Metal immobilization and soil amendment efficiency at a contaminated sediment landfill site: A field study focusing on plants, springtails, and bacteria

Metal immobilization may contribute to the environmental management strategy of dredged sediment landfill sites contaminated by metals. In a field experiment, amendment effects and efficiency were investigated, focusing on plants, springtails and bacteria colonisation, metal extractability and sediment ecotoxicity. Conversely to hydroxylapatite (HA, 3% DW), the addition of Thomas Basic Slag (TBS, 5% DW) to a 5-yr deposited sediment contaminated with Zn, Cd, Cu, Pb and As resulted in a decrease in the 0.01 M Ca(NO3)2-extractable concentrations of Cd and Zn. Shoot Cd and Zn concentration in Calamagrostis epigejos, the dominant plant species, also decreased in the presence of TBS. The addition of TBS and HA reduced sediment ecotoxicity and improved the growth of the total bacterial population. Hydroxylapatite improved plant species richness and diversity and decreased antioxidant enzymes in C. Epigejos and Urtica dïoica. Collembolan communities did not differ in abundance and diversity between the different treatments. - Highlights: ► Thomas Basic Slag and hydroxylapatite were added to a metal-contaminated sediment. ► Plant metal content and (CaNO3)2 extractable sediment fraction decreased with TBS. ► The growth of the total bacterial population was improved in the presence of TBS. ► Hydroxylapatite favored plant diversity and physiological plant welfare. ► No significant difference was pointed out in collembolan colonization. - In-situ incorporation of Thomas Basic Slag into a landfilled metal-contaminated sediment decreases metal mobility and ecotoxicity and increases bacterial activity.