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| Titel |
Temporal variability and spatial dynamics of CO2 and CH4 concentrations and fluxes in the Zambezi River system |
| VerfasserIn |
Cristian Teodoru, Alberto Borges, Steven Bouillon, Frank Nyoni, Imasiku Nyambe |
| 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 |
250090105
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| Publikation (Nr.) |
 EGU/EGU2014-4321.pdf |
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| Zusammenfassung |
| Spanning over 2900 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. Yet, there is surprisingly little or no information on carbon
(C) cycling in this large river system. As part of a broader study on the riverine
biogeochemistry in the Zambezi River basin, we present here mainstream dissolved CO2 and
CH4 data collected during 2012 and 2013 over two climatic seasons (dry and wet) to
constrain the interannual variability, seasonality and spatial heterogeneity of partial pressure
of CO2 (pCO2) and CH4 concentrations and fluxes along the aquatic continuum, in
relation to physico-chemical parameters (temperature, conductivity, oxygen, and
pH) and various carbon pools (dissolved and particulate, organic and inorganic
carbon, total alkalinity, primary production, respiration and net aquatic metabolism).
Both pCO2 and CH4 variability was high, ranging from minimal values of 150
ppm and 7 nM, respectively, mainly in the two large reservoirs (the Kariba and the
Cabora Bassa characterized by high pH and oxygen and low DOC), up to maximum
values of 12,500 ppm and 12,130 nM, CO2 and CH4, respectively, mostly below
floodplains/wetlands (low pH and oxygen levels, high DOC and POC concentrations). The
interannual variability was relatively large for both CO2 and CH4 (mean pCO2: 2350
ppm in 2013 vs. 3180 ppm in 2013; mean CH4: 600 nM in 2012 vs. 1000 nM in
2013) and significantly higher (up to two fold) during wet season compared to dry
season closely linked to distinct seasonal hydrological characteristics. Overall,
no clear pattern was observed along the longitudinal gradient as river CO2 and
CH4 concentrations are largely influenced by the presence of floodplains/wetlands,
anthropogenic reservoirs or natural barriers (waterfalls/ rapids). Following closely the
concentration patterns, river CO2 and CH4 mean fluxes of 3440 mg C-CO2 m-2 d-1
and 50 mg C-CH4 m-2 d-1, respectively, were well within the range of literature
data for tropical river systems, while the two reservoirs were a sink of atmospheric
CO2 (-240 mg C-CO2 m-2 d-1) and a low CH4 source (4 mg C-CH4 m-2 d-1). |
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