Platinum and rhodium in Tagus estuary, SW Europe: sources and spatial distribution

16 pages, 7 figures, 1 table
The spatial distribution of Pt and Rh was assessed in Tagus estuary and their sources discussed. Both elements were analysed in superficial sediment samples (n = 72) by adsorptive cathodic stripping voltammetry. Concentrations varied within the following ranges: 0.18–5.1 ng Pt g−1 and 0.02–1.5 ng Rh g−1. Four distinct areas were established: “reference”; waste- and pluvial water discharge; motorway bridges and industrialised areas. The calculated reference median concentrations were 0.55 ng Pt g−1 and 0.27 ng Rh g−1. Linear relationships were found between Pt and Al, Fe and LOI, whereas Rh depicted scattered patterns. The highest concentrations were found nearby industrialised areas and a motorway bridge, corresponding to the enrichment of 10 and 6 times the background of Pt and Rh, respectively. The main sources of contamination to the Tagus estuary derived from historical and present industrial activities and from automotive catalytic converters. Large variations of Pt/Rh ratio (0.48–39) point to different sources, reactivity and dilution effects
Carlos E. Monteiro (CEM) acknowledges the Portuguese Foundation for Science and Technology (FCT) for the grant funding of his PhD (SFRH/BD/111087/2015). The authors would like to gratefully acknowledge also the support of FCT projects UID/QUI/001002013 and PTDC/QEQ-EPR/1249/ 2014 ‘Recovery versus environmental impacts of Rare Earth Elements derived from human activities’ (REEuse); the COSTAction TD1407, Network on Technology-Critical Elements (NOTICE), from environmental processes to human health threats, by means of a short-term scientific mission support to CEM; and the support of Rute Cesário in part of the field work and ICP-MS analysis