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Bioremediation: Plants and Microbes for Restoration of Heavy Metal Contaminated Soils
Published in Jos T. Puthur, Om Parkash Dhankher, Bioenergy Crops, 2022
Harsh Kumar, Shumailah Ishtiyaq, Mayank Varun, Paulo J.C. Favas, Clement O. Ogunkunle, Manoj S. Paul
As3+ and As5+ are toxic and they interrupt plant physiology in a different manner. It has been reported that the As3+ form is more soluble (5-10 folds) in water than As5+. Methylated arsenic (+3) is perhaps more noxious than inorganic arsenic because it is more effective at inducing the breakdown of DNA (Vaclavikova et al. 2008). However, As5+ appears to be less harmful than As3+ because it is thermodynamically more steady due to its predominance under ideal circumstances and is the source of significant groundwater contaminant. Arsenate in the (As5+) state is often known to be toxic and carcinogenic to humans (Yusof and Malek 2009). It interrupts oxidative phosphorylation and ATP production. In plants, transition of arsenate to arsenite results in the development of reactive oxygen species leading to damage to DNA, protein, and lipids. The high toxicity of arsenate is due to its chemical resemblance with phosphate. Arsenic reduces the germination percentage and chlorophyll content in Triticum aestivum (Chun-xi et al. 2007), root and shoot dry weight in Oryza sativa (Shri et al. 2009), decreased fresh weight in Cicer arietinum (Gunes et al. 2009), and Arabidopsis thaliana (Leterrier et al. 2012).
Liquid–Liquid Separation by Supramolecular Systems
Published in Bruce A. Moyer, Ion Exchange and Solvent Extraction: Volume 23, 2019
Gabriela I. Vargas-Zúñiga, Qing He, Jonathan L. Sessler
Metallic oxoanions, such as arsenate and dichromate, are highly toxic and carcinogenic and represent an environmental concern due to their high solubility in water. Arsenate (e.g., H2AsO4−/H2AsO42−) is largely produced through anthropogenic activities (e.g., from pesticides, fossil combustion, or mining) and is readily accumulated in soils and groundwater.16 Several methods to treat arsenate-containing wastewater are known, including precipitation, co-precipitation, ion exchange, ultrafiltration, reverse osmosis, and solvent extraction; in many instances, these methods are effective.17,18 Dichromate salts (e.g., K2Cr2O7) are commonly used as additives in cement, photographic screen printing, and for the treatment of wood.19 Dissolved in water, dichromate is highly corrosive due to its powerful oxidizing properties. Dichromate is also harmful to living organisms. It easily diffuses through cell membranes producing hydroxyl radicals and other reactive oxygen species (ROS) that react adversely with DNA and proteins.20,21 This chemistry is thought to underlie the carcinogenicity of Cr(VI) species.
Reciprocal influence of arsenic and iron on the long-term immobilization of arsenic in contaminated soils
Published in Yong-Guan Zhu, Huaming Guo, Prosun Bhattacharya, Jochen Bundschuh, Arslan Ahmad, Ravi Naidu, Environmental Arsenic in a Changing World, 2019
Y. Sun, J. Antelo, J. Lezama-Pacheco, S. Fiol, S. Fendorf, J. Kumpiene
A cost-effective method to reduce the risk, i.e. mobility and bioavailability, of As in a contaminated site is to apply in situ stabilization techniques, keeping the soil on site. This technology is based on changing the As geochemistry of the soil by adding a chemical amendment which promotes As immobilization by for example precipitation or adsorption. Addition of ZVI to the soil, which will immobilize arsenate after ZVI oxidation, is usually proposed as an effective in-situ remedation technique reducing As leaching up to 98% (Kumpiene et al., 2008; 2006; Mench et al., 2002). The applicability of these techniques is becoming possible as more European countries are accepting a risk-based approach when defining whether the site is contaminated or not. In this approach the main risk-defining factor of a site is the contaminant bioavailability and mobility and not on its total concentration in the soil. Although the promising results obtained using this technique, questions regarding the long-term stability of the immobilized contaminant in the soil must be answered before establishing in-situ chemical stabilization as a widely accepted technique. The particle size of the Fe oxide particles in the soil will ultimately define the arsenate adsorption (immobilization), e.g. the smaller the Fe oxide particles are the higher the arsenate adsorption capacity of the Fe oxide (Waychunas et al., 2005). Since very small Fe oxide nanoparticles are formed upon the oxidation product of metallic ZVI, the immobilization of As in soils by Fe amendments can reach a high efficiency. The oxidation products of ZVI would be at first small Fe oxy-hydroxides such as ferrihydrite or lepidocrocite (γ-FeOOH) (Cornell & Schwertmann, 1996). The ageing of these nanoparticles in the soil might induce crystal growth and/or phase transformation, which would plausibly decrease the effectiveness of the remediation method with time.
Optimization of arsenic phytoremediation using Eichhornia crassipes
Published in International Journal of Phytoremediation, 2018
Tamara Daiane de Souza, Alisson Carraro Borges, Antonio Teixeira de Matos, Renato Welmer Veloso, Amanda Fernandes Braga
Arsenic can be found in water mainly in the forms of arsenate (As(V)) and arsenite (As(III)). The dominant As(V) species are negatively charged (H2AsO4− and HAsO42−), while the dominant As(III) species is neutrally charged (H3AsO3). According to Wan et al. (2011), the negatively charged As(V) species are more likely to be adsorbed and are generally more easily removed than As(III) in treatment systems. Water chemistry factors may affect arsenic removal by phytoremediation. The pH and nitrate can affect oxidation potential, arsenic species distribution and its availability for plants (Farnese et al. 2014). Phosphate compete with arsenic for absorption and affects process efficiency (Bertolero et al. 1987; Mkandawire and Dudel 2005; Duman et al. 2010; Wan et al. 2011).