Evaluation of the autochthonous free-floating macrophyte Salvinia biloba Raddi for use in the phytoremediation of water contaminated with lead

Abstract

Plant-based systems for the treatment of contaminated environments (phytoremediation) have been proved to be highly efficient in removing pollutants, especially heavy metals. However, in strictly aquatic and high-flow treatment systems, the use of free floating plants could be more adequate. For a treatment system based on phytoremediation strategies to be feasible and sustainable, it is essential that the plants used are not only efficient in pollutants removal, but also abundant in the region, easily accessible, and do not require special culture conditions. In this work, we evaluate the capacity of four different autochthonous macrophytes obtained from the Paraná river (Argentina) to adapt and reproduce without any additional nutrient supply or temperature special conditions (laboratory «indoor» environment). Only those specimens that doubled their biomass in a two-week period without any visual signs of deterioration (loss of turgor, chlorosis and/or necrosis of leaves) were considered for further analysis. From different pre-selected species, only Salvinia biloba Raddi showed a wide capacity to adapt and reproduce under these conditions. Moreover, the ability to remove lead (Pb 2+) by S. bilobawas evaluated in water samples contaminated with three metal concentrations (4.8 ± 0.3, 9.1 ± 0.4 and 19.6 ± 0.5 mg/L) at different exposure times (0-24 h), showing a high efficiency in the pollutant elimination. A compartmentalization analysis indicates that surface adsorption was the predominant mechanism for Pb 2+ removal at the first 24 h. Finally, the bioconcentration factor (BCF) was calculated at the end of the exposure time,reflecting both hyperaccumulation capacity and high metal tolerance by this plant. Our results suggest that incorporation of S. biloba in wastewater treatment systems could be a successful strategy to efficiently remove heavy metals by bioremediation processes.

Variations in the Phytoremediation Efficiency of Metal-polluted Water with Salvinia biloba: Prospects and Toxicological Impacts

“…Naturally-occurring S. biloba specimens were manually collected from a shallow lake located in the Middle Paraná River, Entre Rios, Argentina (32 • 52 35" S; 60 • 40 33" W), with no pollution load, as described in previous works [18,19]. Three different sampling campaigns were carried out between February and April (2019).…”

“…Selected S. biloba specimens were gently rinsed with deionized water and placed (10.0 g wet basis) in beaker glass (500 mL) with artificially-contaminated water at independently equal molar concentrations (50 ± 2 and 100 ± 1 µM) of Cd (5.6 ± 0.2 and 11.2 ± 0.1 mg/L), Cu (3.2 ± 0.1 and 6.4 ± 0.1 mg/L), Pb (10.4 ± 0.4 and 20.7 ± 0.2 mg/L) or Zn (3.3 ± 0.1 and 6.5 ± 0.1 mg/L). Metal concentrations were selected in accordance with previously reported data [12][13][14][15][16][17][18][19]. The experiments were carried out in controlled conditions at an average room temperature of 24 ± 2 • C under artificial light with a photon flux intensity of 50 µmol m −2 s −1 (Osram Dulux L HE, Munich, Germany) and 12 h photoperiod according to [18,19].…”

“…Metal concentrations were selected in accordance with previously reported data [12][13][14][15][16][17][18][19]. The experiments were carried out in controlled conditions at an average room temperature of 24 ± 2 • C under artificial light with a photon flux intensity of 50 µmol m −2 s −1 (Osram Dulux L HE, Munich, Germany) and 12 h photoperiod according to [18,19]. Three experimental units (n = 3) were used as replicates for each exposure time (0, 2, 4, 6, 10, 24, and 48 h) and the data were reported as mean value ± standard deviation (S.D.).…”

“…The Salvinia species most amply found in Argentina are S. auriculata Aubl., S. minima Baker, S. natans (L.) All., and S. biloba Raddi (synonym: S. herzogii de la Sota). Only a reduced number of studies have analyzed the capacity of S. biloba to phytoremediate water contaminated with heavy metals (e.g., Cd, Cr, Zn, Ni, Cu, and Pb) [12][13][14][15][16][17][18][19]. In general, most of them have focused on individual metals, at different concentrations [12,13,[17][18][19].…”

“…Only a reduced number of studies have analyzed the capacity of S. biloba to phytoremediate water contaminated with heavy metals (e.g., Cd, Cr, Zn, Ni, Cu, and Pb) [12][13][14][15][16][17][18][19]. In general, most of them have focused on individual metals, at different concentrations [12,13,[17][18][19]. To the best of our knowledge, only three of such works [14][15][16] have analyzed S. biloba metal-phytoremediation efficiency for two or more metals, but submitting plants to different metal molarity (i.e., the molar amount of cation ions at the sample solution was different between the analyzed metals), rendering comparisons between elements difficult to carry out.…”