Brackish water promote the ecological restoration of estuarine wetland

Abstract

By taking the indoor soil column experiment as the experimental simulation object, an infiltration experiment was conducted using freshwater and brackish water with different concentrations (3-g/L, 9-g/L). The constant head or air boundary of 3 cm was set as different variables (Where the air boundary means the water surface is flush with the soil interface, and the 3 cm fixed head boundary means the water accumulation depth is 3 cm above the soil interface). By analyzing the cumulative infiltration, soil water content, wetting peak, and infiltration rate, the effects of different water and salt conditions and different boundary conditions on the infiltration process were summarized and analyzed. The results show that the infiltration rate was most favorable under the 3-g/L brackish water infiltration. Under this condition, the cumulative infiltration was the largest, the time for the soil moisture content to reach saturation was the shortest, the wetting peak first reached the bottom of the soil column, and the soil water potential changed first. The constant head condition accelerated the infiltration rate of soil water, increased the cumulative infiltration, increased the soil water content, and reduced the time for the wetting peak to reach the bottom. Compared with that in the air boundary condition, the soil water potential under the constant head infiltration condition was larger. These experimental results show that to some extent, proper concentrations of saltwater are conducive to the infiltration and circulation of soil water. The demand for water saving in agricultural irrigation is increasing, and the efficiency of agricultural irrigation can be improved by making full use of the theory of unsaturated soil infiltration. The instability and complexity of unsaturated soil is due to the presence of matrix suction, so the study of unsaturated soil has profound theoretical significance.