Development of gas microanalysis method in ice cores

冰芯中过去20万年的大气成分信息存储在气泡和笼形水合物中，这些气泡和笼形水合物的尺寸小于或等于1 mm，为了精确解释大气成分信息，对分析方法的可靠性要求很高。本研究考虑到气泡向笼形水合物转变过程中气体分馏的影响，旨在发展一种测量局部N_2和O_2组成的方法。我们将显微拉曼散射方法应用于测量，并建立了笼形水合物晶体各向异性数据的校正方法。结果，我们成功地阐明了冰盖中的气体分馏过程。我们证明了显微拉曼散射法是一种可靠的方法来揭示单个笼形水合物中N_2/O_2比的分布。然而，为了保证气体成分的绝对精确度，这些数据应与化学分析获得的数据进行比较。我们还开发了一个系统的定量分析的气体使用气相色谱-质谱仪。

Information of the atmospheric composition over the past 200,000 years in ice cores is stored in air bubbles and clathrate hydrates, of which sizes are as small as 1mm or less. In order to interpret information of the atmospheric composition precisely, high reliability is required in the analysis method. In this study, considering gas fractionations caused by the transition process of the air bubble to the clathrate air-hydrates, we aimed at development of the method to measure the local composition of N_2 and O_2.We have applied a micro-Raman scattering method to the measurements, and we have established the method to correct the data for crystal anisotropy of the clathrate hydrates. As a result, we have successfully clarified the gas fractionation process in ice sheets. We proved that the micro-Raman scattering method is a highly reliable method to reveal the distribution of N_2/O_2 ratio in the individual clathrate hydrates. For the absolute precision of the gas compositions, however, the data should be compared with those obtained by the chemical analysis. We also developed a system of the quantitative analysis of gases using the gas chromatography I mass spectrometer.