Geochemical Evidence for Climate Change Impacts on Weathering Regimes in the Niger-Benue Confluence Region

Contemporary climate change is expected to alter the intensity and seasonality of chemical weathering in tropical basement terrains, with cascading effects on solute fluxes, soil development, and groundwater chemistry, yet empirical geochemical monitoring data documenting these changes across Nigerian river basins remain scarce. This study investigates geochemical evidence for changing weathering regimes in the Niger-Benue confluence region by analysing the temporal evolution of river water chemistry in relation to hydroclimatic variables over a fifteen-year period. Monthly river water samples collected from six stations on the Niger and Benue rivers in Kogi State were analysed for major ions, dissolved silica, and bicarbonate alkalinity. Mass flux calculations were performed using simultaneous discharge measurements to derive weathering-derived solute fluxes. Long-term trends in weathering flux were tested against concurrent rainfall, temperature, and discharge time series using non-parametric Spearman correlation and Mann-Kendall trend analysis. A geochemical mass balance approach was applied to estimate the relative contributions of carbonate dissolution, silicate weathering, and atmospheric deposition to observed ion budgets. The study evaluates whether detected flux trends are consistent with the hypothesis of increasing weathering intensity driven by rising temperatures, or alternatively with changes in agricultural land cover altering chemical export pathways. Findings contribute to Nigerian baseline data for global geochemical cycling research. Keywords: chemical weathering, river geochemistry, climate change, Niger-Benue confluence, solute flux.