Diagnosis of river basins as CO2 sources or sinks subject to sediment movement

Authors

  • Yao Yue,

    1. The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing, P. R. China
    2. Department of Environmental Engineering, Peking University, P. R. China
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  • Jinren Ni,

    Corresponding author
    1. The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing, P. R. China
    • Department of Environmental Engineering, Peking University, P. R. China
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  • Alistair G. L. Borthwick,

    1. Department of Civil and Environmental Engineering, University College Cork, Ireland
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  • Chiyuan Miao

    1. State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University, P. R. China
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Jinren Ni, Department of Environmental Engineering, Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing 100871, P. R. China. E-mail: nijinren@iee.pku.edu.cn

ABSTRACT

Sediment movement during erosion, transport and deposition greatly affects the ecosystem of river basins. However, there is presently no consensus as to whether particular river basins act as carbon dioxide (CO2) sources or sinks related to these processes. This paper introduces a rule-of-thumb coordinate system based on sediment delivery ratio (SDR) and soil humin content (SHC) in order to evaluate the net effect of soil erosion, sediment transport and deposition on CO2 flux in river basins. The SDR–SHC system delineates CO2 source and sink areas, and further divides the sink into strong and weak areas according to the world-average line. The Yellow River Basin, most severely suffering soil erosion in the world, only appears to be a weak erosion-induced CO2 sink in this system. The average annual CO2 sequestration is ~0·235 Mt from 1960 to 2008, a relatively small value considering its 3·1% contribution to the World's sediment discharge. The temporal analysis shows that the Yellow River Basin was once a source in the 1960s, but changed its role to become a weak sink in the past 40 years due to both anthropogenic and climatic influences. The spatial analysis identifies the middle sub-basin as the main source region, and the lower as the main sink. For comparison, sediment-movement-related CO2 fluxes of eight other major basins in four continents are examined. It is found that the six basins considered in the Northern Hemisphere appear to be sinks, while the other two in the Southern Hemisphere act as sources. Copyright © 2012 John Wiley & Sons, Ltd.

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