SOIL COLLOID MOBILIZATION AND TRANSPORT IN INTACT AND REPACKED SOIL COLUMNS DURING PERIODS OF IRRIGATION

Abstract

This study investigated soil colloid mobilization and leaching through a Hiroshima loam soil during three irrigation periods. The experiments were carried out using both intact soil columns and repacked columns with and without continuous macropores. Large effects of irrigation intensity and of irrigation water chemical composition (sodium content and ionic strength) were seen. Colloid leaching was higher in repacked soil than in undisturbed soil. During the first irrigation, an enhanced colloid leaching in soil containing macropores was seen, but during the next two irrigation the leaching became smaller and could be described by a parabolic diffusion type model. This suggests that the mobilization of colloids is controlled by colloid diffusion from the soil into the macropores. This mechanism needs to be included in models for transport of colloid-bound contaminants in macropore soils.