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| Titel |
Quantifying the magnitude and spatiotemporal variation of aquatic CO2 fluxes in a sub-tropical karst catchment, Southwest China |
| VerfasserIn |
Hu Ding, Susan Waldron, Jason Newton, Mark H. Garnett |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250150810
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| Publikation (Nr.) |
 EGU/EGU2017-15319.pdf |
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| Zusammenfassung |
| The role played by rivers in regional and global C budgets is receiving increasing attention. A
large portion of the carbon transported via inland waters is returned to the atmosphere by
carbon dioxide evasion from rivers and lakes. Karst landscapes represent an important C store
on land, and are also considered to play an important role in climate regulation by consuming
atmospheric CO2 during chemical weathering. However, we cannot be certain how effective
this sink is if we do not know how efficiently the rivers draining karst landscapes remobilise
weathered C to the atmosphere as CO2. pCO2 in karst waters is generally greater than
atmospheric equilibrium, indicating that there can be a net CO2 efflux to the atmosphere.
However, measurement confirming this and quantifying flux rates has been rarely
conducted.
Using a floating chamber method, in 2016 we directly measured CO2 fluxes from
spatially distributed freshwaters (springs, sinkholes, streams and reservoirs/ponds) in the
Houzhai Catchment, a karst region in SW China. Fluxes ranged from -0.5 to +267.4 μmol
CO2 m−2s−1, and most sites showed seasonal variations with higher CO2 efflux rates in the
wet (April - September) than dry season (October - March). There was a significant positive
relationship between CO2 efflux and flow velocity, indicating that hydraulic controls on
CO2 efflux from flowing water are important, while for water with little movement
(sinkholes and reservoirs/ponds), pCO2 appears a more important control on efflux
rates.
Conditions similar to this study area may exist in many sub-tropical rivers that
drain karst landscapes in South China. These waters are rich in DIC which can
be an order of magnitude greater than some non-karst catchments. The large DIC
pool has the potential to be a considerable source of free CO2 to the atmosphere.
Considering that carbonate lithology covers a significant part of the Earth’s surface, CO2
evasion in fluvial water from these regions is expected to contribute notably to the
annual carbon dioxide release from global freshwater systems, thus must be better
represented in global spatial analyses of CO2 evasion. This research advances this need. |
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