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An intercomparison of oceanic methane and nitrous oxide measurements

October 5, 2018

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.

Publication Year 2018
Title An intercomparison of oceanic methane and nitrous oxide measurements
DOI 10.5194/bg-15-5891-2018
Authors Samuel Wilson, Hermann Bange, Damian Arevalo-Martinez, Jonathan Barnes, Alberto V. Borges, Ian Brown, John Bullister, Macarena Burgos, David Capelle, Michael Casso, Mercedes de la Paz, Laura Farias, Lindsay Fenwick, Sara Ferron, Gerardo Garcia, MIchael Glockzin, David Karl, Annette Kock, Sarah Laperriere, Cliff S. Law, Cara Manning, Andrew Marriner, Jukka-Pekka Myllykangas, John Pohlman, Andrew Rees, Allison Santoro, Philippe Tortll, Robert C. Upstill-Goddard, David Wisegarver, Gui-Ling Zhang, Gregor Rehder
Publication Type Article
Publication Subtype Journal Article
Series Title Biogeosciences
Index ID 70225826
Record Source USGS Publications Warehouse
USGS Organization Woods Hole Coastal and Marine Science Center