Distribution of toxic elements and transfer from the environment to humans traced by using lead isotopes. A case of study in the Sarno River basin, south Italy

The results of a large geochemical study on various environmental media (soil, stream sediment, groundwater, surface water, lettuce and human hair) of the Sarno River basin, which is one of the most polluted areas in Italy, are presented. Further, it aims to deepen our understanding of the distribution of Pb and its isotope composition for the differentiation between natural and anthropogenic metal sources. Our results show the environmental media to be significantly enriched in Cr, Cu, Pb, Hg, Zn, and to a lesser extent in Sb, Cd and Ni compared to the natural local background variation. The numerous industrial activities (mainly tanneries) have caused environmental pollution especially Cr and Hg in soils and sediment samples. Such contamination is also evident in lettuce and in the hair of the resident population, which shows particularly high values for both Cr and Hg. The unusually high As, Be and Sn concentrations arise mostly from natural sources due to the volcanic nature of the investigated area. Lead isotope measurements indicate a trend suggesting mixing between two end-members, one of clear natural origin (geogenic) and another related to human activities (anthropogenic). Lead isotope results demonstrate that Pb in hair of inhabitants is similar to those in the local topsoil and that gasoline is one of the main, but not the only source of metal pollution. The most important exposure risks within the study area are associated with toxic elements levels in topsoil and stream sediment, and the ingestion of locally grown lettuce. The high concentrations of these elements in hair are a further confirmation of this exposure pathway.