The process of soil construction for the reclamation of degraded sites is based on the recycling of wastes and by products,such as compost,paper sludge or treated industrial soil.Based on the pedological engineering concepts,these technic materials are used to construct a new soil (Technosol) over in situ brownfield substrates.They are associated and stacked in layers to form new horizons and reproduce the basic soil functions (vegetation support,filter/exchange,biodiversity support).A major scientific issue is to assess the sustainability of such Technosols.Integrating the fact that constructed soils interact with their environment (climate,vegetation,biological activity),they are submitted to a pedogenic evolution.Our work aims at understanding and predicting the pedogenic processes-with a particular attention on minerals weathering and organic matter evolution-that are already in place and will occur in those soils.The project relies on both in situ pilot scale application and lab-scale experiments.At the laboratory,column experiments,under controlled conditions,have been realised to precise the mechanisms involved and to simulate the constructed soil evolution in a simplified system.The field experimental set-up consisted in three lysimetric plots (10 × 10 m) that enabled the collection and analysis of plants,rainwater,leached water and soil.Technic parent materials were characterized for their elemental composition as well as for their mineralogy by X-ray diffraction.Some major physico-chemical parameters (pH,redox potential,bulk density) were measured as well on the constructed soil pedons.The evolution of mineral and organic phases was essentially monitored by the analysis (ionic chromatography and TOC analyser) of major and geochemical elements and organic carbon in the leached water from the in situ plots and lab columns.The results are notably expressed as the evolution of concentrations in leachates.This breakthrough curves were good indicators of the chemical reactions.They revealed a succession of clearly identified pedogenic processes such as i) the solubilization of salts,ii) the weathering of gypsum and amorphous silica,iii) the mobilization of Fe by oxido-reduction reactions and iv) the decarbonatation of calcite and dolomite.Moreover,our monitoring enabled the evaluation of the intensity ank kinetics of each mechanism.Furthermore,in order to compare and confront the laboratory results and the in situ results,we developped a simplified analogy model.Thanks to this tool,we not only highlighted some complementary reactions (such as the initial residual water evacuation),but we also evaluated the relevance of this experimental modelling approach to describe pedogenic processes in constructed soils.