Contribution of the Lambro River to the total pollutant transport in the Po watershed (Italy)

Abstract

Abstract Major ionic components and pollutants including the elements As, Cd, Co, Cr, Cu, Ni, Pb, Zn, Fe and Mn and some organic compounds (anionic surfactants and organohalogenated compounds) were monitored in the middle and lower stretches of the Po River and in its most polluted tributary, the Lambro River. Variations in major ions and pollutant levels between the main river system and its tributary clearly indicate that anthropogenic 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 ions (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 increasing factors (ICF) in both phases. With reference to more toxic elements, 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 modes of metal transport between the main river system and its tributary were significant for Cu and Cd, in particular, and were interpreted on the basis of differences in water redox conditions and solid composition. Data collected allowed the polluting contribution of the Lambro discharge to the overall Po watershed to be evaluated.