Study on Chromium-Binding Capacity of Callitriche cophocarpa in an Aquatic Environment

Abstract

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.

Mechanical properties of Callitriche cophocarpa leaves under Cr(VI)/Cr(III) influence

“…1,000 mg/kg d.w. after incubation in Cr(VI) (Augustynowicz et al 2010). Moreover, the accumulation levels following exposure to Cr(III) are usually 5-10 times higher, and, up to now, the maximum detected level of Cr was almost 0.3 % d.w. (Augustynowicz et al 2013). In accordance with the definition of hyperaccumulation (Van der Ent et al 2013), when it grows in the natural environment, the C. cophocarpa would be called a Cr hyperaccumulator.…”

“…Secondly, it is known that submerged macrophytes can reveal a higher metal uptake than floating aquatic plants due to a high contact area with the surrounding water (Chandra and Kulshreshtha 2004). C. cophocarpa reveals the extraordinary accumulation capacity of Cr ions comparable with those described for commercially used sorbents (Augustynowicz et al 2013).…”

“…Before the experiment, the water was filtered to prevent the growth of microorganisms (Supelco filters, 0.2 lm pore size). The Cr concentration was selected according to earlier experiments (Augustynowicz et al 2010(Augustynowicz et al , 2013 The average electrical conductivity of water was equal to 0.335 mS/cm, pH = 7.8 and Eh (redox potential) = 180 mV. An amount of 1.5 g of shoots was submersed in 300 ml of the aforementioned Cr solutions.…”

“…The Callitriche cophocarpa, a widely distributed aquatic higher plant (macrophyte), was recently proven to be an excellent candidate for both the Cr(III) and Cr(VI) phytoextraction purpose (Augustynowicz et al 2010(Augustynowicz et al , 2013. This submersed macrophyte is of great interest as regards the phytoremediation of polluted water for two key reasons.…”

“…This method enables the measurement of the intensity of the fluorescence signal of the particular element, which is proportional to the element content. In this study, we attempted to find a new basic mechanism of Cr influence on Callitriche leaves, but we did not focus on the applicability of the results in the context of the phytoremediation technology, which was rather the subject of our earlier works (Augustynowicz et al 2010(Augustynowicz et al , 2013(Augustynowicz et al , 2014. We believe that this study will contribute to the understanding of the mechanisms controlling the influence of heavy metal ions on higher plant species in the aquatic environment.…”