| 摘要: | 每年3至4月中南半島北部山區有大規模生質燃燒，燃燒煙團因熱力上升到高層大氣後，受盛行西風傳輸至東亞，影響範圍甚大，當傳輸煙團氣膠與雲層交會，將影響雲內水珠輻射收支，對區域氣候變遷有重大影響。
本研究於2015年8月至2016年4月在台灣鹿林山大氣背景觀測站(海拔2,862 m)，以去除前驅酸、鹼性氣體干擾並補償揮發氣膠成分的方法採集分析大氣氣膠化學成分。採樣分成兩個時期，前期為相對乾淨期間，可分成背景(Background, BK)與山谷風(Valley, VALY)期間，後期受中南半島生質燃燒長程傳輸影響(Biomass Burning, BB)，可分成受BB及不受BB影響(Non-Biomass-Burning, NBB)期間。在BK期間，PM2.5與PM10質量濃度平均為2.3 ± 1.8 µg m-3和3.5 ± 2.4 µg m-3，可視為東亞高山氣膠背景濃度。在採樣期間氣膠質量濃度是BB>NBB>VALY>BK，氣膠都以細粒徑為主。BB和NBB期間PM2.5水溶性無機離子主要物種為NH4+與SO42-，但BB期間nss-K+及NO3-濃度和占比都較NBB期間增大。
BB期間PM2.5碳成分的主導成分為OC3和EC1-OP，但OC4與K+相關性非常好(R=0.91)，有潛力成為生質燃燒指標成分。各碳成分中char-EC/soot-EC比值比OC/EC更能反應受生質燃燒影響。NBB期間PM2.5碳成分的主導成分為OC3和EC2。在BB期間採樣過程中，微粒揮發碳成分以低溫解析出的OC1與OC2為主，濾紙吸附的揮發性有機氣體以OC1濃度最高，PM10吸附的OC1/OC比例為其他粒徑的兩倍以上。由於微粒揮發碳成分沒有分析出OP，根據前述可推論低溫解析出的OC不易產生OP。
;Biomass burning (BB) occurs frequently in the mountain area of the northern Indochina from March to April evry year. The produced BB plume is uplifted thermodynamically to high altitude and transported by the prevailing westerly from Indochina to East Asia. As the plume distributes spatially during transport, it will affect solar radiation budget of cloud droplets when mixing with cloud layers to cause a significant effect on regional climate change.
This study collected atmospheric aerosol at Lulin Atmospheric Background Station (2,862 m) in Taiwan by adopting a denuder system to remove interfering precursor gases and correct for aerosol volatilization from August 2015 to April 2016. The sampling campaign split into two parts with the background (BK) and valley wind (VALY) periods in the relatively clean front part and under the influence of long-range BB plume transport and without the influence of BB (NBB) in the rear part. During the BK period, the mass concentrations of PM2.5 and PM10 were 2.3 ± 1.8 µg m-3 and 3.5 ± 2.4 µg m-3, respectively, representing aerosol background concentration in high mountain area of East Asia. Aerosol mass concentrations varied following the order of BB >NBB >VALY >BK and fine particles dominated over all periods. For water-soluble inorganic ions in PM2.5, NH4+ and SO42- were the major components during the BB and NBB periods, while nss-K+ and NO3- ratios were enkanced additionally during the BB period.
As for PM2.5 carbonaceous content, OC3 and EC1-OP were the predominant components and OC4 correlated with K+ excellent well (R=0.91) to become potential BB tracers during the BB period. Among various carbonacous components, the ratio of char-EC/soot-EC was apparently more sensitive to BB than OC/EC. In contrast, OC3 and EC2 were predominant in PM2.5 carbonacous components during the NBB period. Interestingly, during the BB period, low-temperature resolved OC1 and OC2 were the predominant components of volatilized carbonaceous content from the preceeding filter and OC1 concentration was the highest component among the volatilized organic gases adsorbed in the back-up filter. In addition, the adsorbed OC1/OC ratio of PM10 were more than two-folds compared with that of other size intervals. Since no OP was resolved from the volatilized carbonaceous content, it implied from previous findigs that low-temperature resolved OC could hardly produce OP. |
