Sediment metal-magnetic properties in urban catchments
This research project examines the application of mineral magnetic techniques to the characterisation of particulates and their sources in the urban highway environment and in stormwater runoff. A review of previous investigations into sources, levels and pathways of metals through the urban highway environment is presented. The principles upon which the mineral magnetic techniques are based and those parameters employed in this study are described. Previous environmental applications are reviewed. A representative sampling scheme was established in a small well-defined sub-catchment. Copper, Fe, Pb and Zn concentrations in highway associated sediments increased with proximity to the road centre and seasonal maxima occurred in summer. Heavy metal loadings were dominated by the sediment loadings. Strong linear relationships between the metals, Cu, Fe, Pb and Zn, and magnetic mineral concentration related parameters, X and IRM3oomT, were observed. Mineral magnetic characterisation achieved complete discrimination between highway associated sediments and roof sediments allowing the derivation of equations defining the sediment groupings. Variations in metal-magnetic properties of sediments with particle size ,were investigated. Primary source materials and particulates were analysed. Metallic and magnetic mineral parameters indicated that atmospheric and vehicle derived· particulates were probably the dominant origins of source particulates. The variation of particulate associated heavy metals in stormwater runoff at the sub-catchment is discussed. Mineral magnetic parameters characterised the majority of stormwater particulates with the roof sediment grouping. The implications of these investigations is discussed. The study was expanded to encompass the parent c~tchment. The characterisation of source sediments from land use and road types other than that· represented by the sub-catchment was carried out. Stormwater particulates collected at the main catchment'· outfall were found to be generally characterised with soil and roof sediment groupings. The further application and use of mineral magnetic parameters in similar research is discussed.