本研究以自行設計組裝甲烷自動化分析裝置，自動量測大氣中之甲烷。利用溫度程序控制器與直接電阻加熱層析管柱做程式升溫，可解決層析在長期量測因高沸點物種在分子篩層析管柱的堆積而使感度下降之困擾，提供分析管柱快速升、降溫，並且能夠精確地控制分析管柱的溫度程式，使其具備GC的功能，但免除一般商業化GC因質量大而造成升降溫過慢的缺點，不但提升功能且節省了購買GC的成本。如此一來，也可避免使用heat-cut及backflush之技術，而需要一根預層析管柱與大量的載流氣體來去除高、低沸點物質的缺點。因此，在評估系統效能時，於濃度趨於1.8ppmv下，其精確度(n=47)在0.20%以下，且線性關係更佳於0.9990。 利用甲烷自動化系統分別在不同季節下對大氣中甲烷進行連續性監測，發現甲烷濃度的變化能夠靈敏的指示輻射冷卻的現象，且兩倍甲濃度的增加也反應出此效應的強弱。 A fully automated gas chromatographic system was constructed to perform in-situ continuous measurement of atmospheric methane. To reduce cost, this system avoided the use of a conventional GC, instead a direct resistive heating of the molecular sieve packed column with precise temperature control was integrated to permit rapid temperature ramping and cooling and, therefore, shorter turn-over time. No heat-cut or back-flush of high boiling residue was necessary, which often requires a pre-column and additional flow of carrier gas. The precision (n=47) of the system was better than 0.20 % at near background level (1.8 ppmv), and the linearity of the system was better than 0.9990. The system was deployed in the field to perform continuous unattended measurement of ambient methane in different seasons. The fast cycled measurement facilitated detailed observation of diurnal concentration variation caused by radiational inversion, which could induce nearly 2 fold of concentration enhancement.
