Pollution métallique associée au dépôt du réseau d'assainissement de la ville de Paris

This research program aims to improve the knowledge on metallic pollution fixed to sewer deposits. Deposit samples were extracted from 40 silt traps spread out all over the Paris combined sewer system and were analysed for Cd, Cr, Cu, Fe, Hg, Ni, Pb and Zn. Results show that there is a spatial variation of metal contents probably induced by the presence of local metallic sources, such a metallic roofs, major roadways (ring and embankment roads), etc. Moreover, the collection of 6 sub-samples in each silt trap allows the evaluation of the intra-site variation. Results show that, in each silt trap, metallic contents strongly vary from on sample to another. These inter-site and intra-site variations of metallic contents pose a problem for municipalities which manage these sewer sediments. Indeed, an accurate knowledge of the sediment contamination levels is necessary for municipalities in order to take optimal decisions on how to manage sediment deemed to be an ecological risk or regulatory violation.