The nickel cycles of Figure 17.4 are not at steady state. What does this imply for glacial in-use reservoirs of nickel? Which reservoirs are changing most rapidly? What will be the change in the contents of cach of the in-use reservoirs after 10 years, given constant flow rates?

248 Chapter 17 Material Flow Analysis 199 25 M w RU US (a) (b) CN+HK JP 18 66 14 14 Mi (c) (d) Figure 17.4 Circular nickel diagrams for year 2000 for the largest extractor, (a) Russia, and the three principal users: (b) United States; (c) China; and (d) Japan. The units are gigagram per year nickel (Gg/a N. 1 gigagram = 1000 metric tons). The widths of the arrows are proportional to the flow magnitudes If no data are provided, nickel flows are 0 Gg/a Ni. The data are in units of Tg Ni/yr for 2000. The dotted circle at life stage W indicates a "phantom flow" required for mass balance but not reflected in the available statistics or calculations. (Reproduced by permission from B. Reck, et al., The anthropogenic nickel cycle: Insights into use, trade, and recycling, Environmental Science & Technology, 42, 33943400, 2008.)