Speciation of iron, copper and zinc in the Hawkesbury River

Abstract

A combination of membrane filtration, ion exchange, coprecipitation and thin-film X-ray fluorescence spectrometry was used to obtain data on the chemical speciation of iron, copper and zinc in surface waters, ranging in salinity from 0 to 30Ym, of the Hawkesbury River, N.S.W. Iron, the principal trace metal, was found mainly (>90%) in the particulate form. The dissolved (filterable) iron fraction was largely non-ion- exchangeable (colloidal) in the freshwater region and ion-exchangeable in saline waters (as hydrated ions or metal complexes that dissociate on the chelating resin column). Copper and zinc, by contrast, were almost entirely filterable over the whole salinity range, copper being 50-100% in the non-ion-exchangeable fraction, and zinc, 70-100% ion-exchangeable.