The contamination legacy of a decommissioned iron smelter in the Italian Alps

Abstract

The economically important activity of metal processing can tend to contribute to the degradation of the environment. Smelting is an important source of contaminants, dispersing large quantities of potentially toxic elements (PTE) and coproducts into the environment. Soils in the vicinity of smelters frequently contain high concentrations of PTE. In terms of the quantities processed, the major PTE are iron (Fe), aluminium (Al), copper (Cu), lead (Pb), manganese (Mn), and zinc (Zn); of these Cu, Pb and Zn are, potentially, highly hazardous elements. The general problem addressed by this study is to determine if the PTE concentration in the soils of an area downwind from a decommissioned iron smelter (46°04′16″N, 8°15′47″E) still shows signs of past contamination, and to discuss the options for intervention. The history of pollution of Villadossola soils due to the steel business comprises the last 150years. We measured pseudo-total (aqua regia) and available (EDTA) PTE in soils over an area of 15km2 near to the pollution source. Here we show that four decades after the end of the polluting event, when the total emissions originating from the smelter followed the order of magnitude Zn≫Cr≫Fe≈Pb≈Ca>Mn≫Cu>Ni≈Cd, the soil feedback, presented in terms of enrichment ratios, follows the order Cd>Bi≫Pb>Cu>Zn>Sb≈As>Cr. The total concentrations of PTE in the topsoil are: 101mg Cr, 8mg Co, 41mg Ni, 70mg Cu, 143mg Zn, 6mg As, 1.3mg Cd, 0.5mg Sb, 92mg Pb, and 1.3mgBikg−1 soil, with standard errors exceeding 50%. Our results show that it is unlikely that soils in the vicinity of the former smelter are a source of disproportionate human intake of PTE, and that the cost of reclamation would reach one quarter of the total annual budget of the municipality. Options for reducing the risks rely on the optimisation of the risk assessment factors, by adopting soil conservation practices.