In the last decades, many anthropogenic activities have resulted in heavy metal contamination of freshwaters and surrounding environments. This poses serious threats to human health. Phytoremediation is a cost-effective technology which is useful for remediating polluted soils and water. Recently, the use of aquatic free-floating plants has been proposed to remediate polluted water. In this context, a study on the capacity of two aquatic plants, Lemna minor (duckweed) and Salvinia auriculata (salvinia), to remediate Cu+2 (Cu) polluted water was carried out. Initially, the species were exposed to different copper concentrations (1, 5, 10, 20 and 50μmolL-1) in order to assess Cu+2 toxicity to the plants. In addition, plants were treated with two safeners (benoxacor and dichlormid), with the aim of pointing out any safening effect of these compounds on the aquatic species. Toxicity tests showed that safened plants had a greater Cu resistance, especially at the higher Cu doses. Finally, unsafened and safened plants were tested in the decontamination of water polluted by copper (1.2mgL-1). In general, duckweed removed higher amounts of Cu from polluted water than salvinia, and, surprisingly, for both the species the safeners significantly increased the plants' capacity to remove the metal from the polluted waters. Lastly, an HPLC-based method was developed and standardized to monitor the residual amounts of the two safeners in the water. While dichlormid was completely absorbed by duckweed within few days after the treatments, some residual amounts of both safeners were found in salvinia vegetated water after two weeks. In conclusion, the results of this research show that the use of aquatic species in combination with safeners is an attractive and reliable tool to make plants more effective in phytoremediation of water polluted with metals (or other toxic compounds).
Keywords: Copper; Duckweed; Safeners; Salvinia; Water remediation.
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