Iron and copper complexation in Macaronesian coastal waters

Dissolved iron (dFe) and copper (dCu), the concentration and the conditional stability constants of organic binding ligands (LFe, LCu, log KcondFe3+L and log KcondCu2+L) were studied in the surface coastal waters of the Macaronesia region (Cape Verde, Canary Islands, and Madeira) using competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV). Two oceanic stations were also studied: the Cape Verde Ocean Observatory (CVOO) and the European Station for Time Series in the Ocean in the Canary Islands (ESTOC). Dissolved Fe varied from 0.46 to 1.32 nM and LFe concentrations were between 0.56 and 2.96 nM. More than 98% of the total dFe was complexed with conditional stability constants (log KcondFe3+L) between 20.77 and 21.90 (L2-type ligands). Dissolved Cu concentrations ranged between 0.07 and 4.03 nM and the amount of LCu varied between 0.54 and 2.59 nM, with more than 99% of dCu organically complexed. The conditional stability constant (log KcondCu2+L) showed values between 13.40 and 14.42 (L1-type).