Copper complexation in marine and terrestrial rain water

The complexation of copper was studied in rainwater collected in Norwich, UK, and during Atlantic and Indian Ocean cruises. The complexation was measured with Chelex resin, Sep-Pak columns and adsorptive cathodic stripping voltammetry with tropolone as a competing ligand. Strong organic complexation was observed in semi-urban and marine rain samples with conditional stability constants between 1011 and 1014. Model solutions of copper and humic matter found organic complexes of a similar strength to those observed in the rain samples suggesting humic material as a potential ligand. A large proportion of the copper in the rains was associated with strong organic complexes over the pH range 4–8 in both filtered and unfiltered rain samples suggesting organic complexation is an important process both in the atmosphere and on arrival to oceans.