No abstract

The Water Framework Directive 2000/60/EC [1] has been in force in the EU since 2000. Its main aim is to ensure the protection of waters and help them to obtain the socalled "good" status until 2015. Accomplishing these tasks requires identifying the threat and evaluating its influence on the environment. When necessary, it also means undertaking some remedy procedures to achieve the environmental aims in the assumed range and time concerning the "good" chemical status of waters. Discharging industrial and municipal wastewater (rich in metal and metalloid ions) into rivers and streams is one of the many factors affecting environmental water quality.

The aim of the present study was to investigate the binding strength of chromium (Cr) ions to aquatic macrophyte Callitriche cophocarpa. Shoots of the plants were incubated in a natural water solution containing Cr(III) or Cr(VI) at a concentration ranging from 0.5 to 4 mM under laboratory conditions. We found that C. cophocarpa has an extremely high capacity to bind Cr. The average level of accumulation reached 28,385 or 7,315 mg kg−1 dry weight for plants incubated with Cr(III) or Cr(VI), respectively. Shoots incubated in a 0.5 mM concentration of Cr(III) for 5 days removed almost 100 % of the metal from solution. The major pool of the bound Cr(III) ions follows the strongest mechanism of metal-binding to an organic matter. In contrast, we found that only 25 % of Cr(VI) ions are bound into the metallo-organic compounds and 57 % of Cr(VI) exists in an easily remobilizable form. Activity of a photosynthetic electron transport (as FV/FM) was evaluated with respect to the Cr-binding mechanism. Our results contribute to the development of knowledge on processes controlling bioremediation of heavy-metallic compounds in aquatic systems.