Sulphuric acid-mediated weathering on Taiwan buffers geological atmospheric carbon sinks

The chemical composition of the Gaoping River in Taiwan reflects the weathering of both silicate and carbonate rocks found in its metasedimentary catchment. Major dissolved ion chemistry and radiocarbon signatures of dissolved inorganic carbon (DIC) reveal the importance of pyrite-derived sulphuric acid weathering on silicates and carbonates. Two-thirds of the dissolved load of the Gaoping River derives from sulphuric acid-mediated weathering of rocks within its catchment. This is reflected in the lowest reported signatures DI¹⁴C for a small mountainous river (43 to 71 percent modern carbon), with rock-derived carbonate constituting a ¹⁴C-free DIC source. Using an inverse modelling approach integrating riverine major dissolved ion chemistry and DI¹⁴C, we provide quantitative constraints of mineral weathering pathways and calculate atmospheric CO₂ fluxes resulting from the erosion of the Taiwan orogeny over geological timescales. The results reveal that weathering on Taiwan releases 0.31 ± 0.12 MtC/yr, which is offset by burial of terrestrial biospheric organic carbon in offshore sediments. The latter tips the balance with respect to the total CO₂ budget of Taiwan such that the overall system acts as a net sink, with 0.24 ± 0.13 MtC/yr of atmospheric CO₂ consumed over geological timescales.