The reversible electrodeposition of trace metal ions from multi-ligand systems: Part II. Calculations on the electrochemical availability of lead at trace levels in seawater

A general method for calculating the electrochemical availability of a trace metal in a multi-ligand system is illustrated by calculations on lead in artificial seawater. The procedure adopted assumes that the metal is accumulated at a mercury-coated rotating disc electrode during the plating process by the reversible reduction of metal ions. Although uncertainties in the rate constants and stability constants employed prevent the model from being used predictively, qualitative relationships between chemical speciation and electrochemical availability are discussed. The sensitivity of the calculated electrochemical availability to uncertainties in the stability constants and rate constants and variations in diffussion layer thickness and pH is considered in some detail. The results of the calculations are used to formulate recommendations for the electrochemical analysis of untreated natural samples.