Atmospheric Deposition of Inorganic Pollutants Close to a Steel Mill ( Aosta , Italy )

Atmospheric depositions were collected monthly by bulk passive samplers in different sites located in Aosta Valley, in the north west of Italy. The town of Aosta has grown around an industrial complex making stainless steel products. The characterization of atmospheric deposition allows evaluating the impact on pollution caused by airborne metals released by the electrical steel mill and the study of the spatial variability of the atmospheric fall-out, taking also meteoclimatic conditions into accounts. The entire volume gathered was filtered to obtain soluble and insoluble fractions. As, Cd, Co, Cr, Fe, Mn, Mo, Ni, Pb and Zn were analysed on both fractions and the total deposition is the sum of the two fractions. The study identifies Cr, Ni and Mo as typical markers of stainless steel production. In urban sites, deposition fluxes of typical stainless steel production metals are higher than those measured in the rural site. The wind direction recorded in the period considered explains the higher correlation values of typical steel production metals in sites located downwind from the plant. Small differences were observed among urban sites for metal deposition fluxes, confirming the fact that industrial contribution is localized in a restricted area. Moreover, a comparison with other urban and industrial locations highlights similar data in urban sites for different metal fluxes and important differences between industrial sites, characterized by the presence of typical production markers. Finally, the characterization of solubility of the entire group of analyzed metals underlines that the percentage of soluble fraction of typical production markers (Cr, Ni and Co) is lower in urban sites than in the rural one.