- A fast and sensitive method for the continuous determination of methane (CH4) and its stable carbon isotopic values (delta C-13-CH4) in surface waters was developed by applying a vacuum to a gas/liquid exchange membrane and measuring the extracted gases by a portable cavity ring-down spectroscopy analyser (M-CRDS). The M-CRDS was calibrated and characterized for CH4 concentration and delta C-13-CH4 with synthetic water standards. The detection limit of the M-CRDS for the simultaneous determination of CH4 and delta C-13-CH4 is 3.6 nmol L-1 CH4. A measurement precision of CH4 concentrations and delta C-13-CH4 in the range of 1.1%, respectively, 1.7 parts per thousand (1 sigma) and accuracy (1.3%, respectively, 0.8 parts per thousand [1 sigma]) was achieved for single measurements and averaging times of 10 min. The response time tau of 57 +/- 5 s allow determination of delta C-13-CH4 values more than twice as fast than other methods. The demonstrated M-CRDS method was applied and tested for Lake Stechlin (Germany) and compared with theA fast and sensitive method for the continuous determination of methane (CH4) and its stable carbon isotopic values (delta C-13-CH4) in surface waters was developed by applying a vacuum to a gas/liquid exchange membrane and measuring the extracted gases by a portable cavity ring-down spectroscopy analyser (M-CRDS). The M-CRDS was calibrated and characterized for CH4 concentration and delta C-13-CH4 with synthetic water standards. The detection limit of the M-CRDS for the simultaneous determination of CH4 and delta C-13-CH4 is 3.6 nmol L-1 CH4. A measurement precision of CH4 concentrations and delta C-13-CH4 in the range of 1.1%, respectively, 1.7 parts per thousand (1 sigma) and accuracy (1.3%, respectively, 0.8 parts per thousand [1 sigma]) was achieved for single measurements and averaging times of 10 min. The response time tau of 57 +/- 5 s allow determination of delta C-13-CH4 values more than twice as fast than other methods. The demonstrated M-CRDS method was applied and tested for Lake Stechlin (Germany) and compared with the headspace-gas chromatography and fast membrane CH4 concentration methods. Maximum CH4 concentrations (577 nmol L-1) and lightest delta C-13-CH4 (-35.2 parts per thousand) were found around the thermocline in depth profile measurements. The M-CRDS-method was in good agreement with other methods. Temporal variations in CH4 concentration and delta C-13-CH4 obtained in 24 h measurements indicate either local methane production/oxidation or physical variations in the thermocline. Therefore, these results illustrate the need of fast and sensitive analyses to achieve a better understanding of different mechanisms and pathways of CH4 formation in aquatic environments.…
MetadatenAuthor details: | Jan F. HartmanORCiD, Torben Gentz, Amanda Schiller, Markus GreuleORCiD, Hans-Peter GrossartORCiDGND, Danny Ionescu, Frank KepplerORCiD, Karla Martinez-Cruz, Armando Sepulveda-JaureguiORCiD, Margot Isenbeck-Schroeter |
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DOI: | https://doi.org/10.1002/lom3.10244 |
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ISSN: | 1541-5856 |
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Title of parent work (English): | Limnology and Oceanography-methods |
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Publisher: | Wiley |
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Place of publishing: | Hoboken |
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Publication type: | Article |
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Language: | English |
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Date of first publication: | 2018/04/27 |
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Publication year: | 2018 |
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Release date: | 2021/12/06 |
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Volume: | 16 |
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Issue: | 5 |
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Number of pages: | 13 |
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First page: | 273 |
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Last Page: | 285 |
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Funding institution: | German Research Foundation (DFG)German Research Foundation (DFG) [KE 884/8-1, KE 884/8-2, GR1540/21-1, GR1540/23-1]; Conacyt-MexicoConsejo Nacional de Ciencia y Tecnologia (CONACyT) [233369, 232083] |
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Organizational units: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Geowissenschaften |
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DDC classification: | 5 Naturwissenschaften und Mathematik / 55 Geowissenschaften, Geologie / 550 Geowissenschaften |
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Peer review: | Referiert |
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Publishing method: | Open Access / Hybrid Open-Access |
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License (German): | CC-BY-NC-ND - Namensnennung, nicht kommerziell, keine Bearbeitungen 4.0 International |
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