Heavy metals are major soil pollutants since a lot of former industrial soils are polluted by these contaminants. In the context of risk assessment of contaminated sites, they are of particular concern because of their toxicity toward human beings. Nevertheless, the vadose zone of the soil is not taken into consideration in this kind of study, although this is where the pollution enters the soil. That is why mechanisms responsible for trace element release in the unsaturated zone of the soil have to be understood. In addition, tools and methods to measure and put forward interactions between contaminants and the solid matrix have to be provided. Therefore, we selected a soil from a wood preserving facility site (contaminated by As) and decided to follow As release as it was the only trace element measured on site at a concentration in groundwater above the EU guidelines for drinking water quality. We designed an original laboratory set up: two columns were filled with 2 sub-samples of the As contaminated soil (202 and 253mg/kg) and As release was studied as it could occur on site. Two main phenomena were simulated during these experiments: rain water infiltration and an increase in the water table level. After the results of the two experiments, it was shown that As concentrations at the outlet of the two columns were constant over time. Given that and the results of the sequential extraction carried out on this soil, As release could mainly occur from the soluble and exchangeable parts. This will be modeled in a future work in order to confirm this hypothesis.