| 摘要: | 本研究於2002年9月至2003年8月分別於高雄縣之大寮、林園、仁武以及美濃等地區，分別採集PM10與PM2.5之大氣懸浮微粒，探討全年大氣懸浮微粒區域變化與季節性之差異，密集採樣探討高污染季節期間(2002年10月至2003年3月)日夜以及不同空氣品質狀態大氣懸浮微粒之質量濃度變化與化學組成特性。
2002年9月至2003年8月PM2.5年平均質量濃度在大寮、仁武、林園以及美濃地區，分別為47.9±5.7 g m-3、43.9±7.4 g m-3、53.9±8.6 g m-3、44.6±6.2 g m-3，而PM2.5-10年平均濃度則分別為31.3±5.7 g m-3、29.4±4.7 g m-3、33.2±5.6 g m-3、24.1±2.9 g m-3，四個研究地點以林園地區質量濃度年平均值最高，年平均質量濃度最低為美濃地區。而四個研究地區其懸浮微粒組成以有機碳(Organic carbon, OC)、SO42-、NO3-、無機碳(Element carbon, EC)、NH4+為主，平均合佔PM2.5及PM2.5-10之36%~71%，此地區OC/EC皆在1.0以上，顯示此地區含碳氣膠以光化反應產生之二次氣膠為主。而金屬元素Al、K、Ca、Fe合佔PM2.5與PM2.5-10金屬平均濃度為1500~2000 ng m-3，PM2.5與PM2.5-10分別佔平均金屬濃度之70.9%、77.5%，顯示懸浮微粒當中之金屬元素以地殼元素貢獻最多。位於工業區如林園、大寮、仁武地區PM2.5中Pb、Zn平均濃度分別為109.1±116.4 ng m-3、261.8±215.5 ng m-3，較美濃地區PM2.5中Pb、Zn金屬平均濃度63.3±33.1 ng m-3、153.2±63.6 ng m-3高出釵h，顯示此三地區因工廠之作業如燃燒重油以及交通污染明顯導致懸浮微粒中之Pb、Zn濃度較高。林園地區因為位於沿海地區Sea salt佔PM2.5-10比例分別為5.9%，較仁武與大寮地區之PM2.5-10微粒平均比例為9.5%為高，而美濃地區Sea salt佔PM2.5-10分別為為6.7%，因位於內陸比例較低，此外於林園地區Sea salt於日間PM2.5-10平均比例為9%，較夜間PM2.5-10平均比例3%來的高，顯示海陸風的效益明顯。
採樣期間大部分的PM2.5-10氣膠多呈現中性，但在仁武地區PM2.5-10之NR值為0.7±0.1，屬偏酸性。在PM2.5之NR值較PM2.5-10為低，顯示SO42-、NO3-在細微粒貢獻量較粗微粒多。在高雄地區SOR與NOR表現，PM10氣膠微粒SOR及NOR平均轉化率分別為0.690.13、0.230.06。而在美濃地區SOR的轉換速率是其他三地點之2倍，不論何地其SO2轉化成硫酸鹽的轉化速率比NO2轉化成硝酸鹽的轉化速率為大，而靠近山區之美濃無明顯SO2污染排放，然而美濃之SOR較其他地區為高，顯示美濃地區之SO42-主要由遠處SO2排放及轉化傳輸而來。
於不同污染狀態下，於高污染事件發生時，平均混合層高度為832.3±422.4 m，較低導致污染物不易擴散，在良好空氣品質狀態下平均混合層高度為1487.6±662.2 m，高度較高能將污染物均勻擴散至大氣中，不致累積於同一區域。在高污染事件日PM2.5主要成份SO42-、NO3-、NH4+、OC與EC比一般空氣品質分別為1.5、1.9、1.7、1.6及1.6倍，顯示在高污染事件日NO3-、SO42-與OC都是主要污染物種。PM2.5-10分別為1.6、1.5、1.5、1.9及1.5倍，NO3-較其他主要成份有較多之增量，顯示高污染事件日發生時，產生之NO3-微粒污染物較多，不易擴散而滯留當地。
The long-term compared the temporal and spatial variations of PM10 and PM2.5 aerosol components at Daliau (DL), Jenwu (JW), Linyuan (LY) and Meinong (MN) in the southern Taiwan from September 2002 to August 2003. The whole sampling program included intensive studying the characteristics of daytime and nighttime aerosol during the seasons of particulate matter (PM) episodic occurrence from October to March and the aerosol characteristics of 24-hour sampling during the various air qualities.
The annual mean concentrations of PM2.5 (fine particle) were 47.95.7 g m-3 at site DL, 43.97.4 g m-3 at site JW, 53.98.6 g m-3 at site LY and 44.66.2 g m-3 at site MN, respectively. Meanwhile, the mass concentrations of PM2.5-10 (coarse particle) were lower than PM2.5 at all the four sites. The annual mean concentrations of coarse particle were 31.35.7 g m-3 at site DL, 29.44.7 g m-3 at site JW, 33.25.6 g m-3 at site LY and 24.12.9 g m-3 at site MN, respectively. The mass concentration of fine and coarse particles at site LY was the highest at all the four sites. The mass annual mean mass concentration of PM10 at site MN was the lowest. Among the detected 29 components, organic carbon (OC) was always the most abundant chemical component of PM10 at all the four sites, followed by sulfate, elemental carbon (EC), nitrate and ammonia. Those above major components together accounted for 36~71 % of mass concentration in fine and coarse particles. Mean ratio of OC/EC at all the four sites was over than 1, including the organic carbon in aerosol resulted from the photochemical activity was dominant.
Amount of Al, K, Ca, and Fe either in PM2.5 or in PM2.5-10 was measured 1500~2000 ng m-3, which accounted for 70.9% and 77.5% of total determined fine and coarse particle metals, individually, indicating the crustal matter was the dominant species in particulate metals, specially for coarse particle. Higher abundance of traffic indictors such as Zn (261.8215.5 ng m-3) and Pb (109.1116.4 ng m-3) in PM2.5 were observed at the industrial and heavily trafficked areas such as LY, JW and DL, compared with 153.263.6 ng m-3 of Zn and 63.133.1 ng m-3 at site MN, which was the country and lowly trafficked area, indicating the emission effect of motor vehicle and heavy-oil burning contributed to airborne environment at industrial and high-density traffic areas was evident in larger abundance of Zn and Pb.
Sea salt in PM2.5-10 at the coastal site, site LY, accounted for upper than 10.4 %, compared with 9.5 % of PM2.5-10 at sites JW and DL and 6.7 % of PM2.5-10 at site MN. Apparent discrepancy of amount of sea salt in PM2.5-10 at site LY and other inland sites was caused by decreasing with increasing distance from the coast to the inland. On the other hand, the higher amount of sea salt at coastal site LY in the coarse fraction during daytime occurred with 9% of PM2.5-10, compared with 3% of PM2.5-10 during nighttime. The result was caused by stronger air circulation between the coast and inland under the effect of daytime sea breezes.
Neutralization ratio (NR) judged the aerosol acidity. Except that PM2.5-10 at site JW presented acidic, the PM2.5-10 at other sites presented neutral even alkaline. Acidic degree of aerosol was enriched in the fine size fraction as compared with alkaline and neutralization in the coarse fraction, indicating the sulfate and nitrate contributed to fine particle more than coarse particle. On average, the sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR) in PM10 at all four sites were 0.690.13 and 0.230.06, respectively. There was no significant SO2 pollution source at the MN region, but average SOR at site MN exceeded that value at other three sites by a factor of 2, indicating aerosol sulfate at site MN mainly came from the transport from long distance sources to the sampling site MN with the SO2 gas-to-particle photochemical conversion.
When the good air quality occurred, the average mixing height of 1487.6662.2m was higher than 832.3422.4m during the period of PM10 episode, indicating the higher mixing height conduced to disperse air pollutions better and dilute their concentration more significantly. The amounts of sulfate, nitrate, ammonia, OC and EC in PM2.5 increased by factors of 1.5, 1.9, 1.7, 1.6 and 1.6 (highest for nitrate), respectively, from during the period of moderate air quality to during PM10 episodic event. Although sulfate was generally more abundant than nitrate, they were quite comparable during PM10 episodic event. Compared to lower amounts of nitrate in PM2.5 during the period of moderate air quality, the amount of nitrate in PM2.5 increased significantly more than other chemical species in PM2.5 during PM10 episodic event. The reason of significantly increased aerosol nitrate during PM10 episode might cause by that nitrate gas-to-particle concentration increased and was difficult to disperse when lower mixing height occurred. |
