SREL Reprint #2429

Effects of calcium, magnesium, and sodium on alleviating cadmium toxicity to Hyalella azteca

B. P. Jackson1, R. J. Lasier2, W. P. Miller3, and P. W. Winger2

1Advanced Analytical Center for Environmental Sciences, Savannah River Ecology Laboratory,
University of Georgia, Post Office Drawer E, Aiken, SC 29802, USA
2U.S. Geological Survey, Patuxent Wildlife Research Center, Warnell School of Forest Resources,
University of Georgia, Athens, GA 30602, USA
3Department of Crop and Soil Sciences, University of Georgia, Athens, GA 30602, USA

Introduction: Toxicity of trace metal ions to aquatic organisms, arising through either anthropogenic inputs or acidification of surface waters, continues to be both a regulatory and environmental problem. It is generally accepted that the free metal ion is the major toxic species (Florence et al., 1992) and that inorganic or organic complexation renders the metal ion non-bioavailable (Meador, 1991, Galvez and Wood, 1997). However, water chemistry parameters such as alkalinity, hardness, dissolved organic carbon and pH influence metal ion toxicity either directly by lowering free metal ion concentration or indirectly through synergistic or antagonistic effects. Alkalinity and salinity can affect the speciation of metal ions by increasing ion-pair formation, thus decreasing free metal ion concentration. For example, Cu was found to be less toxic to rainbow trout in waters of high alkalinity (Miller and Mackay, 1980), due to formation Of CuCO3 ion pair, and corresponding reduction in free Cu2+ concentration. The influence of salinity on the toxicity of cadmium to various organisms has been demonstrated in a number of studies (Bervoets et al., 1995, Hall et al., 1995, Lin and Dunson, 1993, Blust et al., 1992). In all these studies the apparent toxicity of cadmium was lowered as salinity was increased due to increased formation of CdCl+ and CdCl2 aqueous complexes that are non-toxic or of much lower toxicity than the free Cd2+ ion. Changes in pH exert both a biological and chemical effect on metal ion toxicity (Campbell and Stokes, 1985). Low pH favors greater metal ion solubility, and, in the absence of complexing ions, reduced speciation of the metal ion, which tends to increase toxicity compared to higher pH. However, low pH also enhances competition between H+ and metal ion for cell surface binding sites, which tends to decrease metal ion toxicity. . . .

SREL Reprint #2429

Jackson, B. P., P. J. Lasier, W. P. Miller, and P. W. Winger. 2000. Effects of calcium, magnesium, and sodium on alleviating cadmium toxicity to Hyalella azteca. Bulletin of Environmental Contamination and Toxicology 64:279-286.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).