By James A. Buckley, Gary A. Yoshida, Norman R. Wells, Romeo T. Aquino
Water Research, Volume 19, Issue 12, 1985, Pages 1549-1554, ISSN 0043-1354, DOI: 10.1016/0043-1354(85)90400-2.

The LC50 for total Cd averaged 4.8 and 8.0 [mu]g1-1 in river water and 33% sewage-treatment-plant effluent (STPE), respectively, and for Chelex-labile Cd, 3.9 and 5.6 [mu]g1-1, respectively. The LC50 values for total Cd were significantly (P < 0.05) different, indicating a reduction in toxicity of Cd in the presence of 33% STPE, presumably due to complexation of Cd2+. The similarity of LC50 values for Chelex-labile Cd indicates that that fraction contained toxic species of Cd at approximately the same concentration(s) in both river water and 33% STPE; it is therefore considered a better measure of Cd toxicity than total Cd. Furthermore, mortality was correlated with the concentration of Chelex-labile Cd but not with that of Chelex-nonlabile Cd. Measurements of Cd2+-complexing capacity by the Chelex method indicated that toxicity was due, at least in part, to Cd2+. Values were less than those obtained by the ion-selective-electrode method; these indicated that toxicity was due only to complexed Cd. Values from both methods were uncorrelated with LC50 values.
Keywords: cadmium; complexing capacity; Chelex 100 resin; sewage; river water; LC50; ion-selective electrode; salmon

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