Capacity of Nerium oleander to Phytoremediate Sb-Contaminated Soils Assisted by Organic Acids and Oxygen Nanobubbles

Abstract

Antimony (Sb) is considered to be a toxic metalloid of increasing prevalence in the environment. Although several phytoremediation studies have been conducted, research regarding the mechanisms of Sb accumulation and translocation within plants remains limited. In this study, soil from a shooting range was collected and spiked with an initial Sb(III) concentration of 50 mg/kg. A pot experiment was conducted to investigate whether Nerium oleander could accumulate Sb in the root and further translocate it to the aboveground tissue. Biostimulation of the soil was performed by the addition of organic acids (OAs), consisting of citric, ascorbic, and oxalic acid at low (7 mmol/kg) or high (70 mmol/kg) concentrations. The impact of irrigation with water supplemented with oxygen nanobubbles (O2NBs) was also investigated. The results demonstrate that there was a loss in plant growth in all treatments and the presence of OAs and O2NBs assisted the plant to maintain the water content at the level close to the control. The plant was not affected with regards to chlorophyll content in all treatments, while the antioxidant enzyme activity of guaiacol peroxidase (GPOD) in the roots was found to be significantly higher in the presence of Sb. Results revealed that Sb accumulation was greater in the treatment with the highest OAs concentration, with a bioconcentration factor greater than 1.0. The translocation of Sb for every treatment was very low, confirming that N. oleander plant cannot transfer Sb from the root to the shoots. A higher amount of Sb was accumulated in the plants that were irrigated with the O2NBs, although the translocation of Sb was not increased. The present study provides evidence for the phytoremediation capacity of N. oleander to bioaccumulate Sb when assisted by biostimulation with OAs.

Hydroponic phytoremediation of antimony by Tamarix smyrnensis and Nerium oleander

“…The same pattern was followed in the antioxidative response of maize roots, where the CAT and POD activity increased and decreased, respectively, with increasing concentration of Sb 40 . More recent evidence shows that CAT activity in the roots of N. oleander was not significantly affected by exposure to Sb, while the GPOD in the roots was found to be significantly higher in the presence of Sb 41 . As the selected plant species accounts for the activity of antioxidant enzymes, it is essential to monitor their response in order to provide precise information about the antioxidant defense under heavy metal stress.…”

“…significantly higher in the presence of Sb. 41 As the selected plant species accounts for the activity of antioxidant enzymes, it is essential to monitor their response in order to provide precise information about the antioxidant defense under heavy metal stress.…”