Gas exchanges between streams and atmosphere strongly impact biogeochemical cycles, yet their quantification in space and time remains challenging. We propose a new method to measure gas exchange rate coefficients in headwater streams. The method is based on simultaneous slug injections of a conservative tracer and a volatile tracer, coupled to in situ semicontinuous measurements. Its originality lies in the mathematical exploitation of the tracers' breakthrough curves. Taking advantage of the entire breakthrough curves, we infer the gas exchange rate coefficient from a comparative analysis of the shape of the volatile and the conservative breakthrough curves. Tests on synthetic datasets confirmed the validity of the mathematical framework for the whole range of gas exchange rate coefficients found in headwater streams. Field experiments further attested to the real‐world applicability of the method. Salt and helium injections were performed in a first‐order stream and the helium breakthrough curves were obtained using in situ membrane inlet mass spectrometry. This new method allows to determine the gas exchange rates directly in the field, without any external calibration of the data. Its fast implementation enables a wider spatial coverage of the measurements of gas exchange rates, and thus offers an opportunity to improve the large‐scale estimates of CO₂ emissions from headwater streams. More generally, our study highlights the informative potential of semicontinuous datasets and encourages further investigation of possible use of temporal signals.

中文翻译：

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一种基于团状注入和半连续测量来量化流中空气-水气体交换的新方法

溪流与大气之间的气体交换强烈影响着生物地球化学循环，但是它们在空间和时间上的量化仍然具有挑战性。我们提出了一种测量源头水流中气体交换率系数的新方法。该方法基于保守示踪剂和挥发性示踪剂的同时注入，并结合到原位半连续测量中。它的独创性在于对示踪剂突破曲线的数学利用。利用整个突破曲线，我们通过对挥发物和保守突破曲线的形状进行比较分析，推断出气体交换系数。对合成数据集的测试证实了该数学框架对于源头水流中发现的整个气体交换率系数范围的有效性。现场实验进一步证明了该方法在现实世界中的适用性。在一级流中进行盐和氦气注入，并使用原位膜入口质谱法获得氦气穿透曲线。这种新方法可以直接在现场确定气体交换速率，而无需对数据进行任何外部校准。它的快速实施使气体交换率测量的空间覆盖范围更广，从而为改进对二氧化碳的大规模估算提供了机会。无需对数据进行任何外部校准。它的快速实施使气体交换率测量的空间覆盖范围更广，从而为改进对二氧化碳的大规模估算提供了机会。无需对数据进行任何外部校准。它的快速实施使气体交换率测量的空间覆盖范围更广，从而为改进对二氧化碳的大规模估算提供了机会。₂源头水流的排放。更广泛地说，我们的研究突出了半连续数据集的信息潜力，并鼓励进一步研究时间信号的可能使用。