Publication Date:
2017-12-13
Description:
The Red River (Vietnam) is a good example 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 carbon dynamic and CO2 outgassing at the water–air interface of the lower Red River system. The monitoring of water quality and CO2 emission were carried out for 24 h cyclings at the five stations during the dry and monsoon seasons. The riverine water pCO2 was supersaturated with CO2 in contrast to the atmospheric equilibrium (400 ppm), averaging about 1588.6 ± 884.6 ppm, thus resulting in a water–air CO2 flux of 26.9 ± 18.4 mmol m−2 day−1. The CO2 outgassing rate was characterized by significant spatial variations, highest at Hoa Binh station (Da River) due to the dam impoundment and the highest river flow. Surprisingly, CO2 outgassing was higher in the day time (30.4 ± 21.2 mmol m−2 day−1) than in the night time (23.3 ± 15.4 mmol m−2 day−1), probably as a result of the combined effect of higher wind speed and water temperature in the day time. Seasonal differences were also observed, higher in the wet season (30.7 ± 23.1 mmol m−2 day−1) than in the dry season (23.0 ± 12.2 mmol m−2 day−1), due to higher river discharges and higher external inputs of organic matters from watersheds. Conversely during dry season, temperature was among the main factors influencing C dynamic, with higher pCO2 and fluxes, probably as a result of increased metabolic rates.
Print ISSN:
1810-6277
Electronic ISSN:
1810-6285
Topics:
Biology
,
Geosciences
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