Deciphering water salinization mechanisms of arid lake-groundwater systems in Inner Mongolia, China: An integration of multi-isotopic models

Study region Three representative arid lake-groundwater systems in Inner Mongolia, China: Daihai Lake (DL), Ulansuhai Lake (UL), and the Bahannao Lake Group (BL). Study focus Salinization severely threatens water security of arid lake-groundwater systems, yet the coupled mechanisms linking salinity sources, geochemical transformations and groundwater salt transport have not been well understood. This study established an innovative multi-isotope framework integrating the Rayleigh fractionation model (RFM), Bayesian isotope mixing model (MixSIAR), and ²²²Rn mass balance model (RMBM) to decipher dominant drivers of salinity evolution and their environmental implications for typical inland lake-groundwater systems. New hydrological insights for the region Salinization within the studied systems arises from combined natural geochemical processes and anthropogenic solute inputs, where human-derived sources exert a predominant role. Evaporite and silicate weathering supply primary natural salinity loads, while irrigation water, municipal water and sewage constitute major anthropogenic contributors. evaporation and cation exchange further accelerate salinity enrichment. Lacustrine groundwater discharge functions as a pivotal transport pathway delivering large salt fluxes into lakes, with pronounced spatial heterogeneity governed by local hydrogeological conditions. Salinity-related risks to drinking and irrigation proposes are widely identified across the basins. This integrated modeling framework advances the mechanistic understanding of salinization in arid lake-groundwater systems and offers practical support for water resource regulation in analogous endorheic basins.