Open access publications in the SLU publication database

Abstract

Colloid-facilitated transport can cause a considerable increase in the mobility of lowsolubility contaminants in soil. Preferential macropore flow in structured clay soils decreases the filtering of colloids during transport to groundwater. This experimental study was carried out to improve knowledge on how filtering is influenced by flow velocity of a percolating colloid suspension. A colloid suspension was applied with different irrigation intensities to each of four undisturbed clay soil lysimeters. Breakthrough curves were constructed based upon turbidity measurements on the samples, since no satisfactory calibration function between turbidity and colloid concentration could be obtained. The breakthrough curves did not reach a plateau level during the experiment. Instead, turbidity increased steadily until the application was stopped. Too low ionic strength of the water used for saturation of the lysimeters before the start of the experiments may have initiated a dispersive process causing internal colloid mobilization. Another explanation is that the relationship between turbidity and colloid concentration may depend on the particle size distribution in the effluent, which may have varied during the experiment. There is a need to further develop the methodology for working with colloid suspensions.