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| Titel |
CO2 consumption and bicarbonate fluxes by chemical weathering in North America. |
| VerfasserIn |
Nils Jansen, Jens Hartmann, Ronny Lauerwald |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042496
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| Zusammenfassung |
| Cations released by chemical weathering are mainly counterbalanced by atmospheric/soil
CO2 dissolved in water. Existing approaches to quantify CO2 consumption by chemical
weathering are mostly based on the parameters runoff and lithology. Land cover is not
implemented as predictor in existing regional or global scale models for atmospheric/soil
CO2 consumption.
Here, bicarbonate fluxes in North American rivers are quantified by an empirical forward
model using the predictors runoff, lithology and land cover. The model was calibrated on
chemical data from 338 river monitoring stations throughout North America. It was
extrapolated to the entire North American continent by applying the model equation spatially
explicitly to the geodata used for model calibration. Because silicate mineral weathering
derived bicarbonate in rivers originates entirely from atmospheric/soil CO2, but
carbonate mineral weathering additionally releases lithogenic bicarbonate, those
source minerals are distinguished to quantify the CO2 consumption by chemical
weathering.
Extrapolation of the model results in a total bicarbonate flux of 51 Mt C a-1 in North
America; 70% of which originate from atmospheric/soil CO2. On average, chemical
weathering consumes 2.64 t atmospheric/soil C km-2 a-1 (~ 30%-40% above
published world average values). For a given runoff and land cover, carbonate-rich
sedimentary rocks export the most bicarbonate. However, half of this is assumed to be of
lithogenic origin. Thus, the most atmospheric/soil CO2 per runoff is modeled to be
consumed by basic plutonics. The least bicarbonate is exported and the least CO2 is
consumed per runoff by weathering of metamorphic rocks. Of the distinguished different
land cover classes of which urban areas export the most bicarbonate for a given
lithology and runoff, followed by shrubs, grasslands and managed lands. For a given
runoff and lithology, the least bicarbonate is exported from areas with forested land
cover.
The model shows 1) that chemical weathering induced CO2 consumption in North
America is above world average, and 2) that some regions (e.g. the Rocky Mountains) show
extraordinary high CO2 consumption. 8% of the area of North America are responsible for
50% of the total bicarbonate flux and associated CO2 consumption by chemical weathering.
The successful implementation of land cover as predictor in the bicarbonate flux model of
North America allows the representation of biological factors which may be relevant for
processes in the critical zone. |
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