Water and bromide transport in a heterogeneous glacial sand

Abstract

We investigated water flow and bromide transport under agricultural field conditions, using TDR and tensiometer measurements as well as a bromide tracer experiment. The soil an Albic Luvisol consisting of sand covering glacial loam, is highly heterogeneous with polygon nets formed by sand-filled frost wedges. Water flow and bromide transport are influenced by the thickness of the glacial sand horizon and the soil structure. Both cause a variation of the actual evapotranspiration up to ± 25 mm/ yr. Water and bromide are preferentially transported on the inclined soil layer boundaries into the sand wedges. From there infiltrating water may be redistributed into the surrounding glacial till. Approximately, the depths of the bromide centers of mass can be deduced using the piston flow concept. Small-scale mass balances of the tracer show that vertical sections with bromide deficits and bromide surpluses are well balanced within a horizontal range of 1.8 m to 2.8 m. This distance is interpreted as the lateral influence of the sand wedges.