Daphnia magna as a Test Organism for Assessing the Impact of Cr(III) and Cr(VI) on Water Quality

Abstract

The importance of a comprehensive assessment of the quality of surface water environments as sources of drinking water, especially in conditions of global ecological disasters, is shown by the example of pollution by heavy metals (by Cr(III) and Cr(VI), in particular) as ecotoxicants. The solution to this problem is successfully achieved through complex biotesting, which provides an integral assessment of the danger of contaminated water for living organisms, including man. Daphnia magna is used among standardized test organisms to assess the quality of natural waters as sources of drinking water supply. Some aspects of the toxic effect of chromium ions on daphnia have been established: the greatest toxicity effect depends on the degree of chromium oxidation, which corresponds to its MPC for drinking water. Chromium(VI) compounds are characterized by a significantly higher acute toxicity than chromium(III) compounds; and their concentration in aqueous solution, the duration of impact on test organisms, and the presence of complexing ligands (shown by the example of EDTA as an analogue of natural humic acids) also exert a significant effect. The death of Daphnia magna significantly increases with the rise in the concentration and the duration of exposure to chromium ions.