Arrêt-reprise de l’Écoulement : influence sur la mobilisation des éléments traces d’un sédiment de bassin d’infiltration

Influence of infiltration flowrate on trace elements mobilisation from an infiltration basin sediment

¹ Laboratoire central des ponts et chaussées Division Eau et Environnement, BP 4129, 44341 Bouguenais Cedex, France
² École Nationale Supérieure de Chimie de Rennes (ENSCR) Campus de Beaulieu, Avenue du Général Leclerc, 35700 Rennes, France

Auteurs de correspondance : beatrice.bechet@lcpc.fr pierre.le-cloirec@ensc-rennes.fr

Abstract

Highway and urban runoff stormwaters are a potential source of contamination for the environment due to their pollutant loading. Intentional infiltration systems are widely used for mitigating particulate pollutant loads even if mechanisms are not known very well. There is a potential for leaching of colloid-mediated heavy metals trapped in sediments through variations of infiltration rates during rain storm events and drying periods. Stop flow experiments were conducted in laboratory columns with the sediment of a retention-infiltration pond. Trace metals behave differently, depending on their interaction with colloidal particles. Lead, zinc, cadmium and chromium are not sensitive to variations of flow. The concentrations of copper and nickel increased as the flow started. These trace elements are probably associated with organic compounds and iron oxides which mobilisation was shown to be time-dependent.