甲烷自動化分析系統之建立與大氣連續量測

本研究針對大氣中甲烷開發一套自動化連續分析系統，利用個人電腦精確的控制進樣系統與分析流程，有效提高精確度與穩定度。此系統利用預先設計時間序列控制電驛卡上指定之電驛以驅動電磁閥門與轉動氣動閥門進行閥門的開關，完成清淨管路、進樣、分離、偵測等分析流程。同時為了使量測數據更為精確，在進樣體積上連通一電容氣壓計以反饋迴路精確控制進樣閥門開關，使進樣壓力能夠依照壓力設定點精確控制進樣壓力。在系統效能評估上我們利用此系統對校園大氣進行了大約三週的全天候連續量測，每次量測間隔為一小時，發現在系統穩定的情况下觀測到甲烷濃度隨時間呈現日夜週期性變化，並與氣象條件有密切關聯。

關鍵字

自然化分析系統；火焰離子化偵測器；周期性變化；幅射逆溫

並列摘要

An automated gas chromatographic system was constructed for continuous measurements atmospheric methane. Analytical steps were controlled by a Personal computer with prescribed commands to ensure highly reproducible measurements and long term stability. Those time series commands controlled 5 electrical relays on a relay board, which in turn triggered the solenoid valves and, subsequently two switching valves and three pneumatic shut-off valves for analytical steps involving sample loading, flushing, pumping, and sample injection, etc. A capacitance pressure gauge was installed with a build-in set point relay connected in series with one of the 5 relays to provide precise sample loading. The chromatography employed a packed column built in-house and a domestically made flame ionization detector. To evaluate the overall performance, we deployed this system on the NCU campus for three weeks of continuous hourly measurement of methane in May with time resolution of 1 hour. Distinct diurnal cycles of methane were observed with mixing ratios peaking in the late evening or at dawn, and becoming low or even close to the background values in the afternoon. The diurnal cycles were mainly caused by the radiative cooling plus stable air conditions normally observed in May. A sharp contrast of no apparent diurnal variations was noticed for the days with significant precipitation and strong wind.

並列關鍵字

Automated gas chromatographic system ； Flame ionigation detector ； Diurnal cycle ； Radiation inversion

國際替代計量

甲烷自動化分析系統之建立與大氣連續量測

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