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| Titel |
Seasonal, inter-annual and decadal changes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in the Scheldt estuary (Belgium, The Netherlands) |
| VerfasserIn |
Alberto V. Borges, Jack J. B. Middelburg, Lei Chou, Jacco Kromkamp, Marco Houtekamer, Jérôme Harlay |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094916
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| Publikation (Nr.) |
 EGU/EGU2014-10351.pdf |
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| Zusammenfassung |
| We carried out monthly cruises to study the seasonal and spatial variations of the partial
pressure of carbon dioxide CO2 (pCO2), methane (CH4) and nitrous oxide (N2O)
concentrations in the Scheldt estuary, a strongly human impacted system located in Belgium
and the Netherlands. This survey was initiated in 2008 for pCO2, and from 2009 onwards for
methane (CH4) and nitrous oxide (N2O). In the lower estuary, pCO2 strongly decreased and
oxygen saturation level (%O2) strongly increased during the spring phytoplankton bloom. In
the upper estuary, two yearly maxima of pCO2 coinciding with minima of %O2
occurred in spring and fall due to enhanced nitrification and/or net heterotrophy. In
the upper estuary, pCO2 decreased in winter due to lower temperature (affecting
solubility and inhibiting biological activity). pCO2 also decreased in summer due
to increase in primary production and decrease of net heterotrophy. In the upper
estuary, maxima of CH4 were observed in winter due to enhanced river inputs (high
discharge) while in the lower estuary higher CH4 was observed in summer. This
was probably due to inputs of CH4 from inter-tidal areas at the mouth of estuary
that increased in summer due to higher temperatures and higher organic matter
availability. N2O also showed higher values during winter in the upper estuary, but in
summer N2O was low in the lower estuary due to decreased solubility due to higher
temperature. During winter 2009, extremely high N2O values were observed in the
upper estuary, up to 3257 nM (23738% saturation). This was related to the problems
encountered by the Brussels North waste water treatment plant (WWTP) in late
2009. One of the collectors of the station was shut down in 25 November 2009, and
by 8 December 2009, the whole WWTP was shut down and the waste-water was
delivered directly to the Rupel. Extremely high N2O values were observed in the upper
estuary on 7 December 2009, and abnormally high N2O values (compared to other
years) persisted until April 6 2010. The comparison of present day N2O values with
historical data obtained in 1993-1997 and 1978 shows a spectacular decrease of
N2O levels from maximal values of about 350 nmol L-1 in the 1990’s to 50 nmol
L-1 in 2009-2012. This decrease reflects the collapse of NH4+ concentrations
in the estuary due to the overall improvement of water quality in relation to the
implementation of WWTPs, leading to a decrease of nitrification rates. The maximum of
N2O concentration in 1978 was located between salinities 10-15, in the 1990’s it was
located between salinities 2 and 5, and nowadays it is located at salinities < 2.5. This
suggests that the maximum of nitrification has migrated upstream in the estuary. |
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