Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 8
Biogeosciences, 14, 2183–2198, 2017
https://doi.org/10.5194/bg-14-2183-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 14, 2183–2198, 2017
https://doi.org/10.5194/bg-14-2183-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 28 Apr 2017

Research article | 28 Apr 2017

Dynamics of riverine CO2 in the Yangtze River fluvial network and their implications for carbon evasion

Lishan Ran1, Xi Xi Lu2,3, and Shaoda Liu2 Lishan Ran et al.
  • 1Department of geography, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China
  • 2Department of geography, National University of Singapore, 117570, Singapore
  • 3College of Environment & Resources, Inner Mongolia University, Hohhot, 010021, China

Abstract. Understanding riverine carbon dynamics is critical for not only better estimates of various carbon fluxes but also evaluating their significance in the global carbon budget. As an important pathway of global land–ocean carbon exchange, the Yangtze River has received less attention regarding its vertical carbon evasion compared with lateral transport. Using long-term water chemistry data, we calculated CO2 partial pressure (pCO2) from pH and alkalinity and examined its spatial and temporal dynamics and the impacts of environmental settings. With alkalinity ranging from 415 to > 3400 µeq L−1, the river waters were supersaturated with dissolved CO2, generally 2–20-fold the atmospheric equilibrium (i.e., 390 µatm). Changes in pCO2 were collectively controlled by carbon inputs from terrestrial ecosystems, hydrological regime, and rock weathering. High pCO2 values were observed spatially in catchments with abundant carbonate presence and seasonally in the wet season when recently fixed organic matter was exported into the river network. In-stream processing of organic matter facilitated CO2 production and sustained the high pCO2, although the alkalinity presented an apparent dilution effect with water discharge. The decreasing pCO2 from the smallest headwater streams through tributaries to the mainstem channel illustrates the significance of direct terrestrial carbon inputs in controlling riverine CO2. With a basin-wide mean pCO2 of 2662 ± 1240 µatm, substantial CO2 evasion from the Yangtze River fluvial network is expected. Future research efforts are needed to quantify the amount of CO2 evasion and assess its biogeochemical implications for watershed-scale carbon cycle. In view of the Yangtze River's relative importance in global carbon export, its CO2 evasion would be significant for global carbon budget.

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Understanding riverine carbon dynamics is critical for not only better estimates of various carbon fluxes but also evaluating their significance in the global carbon budget. In this study, we examined the dynamics of riverine CO2 partial pressure (pCO2) in the Yangtze River basin. Its pCO2 was characterized by strong spatial and temporal variations. With a basin-wide mean pCO2 of 2662(±1240) μatm, substantial CO2 evasion is expected. Future efforts are needed to evaluate its significance.
Understanding riverine carbon dynamics is critical for not only better estimates of various...
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