A study of the geochemical behaviour of anthropogenic platinum-group elements in a mixed urban-rural catchment : the River Stour, Kent, U.K

A baseline survey of contemporary fluvial sediments in the Kentish Stour, east Kent, England, has been undertaken to document the sources and distribution patterns of anthropogenic PGE in an attempt to constrain some of the physical and chemical parameters that may influence the distribution of these elements. Nine sedimentary rocks, four motorway-runoff sediments and twenty-one river sediments were analysed for PGE by NiS fire assay pre-concentration and ICP-MS. The highest element abundances occur in a sample of ashed sewage sludge (total PGE content of 392 ng/g), whilst the lowest values were recorded in the soils and sedimentary rocks. The total PGE content of the river sediments ranged from 0.4 to 14.2 ng/g in 1999 and from 0.6 to 167 ng/g in 2001, and exhibited significant variation along the river. This variation corresponds strongly with land use changes (urban versus rural) and with points of discharge from sewage treatment works. The PGE and trace element concentrations of the river sediments, sedimentary rocks, motorway runoff sediments and ashed sewage sludge were normalised against their average crustal abundance to identify characteristic normalisation patterns. With this technique, high Pd concentrations in the River Stour sediments were found to be indicative of sewage inputs. The partitioning of Pt, Pd and Rh was investigated in a novel combination of Tessier’s (1979) sequential extraction technique and a Te coprecipitation. The partitioning in the sediments of a sediment retention lagoon progressed from more to less mobile sediment phases. The PGE are emitted in a form (possibly particulate) that becomes predominantly associated with the silicates fraction. The behaviour of the PGE in the River Stour is predicted to be controlled predominantly by physical processes.EThOS - Electronic Theses Online ServiceGBUnited Kingdo