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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.

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conicet.gov.ar, +54-341-4368000/int.1495).

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Electrical trees in liquids (streamers) occur on the nano-second timescale and produce structures that dissipate on voltage removal and sometimes even during voltage application. In AC fields the structures are a combination of fine filaments from the positive half-cycle and spheroidal cavities from the negative half-cycle. In contrast electrical trees in solids are permanent filamentary structures with a fractal geometry that grow on timescales of hours or longer at typical field values. Here we present the results of tree formation in a silicone gel under an AC applied electric field. These grow on timescales of minutes and possess a fine branched filamentary structure as well as spheroidal cavities. As in liquids, the cavities can collapse during tree growth. In contrast the filamentary structure is permanent as in solids. However the whole tree contracts following the removal of the applied voltage. The observed stability of the partial self-healing tree features are discussed in terms of the mixed liquid and solid features of the gel structure.

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