Potentially toxic elements in agricultural soils from the Lombardia region of northern Italy

The aim of this survey was to assess the concentration range of potentially toxic elements (PTE) in agricultural soils of the Lombardia plain and to consider their spatial variability across the catchments of the Ticino, Adda, Oglio, Mincio and Po rivers. Agricultural soils were sampled at depths of 0–30 cm based on the LUCAS (Land Use/Cover Area frame statistical Survey) using a pre-existing network of geo-referenced points. The samples from each catchment were analysed to determine their main properties and their concentrations of As, Be, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Tl, V and Zn. The spatial distribution of PTEs reflected the predominant lithology on which the soils developed and the sediment deposition along the river catchments. The highest concentrations of As and Sb in the Adda basin and of Co, Cr and Ni in the Po basin were due to their geological origin. The elevated concentrations of Hg and Pb in the Adda basin probably arose from old mining operations. Italian legislation includes two legislative levels: A for residential/recreational areas and B for commercial/industrial areas. The A levels were exceeded only for As, Be, Co, Cr, Cu, Ni and Zn. The percentage of soils exceeding this threshold was low and consistently below 15% of the measured samples for all elements.