| 摘要: | 本研究為調查中部地區之空氣品質特徵，選擇環保署設置之西屯及竹山測站為採樣地點，西屯測站位於台中市，緊臨台中工業區、台中市焚化爐及中部科學園區，亦位於交通重要地區，如：國道一號、快速道路等附近；另竹山測站位於南投縣，屬於鄉村之生活型態，但當地砂石業密集，砂石車輛亦往來頻繁。本研究於兩測站同時架設雙道粒徑採樣器(Dicho)、泛用型空氣採樣器(UAS)及環形擴散採樣器(ADS)，於春末夏初時採集懸浮微粒包括細微粒(PM2.5)及粗微粒(PM2.5-10)與酸鹼性氣體(HCl、HNO3、HNO2、SO2及NH3)分析其組成並解析可能之污染來源。
研究結果顯示西屯地區PM2.5及PM10之濃度分別為25.4±11.5及40.5±14.5 μg/m3；而竹山測站則分別為20.7±10.6及33.3±14.0 μg/m3。西屯測站懸浮微粒(PM2.5)之Dicho、UAS及ADS手動採樣測值與測站值之偏差，分別為-8%、-5%及2.8%；竹山測站則依序分別為-35%、-10%及-16%。
PM2.5及PM2.5-10主要組成為水溶性離子約佔48-53 %及31-36 %，其中NO3-、SO42-及NH4+為水溶性離子之主要貢獻物種。西屯測站細微粒之衍生性氣膠(SO42-、NO3-及NH4+)及粗微粒之海鹽氣膠(Na+及Cl-)高於竹山測站，分別高出14 及42 %。碳組成於西屯測站PM2.5及PM2.5-10約佔13 %及11 %；竹山測站 (PM2.5及PM2.5-10) 則分別為12及15 %。微量元素於西屯測站PM2.5及PM2.5-10約占10及11 %；竹山測站則分別為11及9 %。西屯測站之微量元素濃度約高於竹山1.3-1.4倍。兩測站微量元素粗微粒主要以塵土元素(Al、Mg及Ca)為主，細微粒之主要微量元素為S約佔微量元素50-80%。
酸鹼性氣體(HCl、HNO3、HNO2、SO2及NH3)之濃度於西屯地區皆高於竹山地區，依序為1.4、1.6、3.1、2.9及1.2倍。HCl、HNO3及SO2於日間高於夜間；HNO2則為夜間高於日間。硫轉化率夜間高於日間；氮轉化率日間高於夜間，竹山測站之氮及硫轉化率高於西屯測站，結果顯示當地可能受外來傳輸影響較大。
西屯及竹山測站之富集因子分析結果相似。粗微粒之Al、K、V、Mn、Co、Sr及Ba，皆主要由地殼源貢獻。人為污染源元素主要集中於細微粒，S、Cu、Zn、As、Se、Ag、Cd、Sb及Pb為主要成分。因子分析結果西屯測站細微粒主要以光化反應、交通污染源及工廠排放居多，但亦解析海鹽飛沫及地殼元素之貢獻。竹山測站粗微粒則以地殼元素為主。
Characteristics of ambient air quality including particulate matter and gas pollutants were investigated in central Taiwan. Two sampling sites were set up on Taiwan Environmental Protection Administration stations at Situn and Jhushan. At Situn station in Taichung city, the emission sources, including the Taichung industrial park, metropolitan waste incinerator, central Taiwan Science Park, and highway #1, were located in the vicinity of the sampling site. Jhushan station is located in Nantou County, which is regarded as a rural site; however, gravel trucks associated with holystone facilities cause heavy road dust and exhaust emission. This study focused on the compositions and source apportionment of particulate matter (PM2.5 and PM10) and the acid-base gas (HNO3, HCl, HNO2, SO2 and NH3). Samples were taken by Dichotomous Sampler (Dicho), Universal Air Sampler (UAS) and Annular Denuder System (ADS) during the periods of spring and summer.
Results indicated that PM2.5 and PM10 concentrations were 25.4±11.5 and 40.5±14.5 μg/m3, respectively, at Situn. PM2.5 and PM10 concentrations were 20.7±10.6 and 33.3±14.0μg/m3, respectively, at Jhushan. Differences in the amount of fine particles (PM2.5) using Dicho, UAS and ADS with MS (monitoring station) were -8, -5 and 2.8%, respectively, at Situn and -35, -10 and -16%, respectively, at Jhushan.
Water-soluble ionic species are the major components of both fine and coarse particles, which contributed 48-53 and 31-36% of mass, respectively. The portion of secondary inorganic aerosols (such as NO3-, SO42- and NH4+) in fine particles and sea salt (such as Na+ and Cl-) in coarse particles was 14 and 42% higher at the Situn station than at the Jhushan station. At Situn, carbon fractions were about 13 and 11% in PM2.5 and PM2.5-10, and element constituents were 10 and 11% in PM2.5 and PM2.5-10, respectively. At Jhushan, carbon fractions were about 11 and 9% in PM2.5 and PM2.5-10, and element constituents were 11 and 9% in PM2.5 and PM2.5-10, respectively. Element concentrations at Situn were approximately 1.3-1.4 times higher than at Jhushan. Crustal elements including Al, Mg and Ca were the main elements of coarse particles, and S was the main element (50-80%) of fine particles at both stations.
Acid-base gases (HCl, HNO3, HNO2, SO2 and NH3) were approximately 1.4, 1.6, 3.1, 2.9 and 1.2 times higher at Situn than Jhushan, respectively. HCl, HNO3 and SO2 were higher during the day than at night. HNO2 was higher at night than during the day. Sulfur conversion ratios (Fs) were higher at night than during the day. Nitrogen conversion ratios (Fn) were higher during the day than at night. Fn and Fs were higher at Jhushan than at Situn, which could be attributed to the effect of long-range transport of air pollution at Jhushan station.
Results of enrichment factor (EF) analysis were similar at both stations. Crustal elements, including Al, K, V, Mn, Co, Sr and Ba, were a major source in coarse particles. The EF values increased with the decrease of particle size at both stations, suggesting a high contribution of anthropogenic sources (S, Cu, Zn, As, Se, Ag, Cd, Sb and Pb) in the fine particles.
Factor analysis indicated that photochemical reactions, traffic sources and industrial emissions were dominant contributors to fine particles. But sea salt and crustal elements were also found in fine particles. In addition, crustal elements contributed to coarse particles. |
