1 FEASIBILITY OF HEAVY METAL POLLUTED LAGOON SEDIMENT PHYTOREMEDIATION: A PILOT-SCALE APPLICATION Andrea Giordano, and Carmela M. Cellamare (ENEA, Bologna, Italy) Raffaele Cesaro and Francesco Pirozzi (University of Naples Federico II) Giuseppe Bortone (Emilia Romagna Region, Bologna, Italy) Corresponding Author: Andrea Giordano ENEA – Protezione e Sviluppo dell’Ambiente e del Territorio, Tecnologie Ambientali - Sezione Gestione Risorse Idriche, Via Martiri di Monte Sole, 4, 40129 – Bologna. andrea.giordano@bologna.enea.it ABSTRACT: This paper reports the results of experimental investigations carried out on a pilot scale phytoremediation plant for high salinity and heavy metal polluted sediment decontamination. The sediments (dredged in the Venice Lagoon) were taken from the Alles dewatering plant (located in Fusina, Venice). The results obtained after 1.5 years of experimentation confirmed the ability of some spontaneous vegetation to survive under such adverse conditions; a 30% reduction of chromium concentration in the superficial layer of vegetated beds was observed, confirmed by chromium accumulation in the biomass tissues (in particular Conyza spp.). INTRODUCTION Sediments are loose particles of sand, clay, silt and other substances that settle at the bottom of water bodies (lakes, estuaries, rivers and oceans), coming from eroding soil and from decomposing plants and animals. Most of the particles have been transported by wind, ice or water (U.S. EPA, 1999). The sediments can be considered as a heterogeneous mixture of dissimilar particles (Gulmini et al., 1996). A sediment particle is generally composed of an inorganic fraction and an organic one: the inorganic fractions are silicates (clays and not clays), carbonates, iron and manganese oxides, phosphates and sulphides, in varied chemical and crystalline forms; the organic fractions include living organisms, compounds of human origin and natural organic substances (Gulmini et al., 1996). Heavy-metal polluted sediments represent an increasing environmental problem within the harbour and inland waterways management: dredging activity is necessary for maintance shipping depth and, on the other hand, disposal in sea or landfilling is restricted more and more due to new stringent regulations. Once contaminated, sediments are removed by dredging, an alternative to open water discharge could be the use of dredged material as a soil resource offsite, avoiding the need to place the sediments in confined upland placement: recent researches indicate that contaminated dredged material can be used as substrate for wood production and the plants can enhance the remediation process (Vervaeke et al., 2001). When freshly dredged heavy metal polluted sediment comes into contact with the air, it turns acidic due to microbial oxidation processes, the heavy metals became partly soluble and dredged material poses a serious environmental risk (Loser et al., 2001). Some plants have shown to retain metals in their roots, stems and leaves; the use of green plants to remove pollutants from the environment or to render them harmless is defined phytoremediation (Raskin et al., 1997). There is a lot of interest in the use of fast growing, bushy species, which can be readily grown under a short rotation coppice system; the fast growth and regular