The mesocosm study of cadmium and copper bioaccumulation by water hyacinth in one-time and sequentially contaminated system

The results of investigation of cadmium and copper accumulation by water hyacinth, depending on the conditions of exposure, are discussed. The main specialty of the study consists in the use of mesocosm approach that allows estimating consequences of pollutant effect on ecosystem in conditions as close to natural as possible. It includes the use of mesocosms - polyethylene capacities installed directly into studied water reservoir. This approach provides data that allow describing the course of studied processes in nature due to taking into consideration a climatic factor as well as buffer capacity of the real system to pollutants in its current state. Test substances were introduced in mesocosms followed by the study of their elimination dynamics and accumulation in plants. It was shown that the degree of cadmium and copper removal by water hyacinth is 74-92% and 88-91%, respectively, and it depends on the way of pollutant introducing into the reservoir. Uptake by plankton and sedimentation do not contribute significantly in this process. It was found that cadmium does not affect the accumulation of copper, whereas the presence of copper inhibits removal of cadmium in case of sequential addition. Nevertheless for both the elements, the values of bioconcentration factor (BCF) are high enough: BCFCu=3500 +/- 200 and BCFCd=2600 +/- 150, which indicates a high ability of the plant to accumulate these elements. About 9% of Cd migrates to the stems and leaves of water hyacinth in the process of bioaccumulation, while more than 97% of copper concentrates in the roots.