Residues from Municipal Solid Waste Incineration (MSWI) are an issue in waste management. Heavy metal content and leaching of these metals are a major problem for the use of these materials and especially bottom ash which is the main residue from MSWI. In some countries, bottom ash is used as a road construction material. In this case, an issue is to control the leaching of the ash disposed in the road. Leachates are coming due to the rain water infiltrating through the cover of the road. These leachates may contain high heavy metals concentrations and contaminate groundwater. Within the framework of the BARC project (Bottom Ash in Road Construction) conducted at Luleå University of Technology, Sweden, the possibility to use soil in road ditches to filtrate and treat the leachates is studied. This Master Thesis aimed to 1) assess knowledge about leachate quality coming from ash and 2) study the adsorption capacity of different soils which may be used in ditches. Leachates were produced at the laboratory and the influence of the Liquid to Solid ratio (L/S ratio) on the trace elements concentration was studied. It was found that most of the elements show linear decrease in concentration when increasing L/S ratio. The element concentration is controlled by dissolution reactions. For aluminium, it seems that precipitation reactions influence Aluminium concentration which is higher at high L/S ratio. Adsorption batch tests with leachates were realised on four different soils: sand, peat, mould and forest soil. Peat shows the best adsorption capacity considering all the elements. Mould and forest soil are efficient to adsorb lead and zinc. The organic matter content of the soil plays a major role in the pollutant adsorption mechanisms and capacity. The maximum adsorption capacity was assess for only some soils and elements. Peat is able to adsorb much more than 40 mg of Cu per kg of dry peat whereas mould and forest soil can only adsorb 17.9 and 20.2 mg of Cu per kg of dry soil respectively. Pb soil adsorption capacity is more than 13.3 mg/kg (peat) and 17.2 mg/kg (mould and forest soil). Zn soil adsorption capacity is more than 5.6 (peat) and 7.2 mg/kg (mould and forest soil). A simulation of what may happen in the experimental road built for the project was made. It was found that soils are able to filter the leachate coming from the ash for at least 25 or 80 years depending on the different parts of the road. A mixture of different soils, peat, mould and forest soil for example, may give the best results considering both pollutant adsorption efficiency and make easier the material implementation in the ditches.