Variations in the Phytoremediation Efficiency of Metal-polluted Water with Salvinia biloba: Prospects and Toxicological Impacts

Abstract

The occurrence of heavy metals in industrial wastewater is unanimously considered a major concern since these pollutants cannot be chemically or biologically degraded and therefore have long residence times. Phytoremediation is one of the most widespread biotechnological applications worldwide, which consists in the use of plants to adsorb or accumulate a broad range of inorganic and organic contaminants from water, air, and soil. To improve the cost-effectiveness and sustainability of phytoremediation-based wastewater treatment systems, it is essential to use plants that are not only efficient in pollutants removal, but also abundant and easily accessible at the target site, requiring no-special culture conditions. In this study, we have evaluated the capacity of naturally-occurring aquatic macrophytes of the genus Salvinia (classified as Salvinia biloba) to phytoremediate water artificially contaminated with cadmium (Cd), copper (Cu), lead (Pb), or zinc (Zn) at equal molar concentrations (50 ± 2 and 100 ± 1 µM), during 48 h. Additionally, photosynthetic and antioxidant pigments (carotenoids, chlorophylls, anthocyanins, and flavonoids), and soluble carbohydrate content was also measured in floating leaves of Salvinia specimens to appraise heavy metals phytotoxicity. Elemental analyses to plant tissue indicate that S. biloba was able to bioconcentrate all four metals analyzed, albeit with different degrees of affinity. In addition, the mechanisms of uptake and detoxification were dissimilar for each ion, resulting in greater removal of Cu and Pb (≥96%, at both concentrations), in comparison to Cd (79 ± 4% and 56 ± 2% for 50 ± 2 and 100 ± 1 µM, respectively) and Zn (77 ± 5% and 70 ± 4% for 50 ± 2 and 100 ± 1 µM, respectively). Accordingly, the assessment of the selected physiological parameters in floating leaves suggests that different response mechanisms are triggered by each metal in S. biloba to counteract the corresponding toxicological stress.

Prospects of Plant-Based Systems as an Eco-Technological Approach for Heavy Metals Removal from Polluted-Waters

“…The content of macromolecules such as polysaccharides, lipids, and proteins with negatively charged groups (e.g., carboxyl, sulphate, phosphate) at the plant's surfaces are key factors that determine the binding mechanism between the positively charged metal ions and the biomass [9]. In addition, different biologicalregulated processes such as metal uptake by transmembrane proteins and/or ionic channels, expression of metalloproteins and phytochelatins, and translocation to leaves are also part of the heavy metals' removal mechanisms used by plants [10].…”

IoT Based Real-Time Monitoring of Phytoremediation of Wastewater using the Mathematical Model Implemented on the Embedded Systems

“…Many works [1][2][3][4][5][6][7][8][9][10][11][12] adopted phytoremediation in the wastewater treatment processes. Usually, they differ in the types of green plants and the pollutants to be removed.…”

“…The water hyacinth was used in [1][2][3][4][5] as the plant for phytoremediation. The other types of plants are water lettuce [5], lettuce [6], kale [6][7][8], bamboo species [9], ornamental plant species [10], Rhizophora mangle [11], and Salvinia biloba [12].…”

“…Meanwhile, the common types of the pollutants to be removed are: NO3 [1,6,10], N [2], PO4 [1], Na [3], K [3], P [4], NH3 [4,6], Zn [5,12], Pb [5,8,12], Fe [5], Cu [5,9,12], Ni [5], Cd [7,8,12].…”

“…Compared to the existing systems, our work has several distinctive approaches. First, compared to the conventional methods [1][2][3][4][5][6][7][8][9][10][11][12], our approach provides real-time monitoring of pollutant's concentration in the phytoremediation. Second, compared to the existing real-time monitoring in phytoremediation [13,14], our approach offers a simple hardware configuration and adopts a recent IoT technology.…”