols. Several aerosol size spectrometers including a scanning mobility particle sizer, an electrical low pressure impactor, an engine exhaust particle sizer, and a multi-orifice uniform deposition impactor, were used in this work to measure the aerosol number concentration and size distribution. A PM2.5 cyclone was employed as the size-selective device. An aerodynamic particle sizer was used to verify the cut-off size of this pre-separator. A sampling chamber was used as an adaptor connecting to the tailpipe. This system allowed the emitted aerosol particles to coagulate for up to 2 seconds when the engine was set at idle condition, so that the number concentration could be reduced to 106 particle/cm3 to lower the effect of aerosol coagulation. A dilution system was made and mainly used reduce the relative humidity of cooled exhaust air to avoid the waster condensation. This diluter also helped to bring the aerosol concentration down to the working range of some aerosol instruments. The results showed that the aerosol number concentration decreased from 1.5×107 #/cm3 at tailpipe exit with the distance downstream of the sampling chamber to 106 #/cm3. However, the mass concentration remained unchanged, indicating that the decrease in number concentration was mainly due to aerosol coagulation. The water content in the exhaust air was higher than the saturated vapor pressure when the exhaust air cooled down along the exhaust pipe. Therefore, the use of diluter was essential to eliminate the contamination and interference caused by waster condensation. The use of SMPS and EEPS was limited because of the pre-impactor equipped upstream of the sampling line. The ELPI appeared to be an ideal aerosol instrument for investigating the PM2.5 of motorcycle engine exhaust from the working size range manufacturer claimed, but the mass concentration converted from ELPI’s number concentration did not match with the filter weighing data. Therefore, the ELPI performance needs to be re-validated. For the time being, the use of TEOM with a PM2.5 pre-separator was recommended. The use of opacity together with PM2.5 separator is also a potential option if the device is well designed and engineered. The filter samples showed that PM2.5 accounted for over 90% of total aerosol mass concentration.
ProjectYear 101
SponsorOrg 環檢所
ExecutingOrg 國立台灣大學
PublicFullVersionURL http://epq.epa.gov.tw/project/FileDownload.aspx?fid=41516