TOXICITIES OF TOTAL AND CHELEX-LABILE CADMIUM TO SALMON IN SOLUTIONS OF NATURAL-WATER AND DILUTED SEWAGE WITH POTENTIALLY DIFFERENT CADMIUM COMPLEXING CAPACITIES

The toxicity of Cd to aquatic organisms varies with chemical form and species. In this study we undertook to determine how differential complexation, complexing capacity, water quality, total Cd and Chelex- (an ion exchange resin) labile Cd influence the acute toxicity of Cd to salmon in natural (river) water and diluted STPE. Complexing capacity was measured titrimetrically by ion-selective electrode (ISE) and by the Chelex method and is defined as the capacity of Cd**2** plus -reactive organic and inorganic compounds to render Cd**2** plus unmeasurable by the ISE and nonlabile to Chelex resin. Refs.