Characterisation of River Po particles by sedimentation field-flow fractionation coupled to GFAAS and ICP-MS

A procedure for elemental composition determination of water-borne rixer particles (Po River) on both sizefractionated and unfractionated submicron particles (0.1 1 lam) by graphite furnace atomic absorption spectroscopy tGFAAS) and inductively coupled plasma-mass spectrometry (ICP-MSI is reported. Sample fractionation was performed using sedimentation field-flow fractionation (SdFFF). The distribution of relative mass vs. particle size was determined using UV detection. Fractions were collected over a narrow size range for scanning electron microscopy. With this combination of techniques the mass, elemental composition, and shape distributions can be ~btained across the size spectrum of the sample. The size distributions of the major elements (A1, Fe) were determined by coupling both GFAAS and ICP MS techniques to the SdFFF. The procedure was validated using a reference chty sample. Satisfactory agreement was found between both the GFAAS and ICP MS aluminium signal and the UV detector signal. Some discrepancies were observed in the Fe/AI ratios when comparing GFAAS and ICP MS. Thus further investigation is in order to fully assess the role of SdFFF-ICP MS and SdFFF-GFAAS techniques for elemental characterisation of aquatic colloids. Both GFAAS and ICP MS signals unambiguously indicate a significantly higher Fe content in the lower size range, which is consistent with previous investigations. Trace element levels in unfractionated Po River particles, determined by both GFAAS and ICP MS, show good agreement. The high levels of Cu, Pb, Cr and Cd found associated with the colloidal particles underlines the signiticance of the environmental role played by the suspended matter in rivers in both highly industrialised and intensively cultivated areas