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 DI 14 C for a small mountainous river (43 to 71 percent modern carbon), with rock-derived carbonate constituting a 14 C-free DIC source. Using an inverse modelling approach integrating riverine major dissolved ion chemistry and DI 14 C, we provide quantitative constraints of mineral weathering pathways and calculate atmospheric CO 2 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 CO 2 budget of Taiwan such that the overall system acts as a net sink, with 0.24 ± 0.13 MtC/yr of atmospheric CO 2 consumed over geological timescales.

No abstract

The East China Sea (ECS) features the largest continental shelf in the northwest Pacific Ocean, receiving 924 km 3 freshwater annually from the Changjiang (Yangtze) River (CR), which accounts for 90% of the total freshwater input to the ECS (Dai et al., 2011;Qu et al., 2005). Thus, the Changjiang dilute water (salinity less than 31 psu) exerts a great effect on the physical and chemical structure of the ECS shelf (Chen

We discuss a radiocarbon study of sediment samples collected from Nanfu terrace in western Taiwan. From these, we extracted humic acids (HA) and humin from the very fine and coarse grain-size fractions using a standard acid-alkali-acid pretreatment. The humin extracts were combusted at 400 and 1100 °C by stepped-combustion, to yield a low-temperature (LT) carbon component and a high-temperature (HT) carbon component. We compare the ages of the LT and HT humin fractions to the HA fractions, in samples collected at 2 depths within the Nanfu terrace. As in previous stepped-combustion studies on sediments, we find that the HA ages are the youngest on average, and overlap the LT ages, and that the carbon contained in the HT fraction is always distinctly older than the LT and HA ages. To better understand the relationship between 14C age and combustion temperature, we conducted an incremental stepped-combustion experiment with one of the samples (1E) using 50 °C steps that ranged from 300 to 1100 °C. The 14C results of the stepped-combustion products show a clear division between 2 isotopically identifiable carbon constituents, from carbon released below 400 °C and carbon released above 550 °C. By comparing the δ13C and 14C results, we find evidence for a third carbon isotopic component in the humin that is released when combusted at ∼500 °C.