Dome Fuji and NEEM ice cores, gas data (15N, 18O, O2/N2, Ar/N2, CH4, N2O, CO2, TAC)

Air in polar ice cores provides various information on past climatic and atmospheric changes. We developed a new method combining wet extraction, gas chromatography and mass spectrometry, for high-precision, simultaneous measurements of eight air components (CH4, N2O and CO2 concentrations, delta15N, delta18O, deltaO2/N2, deltaAr/N2 and total air content) from an ice core sample of ~60 g. The ice sample is evacuated for ~2 hours and melted under vacuum, and the released air is continuously transferred into a sample tube at 10 K within 10 minutes. The air is homogenized in the sample tube overnight, and split into two aliquots for mass spectrometric and gas chromatographic measurements. Cares are taken to minimize contamination of greenhouse gases with long evacuation time, consumption of oxygen during sample storage by passivation treatment on sample tubes, and fractionation of isotopic ratios with long homogenization time for splitting. Precisions are assessed by analysing standard gases with artificial ice, and by duplicate measurements of the Dome Fuji and NEEM ice cores. The overall reproducibility (one standard deviation) from duplicate ice-core analyses are 3.2 ppb, 2.2 ppb and 3.1 ppm for CH4, N2O and CO2 concentrations, 0.006, 0.010, 0.09 and 0.12 per mille for delta15N, delta18O, deltaO2/N2 and deltaAr/N2, and 0.67 mlSTP kg-1 for total air content, respectively. Our new method successfully combines the high-precision, small-sample and multiple-species measurements, with a wide range of applications for ice-core paleoenvironmental studies.极地冰芯中的空气可为古气候与古大气变化提供多维度信息。我们开发了一种结合湿法萃取、气相色谱与质谱联用的全新方法，可对约60克的冰芯样品中的8种空气组分实现高精度同步测量，涵盖甲烷（CH₄）、一氧化二氮（N₂O）、二氧化碳（CO₂）浓度，以及δ¹⁵N、δ¹⁸O、δO₂/N₂、δAr/N₂与总空气含量。 将冰样品抽真空约2小时后在真空环境下熔融，释放出的空气可在10分钟内以10开尔文（10 K）的低温被持续转移至样品管中。空气在样品管中静置过夜以实现均质化，随后被分为两份等分试样，分别用于质谱与气相色谱分析。 为最大限度降低污染风险，我们采取了多项管控措施：通过延长抽真空时间减少温室气体污染，对样品管进行钝化处理以避免样品储存过程中发生氧气消耗，同时缩短均质分流时长以抑制同位素比值的分馏效应。 我们通过使用人工冰分析标准气体，以及对富士穹顶（Dome Fuji）冰芯与NEEM冰芯开展重复测量，对本方法的精度进行了评估。冰芯样品重复分析的整体重现性（以单倍标准偏差计）如下：甲烷、一氧化二氮与二氧化碳浓度的重现性分别为3.2 ppb、2.2 ppb与3.1 ppm；δ¹⁵N、δ¹⁸O、δO₂/N₂与δAr/N₂的重现性分别为0.006‰、0.010‰、0.09‰与0.12‰；总空气含量的重现性为0.67 mlSTP kg⁻¹。 本全新方法成功实现了高精度、小样品量与多组分同步测量，可广泛应用于冰芯古环境研究领域。