The Influence of Water Chemistry on Trace Metal Bioavailability and Toxicity to Aquatic Organisms

Quantifying the factors affecting the toxicity and bioaccumulation of trace metals by aquatic organisms is a major goal of aquatic scientists. Overall, these factors can be grouped into four major categories: solution conditions, which affect the chemical form of a given metal ion; the nature of the metal ion and trends in complexation chemistry among metals of the periodic table; the nature of the response being measured; and the nature of the aquatic organisms. Among the general physicochemical factors affecting metal ion speciation, temperature and ionic strength primarily affect the values of equilibrium constants and activity coefficients. Metal ions complexed with natural macromolecular organic matter or strong synthetic chelating agents generally are considered not to be directly available to aquatic organisms, whereas inorganic complexes generally are. Progress in relating measures of metal bioactivity in aquatic organisms to atomic properties or indices thereof has been fairly limited, in spite of much interest among scientists in metal contamination of surface waters.