The determination of the pollutant transfer from the soil with leachate into the groundwater is of fundamental importance for the assessment of the risk potential posed by contaminated sites.
Following the German Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV) the leachate forecast is allowed to perform among others on the basis of material testing in the laboratory (elution) or in-situ investigations in the transition area from the unsaturated to the water saturated zone (place of assessment).
In this study the leaching behaviour of PAH through two lysimeters in laboratory scale was monitored under unsaturated conditions using a PAH contaminated soil from a former tar works site. The glass columns (30 cm in diameter) containing about 30 kg of contaminated soil were irrigated weekly with 300 ml of water. PAHs, pH value, DOC, turbidity, conductivity were determined for periodically taken eluates.
The different leaching behaviour of the various PAHs will be presented by examples on the poster.
After relatively high initial leachate loads of high-water-solubility PAHs the release adjusts relatively quickly to a constant low level. Released concentrations decrease with increasing molecular size. The results indicate a low availability of the studied contaminants after 270 days since only a minor fraction of the initial amount of PAHs was released from the soil during the experiment.
This method seems to be reliable of providing data on leachate amounts of PAHs under field-like conditions over a long period of time.