| 摘要: | 本文於2021年1到2月在臺中市區，3、4月在鹿林山區觀測觀測PM2.5 (氣動粒徑小於或等於2.5 μm的懸浮微粒) 水溶性無機離子(Water-soluble Inorganic Ions, WSIIs)實時變化以解析都市地區和高山地區的污染來源和形成。
臺中市區的主要WSIIs (NO3-、SO42-和NH4+)的動態變化和PM2.5相似，風速小於1.6 m s-1時容易造成污染物濃度增加，風速大於1.6 m s-1時，SO42-主要來自區域外，NO3-受到交通排放影響，Na+和Mg2+受到海鹽影響，Cl-除了海鹽外還有可能有其他污染源，NO2-質量濃度有明顯的日變化，主要的前驅污染物是NO2。
鹿林山站受到生質燃燒(Biomass Burning, BB)煙團影響時PM2.5和主要WSIIs平均質量濃度會有明顯上升；當發生山谷風時，WSIIs質量濃度也有所提升，顯示出山谷風帶來人為污染。在BB事件日觀察到雲霧事件，污染物濃度因為濕清除影而降低。在兩次BB事件日的下午，氣膠粒徑40 nm數目濃度有所提高，且100 nm以上微粒的體積濃度上升，顯示出氣膠吸濕增長特性，同時，主要WSIIs也有相似的濃度變化趨勢，顯示出鹿林山區WSIIs有細粒徑氣膠的貢獻。
本文以[NH4+]/[SO42-]莫耳濃度比值探討大氣主要WSIIs結合型態，發現臺中市區氨氣充足，主要WSIIs呈現(NH4)2SO4、NH4NO3、其他化合物，並有N2O5產生。鹿林山站氨氣較不充足，主要WSIIs除了(NH4)2SO4，可能還包含了NH4HSO4、H(NH4)3(SO4)2 (Letovicite)、NH4NO3等。
;This article observes PM2.5 (suspended particles with aerodynamic diameters less than or equal to 2.5 μm) and water-soluble inorganic ions (WSIIs) in Taichung City from January to February 2021 and in the Lulin Mountain area in March and April, then analyze the sources and formation of pollution in urban and mountainous areas.
In the Taichung metropolitan area, the primary WSIIs (NO3-, SO42-, and NH4+) exhibited dynamic changes similar to PM2.5. When wind speeds were below 1.6 m s-1, pollutant concentrations tended to increase, while wind speeds above 1.6 m s-1 suggested that SO42- originated mainly from outside the region, NO3- was influenced by traffic emissions, Na+ and Mg2+ were affected by sea salt, and Cl- could come from both sea salt and other pollution sources. The mass concentration of NO2- showed significant diurnal variation, with NO2 being its primary precursor pollutant.
At the Lulin Mountain station, when affected by biomass burning (BB) smoke plumes, there is a significant increase in average PM2.5 and primary WSIIs mass concentrations. During valley wind occurrences, the mass concentrations of WSIIs also rise, indicating that valley winds contribute to anthropogenic pollution. During the BB event days, cloud and fog events were observed, leading to a decrease in pollutant concentrations due to wet removal effects. In the afternoons of the two days of BB events, the number concentration of aerosol particles measuring 40 nm increased, along with a rising volume concentration of particles greater than 100 nm. This demonstrates the hygroscopic growth characteristics of aerosols, while the primary WSIIs exhibited similar trends in concentration changes, indicating the contribution of fine particulate aerosols to WSIIs in the Lulin Mountain area.
This article discusses the combination patterns of the primary WSIIs in the atmosphere based on the molar concentration ratio of [NH4+]/[SO42-]. It finds that ammonia is abundant in Taichung City, and the main WSIIs present as (NH4)2SO4, NH4NO3, and other compounds, with the generation of N2O5. In the Lulin Mountain station, ammonia is less abundant, and the main WSIIs may include (NH4)2SO4, along with NH4HSO4, H(NH4)3(SO4)2 (Letovicite), and NH4NO3. |
