Tuesday, 8 November 2005 - 3:30 PM
206-6

The Leaching Potential of Low Contaminated Recycling Material in an Outdoor Lysimeter Experiment.

Thomas Puetz, Herbert Ruetzel, and Harry Vereecken. Agrosphere Institute - Forschungszentrum Juelich, Leo Brandt Strasse, Juelich, 52425, Germany

In Germany, large amounts of low contaminated recycling material are used for road construction. These recycling materials are mixtures of varying components and possibly contain water soluble components, which are dangerous for the ground water. The aim of our study was to test leaching potential of three typical, widely used recycling materials in a lysimeter experiment under outdoor conditions. Three round lysimeters (2 m2 surface, 2.5 m depth) were filled with soil monoliths. The three tested recycling materials were a PAH contaminated soil, ash of domestic waste and material of road and house demolition. For installation of the recycling materials, the top 80 cm of the soil monolith were digged out. Around 1.5 t of each material were installed into a lysimeter as a 50 cm thick layer. The remaining 30 cm up to the top of each lysimeter were filled up with gravel. For soil solution sampling, three replicates of suction candles were installed at 85, 115 and 180 cm depth. For water content measurement, TDR-probes and tensiometers were installed at the same depths. Bromide and D2O were applied as conservative water tracers to characterize the water movement. 2,6-di-fluorobenzoic acid was applied as a well known reactive tracer. Each month, soil solutions and leachates were collected and analyzed. The leaching situation of the lysimeters reflected to a worst case scenario, because a rapid vertical transport was induced by the high amounts of precipitation and the bare gravel surface. Among the analyzed heavy metals, lead was immobile, copper, nickel and zinc were less mobile and chromium and cadmium were mobile. As for PAH contaminated soil, no relevant leaching of PAH were observed.

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