MARINE VS FLUVIAL SUSPENDED MATTER IN THE SCHELDT ESTUARY

The ratio of marine to fluvial suspended matter in the Scheldt Estuary was calculated by applying factor analysis to a data set of elemental concentrations. The data set consisted of 98 samples collected under various river discharge conditions. Each sample was analysed for the c oncentration of Cr, Pb, Fe, Mn, Ni, Co, Ba, Zn, Cu, Cd, S, Ca, Sr, Ag, Sn and Na. Five linearly independent processes were found to describe the variability of the elemental concentrations: (1) the supply of fl uvial material to the mixing zone; (2) manganese oxidation in the tran sition area between the anoxic upper estuary and the oxic lower estuar y; (3) the supply of marine material to the mixing zone; (4) a phytopl ankton bloom in the lower estuary; and (5) the formation of insoluble metal sulphides in the anoxic high-turbidity zone. Scores of the first and third factor were used to calculate the ratio of marine to fluvia l suspended matter in the mixing zone. Information on the origin of bo th the inorganic and organic fraction of suspended matter was obtained in this way. (C) 1998 Academic Press Limited.