Lemna trisulca L.: a novel phytoremediator for the removal of zinc oxide nanoparticles (ZnO NP) from aqueous media.

Several aquatic plant species have been proposed for phytoremediation of waters polluted with heavy metals and pesticides According to the limited information available, aquatic macrophytes also have a promising potential to remove NPs from aqueous media. Although there is considerable information on the remediation potential of Lemna spp., the capacity of Lemna trisulca seems to be neglected, particularly for nanoparticle removal. Therefore, in the current study, we aimed to investigate the removal efficiency of L. trisulca exposed to 3 different ZnO NP concentrations (2.5, 5, and 10 ppm) for 1, 4, and 7 days in Hoagland solutions and the removal percentage were measured on each duration and compared among groups. The accumulated zinc levels were measured in whole plant material and bioconcentration factors were calculated for each group. In addition, the effect of ZnO NPs on the photosynthetic activity of the plant was evaluated via analyzing the photosynthetic pigment (chlorophyll a and b) concentration. The removal percentage ranged between 9.3 and 72.9% and showed a gradual increase in all experimental groups based both on dose and test duration. The statistical comparisons of the removal percentage among the groups with or without the plant indicate that L. trisulca had a significant effect on removal rates particularly between 1st and 4th days of exposure, however, did not show any progress at 7th days. The only significant difference for chl-a and chl-b levels was observed in 10 ppm ZnO NP-exposed plants at 7th days.

A comparison of the removal efficiencies of Myriophyllum spicatum L. for zinc oxide nanoparticles (ZnO NP) in different media: a microcosm approach.

The phytoremediation potential of Myriophyllum spicatum L. has been well documented for bulk-sized heavy metals, including zinc (Zn). However, there is no information on the removal efficiencies of this aquatic macrophyte for zinc oxide nanoparticles contaminated waters. Therefore, the present study was aimed to compare the removal efficiency of M. spicatum in two different media: tap water and pond water. Results were evaluated by comparing percentage (%) removal and goodness-of-fit to regression models. Plants were exposed to 0.8 and 2 ppm nano-sized Zn for 1, 4, and 7 days. The zinc concentrations were monitored using ICP-MS. The %removal in tap water ranged between 29.5 and 70.3%, and slightly higher in pond water. Modeling results confirmed that there was a strong relationship between removal performance and exposure duration. Time-dependent removal shows that %removal shows no further progress after 4 days. Our results also indicate that planktonic communities in pond water might play an important role in the fate of ZnO NPs.

Modeling of the bioaccumulative efficiency of Pistia stratiotes exposed to Pb, Cd, and Pb + Cd mixtures in nutrient-poor media.

The bioaccumulation capacity of water lettuce (Pistia stratiotes) including heavy metals has been well documented. However, its bioaccumulative efficiency for Pb, Cd, and Pb + Cd mixtures in nutrient-poor media is neglected. Therefore, the present study was aimed to investigate the bioaccumulative efficiency of the water lettuce by evaluating the bioconcentration factors (BCFs) and goodness-of-fit to regression models. Plants were exposed to various concentrations of Pb, Cd, and Pb + Cd mixtures in tap water for 1, 4, and 7 days. Heavy metal accumulation in whole plant tissue was measured with ICP-MS. The highest bioaccumulation rate was recorded at 1 day exposure tests for both metals as 14.9 mg/kg for Pb and 2.21 mg/kg for Cd. The BCFs for Pb and Cd ranged between 0.13 and 2.39 and 0.08 to 1.24, respectively. The modeling of the BCFs and exposure duration indicate that all of the models developed were significant. The R2 values were higher for single metal exposure tests. The model fitted curves demonstrate the decrease in BCFs with increasing exposure duration in all groups. Our results indicate that water lettuce can be used to treat nutrient-poor media polluted with low levels of Pb, Cd, and Pb + Cd mixtures for short incubation periods.