| 摘要: | 本文2012年分別在越南山羅高地(以下簡稱山羅)及台灣鹿林山大氣背景監測站(以下簡稱鹿林山)進行氣膠觀測，探討2012年山羅和鹿林山氣膠化學特性、分辨2003-2012年間鹿林山生質燃燒 (Biomass Burning, BB)與非生質燃燒 (Non-Biomass Burning, NBB)氣膠化學特性差異、瞭解生質燃燒煙團從中南半島傳輸至鹿林山的氣膠成分比例變化、並使用PMF受體模式 (Positive Matrix Factorizatio, US EPA, 2008)解析鹿林山氣膠污染來源。研究結果顯示2012年山羅PM10氣膠受PM2.5氣膠主導，以Hysplit模式(Draxler and Rolph, 2010)追溯氣團來源可分為來自中南半島和中國南方，當氣流來自中南半島PM2.5氣膠質量濃度和K+、碳成分及有機成分比例大於來自中國南方，顯示此時氣膠成分受生質燃燒活動影響大；但當氣流來自中國南方，SO42-與NH4+佔PM2.5氣膠質量比例較高，表示受到人為污染源影響較大。近十年鹿林山氣膠觀測資料顯示出，BB的PM2.5氣膠質量濃度、碳成分比例、K+、NO3-、Levoglucosan、OC3、EC1-OP明顯高於NBB，除了表示BB煙團傳輸的現象會造成PM2.5氣膠質量濃度上升外，也凸顯了BB菸團氣膠指標物種的特徵；相反地，BB水溶性離子比例反而低於NBB，這表示NBB的氣膠受到人為污染源影響較BB大。在過去，接近BB發生源氣膠特性的探討很少，本研究比較2010年泰國清邁、2011-2012年越南山羅省以及2010-2012年BB期間鹿林山PM2.5氣膠觀測數據，結果顯示近生質燃燒源和受BB煙團影響下風處鹿林山PM2.5氣膠K+、OC3、EC1-OP及Levoglucosan等BB氣膠特徵指標物比例變化較其他成分穩定，確認這些物種為BB氣膠特徵。另外，BB期間鹿林山PM2.5 NO3-比例較清邁與山羅高，顯示NO3-可能來自於NOx的長程傳輸轉化。PMF解析出鹿林山BB PM2.5污染來源共有6個主要污染源類型，依高低序分別為BB mixing secondary aerosol (28.7 %)、BB mixing soil dust (25.4 %)、BB (17.6 %)、BB _ dicarboxylates (12.0 %)、Diesel emissions (10.0 %)、Sea salt (6.2 %)。PMF來源推估指出受到BB煙團氣流影響的PM2.5質量濃度共有83.7 %是BB類型，這個結果表示PMF污染源解析的正確性和說明了BB煙團經盛行西風長程傳送時，可能會夾帶或混合其他氣流到達下風處的鹿林山。在NBB期間各污染源以二次氣膠貢獻PM2.5質量濃度最多，共有70.6 %，氣流多半源自於海洋(包含太平洋與南中國海)，也有少許氣流混合海洋及人為一次污染物是來自於中國大陸沿岸並透過低層大氣傳輸至鹿林山。總結來說，山羅近BB污染源氣膠多為PM2.5，當氣流來自中南半島，PM2.5氣膠受生質燃燒活動影響較大，但當氣流來自中國南方， PM2.5氣膠受人為污染源影響較大。鹿林山十年氣膠觀測資料指出，生質燃燒煙團經長程傳輸會混合少量其他污染來源；當不受生質燃燒影響時，氣流主要含有二次氣膠，但傳輸過程可能混合少量海洋及人為一次污染物。This work collected armospheric aerosols at Son La, Vietnam and Mt. Lulin Atmospheric Background Site (LABS), Taiwan, respectively. The objectives of this study were to survey Son La and LABS aerosol characteristics, distinguish aerosol chemistry between biomass burning (BB) and non-biomass burning (NBB) periods from 2003-2012, realize the changes of aerosol composition proportion for BB plume transported from Indochina and LABS, and utilize Positive Matrix Factorization (PMF) (US EPA, 2008) for resolving aerosol source contribution at LABS. The results show that PM2.5 dominates PM10 at Son La in 2012. The airmasses were traced back from Indochina and South China by using Hysplit model (Draxler and Rolph, 2010). PM2.5 mass concentration, K+, carbonaceous content, and organic aerosol proportion were greater than that from South China when the airmasses were from Indochina. This implies that aerosol composition is influenced much by BB activities. In contrast, SO42- and NH4+ were higher in PM2.5 mass fractions to indicate the greater influence from anthropogenic sources. The results from ten years’s observation at LABS show that PM2.5 mass concentration, K+, NO3-, Levoglucosan, OC3, and EC1-OP were obviously greater than that of NBB. This phenomenum not only demonstrates the increase of M2.5 mass concentration but also stands out aerosol tracer characterstics from BB plume. On the other hand, the proportion of aerosol water-soluble ions from BB plume was lower than NBB plume, which indicates NBB aerosol is influenced more by anthrpogenic sources.In the past, near-source BB aerosol characteristics were less studied. This work compares PM2.5 observation data from Chiang Mai, Thailand in 2010, Son La in 2011-2012, and LABS in 2010-2012 to show that the variations of BB aerosol tracers such as PM2.5 K+, OC3, EC1-OP, and Levoglucosan were more stable than the other species for near-source BB aerosol and downstream LABS aerosol affected by BB plume. In addition, the proportion of NO3- in LABS PM2.5 during BB period was higher than that of Chiang Mai and Son La, which implies NO3- is transformed from long-range transport. The source contributions of LABS PM2.5 resolved from PMF shows that six major pollution types from high to low are BB mixing secondary aerosol (28.7 %), BB mixing soil dust (25.4 %), BB (17.6 %), BB _ dicarboxylates (12.0 %), Diesel emissions (10.0 %), and Sea salt (6.2 %). PMF source apportionment indicates 83.7% of PM2.5 mass concentration is contributed from BB for the airmasses under the influence of BB plume. This confirms the correctness of PMF source apportionment and accounts for BB plume mixing with other airmasses during transport to reach downstream LABS under the prevailing west wind. In contrast, secondary aerosol contributed more than other sources to PM2.5 to account for 70.6% during NBB period. In addition, the airmasses were mostly originated from ocean (including Pacific Ocean and South China Sea) but some mixed with marine and anthropogenic primary pollutants were transported from costline of China mainland through lower atmosphere to LABS. In summary, PM2.5 is abundant for near-BB source Son La aerosol. Moreover, PM2.5 is influenced more by BB activities when the air masses were from Indochina and anthropogenic sources affect PM2.5 more for air masses from South China. Ten years’s LABS aerosol observation data indicate that BB plume could mix with less other sources during long-range transport and NBB airmasses mainly contain secondary aerosol but might have mixed with marine and anthropogenic primary pollutants. |
