Experimental study on the infiltration and salinity variation of saline soil under simulated rainfall

Soil salt drainage efficiency is of significant interest in quantifying soil remediation, related to external environment, soil properties, and amendment. This study mainly discusses the mechanism of slope gradients and rainfall intensities affecting water-salt transport in saline soils. Laboratory investigations were made to measure the key parameters including the wetting front, water content, and salinity in a flume of almost 1.2 m long under four slope gradients (0°, 5°, 10°, and 15°) and five rainfall intensities (10, 30, 50, 75, and 100 mm/h). The results show that the migration rate of water in soils increased with higher rainfall intensity and at lower slope gradients, in turn resulting in a substantial decrease in soil salinity. The rainfall intensity grew from 10 mm/h to 100 mm/h, and the water content growth rate and salinity decrease rate increased from 0.59%/min to 0.93%/min and 0.044%/min to 0.060%/min, respectively. The rainfall intensity has less influence on the time of salinity stabilization, which is approximately 420 to 480 min. Higher slope gradient and shorter distances from the slope top caused decrease in water-salt migration rate. The wetting front and water content showed a significant linear and exponential relationship with rainfall time respectively, while soil salinity as a function of rainfall time are piecewise functions. The results explicate the water-salt transport behavior of saline soils, and provide a scientific reference for soil remediation.