A number of researchers have published element-specific case studies in recent years. The following is a selective but not exhaustive list:
• Copper: European cycle (Graedel et al. 2002); Latin American and Caribbean cycle (Vexler et al. 2004); U.S. cycle (Zeltner et al. 1999); Swiss cycle (Wittmer et al. 2003); multilevel cycles (Graedel et al. 2004).
• Zinc: Technological characterization (Gordon et al. 2003); European cycle (Spatari et al. 2003); Latin American and Caribbean cycle (Harper et al. 2006).
• Silver: European cycle (Lanzano et al. 2006); multilevel cycles (Johnson et al. 2006).
• Chromium: Multilevel cycles (Johnson et al. 2007).
A dynamic analysis over multiple years was also undertaken to estimate the accumulation of copper in use and in waste reservoirs (Spatari et al. 2005). In this study, stocks and flows in North America during the twentieth century were characterized by a top-down model using consumption rates of various copper-bearing products and their life time. In North America, the study estimated the potential for recovering resources from waste repositories as 55 Tg Cu.
The spatial characterization of multilevel in-use stocks of copper and zinc in Australia was attempted using GIS (van Beers et al. 2007). Bottom-up estimates of the in-use stock of aluminium at the state level (Recalde et al. 2008) and nickel at the municipal level (Rostkowski et al. 2006) were also conducted. For a recent review of in-use metal stocks studies, see Gerst and Graedel (2008).
These studies demonstrate that quantification of flows and stocks at various spatial levels is methodologically feasible. Accuracy, however, is still not sufficient because of limited data availability and consistency.
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