Soil pollution: Anthropogenic versus geogenic contributions over large areas of the Lazio region

During the last three decades, the scientific community, politicians and decision makers have focussed on the behaviours of trace elements in soil, its accumulation and toxicity, the bioavailability and risk of metals, and soil remediation technologies. Trace metals (or metalloids), such as As, Pb, Cr, Cd, and Ni, cause more environmental contamination than organic chemicals. Therefore, it becomes increasingly important to distinguish between the geogenic and anthropogenic sources of these trace metals, and to understand that the background values change depending on the area and the scale of the area investigated. A total of 40 selected topsoil samples were collected near urban areas in the Lazio region of Italy, from sites characterised by different geological substrate, specifically the Appian Way Regional Park, Borgo Monello, Cisterna di Latina and Roccasecca. Concentrations of V, Cr, Mn, Fe, Co, Ni, Cu, As, Cd and Pb in topsoil and background samples collected at a depth of approximately 1 m have been analysed. The analytical results were used to calculate the geoaccumulation index (Igeo) to evaluate possible metal enrichment in topsoil related to human activity. The results indicate that there is no contamination associated with anthropogenic impact at the selected sites; however, a detailed study based on the lithological characteristics of the areas indicates local enrichment by several of the metals considered, especially in the Roccasecca topsoil.