Summary
One main focus of legislation on soil protection and contaminated sites in Germany is the prediction of the contamination of groundwater by seepage water. This includes both the leaching of contaminants from polluted material but also the contaminant transport with the seepage water into the groundwater. An important input parameter for the prediction is the emission potential of a contaminated material concerning the release of certain substances. According to a current regulation (BBodSchV), in the case of organic substances the emission potential has to be determined by column-leaching experiments or lysimeter tests. As the latter are too time consuming and thus expensive, column leaching tests under water saturated conditions are supposed to be more suitable for the risk assessment of contaminated materials. Though there are already some international draft standard protocols for column-leaching experiments including the German draft standard DIN V 19736, all draft documents lack the experimental validation.
In this context, TZW is working on a subproject funded by the Federal Ministry of Education and Research (BMBF). The goal of this project is to validate a method for the preparation of leachates from contaminated materials by using column leaching tests especially with respect to organic pollutants. With an experimental set-up, based on the German draft standard DIN V 19736 (s. figure), the leaching behavior of pre-selected organic substances is investigated by performing long-term (up to 4 weeks) column-leaching tests. Some of the investigated substances are for example polycyclic aromatic carbohydrates and phenols, which are typical substances for contaminated sites and naphthalenesulfonates as characteristic substances in concrete containing recycling materials. Materials, which are investigated, are for example soils from contaminated sites, recycling material from construction waste and a harbor sediment. In the experiments the influence of important test conditions like flow rate, temperature and content of organic matter in the leaching water is tested.