气袋和注射器保存不同浓度甲烷气体的时效分析

气体样品的甲烷(CH4)浓度在取样后往往不能立即测定,需用密封性容器进行保存。本研究调查了保存时间(0、12、24、48、360、720 h)和容器类型(铝箔气袋和注射器)对不同浓度(高:101.9μmol·mol-1、中:8.34μmol·mol-1、低:1.13μmol·mol-1和大气:2.12μmol·mol-1)CH4气体的影响。结果发现,两种容器中的低浓度样品在保存48 h内CH4值无明显变化,而中、高浓度样品在保存24 h后显著低于立即测定值(0 h,P<0.05)。保存15天(360 h)后,中、高浓度样品的CH4值比立即测定值减少17%~28%(气袋)和37%~38%(注射器),而低浓度样品比立即测定值增加28%(气袋)和38%(注射器),表明两种容器都不适合用来长期保存CH4样品。不同浓度样品的CH4值均随保存时间呈线性变化,其变化速率可用样品-大气间的CH4浓度差线性方程拟合,拟合度达99%以上。这些高拟合度线性方程可用于推算样品的初始浓度。

Storing Duration of Methane Gas Samples about Different Concentrations in Gas Bags and Syringes

Methane(CH4)concentration of gas samples can not be measured immediately after sampling,and must be stored in sealed containers.The effects of storage time(0,12,24,48,360 and 720 h)and container types(aluminum foil bags and syringes)on CH4 gas with different concentrations(high:101.9μmol·mol-1,medium:8.34μmol·mol-1,low:1.13μmol·mol-1,air:2.12μmol·mol-1)were investigated.The results showed that the CH4 values of the low concentration samples in the two kinds of containers had no obvious change within 48 h,while the CH4 values of the medium and high concentration samples stored for 24 h were significantly lower than those measured immediately(0 h,P<0.05).After storage for 15 days(360 h),the CH4 values of medium and high concentration samples decreased by 17%~28%(gas bags)and 37%~38%(syringes)compared with the immediately measured values,while increased by 28%(gas bags)and 38%(syringes)in low concentration standards,indicating that both containers are not suitable for long-term storage of CH4 samples.CH4 values of samples with different concentrations changed linearly with storage time,and the change rates can be linearly fitted by the CH4 concentration difference between samples and atmosphere(with the fitting degree over 99%).These highly fitted equations can be used to estimate the initial concentration of samples.