| 摘要: | 中南半島生質燃燒(Biomass Burning, BB)氣膠傳輸分布廣泛，對大氣環境有重大影響。本文在鹿林山背景監測站 (海拔2,862 m)分別於 2018年 10、11月(秋季)及2019年3、4月(春季)觀測BB及其他氣流來向大氣氣膠化學特性，並評估氣膠化學成分對大氣光學的影響。在正式採樣前，本文以 Z-test檢定確認非常陡峭切割旋風集塵器(Very Sharp Cut Cyclone, VSCC)與衝擊板(Impactor)採集PM2.5濃度並無顯著差異(n=36; p=0.42)，但VSCC對於採集濃度的回應比 Impactor好，因此，本文使用VSCC採集的PM2.5。
2018 年秋季PM2.5 (氣動直徑小於或等於2.5 μm粒狀物)和 PM10 (氣動直徑小於或等於10 μm粒狀物)質量濃度分別為2.8 ± 1.6和4.1 ± 2.2 μg m-3，PM2.5占PM10質量濃度的0.68。秋季期間氣流傳輸來向可分為自由大氣(Free Troposphere, FT)及人為污染(Anthropogenic, AN)。FT 類型PM2.5污染來源較紛雜；AN 類型PM2.5來源推論為固定源與BB，PM2.5-10來源則主要為移動源。
2019 年春季PM1 (氣動直徑小於或等於1.0 μm粒狀物)、PM2.5、PM10質量濃度分別為12.3 ± 9.1、15.2 ± 9.9、18.9 ± 11.3 μg m-3，顯示PM1主導鹿林山氣膠質量濃度。BB傳輸期間，PM1、PM2.5、及PM10質量濃度分別高達22.0 ± 7.2、25.4 ± 7.7、30.0 ± 9.0 μg m-3，PM1/PM10為 0.73，顯然BB為春季氣膠主要污染源且由更細粒徑氣膠主導，PM1有機碳 (OC)、元素碳 (EC)、水溶性無機離子的主要成分分別為OC3、EC1-OP、SO42-，SO42-來源推論為中南半島與中國南方工業源。
為了探討氣膠的氣候效應，本文以 Revised IMPROVE模式估算PM2.5 化學成分消光係數，發現與自動儀器量測的氣膠消光係數有良好相關性 (R2 > 0.86)，春季氣流(FT, AN, BB類型)和秋季氣流(FT和AN類型)都以有機物和硝酸銨為消光係數主導化學成分。此外，春季和秋季各類氣流氣膠的單一反照率都大於 0.85，顯示氣膠具有強散光特性，對於氣候暖化有減緩作用。
;Biomass burning (BB) aerosol transported from Indochina spreads broadly
and thus influences the atmospheric environment significantly. This study
observed chemical properties of the atmospheric aerosol transported from BB
and other orientations in October and November (autumn) in 2018 and March
and April (spring) in 2019, respectively, at Mt. Lulin (2,862 m a.s.l.), and
assessed the atmospheric optical effects from the aerosol. Before aerosol
collection, this study applied a Z-test (n=36; p=0.42) to find no significant
differences for the collected PM2.5 mass concentrations betwee Very Sharp Cut
Cyclone (VSCC) and Impactor, but the concentration from VSCC responded
to PM2.5 concentration variations better than Impactor. Consequently, this study
adopted the VSCC for aerosol collection in the following PM2.5 collection.
The mass concentrations of PM2.5 (particulate matter with an aerodynamic
diameter less than or equal to 2.5 μm) and PM10 (particulate matter with an
aerodynamic diameter less than or equal to 10 μm) were 2.8 ± 1.6 and 4.1 ± 2.2
μg m-3, respectively, in autumn of 2018; with PM2.5/PM10 at 0.68. The
orientations of the transported air masses could split into Free Troposphere (FT)
and Anthropogenic (AN) types. The sources of PM2.5 from the FT type were
various. In contrast, the inferences on source contributions of PM2.5 from the AN
type were from stationary sources and BB, and PM2.5-10 was from mobile sources.
The mass concentrations of PM1 (particulate matter with an aerodynamic
diameter less than or equal to 1 μm), PM2.5, and PM10 were 12.3 ± 9.1, 15.2 ±
9.9, and 18.9 ± 11.3 μg m-3, respectively, in spring of 2019. It indicated that PM1
dominated aerosol mass concentration at Mt. Lulin. During the BB transported
period, the mass concentrations of PM1, PM2.5, and PM10 were as high as 22.0 ±
7.2, 25.4 ± 7.7, and 30.0 ± 9.0 μg m-3, respectively. The ratio of PM1/PM10 was
0.73, which demonstrated that BB was the main aerosol source and finer sizes
dominating the spring BB aerosol. The main components of PM1 organic carbon
(OC), elemental carbon (EC), and water-soluble inorganic ions were OC3, EC1-
OP, and SO4
2-, respectively. The sources inferred for SO4
2- was from Indochina
and industrial sector in southern China.
For the inference of climatic effect, this study estimated the atmospheric
extinction coefficient from PM2.5 chemical components using the Revised
IMPROVE model and compared well with that from the automated instruments
(R2
> 0.86). The dominant chemical components were organic matter and
ammonium nitrate for the atmospheric extinction coefficients in the air masses
of spring (FT, AN, and BB types) and autumn (FT and AN types). In addition,
the values of the single scattering albedo were larger than 0.85 for spring and
autumn. It showed that the atmospheric aerosol was with strong light-scattering
characteristics to mitigate climate warming. |
