Heterogeneity Effects on Evaporation-Induced Halite and Gypsum Co-precipitation in Porous Media

Understanding evaporation from porous media in the presence of soluble salts plays a key role in describing many environmental processes. Several studies done in this field led to a wide acceptance that the prediction of soil salinization driven by evaporation from the unsaturated zone and mainly encountered in arid and semiarid regions is a challenging task because of the temporal and spatial variabilities of soil rocks combined with different interactions between the porous medium and the atmosphere. In this work, we present a reactive transport model developed with the aim of describing the processes of evaporation, salt accumulation and precipitation. We took the model presented in our previous paper (Jambhekar et al. in Transp Porous Media 114:341–369, 2016) as the basis and developed it with the required geochemical model to account for evaporative salt co-precipitation. The salts considered in this work are halite (NaCl) and gypsum (CaSO(_{4}cdot 2mathrm{H}_{2})O). We focus particularly on the influence of spatial heterogeneities in the porous medium on the dynamics of the physical processes. In the numerical simulations performed in this work, we distinguished different heterogeneity configurations. The results show that the drying from heterogeneous porous media initially affects the coarser pores, where the salt crystals first appear.