Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 15, issue 19
Biogeosciences, 15, 5891-5907, 2018
https://doi.org/10.5194/bg-15-5891-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Biogeosciences, 15, 5891-5907, 2018
https://doi.org/10.5194/bg-15-5891-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 05 Oct 2018

Research article | 05 Oct 2018

An intercomparison of oceanic methane and nitrous oxide measurements

Samuel T. Wilson1, Hermann W. Bange2, Damian L. Arévalo-Martínez2, Jonathan Barnes3, Alberto V. Borges4, Ian Brown5, John L. Bullister6, Macarena Burgos1,7, David W. Capelle8, Michael Casso9, Mercedes de la Paz10,a, Laura Farías11, Lindsay Fenwick8, Sara Ferrón1, Gerardo Garcia11, Michael Glockzin12, David M. Karl1, Annette Kock2, Sarah Laperriere13, Cliff S. Law14,15, Cara C. Manning8, Andrew Marriner14, Jukka-Pekka Myllykangas16, John W. Pohlman9, Andrew P. Rees5, Alyson E. Santoro13, Philippe D. Tortell8, Robert C. Upstill-Goddard3, David P. Wisegarver6, Gui-Ling Zhang17, and Gregor Rehder12 Samuel T. Wilson et al.
  • 1University of Hawai'i at Manoa, Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), Honolulu, Hawai'i, USA
  • 2GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
  • 3Newcastle University, School of Natural and Environmental Sciences, Newcastle upon Tyne, UK
  • 4Université de Liège, Unité d'Océanographie Chimique, Liège, Belgium
  • 5Plymouth Marine Laboratory, Plymouth, UK
  • 6National Oceanic and Atmospheric Administration, Pacific Marine Environmental Laboratory, Seattle, Washington, USA
  • 7Universidad de Cádiz, Instituto de Investigaciones Marinas, Departmento Química-Física, Cádiz, Spain
  • 8University of British Columbia, Department of Earth, Ocean and Atmospheric Sciences, British Columbia, Vancouver, Canada
  • 9U.S. Geological Survey, Woods Hole Coastal and Marine Science Center, Woods Hole, USA
  • 10Instituto de Investigaciones Marinas, Vigo, Spain
  • 11University of Concepción, Department of Oceanography and Center for climate research and resilience (CR2), Concepción, Chile
  • 12Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, Germany
  • 13University of California Santa Barbara, Department of Ecology, Evolution, and Marine Biology, Santa Barbara, USA
  • 14National Institute of Water and Atmospheric Research (NIWA), Wellington, New Zealand
  • 15Department of Chemistry, University of Otago, Dunedin, New Zealand
  • 16University of Helsinki, Department of Environmental Sciences, Helsinki, Finland
  • 17University of China, Key Laboratory of Marine Chemistry Theory and Technology (MOE), Qingdao, China
  • acurrent address: Instituto Español de Oceanografía, Centro Oceanográfico de A Coruña, A Coruña, Spain

Abstract. Large-scale climatic forcing is impacting oceanic biogeochemical cycles and is expected to influence the water-column distribution of trace gases, including methane and nitrous oxide. Our ability as a scientific community to evaluate changes in the water-column inventories of methane and nitrous oxide depends largely on our capacity to obtain robust and accurate concentration measurements that can be validated across different laboratory groups. This study represents the first formal international intercomparison of oceanic methane and nitrous oxide measurements whereby participating laboratories received batches of seawater samples from the subtropical Pacific Ocean and the Baltic Sea. Additionally, compressed gas standards from the same calibration scale were distributed to the majority of participating laboratories to improve the analytical accuracy of the gas measurements. The computations used by each laboratory to derive the dissolved gas concentrations were also evaluated for inconsistencies (e.g., pressure and temperature corrections, solubility constants). The results from the intercomparison and intercalibration provided invaluable insights into methane and nitrous oxide measurements. It was observed that analyses of seawater samples with the lowest concentrations of methane and nitrous oxide had the lowest precisions. In comparison, while the analytical precision for samples with the highest concentrations of trace gases was better, the variability between the different laboratories was higher: 36% for methane and 27% for nitrous oxide. In addition, the comparison of different batches of seawater samples with methane and nitrous oxide concentrations that ranged over an order of magnitude revealed the ramifications of different calibration procedures for each trace gas. Finally, this study builds upon the intercomparison results to develop recommendations for improving oceanic methane and nitrous oxide measurements, with the aim of precluding future analytical discrepancies between laboratories.

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To determine the variability between independent measurements of dissolved methane and nitrous oxide, seawater samples were analyzed by multiple laboratories. The results revealed the influences of the different parts of the analytical process, from the initial sample collection to the calculation of the final concentrations. Recommendations are made to improve dissolved methane and nitrous oxide measurements to help preclude future analytical discrepancies between laboratories.
To determine the variability between independent measurements of dissolved methane and nitrous...
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