The distribution of salt by infiltration of water into dry soil and sand

Abstract

Sulphate and chloride ions (as magnesium salts) were added in solution form, as a slug, to the surface of columns of two air-dry soils and a sand. The soils were pretreated to avoid precipitation of, and exchange effects with, the added salts. Leaching was carried out by ponded fresh water, and the salt and water profiles in the columns determined. In every case the salt was distributed through the column with a pronounced peak nearly halfway between the surface and the wetting front. It is pointed out that existing leaching theories derived for steady-state conditions do not apply to the infiltration case, an extreme example of non-steady-state flow. The differences between the two types of flow, in relation to leaching, and a possible mechanism by which fresh water moved through and advanced ahead of the salt slug during infiltration, are discussed.