SPECIATION OF HEAVY-METALS IN FLOODPLAIN AND FLOOD SEDIMENTS - A RECONNAISSANCE SURVEY OF THE AIRE VALLEY, WEST YORKSHIRE, GREAT-BRITAIN

A five-step sequential extraction technique was used to determine the chemical association of heavy metals (Pb, Zn, Cu and Cd), with major s edimentary phases (exchangeable, surface oxide and carbonate, Fe and M n oxides, organic and residual metal ions), in samples from floodplain and recent flood sediments of the River Aire, West Yorkshire. Analysi s indicates that metals Pb and Zn are primarily associated with the Fe and Mn oxides, Cu with the organic fraction and Cd with exchangeable and surface oxide and carbonate metal ions. Knowledge of the chemical speciation of heavy metals in river sediment, despite the procedure's inherent limitations, facilitates an understanding of their bioavailab ility, storage and remobilisation in floodplain and river channel envi ronments.