Spatial characterisation of multi-level in-use copper and zinc stocks in Australia
A methodology has been developed to characterise the in-use stocks of copper and zinc at a variety of spatial levels. The approach employs representative concentrations of copper and zinc in their main in-use reservoirs (which account for virtually all the metal put into service) together with geographic information system (GIS) data sets of the spatial locations and densities of these reservoirs. The authors have applied this methodology to Australia at four spatial levels: central city, urban region, states/territories, and country, to produce what is believed to be the first multi-level spatial characterisations of the in-use stocks of technological materials. The results are presented quantitatively and as a series of stock density maps for Inner Sydney, Sydney Metro, all Australian states/territories, and Australia itself. The total stocks in Australia are estimated at about 4.3 Tg Cu (4.3 thousand million kg) and 3.8 Tg Zn (3.8 thousand million kg), or about 240 kg Cu/capita and 205 kg Zn/capita. A statistical analysis of the data shows that the metal stock density at a given spatial level is largely determined by a small number of high-density components at the next lower level. The spatial analysis of the in-use stocks indicates that 50% of all copper and zinc stock resides in just 10% of Australia's local government areas. The largest stocks occur in large urban regions, which can contain copper and zinc densities more than a hundred times higher than rural areas. These regions are expected to be major Australian 'metal mines' in the future.