Field-scale transport of water and bromide in a cracking clay soil

The transport of a bromide tracer was studied in a cracking heavy clay soil. The soil was sampled six times and the groundwater and drain discharge were sampled frequently. Samples were analysed for bromide content. Solutes were transported in three domains: macropores, such as large continuous shrinkage cracks, with rapid transport of water and solutes through the unsaturated zone; smaller, more tortuous mesopores, which are quantitatively the most important, with lateral and vertical transport through the soil between the large macropores; micropores in the soil aggregates, which play only an indirect role in transport through solute retardation.