The toxicity and bioaccumulation of cadmium and copper as affected by humic acid

The toxicity of Cd and Cu to daphnids was evaluated over a 42-day exposure period at three humic acid concentrations. The addition of humic acid to test water decreased the acute and chronic toxicity of Cu but increased the acute and chronic toxicity of Cd. However, there was no effect of HA on the bioaccumulation of either metal. At the highest concentration, the presence of humic acid actually resulted in an increase in mean brood sizes of Cu-exposed animals and prevented a reduction in mean brood sizes of Cd-exposed animals.