The Kinetics of Cadmium in Daphnia magna as Affected by Humic Substances and Water Hardness

In order to investigate mechanisms causing enhanced toxicity of cadmium in humic lake waters the kinetics of cadmium in Daphnia magna was studied. The uptake rate of cadmium was two times faster in humic lake water than in the humic-free reference water. On the other hand, the depuration rate was equal in humic and reference waters. Thus the acutely lethal concentration in animal is reached faster in humic than in humic-free water. However, altered kinetics of cadmium in humic lake water was also affected by lower water hardness compared to the reference.