Dissolved gas concentrations in surface waters can have sharp gradients across marine and freshwater environments, which often prove challenging to capture with analytical measurement. Collecting discrete samples for laboratory analysis provides accurate results, but suffers from poor spatial resolution. To overcome this limitation, water equilibrators and gas membrane contactors (GMCs) have been used for the automated underway measurement of dissolved gas concentrations in surface water. However, while water equilibrators can provide continuous measurements, their analytical response times to changes in surface water concentration can be slow, lasting tens of minutes. This leads to spatial imprecisions in the dissolved gas concentration data. Conversely, while GMCs have proven to have much faster analytical response times, often lasting only a few minutes or less, they suffer from poor accuracy and thus require routine calibration. Here we present an analytical system for the high accuracy and high precision spatial mapping of dissolved methane concentration in surface waters. The system integrates a GMC with a cavity ringdown spectrometer for fast analytical response times, with a calibration method involving two Weiss‐style equilibrators and discrete measurements in vials. Data from both the GMC and equilibrators are collected simultaneously, with discrete vial samples collected periodically throughout data collection. We also present a mathematical algorithm integrating all data collected for the routine calibration of the GMC dataset. The algorithm facilitates comparison between the GMC and equilibrator datasets despite the substantial differences in response times (0.7–2.1 and 4.1–17.6 min, respectively). This measurement system was tested with both systematic laboratory experiments and field data collected on a research cruise along the US Atlantic margin. Once calibrated, this system identified numerous sharp peaks of dissolved methane concentration in the US Atlantic margin dataset that would be poorly resolved, or outright missed with previous measurement techniques. Overall, the precision and accuracy for the technique presented here were determined to be 11.2% and 10.4%, respectively, the operating range was 0–1000 ppm methane, and the e‐folding response time to changes in dissolved methane concentration was 0.7–2.1 min.

中文翻译：

---

开发具有集成校准功能的快速响应系统，用于地表水中溶解甲烷浓度的高分辨率绘图

地表水中的溶解气体浓度在海洋和淡水环境中可能具有急剧的梯度，这通常很难通过分析测量来捕获。收集离散样本进行实验室分析可以提供准确的结果，但空间分辨率较差。为了克服这一限制，水平衡器和气膜接触器 (GMC) 已用于自动测量地表水中溶解气体的浓度。然而，虽然水平衡器可以提供连续测量，但它们对地表水浓度变化的分析响应时间可能很慢，可持续数十分钟。这导致溶解气体浓度数据的空间不精确。相反，虽然 GMC 已被证明具有更快的分析响应时间（通常仅持续几分钟或更短），但它们的精度较差，因此需要进行常规校准。在这里，我们提出了一种用于地表水中溶解甲烷浓度的高精度和高精度空间绘图的分析系统。该系统将 GMC 与腔衰荡光谱仪集成在一起，以实现快速分析响应时间，并采用涉及两个 Weiss 式平衡器和小瓶中离散测量的校准方法。来自 GMC 和平衡器的数据是同时收集的，在整个数据收集过程中定期收集离散的小瓶样品。我们还提出了一种数学算法，集成了为 GMC 数据集的常规校准而收集的所有数据。尽管响应时间存在显着差异（分别为 0.7-2.1 分钟和 4.1-17.6 分钟），该算法还是有利于 GMC 和平衡器数据集之间的比较。该测量系统通过系统的实验室实验和沿美国大西洋边缘的研究巡航收集的现场数据进行了测试。经过校准后，该系统在美国大西洋边缘数据集中识别出许多溶解甲烷浓度的尖锐峰值，而以前的测量技术很难解决这些峰值，或者完全错过这些峰值。总体而言，本文介绍的技术的精密度和准确度分别确定为 11.2% 和 10.4%，操作范围为 0-1000 ppm 甲烷，并且e‐溶解甲烷浓度变化的折叠响应时间为 0.7-2.1 分钟。