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| Titel |
Dynamic biogeochemical controls on river pCO2 under increasing impoundment: an example of the Yangtze River |
| VerfasserIn |
Shaoda Liu, Xi Xi Lu |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250122623
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| Publikation (Nr.) |
 EGU/EGU2016-1703.pdf |
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| Zusammenfassung |
| We highlight two aspects of the dynamic biogeochemical controls of riverine pCO2 in an increasingly impounded large subtropical river (the Yangtze River): the terrestrial dominance through internal respiration of terrestrially derived organic carbon and the influence of increased autotrophic activity in impounded areas on river pCO2. River pCO2 and total organic carbon (TOC) increase downstream on the mainstem (pCO2: 528–1703 µatm; TOC: 137–263 µmol/L) and vary significantly among tributaries (464–3300 µatm; TOC: 109–340 µmol/L). pCO2 displays larger spatial variability than temporal variability and is spatially correlated with river organic carbon across the river (p < 0.05–0.0001) (seasonal independent). pCO2 is also negatively correlated with dissolved oxygen (r2 = 0.46, p < 0.0001). Heterotrophic respiration of river organic carbon is concluded as an essential source of CO2 supersaturation and river heterotrophy. However, preliminary budgeting indicates that water column respiration alone cannot explain the magnitude of CO2 emission from the river, and significant benthic respiration and/or direct soil CO2 transport (e.g., via groundwater) (~ 80%) must exist to account for the discrepancy. The temporal and spatial distribution of POC compositional characteristics and chlorophyll a indicate the dominant control of terrestrial processes (e.g., organic matter transport and soil erosion) on the river pCO2 biogeochemistry, especially in warm seasons. Increased autotrophy and significant pCO2 decrease (> 60%) do occur in impounded areas (especially in nutrient-rich rivers), but the decrease is mostly temporal and regional (~ 8% of the data points are significant influenced, all from the upper reach and/or major tributaries). The paper concludes that terrestrial influence still dominate the pCO2 biogeochemistry in this increasingly intercepted and regulated river system. However, the effect of continuing river impounding and increased nutrients input is to be watched. |
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