A solar-driven system with a closed-loop water cycle for passive and sustainable saline soil remediation

Soil salinization severely degrades arable land and poses a significant threat to global food security. Different from the commonly adopted saline soil leaching method, this work proposes a sustainable and water-efficient soil remediation system. Mimicking the natural water cycle, this system, configured as a microclimate chamber, leaches salts from the soil and ultimately transfers them to the evaporator. 7-day operation demonstrates that the system can work steadily and achieve a water cycling rate of 7.12 kg m⁻² day⁻¹, removing 95.9 % of the salt from the soil. Scaled-up field tests indicate that, within 10 days, the majority of dissolved salts are transferred from the soil to the evaporator in two seasons, resulting in an efficient salinity reduction of the leachate (>90 %) and less water consumption, saving 87.13 % and 79.65 % water resources compared to the traditional method. The treated soil regained its capacity to support plant cultivation. By harnessing ambient solar energy and closed-loop water cycling, this work offers a sustainable, water-efficient strategy for saline soil remediation.