Bicarbonate Daily Variations in a Karst River: the Carbon Sink Effect of Subaquatic Vegetation Photosynthesis

Authors

  • ZHANG Cheng,

    Corresponding author
    1. Institute of Karst Geology, Chinese Academy of Geological Sciences; Karst Dynamics Laboratory, Ministry of Land and Resources; International Research Center on Karst Under the Auspices of UNESCO, Guilin 541004, China
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  • WANG Jinliang,

    1. Institute of Karst Geology, Chinese Academy of Geological Sciences; Karst Dynamics Laboratory, Ministry of Land and Resources; International Research Center on Karst Under the Auspices of UNESCO, Guilin 541004, China
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  • PU Junbing,

    1. Institute of Karst Geology, Chinese Academy of Geological Sciences; Karst Dynamics Laboratory, Ministry of Land and Resources; International Research Center on Karst Under the Auspices of UNESCO, Guilin 541004, China
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  • YAN Jun

    1. Department of Geography and Geology, Western Kentucky University, Bowling Green 42101, USA
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Corresponding author. E-mail: chzhang@karst.ac.cn

Abstract:

Using the Guancun River, an underground stream-fed river, in Rong'an County of Guangxi, China as a case study, the daily biochemical cycle was examined in this paper based on the data collected a weeklong via high resolution data logger monitoring and high-frequency sampling. Furthermore, the loss of inorganic carbon along its flow path was estimated. Results show that chemical components of the groundwater input are quite stable, showing little change extent; while all of the chemical parameters from two downstream monitoring stations show diel variation over the monitoring period, suggesting that plant activity in the river has a strong influence on water chemistry of the river. The comparison of the input fluxes from the groundwater with the output fluxes of HCO3 estimated at the downstream monitoring station during the high-frequency sampling period shows a strong decrease of HCO3, indicating that the river is losing inorganic carbon along its flow path. The loss is estimated to be about 1,152 mmol/day/m of HCO3 which represent about 94.9 kg/day of inorganic carbon along the 1,350 m section of the Guancun River. It means that HCO3 entering the river from karst underground stream was either consumed by plants or trapped in the authigenic calcite and thus constitutes a natural sink of carbon for the Guancun karst system.

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