| 摘要: | 氣膠水溶性無機離子散射太陽光直接影響地球輻射平衡，當成為雲凝結核又間接影響降雨、雲滴散光。生質燃燒普遍在全球各地都有發生，煙團氣膠水溶性無機離子長程傳輸後的短時間變化值得關注。本文於2016年秋季及2017年春季在鹿林山大氣背景觀測站(2,862 m a.s.l.)以自動監測設備觀測PM2.5水溶性無機離子並結合現場相關量測項目進行分析。
2016年秋季在沒有山谷風循環時PM10質量濃度為4.6 ± 2.1 ug m-3，水溶性無機離子只有SO42-高於偵測極限，平均濃度為0.8 ± 0.6 ug m-3；PM10和PM1散光係數分別為14.8 ± 13.5與9.6 ± 9.1 M m-1，吸光係數分別為1.4 ± 0.9與1.1 ± 0.8 M m-1，可視為秋季東亞高山大氣背景數值。發生山谷風時氣膠水溶性離子SO42-、NO3-、NH4+濃度明顯上升。
2017年春季扣除生質燃燒與山谷風循環後，PM2.5質量濃度、PM10和PM1光學係數、PM2.5水溶性無機離子濃度都較2016年秋季為高。發生山谷風時，各測項數值也都比秋季高，顯示春季大氣背景濃度較高於秋季。春季生質燃燒事件中PM2.5質量濃度上升至22.0 ± 8.3 ug m-3，指標物種K+濃度明顯增加為0.3 ± 0.1 μg m-3，其餘三種無機離子SO42-、NO3-、NH4+濃度分別增加為4.3 ± 1.9、1.1 ± 1.0、1.7 ± 0.8 ug m-3，PM10和PM1散光係數分別上升至164.4 ± 46.4與108.2 ± 30.3 M m-1，吸光係數分別達21.8 ± 7.7與16.8 ± 6.3 M m-1，利用ISORROPIAⅡ模式顯示氣膠水溶性無機離子結合型態可能為硫酸銨、硫酸氫銨、硫酸鉀、硝酸銨、硝酸鉀。最後，針對氣膠水溶性無機離子和大氣輻射衰減的探討，本文發現低相對濕度、非靜風、現址無雲霧的環境，大氣氣膠水溶性無機離子對大氣氣膠光學厚度具有重大影響。
;Light scattering from aerosol water-soluble inorganic ions (WSIIs) directly influences solar radiation budget of the Earth. In addition, aerosol WSIIs may indirectly affect light scattering and precipitation of cloud droplets when they act as cloud condensation nuclei. As biomass burning (BB) occurs commonly around the glBBe, short-interval variations of WSIIs from the long-range transported BB smoke are thus interesting to investigate. This work monitored short-interval values of PM2.5 WSIIs and accompanied with the related measuring items at the Lulin Atmospheric Background Station (2,862 m a.s.l.) for analysis in autumn 2016 and spring 2017.
The campaign in autumn 2016 showed that PM10 mass concentration was averaged at 4.6 ± 2.1 ug m-3 excluding the influence of mountain-valley wind. Among various PM2.5 WSIIs, SO42- was the sole ion exceeding detection limit with an average of 0.8 ± 0.6 ug m-3. Light-scattering coefficients of PM10 and PM1 were averaged at 14.8 ± 13.5 and 9.6 ± 0.8 M m-1, respectively. In contrast, PM10 and PM1 light-absorption coefficients were 1.4 ± 0.9 M m-1 and 1.1 ± 0.8 M m-1, respectively. These aerosol properties characterized background air of a high-elevation site in East Asia in autumn 2016. Note that the levels of WSIIs such as SO42-, NO3-, and NH4+ increased greatly when mountain-valley wind occurred.
In the field study of spring 2017, however, PM2.5 mass concentration, PM10 and PM1 optical coefficients, and PM2.5 WSIIs all exceeded the corresponding values in autumn 2016 when excluding the influences of BB and mountain-valley wind. Similarly, all measurements in spring 2017 exceeded that in autumn 2016 under the influence of mountain-valley wind, which was prBBably due to higher background values. During the BB events in spring 2017, levels of PM2.5 mass increased to 22.0 ± 8.3 ug m-3 and K+, a BB tracer, also increased greatly to 0.3 ± 0.1 μg m-3. The mean levels of other three major WSIIs, namely, SO42-, NO3-, and NH4+, were 4.3 ± 1.9, 1.1 ± 1.0, and 1.7 ± 0.8 ug m-3, respectively. Moreover, PM10 and PM1 light-scattering coefficients increased to 164.4 ± 46.4 and 108.2 ± 30.3 M m-1, respectively. The light-absorption coefficients were 21.8 ± 7.7 and 16.8 ± 6.3 M m-1, respectively. For the possible associated compound forms of WSIIs, the ISORROPIAⅡ model simulation came up with ammonium sulfate, ammonium bisulfate, potassium sulfate, ammonium nitrate, and potassium nitrate. Finally, the investigation of aerosol WSIIs on atmospheric radiation degradation showed that WSIIs influenced aerosol optical depth greatly. |
