台北都會區外圍城市大氣氣膠光學效應; The effect of Atmosphere aerosol optical in Taipei at HSIN-CHUANG

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题名:	台北都會區外圍城市大氣氣膠光學效應;The effect of Atmosphere aerosol optical in Taipei at HSIN-CHUANG
作者:	呂理德;Li-TE LU
贡献者:	環境工程研究所
关键词:	粒徑分布;氣膠光學效應;即時監測值;黃沙時期;scattering effect;Yellow Dust;size distribution;continually monitoring;aerosol optical effect
日期:	2002-07-07
上传时间:	2009-09-21 12:14:41 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	氣膠由於化學組成、粒徑分布、形狀等差異，造成氣膠在光學效應影響的變化，進而影響地球接收太陽輻射。本文選擇超級測站在2002年3?9月間，於台北縣新莊市進行的氣膠粒徑與散光係數連續監測監測資料，配合鄰近環保署新莊空氣品質監測站資料，並區分特殊事件的影響，用來分析新莊地區氣膠在光學效應的影響。新莊地區下午兩點到晚上十一點氣膠散光係數和相對濕度成高度正相關(R2>0.80)，且背散光係數對總散光係數貢獻比例降低。當散光係數與相對濕度關係良好時(R2>0.75)，散光係數和硝酸鹽與一氧化碳、臭氧和二氧化氮的變化呈高度相關。背散光係數和0.1~0.5mm粒徑範圍內的氣膠變動呈正相關，並發現在這範圍內氣膠對相對溼度變化敏感。本文監測期間的特殊事件，發現第二波大陸黃沙事件影響台灣期間不同波段背散射對總散射的貢獻有收斂的現象發生，並可以觀察到紅光波段背散光係數對總散光係數的比例有一段時間維持變動很小。黃沙事件期間氣膠的體積濃度主要自於2.5~10mm範圍內體積濃度的貢獻。本文三月到九月每天早上7~9點氣膠吸光效應對散光效應貢獻最高的時間，發現OC/EC=2 (R2=0.83)，代表當OC/EC>2時，有二次OC的影響。新莊地區三月至九月散光係數與化學組成的多元線性迴歸為綠光總散光係數(Mm-1)=16〔Sulfate(mgm-3)〕+16〔Nitrate(mgm-3) 〕+6〔Organic carbon(mgm-3)〕-14，此一迴歸模式大約可以解釋新莊地區80%(R2=0.8)散光係數的變化。另外得到新莊地區的BC/EC的質量吸光效率為22±35(m2g-1)。新莊地區春季散光係數高於夏季，背散射對總散射的貢獻比例有明顯的季節性差異，夏季高於春季，但是並沒有發現吸光係數有季節性的差異存在。推估氣膠輻射作用力，可以知道新莊地區的臨界單一散射率(critical single scattering albedo)為0.82，並可以觀察到散射率是有明顯的季節差異存在，當新莊地區氣膠散光係數大於99Mm-1，氣膠的存在是會導致新莊地區的大氣輻射冷卻。 Because the discriminations of aerosol’s chemical components, size distributions and morphology, optical variations of aerosols would influence solar radiation emitted on earth and further the climate change. In this thesis, aerosol size distribution and scattering coefficient datas continually monitored in Taiwan supersite sited in HSIN-CHUANG from March to September in 2002 and Air quality datas monitored synchronously in another site nearby setup by Taiwan Environmental Protection Agency was chosen to be analyzed particularly for aerosols’ optical effects. Analysis revealed that aerosol scattering coefficient was highly positive- correlated(R2>0.80) with relative humidity from 14:00pm to 23:00pm and contribution of backward scattering coefficient in total scattering coefficient was reduced at the same period. When scattering coefficient was well correlated(R2>0.75) with relative humidity, it was also found that scattering coefficient was highly positive-correlated with concentration of nitrate, carbon monoxide, ozone and nitrogen dioxide. Beside, backward scattering coefficient was positive-correlated with variation of aerosol concentration. Aerosol concentration was very sensitive with variation of relative humidity especially with particle size within 0.1?0.5μm. Detail analysis of episodes happened from March to September in 2002 has discovered that during the period of the second event of Yellow Dusts influencing Taiwan area, backward scattering of aerosols induced by different wave length light contributed total scattering convergently. It was observed that backward scattering contributed to total scattering induced by red light vary in small amplitude at some periods in that episode. Aerosol volume concentration was mainly due to particle size with 2.5?10μm during the period of Yellow Dusts. From the regression of organic carbon(OC) and elemental carbon(EC) concentration monitored from 7:00am to 9:00am(the period of aerosol absorption effect contributed scattering effect most), it was found that OC/EC=2(R2=0.83) which represented that there existed secondly organic aerosol when OC/EC>2. Also the regression of green light scattering coefficient and chemical components was formulated as TG(Mm-1)=16Sulfate(μgm-3)+ 16Nitrate(μgm-3)+ 6Organic carbon(μgm-3)-14. It was found the formula above could explain about 80% variations of scattering coefficient datas. In HSIN-CHUANG area, scattering coefficient in spring was higher than that in summer. There was seasonal variations in the ratios of backward scattering to total scattering. The ratio was higher in summer than that in spring. Instead, it was not found that absorption coefficient varied seasonally. By evaluating the radiative forcing, the critical single scattering albedo in HSIN-CHUANG area was about 0.82. It was obviously observed that the scattering rates varied seasonally. When aerosol scattering coefficient was above 99Mm-1, the existence of aerosols suspended would cool the atmospheric radiation.
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