CONTRIBUTION OF THE LAMBRO RIVER TO THE TOTAL POLLUTANT TRANSPORT IN THE PO WATERSHED (ITALY)

Major ionic components and pollutants including the elements As, Cd, C o, Cr, Cu, Ni, Pb, Zn, Fe and Mn and some organic compounds (anionic s urfactants and organohalogenated compounds) were monitored in the midd le and lower stretches of the Po River and in its most polluted tribut ary, the Lambro River. Variations in major ions and pollutant levels b etween the main river system and its tributary clearly indicate that a nthropogenic activities in the watershed have markedly influenced the environmental quality in the Lambro, heavily affecting concentrations of potentially toxic metals and organics as well as those of major ion s (mainly Na+ and Cl-). Metal concentrations were measured in both the dissolved and particulate phases of the Lambro and Po. Metals in the Lambro compared to the corresponding levels in the Po showed either a preferential enrichment in one of the two phases or comparable increas ing factors (ICF) in both phases, With reference to more toxic element s, ICF were found to be higher in the particulate phase for Cd, Cu and Cr while they appeared comparable for Pb and Zn, Differences in the m odes of metal transport between the main river system and its tributar y were significant for Cu and Cd, in particular, and were interpreted on the basis of differences in water redox conditions and solid compos ition. Data collected allowed the polluting contribution of the Lambro discharge to the overall Po watershed to be evaluated. Copyright (C) 1996 Elsevier Science B.V.