Trace metals speciation in sediments of the Basento River (Italy)

The abundance and distribution of selected metals (cadmium, cobalt, chromium, copper, nickel, lead, thallium, vanadium, and zinc) in the stream sediments were studied along the Basento River (Italy). Two hundred eighty samples were collected in seventy stations during four different seasons. Sequential extraction procedures were carried out to define the chemical forms of the metals, in order to better understand the hazardousness of these pollutants, emphasizing the anthropogenic pressure of the sites studied. Different parameters were used to describe the contamination of these metals in the river basin: the Contamination Factor (CF), the Degree of Contamination (C(d)), the Enrichment Index (El), the Individual Contamination Factor (ICF), and the Global Contamination Factor (GCF). By means of a risk assessment methodology, it was calculated that during summer the river system was exposed to a moderate potential ecological risk and that the other three seasons highlighted relatively lower degrees of contamination. Pb and Zn were the metals of most concern with respect to the system pollution, first of all in the form of oxide phases. The metal amounts in the form of oxide phases appeared to be very important also for metals such as Co and Cr. Different metals occurred in critical concentrations in various stations near Potenza town (Industrial Area). The anthropogenic pressure of Tl and V seemed to be lower than for the other metals. The relations between clay minerals and Co, Cr, Ni amounts highlighted the importance of clay minerals for favouring the complexation of these elements by organic matter.