Chemical weathering and associated CO2 consumption in six major river basins, South Korea

We report the chemical, strontium (Sr) and sulfur (S) isotopic compositions of water samples collected from six major South Korean rivers to investigate seasonal and spatial variations in water chemistry and to estimate the chemical weathering rates and associated CO2 consumption. Overall, the chemical compositions of river water exhibited significant temporal and spatial variations, the magnitude of which varied depending on river size and geology. The 87Sr/86Sr ratios and δ34S values of the rivers varied only spatially in close relation to basin lithology. A mass balance calculation indicated that the dissolved loads of the six rivers were controlled by atmospheric (4.3-18.4%), anthropogenic (6.0-27.2%), and chemical weathering inputs (66.1-83.3%). The average rates of carbonate weathering by sulfuric (SCW) and carbonic acids (CCW), and silicate weathering by sulfuric (SSW) and carbonic acids (CSW) were 4.50 and 11.0 t/km2/yr, and 5.77 and 10.8 t/km2/yr, respectively. The associated mean CO2 consumption rates by CCW and CSW were 312 × 103 and 471 × 103 mol/km2/yr, respectively. The calculated chemical weathering rates were closely related to runoff, and the associated CO2 consumption rates tended to be higher in summer than in winter. This study highlights the role of sulfuric acid in chemical weathering, suggesting that it should be carefully considered in studies of CO2 consumption rate.

Research Highlights► We investigated seasonal and spatial variations in chemical and isotopic compositions in six major South Korean rivers. ► We firstly quantified chemical weathering and associated CO2 consumption rates in six major South Korean rivers. ► CO2 consumption rates should be carefully calculated in terms of sulfuric acids.