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  • American Society of Limnology and Oceanography  (2)
  • OceanObs'09  (2)
  • American Chemistry Society  (1)
  • 1
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    Using cavity ringdown spectroscopy for continuous monitoring of δ13C(CO2) and ƒCO2 in the surface ocean (2012)
    American Society of Limnology and Oceanography
    In:  Limnology and Oceanography: Methods, 10 . pp. 752-766.
    Details
    Publication Date: 2019-09-23
    Description: The role of the global surface ocean as a source and sink for atmospheric carbon dioxide and the flux strengths between the ocean and the atmosphere can be quantified by measuring the fugacity of CO2 (ƒCO2) as well as the dissolved inorganic carbon (DIC) concentration and its isotopic composition in surface seawater. In this work, the potential of continuous wave cavity ringdown spectroscopy (cw-CRDS) for autonomous underway measurements of ƒCO2 and the stable carbon isotope ratio of DIC [δ13C(DIC)] is explored. For the first time, by using a conventional air-sea equilibrator setup, both quantities were continuously and simultaneously recorded during a field deployment on two research cruises following meridional transects across the Atlantic Ocean (Bremerhaven, Germany–Punta Arenas, Chile). Data are compared against reference measurements by an established underway CO2 monitoring system and isotope ratio mass spectrometric analysis of individual water samples. Agreement within ΔƒCO2 = 0.35 μatm for atmospheric and ΔƒCO2 = 2.5 μatm and Δδ13C(DIC) =0.33‰ for seawater measurements have been achieved. Whereas “calibration-free” ƒCO2 monitoring is feasible, the measurement of accurate isotope ratios relies on running reference standards on a daily basis. Overall, the installed CRDS/equilibrator system was shown to be capable of reliable online monitoring of ƒCO2, equilibrium δ13C(CO2), δ13C(DIC), and pO2 aboard moving research vessels, thus making possible corresponding measurements with high spatial and temporal resolution.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.4319/lom.2012.10.752
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Sediment Trapping by Dams Creates Methane Emission Hot Spots (2013)
    American Chemistry Society
    In:  Environmental Science & Technology, 47 (15). pp. 8130-8137.
    Details
    Publication Date: 2019-09-24
    Description: Inland waters transport and transform substantial amounts of carbon and account for 18% of global methane emissions. Large reservoirs with higher areal methane release rates than natural waters contribute significantly to freshwater emissions. However, there are millions of small dams worldwide that receive and trap high loads of organic carbon and can therefore potentially emit significant amounts of methane to the atmosphere. We evaluated the effect of damming on methane emissions in a central European impounded river. Direct comparison of riverine and reservoir reaches, where sedimentation in the latter is increased due to trapping by dams, revealed that the reservoir reaches are the major source of methane emissions (0.23 mmol CH4 m–2 d–1 vs 19.7 mmol CH4 m–2 d–1, respectively) and that areal emission rates far exceed previous estimates for temperate reservoirs or rivers. We show that sediment accumulation correlates with methane production and subsequent ebullitive release rates and may therefore be an excellent proxy for estimating methane emissions from small reservoirs. Our results suggest that sedimentation-driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7%
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1021/es4003907
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Toward continuous monitoring of seawater 13CO2/12CO2 isotope ratio and pCO2: Performance of cavity ringdown spectroscopy and gas matrix effects (2010)
    American Society of Limnology and Oceanography
    In:  Limnology and Oceanography: Methods, 8 . pp. 539-551.
    Details
    Publication Date: 2019-09-23
    Description: The potential of a continuous wave cavity ringdown spectrometer for monitoring the isotope ratio 13CO2/12CO2 and the partial pressure pCO2 of CO2 dissolved in water was thoroughly analyzed by quantitative measurements. Running calibration gas standards under typical operation conditions, a relative accuracy of D(d13C[CO2]) = ±0.1‰ with 120 min averaging time has been demonstrated. Absolute uncertainties were determined to be D(d13C[CO2]) = ±0.2‰ and D(xCO2) = ±0.5 ppmv. No principle problems were encountered when using the instrument in combination with a water-air equilibration setup. By contrast, when performing measurements of CO2 in gas matrices with a composition different from that of ambient air, pressure broadening linewidth effects induced significant errors in both d13C(CO2) and xCO2 values. These effects, which compromise the accessible accuracy in environmental studies, can be quantitatively taken into account by using a spectroscopically based correction procedure. Relying on linewidth analysis, the instrument was shown to be capable of continuous and simultaneous measurement of d13C(CO2), pCO2, as well as water content and O2 supersaturation, and thus holds the potential for online monitoring of these quantities aboard research vessels.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.4319/lom.2010.8.539
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Optimization of a Membrane-Based NDIR Sensor for Dissolved Carbon Dioxide (2010)
    OceanObs'09
    In:  In: Proceedings of OceanObs’09: Sustained Ocean Observations and Information for Society Conference. , ed. by Hall, J., Harrison, D. E. and Stammer, D. ESA Publication, WPP-306 . OceanObs'09, Venice, Italy, pp. 1-4.
    Details
    Publication Date: 2012-07-06
    Description: The autonomous measurement of dissolved carbon dioxide (CO2) is of great and still increasing importance for addressing many scientific as well as socio-economic questions. Although there is a need for reliable, fast and easy-to-use instrumentation to measure the partial pressure of dissolved CO2 (pCO2) in situ, only few autonomous underwater sensors are available. Here we present the measuring principle as well as the latest development state of a commercial sensor (HydroC™/CO2, CONTROS Systems & Solutions GmbH, Kiel, Germany), which is optimized in a collaboration between the IFM-GEOMAR and the manufacturer. In situ tests and laboratory experiments are essential parts of the comprehensive optimization process, which aims at the successful autonomous long-term deployment on e.g. surface buoys, underwater observatories and floats.
    Type: Book chapter , NonPeerReviewed
    Format: text
    DOI: 10.5270/OceanObs09
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    OceanRep: Book chapter
  • 5
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    Sensors and Systems for in situ Observations of Marine Carbon Dioxide System Variables (2010)
    OceanObs'09
    In:  In: Proceedings of OceanObs’09: Sustained Ocean Observations and Information for Society. , ed. by Hall, J., Harrison, D. E. and Stammer, D. ESA Publication, WPP-306 . OceanObs'09, Venice, Italy, p. 8.
    Details
    Publication Date: 2012-07-06
    Description: Autonomous chemical sensors are required to document the marine carbon dioxide system's evolving response to anthropogenic CO2 inputs, as well as impacts on short- and long-term carbon cycling. Observations will be required over a wide range of spatial and temporal scales, and measurements will likely need to be maintained for decades. Measurable CO2 system variables currently include total dissolved inorganic carbon (DIC), total alkalinity (AT), CO2 fugacity (fCO2), and pH, with comprehensive characterization requiring measurement of at least two variables. These four parameters are amenable to in situ analysis, but sustained deployment remains a challenge. Available methods encompass a broad range of analytical techniques, including potentiometry, spectrophotometry, conductimetry, and mass spectrometry. Instrument capabilities (precision, accuracy, endurance, reliability, etc.) are diverse and will evolve substantially over the time that the marine CO2 system undergoes dramatic changes. Different suites of measurements/parameters will be appropriate for different sampling platforms and measurement objectives.
    Type: Book chapter , PeerReviewed
    Format: text
    DOI: 10.5270/OceanObs09.cwp.13
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    OceanRep: Book chapter
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