| 摘要: | 揮發性有機化合物 VOCs (Volatile organic compounds)是影響空氣品質、生態健康和氣候的關鍵化學核心，透過連續監測東亞高山唯一背景站鹿林山(Lulin Atmospheric Background Station, LABS, 23.47°N, 120.87°E, 海拔高度 2862 m) 2013 年 11 月至 2025 年八月共近十三年的 VOCs，以中研院改良的 GC–MS/FID 進行分析，了解東亞地區 VOCs 的長期趨勢與特徵；挑選出 19 種代表鹿林山大氣背景 VOCs 濃度；以官能基區分為烷烴 8 種、烯烴4 種、炔類 1 種、芳香烴 7 種、含氧 VOCs (Oxygenated Volatile organic compounds) 4 種。
本研究採用 NOAA 全球監測實驗室（GML）發展之曲線擬合法（Curve
Fitting Method），將 VOCs 濃度序列分解為多項式趨勢及週期性調和項。由多項式趨勢線可明確區分各物種在長年間的趨勢變化，OVOCs 在 2014–2016 年間快速上升，於 2016 年達到高峰（約 0.8–0.85 ppbv），其後濃度持續下降，於 2021 年附近降至最低值（約 0.42 ppbv）。此後開始再次回升，至 2025 年趨勢線已顯示顯著上升至 1.4 ppbv 以上。Alkanes 則呈現溫和遞減趨勢，Aromatics、Alkenes 與 Acetylene 則波動變化小、長期趨勢相對平緩。
針對不同氣團來源，進一步以 HYSPLIT 後推軌跡分群分析，探討 VOCs
濃度及 ratio 特徵。研究發現，鹿林山各氣團來源（如西風帶、南海、東南亞半島等）在 VOCs 物種比例及濃度上差異顯著，特別是來自南海及東南亞的氣團，常伴隨高 OVOCs 與高 Alkanes 的相關性特徵，此現象與生質燃燒及長程傳輸有關。進一步分析顯示，烷類經大氣氧化產生的酮類（如
Acetone、MEK），因其大氣壽命較長，可隨遠距離傳輸累積，成為鹿林山
主要的OVOCs來源。這一現象突顯鹿林山高山背景站所觀測到的高OVOCs
特徵，實為氣團來源、排放型態與大氣反應性交互作用產生的結果，顯示鹿
林山大氣背景監測站在東亞地區氣團的特性。;Volatile organic compounds (VOCs) are key chemical species affecting air quality, ecosystem health, and climate. This study presents a comprehensive
twelve-year continuous observation (November 2013 to November 2024) of VOCs at the Lulin Atmospheric Background Station (LABS; 23.47°N, 120.87°E;
2,862 m a.s.l.), the only high-altitude background site in East Asia. VOCs were analyzed using a GC–MS/FID system optimized by Academia Sinica, with 19 representative VOC species selected to characterize the atmospheric background.
These species were classified by functional groups, including 8 alkanes, 4 alkenes,
1 alkyne, 7 aromatics, and 4 oxygenated VOCs (OVOCs).
We applied the curve fitting method developed by the NOAA Global Monitoring Laboratory (GML) to decompose VOC concentration time series into
polynomial trends and seasonal harmonics. The polynomial trends revealed distinct long-term changes: OVOCs exhibited a rapid increase from 2014 to 2016 followed by a continuous decline, reaching a minimum around 2021 , with trend
values exceeding 1.4 ppbv by 2025. Alkanes displayed a gradual decreasing trend throughout the study period, while aromatics, alkenes, and acetylene remained
relatively stable with minor fluctuations.
To investigate the influence of air mass origins, we employed HYSPLIT backward trajectory clustering to analyze VOC concentrations and characteristic
ratios by source region. Results showed significant differences in VOC iv composition and levels among various air mass types (e.g., westerlies, South
China Sea, Southeast Asia). Air masses from the South China Sea and Southeast Asia were frequently associated with high OVOCs/alkanes ratios and elevated secondary product concentrations, indicating influences from biomass burning and long-range transport. Further analysis suggested that ketones (such as acetone and MEK), produced via atmospheric oxidation of alkanes and characterized by
long atmospheric lifetimes, can accumulate during long-range transport and constitute the main OVOCs at Lulin.
These findings highlight that the elevated OVOCs observed at LABS are the
result of complex interactions among air mass origin, emission patterns, and
atmospheric processing. The results underscore the scientific importance of Lulin
as a regional background station for atmospheric monitoring and transboundary
pollution assessment in East Asia. |
