Use of phytostabilisation to remediate metal polluted dredged sediment

Abstract : Phytostabilisation (combined use of tolerant plants and soil amendments) experiments were conducted at the field scale on dredged sediments polluted with metals. A sediment deposit contaminated with metals and metalloids (Cd, Zn, Pb, Cu and As) was experimentally established in 2002 and monitored until 2004 as part of the European project PHYTODEC (5th Framework Program; EVK1-CT-1999-2004). Six out of nine plots were treated by adding amendments to immobilise metals (Thomas Basic Slags or Hydroxylapatite). Two grass species (Festuca rubra and Deschampsia cespitosa) were sown on six plots previously treated or not. The three unvegetated plots left were taken as controls. After two years of monitoring, the couple Thomas Basic Slags/D. cespitosa was the most efficient additive/plant couple for phytostabilisation purpose. In this 3 years project, we continue to work on the sediment deposit site previously described and propose to demonstrate the long-term sustainability of phytostabilisation by addressing the following points: (i) sustainability and maintenance of the vegetation cover and amendment action, (ii) reduction of metals mobility and bioavailability, (iii) study of metal mobilization and immobilization mechanisms related to specific bacterial microflora.