An intercomparison of oceanic methane and nitrous oxide measurements
<p>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 an...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-10-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/15/5891/2018/bg-15-5891-2018.pdf |
| Summary: | <p>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.</p> |
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| ISSN: | 1726-4170 1726-4189 |