Migration des polluants métalliques : cas d'un dépôt de sédiments contaminés sur un sol non pollué

Evaluation of heavy metals transfer: impact of a dredged sediment deposit on a non-polluted soil

¹ CNRSSP, Centre National de Recherche sur les Sites et Sols Pollués, 930 Bd Lahure, B.P. 537, 59505 Douai Cedex, France
² CEA, Commissariat à l'Energie Atomique-Cadarache

Auteur de correspondance : vauleon@cnrssp.org

Abstract

In many countries and especially in the North of France, inland waterways need to be dredged regularly to provide a high quality environment for customers, staff and local communities. However, dredging operations generate yearly large quantities of sediments, which in spite of their high pollutant contents, are often stored in non-specific sites. Thus, the threat of a spreading contamination for the surrounding environment is important. In order to evaluate this potential risk and to quantify the transfer of heavy metals from the dredged layer to the non-polluted soil below, an interdisciplinary research project was undertaken including, (i) the monitoring of an experimental sediment deposit, (ii) the microscopie study of metal distribution inside this deposit, (iii) the evaluation of microbial activity, (iv) the impact of natural vegetation growth on metal migration. Up to now, the main processes identified (oxidation of sulphur compounds, vertical migration of Zinc) allowed us to make several recommendations for the future management of dredged sediments by: (i) controlling the oxidation processes during dredging operations or (ii) assessing the high neutralising capacity of the local environment of deposition. Moreover, an adequate vegetation management can reduce the heavy metals migration to groundwater's with maximum efficiency and at low costs.