Bioaccumulation and Biosorption of Mercury by Salvinia biloba Raddi (Salviniaceae)

Aquatic macrophytes play a key role in nutrient cycling and in the dynamics of aquatic ecosystems. Many species have been evaluated in terms of their potential in phytoremediation processes in environments contaminated by metals. Considering this kind of application, we evaluated the potential for the bioaccumulation and biosorption of mercury by Salvinia biloba as a function of (i) different concentrations of mercury ions in the solution, (ii) the exposure time of live plants and dry biomass to the contaminant, and (iii) different pH's, besides (iv) analyzing the effects of this metal on morphological and anatomical parameters. Bioaccumulation was evaluated by subjecting live plants to treatments with concentrations of 0.05, 0.1, and 0.2 mu g.mL(-1) of mercury in the solution and the control (0 mu g.mL(-1)), at intervals of 3 days (0, 3, 6, 9, 12, and 15 days) at pH values of 5.5, 6.0, and 6.5. For biosorption, we used the dry biomass applying the same design, only changing the time intervals (0, 4, 8, 12, and 24 h). The bioaccumulated and biosorbed mercury was determined by atomic absorption spectroscopy. High values of mercury were bioaccumulated and biosorbed, and accordingly, as the concentration of mercury ions increases in the solution, the higher the value accumulated by both living plant and dry biomass. The time of exposure and the different pH values presented variation when associated with different concentrations in the bioaccumulation of mercury. Finally, few symptoms of toxicity in living plants were observed, evidencing the resistance of S. biloba to mercury and its potential use as a phytoremediation in water bodies contaminated by this metal.