Heavy Metal Behaviour in an Experimental Free Water Surface Wetland in the Venice Lagoon Watershed

Abstract

Wetlands are effective in the treatment of polluted surface water. A semi-natural wetland pilot plant was established to verify the pollutant abatement effectiveness of the Venice Lagoon inlet water. The unique conditions of this brackish environmental site are: (1) a high concentration of carbonate and low concentrations of sulphides, and (2) the abundance of organic matter in sediments. The goal of this study was to examine how these characteristics influence the metal mobility in the wetland and to compare our results to published literature. The data collected were limited with respect to statistical analysis because the metal concentrations were often below the detection limits. Therefore, we chose to perform non-parametric analyses. To analyse the relationships among heavy metal concentrations and the physical and chemical wetland variables, and to investigate the processes of metal removal, we performed a multivariate statistical analysis and a Spearman correlation analysis. The results indicated that the reduced and basic conditions of the sediments seen in the Venice Lagoon environment facilitated the removal of metals due to the formation of insoluble compounds with sulphides and carbonates.

Evaluating the Impact of Long Term Hydrodynamic Conditions on the Release of Metals from Contaminated Sediments in Taihu Lake, China

“…In the present study, Cd was found to be readily released from the sediment, followed by Pb, Mn, Fe, Cu, Ni, Cr and Zn, in that order. Each type of metal has differrent characteristics during the release process (Caille et al, 2003;Eggleton and Thomas, 2004;Mattiuzzo et al, 2007). Previous studies have demonstrated that Pb and Cu are released more rapidly than Zn (Caille et al, 2003).…”

“…Heavy metals in the sediment of shallow lakes such as Taihu are easily resuspended by hydrodynamic forces and the concentrations of metals in the surface water tend to increase immediately after hydrodynamic changes. Heavy metal contaminants in the surface water are a potential ecological risk because of their biotoxicity (Gao and Chen, 2012;Mattiuzzo et al, 2007;Roberts, 2012). The rate at which metal is released during resuspension is strongly influenced by sediment properties including grain size, sulfide content, organic matter content and the presence of hydrous metal oxides of iron and manganese (Campana et al, 2013;Cantwell et al, 2008).…”