- Title
- Riverine CO₂ supersaturation and outgassing in a subtropical monsoonal mountainous area (Three Gorges Reservoir Region) of China
- Creator
- Li, Siyue; Ni, Maofei; Mao, Rong; Bush, Richard T.
- Relation
- Journal of Hydrology Vol. 558, p. 460-469
- Publisher Link
- http://dx.doi.org/10.1016/j.jhydrol.2018.01.057
- Publisher
- Elsevier BV
- Resource Type
- journal article
- Date
- 2018
- Description
- Rivers are an important source of CO₂ to the atmosphere, however, mountainous rivers and streams with high emission rates are not well studied particularly in China. We report the first detailed investigation on monsoonal mountainous rivers in the Three Gorges Reservoir (TGR) region, with a focus on the riverine CO₂ partial pressure (pCO₂), CO₂ degassing and their potential controls. The pCO₂ levels ranged from 50 to 6019 µatm with averages of 1573 (SD. ±1060) in dry Autumn and 1276 (SD. ±1166) µatm in wet Summer seasons. 94% of samples were supersaturated with CO₂ with respect to the atmospheric equilibrium (410 µatm). Monsoonal precipitation controlled pCO₂ seasonality, with both the maximal and minimal levels occurring in the wet season, and showing the overall effects of dilution. Riverine pCO2 could be predicted better in the dry season using pH, DO% and DTP, whereas pH and DOC were better predictors in the wet season. We conclude that in-situ respiration of allochthonous organic carbon, rather than photosynthesis, resulted in negative relationships between pCO₂ and DO and pH, and thus CO₂ supersaturation. Photosynthetic primary production was effectively limited by rapid flow velocity and short residence time. The estimated water-to-air CO₂ emission rate in the TGR rivers was 350 ± 319 in the Autumn and lower, yet more variable at 326 ± 439 mmol/m2/d in Summer. Our calculated CO₂ areal fluxes were in the upper-level magnitude of published data, demonstrating the importance of mountainous rivers and streams as a global greenhouse gas source, and urgency for more detailed studies on CO₂ degassing, to address a global data gap for these environments.
- Subject
- Riverine carbon flux; CO₂ degassing; partical pressure of CO₂; dissolved inorganic carbon; mountainous streams and rivers; three gorges reservoir catchment
- Identifier
- http://hdl.handle.net/1959.13/1429711
- Identifier
- uon:38755
- Identifier
- ISSN:0022-1694
- Language
- eng
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