Among major volatiles released from the Earth’s interior, CO2 is an important target for the international community. The interest is keenly motivated by the contribution of CO2 in the Earth’s carbon budget and its role on past, current, and future climate dynamics. In particular, the isotopic signature of CO2 is fundamental to characterize the source of this gas and its evolution up to the atmosphere. The recent development of new laser-based techniques has marked an important milestone for the scientific community by favoring both high-frequency and in situ stable isotope measurements. Among them, the Delta Ray IRIS (Thermo Scientific Inc., Waltham, USA) is one of the most promising instruments thanks to its high precision, its limited interferences with other gaseous species (such as H2S and/or SO2), and its internal calibration procedure. These characteristics and the relative easiness to transport the Delta Ray IRIS have encouraged its use on the field to analyze volcanic CO2 emissions in recent years but often with distinct customized protocols of measurements. In this study, various tests in the laboratory and on the field have been performed to study the dependence of CO2 isotope measurements on analytical, instrumental, and environmental conditions. We emphasize the exceptional ability of the Delta Ray IRIS to perform isotope measurements for a large range of CO2 concentration (200 ppm–100%) thanks to a dilution system and to get a reliable estimation of the real CO2 content from the diluted one. These tests lead to point out major recommendations on the use of Delta Ray IRIS and allow the development of adapted protocols to analyze CO2 emissions like in volcanic environments.

中文翻译：

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使用同位素比红外光谱仪 (Delta Ray) 测量 CO2 中的稳定同位素的建议和协议：在埃特纳火山和斯特龙博利火山排放中的应用（意大利西西里岛）

在地球内部释放的主要挥发物中，二氧化碳是国际社会的重要目标。CO2 在地球碳收支中的贡献及其对过去、现在和未来气候动态的作用强烈激发了人们的兴趣。特别是，二氧化碳的同位素特征对于表征这种气体的来源及其向大气的演化至关重要。新的基于激光的技术的最近发展标志着科学界的一个重要里程碑，因为它有利于高频和原位稳定同位素测量。其中，Delta Ray IRIS（Thermo Scientific Inc.，Waltham，USA）是最有前途的仪器之一，因为它具有高精度、对其他气态物质（如 H2S 和/或 SO2）的干扰有限以及其内部校准程序。近年来，Delta Ray IRIS 的这些特性和相对易于运输的特点鼓励其在现场分析火山二氧化碳排放量，但通常采用独特的定制测量协议。在这项研究中，在实验室和现场进行了各种测试，以研究 CO2 同位素测量对分析、仪器和环境条件的依赖性。我们强调 Delta Ray IRIS 凭借稀释系统对大范围 CO2 浓度 (200 ppm–100%) 进行同位素测量的卓越能力，并从稀释系统中可靠地估计实际 CO2 含量。这些测试提出了使用 Delta Ray IRIS 的主要建议，并允许开发适用的协议来分析像火山环境中的 CO2 排放。