A simple dynamic method to estimate anion retention in an unsaturated soil

Abstract

The anions Br − and NO 3 − are commonly adsorbed non-specifically by the highly weathered soils found in tropical regions. We used a simple dynamic technique to determine their retention, using the so-called “Perroux tube”, and we compared these results with those obtained from leaching experiments. The method was tested on a ferrallitic soil from New Caledonia which is rich in aluminium and iron oxides. From the resident concentrations observed, we obtained retardation values of 1.1 and 1.15 for bromide and nitrate respectively, using respective input concentrations of 0.025 and 0.1 M. A numerical model using these results predicted the flux concentrations obtained from the leaching experiments quite well, thereby proving the utility of this simple technique.