A dataset of mixing processes between lake water and subsurface brine in Qarhan Salt Lake during 2024–2025

The data were collected across four hydrological stages (low-water stage in November 2024, early high-water stage in January 2025, mid-high-water stage in May 2025, and late high-water stage in August 2025) along an offshore transect extending from the lake shore to a maximum distance of 600 m (including boreholes D11, D12, D14, and D15).

The dataset comprises:Water chemistry: Concentrations of major ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, SO₄²⁻, HCO₃⁻, CO₃²⁻) and Total Dissolved Solids (TDS) for lake water, subsurface brine, and mixed water samples;Water levels: subsurface brine levels, indicating hydraulic gradients and recharge dynamics;Physicochemical parameters: In-situ temperature (T), pH, Dissolved Oxygen (DO), Oxidation-Reduction Potential (ORP), and Electrical Conductivity (EC);Radium isotope activities: Activities of ²²⁴Ra, ²²³Ra, ²²⁶Ra, and ²²⁸Ra (dpm/L), specifically designed for end-member mixing calculations and coprecipitation corrections.This dataset provides essential baseline information for investigating hydrological cycles, density-driven convection, water-rock interactions (e.g., radium desorption from particles and solid potash dissolution), and potassium flux estimation in salt lake systems.