A fast and sensitive method for the continuous in situ determination of dissolved methane and its [delta]13C-isotope ratio in surface waters
A fast and sensitive method for the continuous determination of methane (CH4) and its stable carbon isotopic values (δ13C-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...
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| Hauptverfasser: | , , , , |
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| Dokumenttyp: | Article (Journal) |
| Sprache: | Englisch |
| Veröffentlicht: |
27 April 2018
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| In: |
Limnology and oceanography. Methods
Year: 2018, Jahrgang: 16, Heft: 5, Pages: 273-285 |
| ISSN: | 1541-5856 |
| DOI: | 10.1002/lom3.10244 |
| Online-Zugang: | Volltext Volltext 
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| Verfasserangaben: | Jan F. Hartmann, Torben Gentz, Amanda Schiller, Markus Greule, Hans-Peter Grossart, Danny Ionescu, Frank Keppler, Karla Martinez‐Cruz, Armando Sepulveda‐Jauregui, Margot Isenbeck‐Schröter |
| Zusammenfassung: | A fast and sensitive method for the continuous determination of methane (CH4) and its stable carbon isotopic values (δ13C-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 δ13C-CH4 with synthetic water standards. The detection limit of the M-CRDS for the simultaneous determination of CH4 and δ13C-CH4 is 3.6 nmol L−1 CH4. A measurement precision of CH4 concentrations and δ13C-CH4 in the range of 1.1%, respectively, 1.7‰ (1σ) and accuracy (1.3%, respectively, 0.8‰ [1σ]) was achieved for single measurements and averaging times of 10 min. The response time τ of 57 ± 5 s allow determination of δ13C-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 δ13C-CH4 (−35.2‰) 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 δ13C-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. |
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| Beschreibung: | Im Titel ist "delta" als griechischer Buchstabe dargestellt im Titel ist die Zahl "13" hochgestellt Gesehen am 05.09.2019 |
| Beschreibung: | Online Resource |
| ISSN: | 1541-5856 |
| DOI: | 10.1002/lom3.10244 |