Temporal variation of copper and zinc complexation capacity in the Humber estuary

The complexation capacity (CC) for zinc and copper in the Humber estuary was determined and compared with data obtained using the same procedures from previous years. The CC for both metals was found to be relatively stable over a time span of 4 years for zinc and 10 years for copper. Levels of CC ranged from, in the upper estuary, 400 nM (copper) and 150 nM (zinc) to between 25 and 50 nM for both metals in the lower estuary. The CC from freshwater inputs appears to be relatively conservative with simple dilution accounting for the decrease in CC as salinity increases. A seasonal effect for copper is suggested.