Effect of Infiltration of Saline Water/Brackish Water on Soil Permeability and Transport of Salt Cations in the Soil
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College of Environmental Science and Engineering,Qingdao University

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Supported by the National Natural Science Foundation of China(Nos.41571214 and 41807010)

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    Abstract:

    【Objective】 In the arid, semi-arid and coastal regions where freshwater resources are scarce, while underground brackish water/saline water resources are abundant. In order to ensure food security and sustainable development of the agriculture development, it is necessary to use brackish water/saline water for reasonable irrigation to alleviate the pressure of shortage of freshwater resources. However, the use of brackish water/saline water for irrigation will certainly cause accumulation of salts in the soil, and trigger secondary salinization of the soil, thus affecting growth of the crops therein. Moreover, it will also alter chemical composition of the soil solution and stability of the soil structure, leading to degradation of soil physical properties and change in chemical reaction in the soil. 【Method】 In this paper, an indoor soil column percolation experiment was conducted to investigate effects of the salts in irrigation water, relative to kind and concentration, on permeability of and transport of salt cations in the soil. In the experiment, to prepare soil columns, plexiglass cylinders, 40 cm in height and 6 cm in diameter, were used, and for irrigation water containing NaCl, MgCl2 and CaCl2, separately, at 3, 5 g·L-1 (as brackish water) and 10 g·L-1 (saline water). A total of 9 treatments were designed, and each had two replicates. 【Result】 It was found that soil relative permeability coefficient K/K0 (K stands for permeability coefficient calculated at each time, and K0 for initial permeability coefficient) decreased with the increasing of Na+ concentration, and permeability declined faster in the topsoil than in the lower soil layers; and Ca2+ and Mg2+ behaved similarly during the process of infiltration, that is, both increasing soil permeability by a rate rising with the increase in Ca2+ and Mg2+ concentration and in soil depth. The effect of Ca2+ was more significant than that of Mg2+. Relative permeability coefficient of the whole soil column was in quadratic relationship with time and ion concentration. In terms of conductivity of soil effluent , the treatments followed an order NaCl > CaCl2 > MgCl2, while in terms of pH, an order of NaCl > MgCl2 > CaCl2. In the columns treated with NaCl solution, both Ca2+ and Mg2+ increased in the soil with rising NaCl concentration in the solution and soil depth. 【Conclusion】 Na+ migration in the soil will leads to decrease in soil permeability; while Ca2+ and Mg2+ migration in the soil does reversely; and the effects of the three ions are more significant in the surface soil layer than in the lower layers. Salt content in the soil depends on kind and concentration of the infiltration water. Irrigation with saline/brackish water tends to lead to accumulation of salts in the soil. The higher the salt concentration in the irrigation water, the higher the salt accumulation. When using saline/brackish water for irrigation, it is advisable to arrange irrigation reasonably in the light of water quality and properties of the soil to be irrigated, coupled timely with certain soil amelioration measures, when necessary, so as to avoid any adverse impacts of the irrigation on soil permeability and crop growth.

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LI Hui, LIN Qing, XU Shaohui. Effect of Infiltration of Saline Water/Brackish Water on Soil Permeability and Transport of Salt Cations in the Soil[J]. Acta Pedologica Sinica,2020,57(3):656-666.

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History
  • Received:May 22,2019
  • Revised:September 11,2019
  • Adopted:October 25,2019
  • Online: March 02,2020
  • Published: