Abstract
BackgroundUnderstanding the responses of riverine dissolved carbon dynamics and chemical weathering processes to short-term climatic variabilities is important to understand the Surface-Earth processes under ongoing climate change. Temporal variations of solutes and stable carbon isotope of dissolved inorganic carbon (δ13CDIC) were analysed during a hydrological year in the Guijiang River, South China. We aimed to unravel the chemical weathering processes and carbon dynamics in karst areas under ongoing climate changes.ResultsSignificant positive relationships were found between weathering rates and climatic factors (i.e. temperature and discharge) over the hydrological year. The total flux of CO2 consumption (760.4 × 103 mol/km2/year) in the Guijiang River was much higher than the global mean flux, with a higher CO2 consumption capacity in the Guijiang River relative to most other global rivers. Chemical weathering fluxes in this karst area showed high sensitivity to global climate change. CO2 evasion during the warm–wet seasons was much lower than those during cold–dry seasons. Light δ13CDIC values occurred under high-flow conditions, corresponding with the high temperatures in high-flow seasons. IsoSource modelling revealed that biological carbon could account for 53% of all dissolved inorganic carbon (DIC), controlling the temporal carbon variabilities.ConclusionThis study quantitatively evaluated the temporal variations in CO2 fluxes and carbon cycling of karstic river systems and demonstrated that riverine carbon cycling will have a higher sensibility to ongoing global climate change. High discharges accelerate solutes transport, with relatively large quantities of 13C-depleted carbon being flushed into rivers. Meanwhile, high temperatures also accelerate organic carbon mineralisation, producing high content of soil CO2, whose influx can shift the 13C-depleted values in the high-flow seasons. Taken together, biological carbon influx should be responsible for the temporal carbon dynamics.
Highlights
Understanding the responses of riverine dissolved carbon dynamics and chemical weathering processes to short-term climatic variabilities is important to understand the Surface-Earth processes under ongoing climate change
As carbonate weathering can be consumed by other acids, it can lead to CO2 release rather than CO2 consumption [7], which can be expressed as Eqs. (3 and 4)
Based on temporal distributions of riverine dissolved solutes and δ13CDIC values throughout a hydrological year in the Guijiang River, we found that the dissolved solutes showed obvious temporal variabilities over the hydrological year
Summary
Understanding the responses of riverine dissolved carbon dynamics and chemical weathering processes to short-term climatic variabilities is important to understand the Surface-Earth processes under ongoing climate change. We aimed to unravel the chemical weathering processes and carbon dynamics in karst areas under ongoing climate changes. Understanding the responses of carbon cycling to shortterm climate variabilities (i.e. temperature and discharge) is necessary to investigate the effects of future global climate change on Surface-Earth processes [1, 2]. Of the different components within the global carbon cycle, the Silicate weathering involves carbonic acid and leads to the net sequestration of CO2, which can be defined by Eq (1). The dissolution of carbonate rocks consumes ~ 0.15 Pg of atmospheric CO2 each year, based on the geochemical data from large rivers worldwide [6]. As carbonate weathering can be consumed by other acids (e.g. nitric, sulfuric, and organic acids), it can lead to CO2 release rather than CO2 consumption [7], which can be expressed as Eqs. (3 and 4)
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