 |
| Titel |
Equilibrator-based measurements of dissolved nitrous oxide in the surface ocean using an integrated cavity output laser absorption spectrometer |
| VerfasserIn |
I. Grefe, J. Kaiser |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1812-0784
|
| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 10, no. 3 ; Nr. 10, no. 3 (2014-06-19), S.501-512 |
| Datensatznummer |
250117005
|
| Publikation (Nr.) |
 copernicus.org/os-10-501-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| Dissolved nitrous oxide (N2O) concentrations are usually determined by
gas chromatography (GC). Here we present laboratory tests and initial field
measurements using a novel setup comprising a commercially available
laser-based analyser for N2O, carbon monoxide and water vapour coupled
to a glass-bed equilibrator. This approach is less labour-intensive and
provides higher temporal and spatial resolution than the conventional GC
technique. The standard deviation of continuous equilibrator or atmospheric
air measurements was 0.2 nmol mol−1 (averaged over 5 min). The
short-term repeatability for reference gas measurements within 1 h of
each other was 0.2 nmol mol−1 or better. Another indicator of the
long-term stability of the analyser is the standard deviation of the
calibrated N2O mole fraction in marine air, which was between 0.5 and
0.7 nmol mol−1. The equilibrator measurements were compared with
purge-and-trap gas chromatography–mass spectrometry (GC-MS) analyses of
N2O concentrations in discrete samples from the Southern Ocean and
showed agreement to within the 2% measurement uncertainty of the GC-MS
method. The equilibrator response time to concentration changes in water was
from 142 to 203 s, depending on the headspace flow rate. The system was tested at
sea during a north-to-south transect of the Atlantic Ocean. While the
subtropical gyres were slightly undersaturated, the equatorial region was a
source of nitrous oxide to the atmosphere, confirming previous findings
(Forster et al., 2009). The ability to measure at high temporal and spatial
resolution revealed submesoscale variability in dissolved N2O
concentrations. Mean sea-to-air fluxes in the tropical and subtropical
Atlantic ranged between −1.6 and 0.11 μmol m−2 d−1 and
confirm that the subtropical Atlantic is not an important source region for
N2O to the atmosphere, compared to global average fluxes of 0.6–2.4 μmol m−2 d−1. The system can be easily modified for
autonomous operation on voluntary observing ships (VOS). Future work should
include an interlaboratory comparison exercise with other methods of
dissolved N2O analyses. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|