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提供过去气候与大气变化的各类信息。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克的冰芯样品同时高精度测量八种空气组分：甲烷（CH4）、一氧化二氮（N2O）与二氧化碳（CO2）浓度，以及δ15N、δ18O、δO2/N2、δAr/N2和总空气含量。该冰样先抽真空约2小时，随后在真空环境下熔融，释放出的空气在10分钟内被连续转移至10 K的样品管中。空气在样品管中静置过夜以实现均质化，之后分装为两份等分试样，分别用于质谱与气相色谱分析。为最大限度降低各类污染与干扰风险，我们采取了针对性防控手段：通过优化抽真空时长抑制温室气体污染，对样品管实施钝化处理以避免样品储存过程中发生氧气消耗，同时缩短均质分装时长以防止同位素比值出现分馏效应。方法的精密度通过两种方式验证：一是使用人工冰与标准气体开展分析，二是对富士穹顶冰芯（Dome Fuji）与NEEM冰芯进行重复测量。冰芯样品重复测量的总重现性（单倍标准偏差）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 标准温度压力毫升每千克（mlSTP kg⁻¹）。我们开发的新方法成功实现了高精度、小样本量与多组分同步测量，可广泛应用于冰芯古环境研究领域。