The application of atomic absorption spectroscopy to the determination of selected trace elements in sediments of the Coxs River Catchment

An investigation of heavy metal concentrations in sediments from Coxs River catchment, a tributary of the Hawkesbury-Nepean River system, has been undertaken. A number of digestion methods were assessed for the determination of Pb, Cu, Cd, Zn, Ni, Mn, Fe, Co and Cr in reference materials by flame AAS. The method that produced the best recovery is reverse aqua regia, HNO3-HC1 with ultrasonification followed by heating on a hotplate. Based on analysis of sediments from 133 sites, background concentrations were established. Elevated heavy metal concentrations were recorded in some samples. The three most polluted areas were investigated for heavy metal associations and distributions. Metal bioavailability was assessed from sediment samples by using selective extraction techniques. The association of heavy metals with different solid phases was assessed by a sequential extraction technique involving a series of extraction reagents. Pd, Cu, Fe and Cr were mainly associated with Fe/Mn oxides and organic matter plus sulphide phases. While Cd, Zn, Ni and Co which behave similarly were extracted from each step, the largest percentages of these metals were found in Fe/Mn oxides and organic matter phases. Mn was different to other metals, in that it predominantly associated with the ion exchangeable form