The effects of hydrological variations on chemical weathering: Evidences from temporal water chemistry, stable carbon and sulfur isotopes

•Water chemistry, δ13CDIC and δ34SSO4 were investigated in the Jialing River.•Sulfide oxidation played an important role in carbon cycling.•Hydrologic variability impacts chemical weathering and carbon cycling. The negative feedbacks between chemical weathering and climate change were hypothesized to regulate the atmospheric CO2 over short-term and geologic timescales. In this study, we collected temporal water samples from the Jialing River, and analyzed water chemistry, stable isotopic compositions of dissolved inorganic carbon (δ13CDIC) and sulfur isotope of sulfate (δ34SSO4) to investigate the effects of hydrological changes on chemical weathering. The results of the inverse model based on the Monte Carlo method showed that major cations were mainly derived from carbonate (63.9%) and silicate (12.0%) weathering, and sulfuric acid plays an important role in carbon biogeochemical processes. Based on water chemistry, δ34SSO4 and δ13CDIC, the carbon biogeochemical processes were investigated, showing the influence of secondary processes. We estimated the weathering rates of carbonate (19.7 t/km2yr) and silicate (3.9 t/km2yr) in the Jialing River, and then estimated CO2 consumption flux by carbonate weathering (24.5 t/km2yr), silicate weathering (8.1 t/km2yr), and total CO2 consumption flux (27.5 t/km2yr) deducting the influence of pyrite oxidation. Our research showed the significant role of pyrite oxidation in carbon cycling. This study highlighted the impacts of hydrological variabilities on the generation and transport of solutes, which have significant implications for understanding carbon cycling under ongoing climate change.