Determination of Free Metal Ion Concentrations Using Bioassays

Abstract

A procedure was developed by which free metal ion concentrations, toxic to aquatic life, can be calculated by comparing metal toxicity before and after addition of a complexing agent of known complexing capacity. Application of this method suggests that the growth of freshwater copepods is affected at free copper concentrations around 10⁻¹⁰ to 10⁻⁹ mol∙L⁻¹. In natural waters, with unidentified ligands of unknown complexing ability, this procedure provides the only method currently available for estimating free metal concentrations at the low levels often causing sublethal toxicity to aquatic organisms.Key words: metal toxicity, complexation, free metal, copepods, copper