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

Interaction of Lead and Cadmium Reduced Cadmium Toxicity in Ficus parvifolia Seedlings

Potentially toxic elements (PTEs) pollution occurs widely in soils due to various anthropogenic activities. Lead (Pb) and cadmium (Cd) coexist in soil frequently, threatening plant growth. To explore the interaction effect between Pb and Cd in Ficus parvifolia and the response of plant physiological characteristics to Pb and Cd stress, we designed a soil culture experiment. The experiment demonstrated that Pb stress improved leaf photosynthesis ability, while Cd stress inhibited it. Furthermore, Pb or Cd stress increased malonaldehyde (MDA) content, but plants were able to reduce it by increasing antioxidant enzyme activities. The presence of Pb could alleviate Cd phytotoxicity in plants by inhibiting Cd uptake and accumulation as well as increasing leaf photosynthesis and antioxidant ability. Pearson correlation analysis illustrated that the variability of Cd uptake and accumulation between Pb and Cd stress was related to plant biomass and antioxidant enzyme activities. This research will offer a new perspective on alleviating Cd phytotoxicity in plants.

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.

Phytoremediation capabilities of Salvinia molesta, water hyacinth, water lettuce, and duckweed to reduce phosphorus in rice mill wastewater

The objective of this study was to investigate the reduction of phosphorus from rice mill wastewater by using free floating aquatic plants. Four free floating aquatic plants were used for this study, namely water hyacinth, water lettuce, salvinia, and duckweed. The aquatic plants reduced the total phosphorus (TP) content up to 80% and chemical oxygen demand (COD) up to 75% within 15 days. The maximum efficiency of TP and COD reduction was observed with water lettuce followed by water hyacinth, duckweed, and salvinia. The study also aims to predict phosphorus removal by three modeling techniques, for example, linear regression (LR), artificial neural network (ANN), and M5P. Prediction has been done considering hydraulic retention time (HRT), hydraulic loading rate (HLR), and initial concentration of phosphorus (Cin) as input variables whereas the reduction rate of TP (R) has been considered as a predicted variable. ANN shows promising results as compared to M5P tree and LR modeling. The model accuracy is analyzed using three statistical evaluation parameters which are coefficient of determination (R2), root mean square error (RMSE), and means absolute error (MAE).