SPECIATION OF HEAVY-METALS ON SUSPENDED SEDIMENT UNDER HIGH-FLOW CONDITIONS IN THE RIVER-AIRE, WEST YORKSHIRE, UK

Concentrations of heavy metals (Cd, Cu, Pb and Zn) on suspended sedime nts during a flood event at Thwaite Mills, River Aire, were analysed u sing a five step sequential extraction technique to determine their ma jor chemical associations (exchangeable, surface oxide and carbonate, Fe and Mn oxides, organic and residual metal ions). Total metal concen trations were lowest at higher discharges, resulting from dilution by clean sediment. The major transport fractions are the Fe and Mn oxides , which carry 29% of the total metals. Knowledge of the chemical forms of heavy metals on suspended sediment is essential for estimating the ir biological availability and physicochemical reactivity. (C) 1998 Jo hn Wiley & Sons, Ltd.