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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 15
Biogeosciences, 15, 4799–4814, 2018
https://doi.org/10.5194/bg-15-4799-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: Human impacts on carbon fluxes in Asian river systems

Biogeosciences, 15, 4799–4814, 2018
https://doi.org/10.5194/bg-15-4799-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 15 Aug 2018

Research article | 15 Aug 2018

CO2 partial pressure and CO2 emission along the lower Red River (Vietnam)

Thi Phuong Quynh Le1,2, Cyril Marchand3,4, Cuong Tu Ho5, Nhu Da Le1, Thi Thuy Duong5, XiXi Lu6, Phuong Kieu Doan1, Trung Kien Nguyen5, Thi Mai Huong Nguyen1, and Duy An Vu1 Thi Phuong Quynh Le et al.
  • 1Institute of Natural Product Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam
  • 2Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam
  • 3IMPMC, Institut de Recherche pour le Développement (IRD), UPMC, CNRS, MNHN, Noumea, New Caledonia, France
  • 4Faculty of Chemistry, University of Science – VNUHCM, 225 Nguyen Van Cu, Ho Chi Minh City, Vietnam
  • 5Institute of Environmental Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam
  • 6Department of Geography, National University of Singapore, Arts Link 1, Singapore 117570, Singapore

Abstract. The Red River (Vietnam) is representative of a south-east Asian river system, strongly affected by climate and human activities. This study aims to quantify the spatial and seasonal variability of CO2 partial pressure and CO2 emissions of the lower Red River system. Water quality monitoring and riverine pCO2 measurements were carried out for 24 h at five stations distributed along the lower Red River system during the dry and the wet seasons. The riverine pCO2 was supersaturated relative to the atmospheric equilibrium (400 ppm), averaging about 1589±43 ppm and resulting in a water–air CO2 flux of 530.3±16.9 mmol m−2 d−1 for the lower Red River. pCO2 and CO2 outgassing rates were characterized by significant spatial variation along this system, with the highest values measured at Hoa Binh station, located downstream of the Hoa Binh Dam, on the Da River. Seasonal pCO2 and CO2 outgassing rate variations were also observed, with higher values measured during the wet season at almost all sites. The higher river discharges, enhanced external inputs of organic matter from watersheds and direct inputs of CO2 from soils or wetland were responsible for higher pCO2 and CO2 outgassing rates. The difference in pCO2 between the daytime and the night-time was not significant, suggesting weak photosynthesis processes in the water column of the Red River due to its high sediment load.

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The Red River is a typical south-east Asian river, strongly affected by climate and human activity. This study showed the spatial and seasonal variability of CO2 emissions at the water–air interface of the lower part of this river due to natural conditions (meteo-hydrological-geomorphological characteristics) and human activities (dam impoundment, population, land use). The Red River water was supersaturated with CO2, providing a mean water–air CO2 flux of 530 ± 17 mmol m−2 d−1.
The Red River is a typical south-east Asian river, strongly affected by climate and human...
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