Heavy metals in tributaries of Tiber River in the urban area of Rome (Italy)

Both natural and anthropogenic activities are responsible for heavy metal abundance in the environment. Due to the high persistence, heavy metals can accumulate and remain in the sediment for very long periods, becoming a source of contaminants for aquatic biota. Within small urbanized watercourse catchments, the accumulation of heavy metals in bottom sediments takes place and sediments can be adopted as an efficient indicator for monitoring heavy metal pollution levels and pollution sources in aquatic environments. Tiber River, the most polluted river among the 20 longest Italian rivers, has different tributaries distributed from north to south of Rome city. The aim of the study was to evaluate the heavy metal pollution in water and sediment of six Tiber River small tributaries through the use of land cover, water physico-chemical parameters and geochemical multi-index (Concentration factor, Pollution Load index, Enrichment factor and Geoaccumulation index). The results indicate that in general the contamination of water and sediments is moderate as the threshold values are exceeded only by some metals and in some sites. As regards the indices that evaluate the enrichment factors, it has been seen that some sampling sites have high values of specific metal enrichment (As, Hg, Pb). A more compromised situation is highlighted by the Concentration Factor and the Pollution Load index where more than half of the sampling sites are found at levels of significant heavy metal pollution suggesting that point sources of heavy metals in the water and sediments should be closely monitored by the use of combined analysis.