Mechanisms controlling evaporation of a saline film

Understanding salt precipitation dynamics during evaporation of saline and sodic soils is necessary for the improvement of agricultural conditions of those soils. In a series of highly controlled laboratory experiments, we found that evaporation of saline solution (copper sulfate) from both homogenous and heterogeneous porous media produces an initial crust followed by subsequent banding patterns. The salt precipitation site represents a rough approximation of the evaporation front. The spacing of the sub fluoresecnt deposition sites indicate that the evaporation front is receding in a non-smooth fashion. During the experiments, mass, matric-potential, and photo data were collected. The data indicates that salt precipitates in from the film region of capillary fringe, and thus many contributing mechanisms control this banding phenomena, particularly surface tension and its' variation with concentration.