Background and baseline values of the Bagnoli brownfield site and sea sediments (Naples, Italy)
|Location||International Geological Congress,oslo 2008|
|Author||Albanese, Stefano; Civitillo, Diego; Cosenza , Antonio; De Vivo, Benedetto; Lima, Annamaria|
|Holding Date||08 September 2008|
The Bagnoli area (Naples) is located along the south-eastern coastal sector of the Phlegrean Fields. Phlegrean Fields are characterized by a large presence of magmatic alkaline rocks and thermal waters, which generally carry high concentrations of toxic metals (e.g. As, Pb, Cd).
An industrial settlement for steel works (ILVA) has been present in the area for about 100 years.
After the ILVA was shut down, the brownfield area and the near coastline underwent remediation.
Actually, the ILVA brownfield is characterized by the presence of industrial filling, scums and slags overlaying volcanic soils; industrial wastes occurr as well in the coastal area mixed with sea sediments.
In 1996, 2535 samples were collected in the brownfield, whereas in 2005, 148 samples of coastal and sea sediments were collected in the Bagnoli bay. All the samples were analyzed to obtain concentration data for 6 toxic elements (As, Cd, Cu, Hg, Pb, Zn), PAH and PCBs.
To define the present environmental conditions of the area, geochemical databases have been processed to produce different kinds of geochemical maps (dot, baseline, background and risk maps). Baseline and background maps have been produced by means of a GIS tool (GeoDAS) based on a multifractal IDW interpolation and a spectral analysis (S-A) method to discriminate between actual and natural concentrations.
The baseline maps show high concentrations for the toxic metals in some sectors of the ILVA brownfield and in the Bagnoli bay. The background maps show that the high concentrations of the considered elements are basically of natural origin being related to the presence in the area of an important fault (NW-SE oriented) characterized by an intense hydrothermal activity.
Furthermore, Pb isotopic data (1) show that metals found in the brownfield area derive from both anthropogenic activities (considered a secondary component of contamination) and hydrothermal activity (which is the primary) producing enrichments of As and other toxic elements in the superficial environment. High contaminations of PAH and PCBs are also distributed in scum, slugs, soils and coastal and sea sediments. PAH and PCBs, as opposed to the metallic elements, are totally anthropogenic.
Risks maps, compilated on the base of Italian legislation (D.Lgs.152/06 and D.M.367/03), show that all the investigated elements overcome intervention limits. An heavy metal remediation of soils in the ILVA brownfield would be useless due to the continuous release of metals to the soils from the hydrothermal fluids. Remediation of fillings, scums and slugs would be also unnecessary since these materials have been proved, through mineralogical investigations and leachate experiments, to be geochemically stable.
Thus, the remediation of the ILVA brownfield area should consist basically in removing PAH and PCB’s from scum, slugs, soils both in the brownfield area and sea sediments.
(1) Tarzia et al., 2002. Geochemistry : Explor., Environ., Analysis, 2, 45-56.