Analysis of solutions of the equation for the convective diffusion of ions in soil.

摘要

New analytical solutions are proposed for the problem of the convective-dispersion transfer of salts in a soil layer of finite and semifinite thickness at the boundary conditions of the first and third kinds on the soil's surface under the alternating (pulsating) impact of washing water. Numerical studies (computer experiments) of the salt transfer equation were performed for the equilibrium sorption and linear sorption isotherms in soils with deep and shallow groundwater tables and for nonequilibrium irreversible sorption (characterized by biological transformation in the soil solution following the first-order kinetics) to examine the effect of the upper and lower boundary conditions on the transfer of salts in a soil. The analysis revealed relationships between the parameters of the convective diffusion equation (for which simpler equations were proposed for calculating the irrigation rates from the average salt content in the soil layer before and after washing), which included the filtration rate, the physicochemical features of the soil and salts, and the degree and depth of the preset desalination. The use of the initial and permissible salt concentrations averaged for the studied layer was substantiated for the first time. After wide experimental validation, the obtained equations can be used in soil-reclamation practice.Notes Translated from Pochvovedenie (2012) 4, 462-469 (Ru).