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| Titel |
Dynamics of greenhouse gases (CO2, CH4, N2O) along the Zambezi River and major tributaries, and their importance in the riverine carbon budget |
| VerfasserIn |
C. R. Teodoru, F. C. Nyoni, A. V. Borges, F. Darchambeau, I. Nyambe, S. Bouillon |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 8 ; Nr. 12, no. 8 (2015-04-24), S.2431-2453 |
| Datensatznummer |
250117911
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| Publikation (Nr.) |
 copernicus.org/bg-12-2431-2015.pdf |
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| Zusammenfassung |
| Spanning over 3000 km in length and with a catchment of
approximately 1.4 million km2, the Zambezi River is the fourth largest
river in Africa and the largest flowing into the Indian Ocean from the
African continent. We present data on greenhouse gas (GHG: carbon dioxide
(CO2), methane (CH4), and nitrous oxide (N2O)) concentrations
and fluxes, as well as data that allow for characterization of sources and dynamics
of carbon pools collected along the Zambezi River, reservoirs and several of
its tributaries during 2012 and 2013 and over two climatic seasons (dry and
wet) to constrain the interannual variability, seasonality and spatial
heterogeneity along the aquatic continuum. All GHG concentrations showed
high spatial variability (coefficient of variation: 1.01 for CO2, 2.65
for CH4 and 0.21 for N2O). Overall, there was no unidirectional
pattern along the river stretch (i.e., decrease or increase towards the
ocean), as the spatial heterogeneity of GHGs appeared to be determined
mainly by the connectivity with floodplains and wetlands as well as the presence
of man-made structures (reservoirs) and natural barriers (waterfalls,
rapids). Highest CO2 and CH4 concentrations in the main channel
were found downstream of extensive floodplains/wetlands. Undersaturated
CO2 conditions, in contrast, were characteristic of the surface waters
of the two large reservoirs along the Zambezi mainstem. N2O
concentrations showed the opposite pattern, being lowest downstream of the
floodplains and highest in reservoirs. Among tributaries, highest
concentrations of both CO2 and CH4 were measured in the Shire
River, whereas low values were characteristic of more turbid systems such as
the Luangwa and Mazoe rivers. The interannual variability in the Zambezi
River was relatively large for both CO2 and CH4, and
significantly higher concentrations (up to 2-fold) were measured during
wet seasons compared to the dry season. Interannual variability of N2O
was less pronounced, but higher values were generally found during the dry
season. Overall, both concentrations and fluxes of CO2 and CH4
were well below the median/average values for tropical rivers, streams and
reservoirs reported previously in the literature and used for global
extrapolations. A first-order mass balance suggests that carbon (C)
transport to the ocean represents the major component (59%) of the budget
(largely in the form of dissolved inorganic carbon, DIC), while 38% of
the total C yield is annually emitted into the atmosphere, mostly as
CO2 (98%), and 3% is removed by sedimentation in reservoirs. |
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