Appendices 5-13 - Nautilus Cares - Nautilus Minerals

Concentration (ppb)
250.0
200.0
150.0
100.0
50.0
0.0
0 200 400 600 800 1000 1200 1400 1600
Time (min)
Figure 3: Concentration (ppb) of Cd, Co, Cu and Pb in 0.45 !m filtered
seawater from 1:10 ore:seawater elutriation at 6 o C
All five metals show similar trends with an initial rapid release of metals followed by
a decrease in dissolved concentration to a minimum at 180 minutes and then a slow
increase in concentration to 720 minutes. Between 720 and 1,440 minutes an
equilibrium appears to have been achieved with little or no increase in concentration
over that time. This result shows that the metal release in the oxic seawater is being
largely controlled by sulfide oxidation and the dissolution of the oxidation products
(see Batterham, 1999 and references therein).
Metal concentrations in filtered seawater form the Phase 2 experiment, effect of
temperature at 12 and 24 o C, is shown in Appendix 5 with associated QC data in
Appendix 6. As observed in the Phase 1 experiment the metals that were
substantially elevated above background seawater were Co, Cu, Cd, Mn, Pb and Zn.
Silver was elevated and was above the ANZECC/ARMCANZ (2000) 95% protection
level by a factor of approximately 2.5.
Figure 4 shows there was a substantial increase in metal dissolution at 12 and 24 o C
compared to 6 o C. The concentration of Zn released was more than order of
magnitude higher than any other metals. Figure 4 shows there was no substantial
Cu
Cd
Pb
Co
12