for copper speciation (Fig. 4). Fig. 4A shows that the activities of free
Cu2+ decrease by several orders of magnitude as the pH and [DOC]/
[Cu] ratio increase. This decrease in free Cu2+ activity is because of formation
of organic Cu-DOM complexes and copper-carbonate complexes
(at high pH). Fig. 4B shows the strong effect of DOC on copper complexation.When
the ratio of DOC to copper exceeds about 1 g DOC/mmol Cu,
copper is predominantly found as organic Cu-DOM complex