Natural and Anthropogenic Components for the Pollution

As stated in Section 1, the Bagnoli brownfield site contains metallic elements whose source overlaps a natural component (ascribable to the CF hydrothermal activity connected to the quiescent volcanism) and an anthropogenic one (due to the industrial activity). The challenge was demonstrating and separating the contribution of these two components. 

Pb isotopes are used to study environmental pollution because of their relative geochemical immobility and the wide use of Pb in industrial processes. Moreover, Pb isotopes are not fractionated by natural or industrial processes Pb isotopic composition in a material remains constant in time and reflects the nature of the source (Ault et al., 1970). 

The use of Pb isotopes in this field dates back to the 1960s (Chow and Johnstone, 1965) and it has been employed in numerous studies in European and Mediterranean regions (Grousset et al., 1995 Hopper et al., 1991 Mating et al., 1987). Fewer studies have been conducted in Italy and they have never been applied to industrial sites (Cochran et al., 1998 Colombo et al., 1988 De Vivo et al., 2001 Facchetti et al., 1982, 1989 Garibaldi et al., 1981 Magi et al., 1975 Monna et al., 1999 Tommasini et al., 2000). 

At the Bagnoli brownfield site, Tarzia et al. (2002) (as part of his PhD program with University of Naples Federico II) carried out a study aimed to discriminate anthropogenic pollution sources from natural pollution sources. For this study, heavy metals and Pb isotope data from soils, waste materials, scum, and slag samples from the brownfield site were used. 

The Pb isotope results showed a linear trend that suggests a mixing between two end members, one natural and related to the CF volcanics, and the other anthropogenic. The large overlap of isotopic data does not allow a precise quantitative discrimination of the contribution of each component, but it is possible to state that the natural component dominates. 

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