低濃度一氧化碳氣相層析自動監測方法之建構

Construction of an Automated GC Method for Background CO Measurement

歐陽長風(Chang-Feng Ouyang) ； 王家麟(Jia-Lin Wang) ； 林能暉(Neng-Huei Lin)

《環境保護》 30卷2期 (2007/12) Pp. 96-104

https://doi.org/10.30017/EP.200712.0004

摘要

本研究成功開發一套低成本、且適用於一氧化碳和甲烷背景值量測之全自動化層析系統。利用程序控制器對分離管柱直接電阻式升控溫，避免了使用商品化氣相層析儀的必要，不僅大幅縮小了分析系統體積，並使系統建購的成木降低，其加熱方式直接且省電，更新了以往對於氣相層析分析系統構造的傳統觀念，對於偏遠無人測站之使用更為有所助益。
利用氣相層析方法搭配鎳觸媒管的催化，將一氧化碳還原為甲烷，使高靈敏的火燄離子偵檢器偵測一氧化碳，本研究中並利用加裝於管柱後端的剪裁技術，成功地將不必要的氧氣峰切除，除在層析上簡化了圖譜外，且讓一氣化碳和甲烷的解析能力增強，順利達成調理管柱的要求，使分析的狀態維持在較佳，並再者，由於此技術也可以令非分析物之其餘高沸點物質不流經鎳觸煤管，而使鎳觸煤被毒化的可能比降低延長其壽命他化了分析系統的長期穩定性。
本研究成功地將所建立的分析系統即時觀測中大周界空氣，並且以採樣罐方式分析鹿林山背景空氣，2004年至2005年間統計114組空氣樣品，平均一氧化碳濃度為227.7±48.5ppb，並且發現一氧化碳存在春季高值及夏季低值的季節陸趨勢，根據逆軌跡資料推論春季多為柬南亞地區的生質燃燒排放，夏季則為海洋性的乾淨背景空氣，因此形成台灣背景一氧化碳之季節性變化。

關鍵字

一氧化碳 ； 背景值

並列摘要

An automated gas chromatography system was constructed to perform in situ measurement of atmospheric carbon monoxide and methane at background levels. While methane can be detected directly by flame ionization detection (FID), carbon monoxide however needs to be methanized by a nickel catalyst under hydrogen provision in order to be detected by FID with adequate sensitivity.
The design of the system involves several innovated features to save space, cost, and power consumption, pivotal to the deployment in an unattended remote monitoring station. First, pressure feedback to the capacitance monometer and the slightly heated sample loop ensure precise air sample loading, which largely control the overall uncertainty of carbon monoxide measurement. Second, to prevent oxygen and heavy residuals from causing unwanted oxidizing reactions and contamination of the nickel catalyst the post-column heart-cut technique was used to safe-guard and prolong the service time of the nickel catalyst tube.
In this study, in-sits, measurement of CO was conducted at NCU campus for 2 weeks. We also have analyzed a one-year CO flask data collected at Mt. Lulin from the end of 2004 to 2005 to investigate the seasonal variations. The average concentration of CO at Mt. Lulin was 227.7±48.5 ppb with a maximum level found in spring and a minimum level in summer. This was due to the air masses mainly came from Southeast Asia in spring, when biomass burning was rampant, but switched mainly to the Pacific marine origin for those of summer. The Pacific oceanic influences are considered as cleaner air masses compared to the continental outflows often carrying land based pollutants, which attributes to the lower level of CO in summer.

並列關鍵字

CO ； background level