Assessment of trace elements natural enrichment in topsoil by some Italian case studies

Trace elements (for example As, V, Cr, Ni, Cu, Z, Cd and Pb) released by human activity are ubiquitously detected in topsoil. They can be conveyed from the topsoil to the ecosystem, thus affecting human health. Also, trace elements are not sensitive to any process of decomposition in soils and the bioavailability is complicated due to the reactive nature of soil constituent. The goal of this assessment is to present a methodology able to evaluate the topsoil trace elements natural enrichment and distinguish between geogenic phenomena and anthropogenic contributions. This paper presents some Italian case studies in Lombardy and Lazio. The potential pollution risks of trace elements in topsoil were evaluated by geoaccumulation index (Igeo) and enrichment factor. The results show an absence of anthropogenic contamination, highlighting the need to consider the local characteristics (landfills, municipal solid waste plants, industrial areas, quarries, etc.). Moreover, a statistical method (cumulative frequency and normalization method) was presented to determine the geochemical baseline values. In the case of Borgo Montello (Lazio), manganese is used as a relative element due to its high presence in soils. The proposed geochemical baseline values of V, Cr, Co and Ni thorough normalization method were, respectively, 123.07, 82.10, 9.41 and 29.70 mg kg−1, instead by cumulative frequency the results were 78.24, 84.10, 6.67 and 23.70 mg kg−1. This methodology shows a potential validity to define the geochemical baseline values, but it is necessary many data (n ≥ 40) and distributed homogeneously over the study area.