Approximately 3% of the Italian territory is included in the National Priority List of Polluted
sites. An example is represented by the “Laguna di Grado e Marano” which lies in Friuli
Venezia Giulia (NE Italy). It includes about 4,200 ha of dry land and ca. 6,800 ha of wetlands
and lagoons. The main pollutant, occurring particularly in wetlands and lagoon, is represented
by mercury. However, heavy metals and organic pollutants were recorded as well.
During Summer 2010, a survey was performed with the objective to observe, if any, the
bioaccumulation of heavy metals in the tissues of Cymodocea nodosa, Zostera marina,
Zostera nolti, aquatic macrophytes commonly found in the lagoon. Samples of sediments and
specimens of macrophytes, were collected and analyzed for the heavy metal content (Cd, Co,
Cd, Cu, Hg, Mn, Ni, Pb and Zn).
The in concentrations, with the exception of Hg, were quite low. The Hg levels found in the
sediments were comprised within the range 610-12,997 μg kg-1. In Cymodocea nodosa and
Zostera marina, Hg was mostly accumulated in the leaves; the average Hg concentrations
were, respectively, 44.5 and 61.8 μg kg-1. The opposite was found in Zostera noltii, being the
leaf concentration of Hg (183 μg kg-1) more than doubled when compared to the root
concentration (71 μg kg-1). For all the species, the bioconcentration factor was very low
(<<1).
