Abstract High sensitivity field-based analysis of dissolved methane in surface water and groundwater is needed to monitor the environmental impacts of natural gas-field development and understand microbial carbon cycling in water bodies. A new analytical technique using a polymer membrane contactor coupled to a laser-based cavity ring-down spectrometer was developed and tested. By recirculating a water sample for approximately 10 mins, equilibrium was established between dissolved methane in the sample and methane in the measured gas phase according to Henry’s Law. The performance of the system was investigated by replicate analyses of several different water samples, spike recovery tests, comparison to analysis by head-space gas chromatography, and consideration of memory effects. The technique provided an adequate detection limit for the determination of natural background concentrations of methane in environmental waters and was approximately 28 times more sensitive than analysis by gas chromatography. The system is field-capable, simple to operate and calibrate, and takes advantage of the low-drift characteristics of the cavity ring-down spectrometer.

中文翻译：

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用于高灵敏度测定环境水中溶解甲烷的耦合聚合物膜平衡和腔衰荡光谱法

摘要 需要对地表水和地下水中的溶解甲烷进行高灵敏度的现场分析，以监测天然气田开发的环境影响并了解水体中的微生物碳循环。开发并测试了一种使用聚合物膜接触器与基于激光的腔衰荡光谱仪耦合的新分析技术。通过将水样再循环约 10 分钟，根据亨利定律，在样品中溶解的甲烷和测量气相中的甲烷之间建立了平衡。该系统的性能通过对几种不同水样的重复分析、加标回收率测试、与顶空气相色谱分析的比较以及记忆效应的考虑进行了研究。该技术为测定环境水中甲烷的天然本底浓度提供了足够的检测限，并且比气相色谱分析的灵敏度高约 28 倍。该系统具有现场能力，易于操作和校准，并利用了腔衰荡光谱仪的低漂移特性。