TRANSPORT OF BROMIDE UNDER FIVE STEADY STATE WATER FLOW RATES AND THREE SOIL DEPTH: FIELD EXPERIMENT IN MOLISOL SOIL

Abstract

Abstract The simulation of solute transport with models provides a cost-effective and rapid assessment tool. However, both model selection and its parameterization using data obtained from field-scale experiments, it is essential to obtain useful and accurate results. In our work under field conditions, we obtained bromide concentration data of soil water samples from three depths and five water flows to adjust 180 breakthrough curves for estimating solute transport parameters in soil: V, D and dispersivity (λ) and we checked the effect of three previous N treatments in these solute transport parameters. The velocity and dispersion parameters were fitted using the CXTFIT 2.1 model. After selecting the best model using Akaike criteria, we analyzed the distribution of transport parameters estimated using a normality test. The transport parameters were analyzed considering each water flow as a locality, prior fertilization treatments (0N, 100N and 200N) and depth (100, 150 and 190cm respectively) as a repeated measure in space using SAS 9.2. The MIM was the best model to fit the data of relative concentration of Br integrating the soil profile compared to CD and CLT models. In general, transport parameters obtained from adjustment breakthrough curves 180 have a normal distribution. In the analysis of the transport parameters, the velocity was seen to be statistically different between water flows, while the dispersion varied both between flows and between sampling depths and prior fertility treatment. The overall average of the mobile water fraction β was 0.35, indicating preferential flow. The soil structure and the physical non-steady state had a greater impact on the movement of solutes at depth than the steady state. The logarithm of the dispersivity differed statistically by flow and by depth.