Fig. 3. Cadmium (a) and copper (b) concentrations in the percolate collected from different micro suction cups at pH 4.5. For the conditions at Steps 1 to 5 of the experiment refer to the Materials and Methods section and Table 3. Volumes are given in multiples of the pore volume (V₀) of the respective cup. The reference lines show the expected metal concentrations if no interaction with the cup materials occurred (i.e., the concentration measured in the initial solution). The reference line for Cu in Step 1 is at the same value as in Steps 3 and 5.