Improvement of numerical simulation of bimolecular reactive transport using time-dependent parameters

Abstract

The overestimation of the contaminant concentration is a main issue in simulating the reactive transport using the common advection-dispersion-reaction equation (ADRE). To solve this problem, a new modeling method is developed. The parameters of the model are identified based on experimental data. The results of the model are compared with previous results in the literature, and the sensitivity of the model is analyzed by examining the model's response to changes of the model parameters. Main conclusions are as follows: (1) The numerical modeling approach is feasible with an improved simulating accuracy. The predicted values are in agreement with the experimental measurements. The relative errors of the peak concentration between the simulated and experimental values are less than 2.5%. The errors are greatly reduced as compared with the results (about 67.8% as the maximum) based on a traditional ADRE in the literature. (2) There are three parameters (m, β0 and D) which can be calibrated on the basis of experimental data in the model. The reactive product concentrations are mainly influenced by the parameters involved in the reactive ratio such as m and β0. The hydrodynamic dispersion coefficient D has almost no influence on the reactive product transport. (3) Our model does not provide better fitting curves for the “early arrival” and the “long tail”. The “early arrival” and the “long tail” are associated with low values of the product AB. Under these conditions, the reaction rate is close to 0, and the model of the ADRE reduces to the advection-dispersion equation (ADE). Further mechanism study is needed in the future.