| Abstract: | Robust and reliable laboratory methods are required to assess the rate of release of pollutants from contaminated materials. A widely used approach to determine release parameters are soil column experiments. Release rates are thereby obtained by the analysis of the concentration time profile measured at the column outlet, the so called breakthrough curve. Insufficient experimental information as a consequence of simple experimental designs, however, results in the non‐unique identification of the release processes. This is due to the equifinality, i.e., different processes result in the same breakthrough behavior. We analyzed column outflow experiments for their suitability for the identification of non‐equilibrium conditions by means of numerical simulations. Results show that non‐equilibrium conditions can be detected only in a small range of release time scale to transport time scale. Most frequently, non‐equilibrium remains undetected due to unmatched experimental conditions. Flow interruptions and modulation of the flow velocity are an important means to allow for better detection of possible non‐equilibrium release processes. The efficiency of flow interruptions sensitively depends on the experimental conditions, such as point of time and duration of the interruption and the imposed flow velocity. Column experiments are a suitable experimental tool to investigate non‐equilibrium. However, the course of the experiment has to be designed very carefully. |
