Behzad Murtaza

Phosphate-assisted phytoremediation of arsenic by Brassica napus and Brassica juncea: Morphological and physiological response

ABSTRACT In this study, we examined the potential role of phosphate (P; 0, 50, 100 mg kg−1) on growth, gas exchange attributes, and photosynthetic pigments of Brassica napus and Brassica juncea under arsenic (As) stress (0, 25, 50, 75 mg kg−1) in a pot experiment. Results revealed that phosphate supplementation (P100) to As-stressed plants significantly increased shoot As concentration, dry biomass yield, and As uptake, in addition to the improved morphological and gas exchange attributes and photosynthetic pigments over P0. However, phosphate-assisted increase in As uptake was substantially (up to two times) greater for B. napus, notably due to higher shoot As concentration and dry biomass yield, compared to B. juncea at the P100 level. While phosphate addition in soil (P100) led to enhanced shoot As concentration in B. juncea, it reduced shoot dry biomass, primarily after 50 and 75 mg kg−1 As treatments. The translocation factor and bioconcentration factor values of B. napus were higher than B. juncea for all As levels in the presence of phosphate. This study demonstrates that phosphate supplementation has a potential to improve As phytoextraction efficiency, predominantly for B. napus, by minimizing As-induced damage to plant growth, as well as by improving the physiological and photosynthetic attributes.

Metal uptake via phosphate fertilizer and city sewage in cereal and legume crops in Pakistan

Crop irrigation with heavy metal-contaminated effluents is increasingly common worldwide and necessitates management strategies for safe crop production on contaminated soils. This field study examined the phytoavailability of three metals (Cd, Cu, and Zn) in two cereal (wheat, maize) and legume (chickpea, mungbean) crops in response to the application of either phosphatic fertilizer or sewage-derived water irrigation over two successive years. Five fertilizer treatments, i.e. control, recommended nitrogen (N) applied alone and in combination of three levels of phosphorus (P), half, full and 1.5 times of recommended P designated as N0P0, N1P0, N1P0.5, N1P1.0, and N1P1.5, respectively. Tissue concentrations of Cd, Cu, Zn, and P were determined in various plant parts, i.e., root, straw, and grains. On the calcareous soils studied while maximum biomass production was obtained with application of P at half the recommended dose, the concentrations of metals in the crops generally decreased with increasing P levels. Tissue metal concentrations increased with the application of N alone. Translocation and accumulation of Zn and Cu were consistently higher than Cd. And the pattern of Cd accumulation differed among plant species; more Cd being accumulated by dicots than monocots, especially in their grains. The order of Cd accumulation in grains was maize > chickpea > mungbean > wheat. Mungbean and chickpea straws also had higher tissue Cd concentration above permissible limits. The two legume species behaved similarly, while cereal species differed from each other in their Cd accumulation. Metal ion concentrations were markedly higher in roots followed by straw and grains. Increasing soil-applied P also increased the extractable metal and P concentrations in the post-harvest soil. Despite a considerable addition of metals by P fertilizer, all levels of applied P effectively decreased metal phytoavailability in sewage-irrigated soils, and applying half of the recommended dose of P fertilizer was the most feasible solution for curtailing plant metal uptake from soils. These findings may have wide applications for safer crop production of monocot species when irrigating crops with sewage effluent-derived waters.

Arsenic Uptake, Toxicity, Detoxification, and Speciation in Plants: Physiological, Biochemical, and Molecular Aspects

Environmental contamination with arsenic (As) is a global environmental, agricultural and health issue due to the highly toxic and carcinogenic nature of As. Exposure of plants to As, even at very low concentration, can cause many morphological, physiological, and biochemical changes. The recent research on As in the soil-plant system indicates that As toxicity to plants varies with its speciation in plants (e.g., arsenite, As(III); arsenate, As(V)), with the type of plant species, and with other soil factors controlling As accumulation in plants. Various plant species have different mechanisms of As(III) or As(V) uptake, toxicity, and detoxification. This review briefly describes the sources and global extent of As contamination and As speciation in soil. We discuss different mechanisms responsible for As(III) and As(V) uptake, toxicity, and detoxification in plants, at physiological, biochemical, and molecular levels. This review highlights the importance of the As-induced generation of reactive oxygen species (ROS), as well as their damaging impacts on plants at biochemical, genetic, and molecular levels. The role of different enzymatic (superoxide dismutase, catalase, glutathione reductase, and ascorbate peroxidase) and non-enzymatic (salicylic acid, proline, phytochelatins, glutathione, nitric oxide, and phosphorous) substances under As(III/V) stress have been delineated via conceptual models showing As translocation and toxicity pathways in plant species. Significantly, this review addresses the current, albeit partially understood, emerging aspects on (i) As-induced physiological, biochemical, and genotoxic mechanisms and responses in plants and (ii) the roles of different molecules in modulation of As-induced toxicities in plants. We also provide insight on some important research gaps that need to be filled to advance our scientific understanding in this area of research on As in soil-plant systems.

Arsenic removal by Japanese oak wood biochar in aqueous solutions and well water: Investigating arsenic fate using integrated spectroscopic and microscopic techniques

In this study, we examined the sorption of arsenite (As(III)) and arsenate (As(V)) to Japanese oak wood-derived biochar (OW-BC) in aqueous solutions, and determined its efficiency to remove As from As-contaminated well water. Results revealed that, among the four sorption isotherm models, Langmuir model showed the best fit to describe As(III) and As(V) sorption on OW-BC, with slightly greater sorption affinity for As(V) compared to As(III) (QL=3.89 and 3.16mgg-1; R2=0.91 and 0.85, respectively). Sorption edge experiments indicated that the maximum As removal was 81% and 84% for As(III)- and As(V)-OW-BC systems at pH7 and 6, respectively, which decreased above these pH values (76-69% and 80-58%). Surface functional groups, notably OH, COOH, CO, CH3, were involved in As sequestration by OW-BC, suggesting the surface complexation/precipitation and/or electrostatic interaction of As on OW-BC surface. Arsenic K-edge X-ray absorption near edge structure (XANES) spectroscopy indicated that 36% of the added As(III) was partially oxidized to As(V) in the As(III) sorption experiment, and in As(V) sorption experiment, 48% of As(V) was, albeit incompletely, reduced to As(III) on OW-BC surface. Application of OW-BC to As-contaminated well water (As: 27-144μgL-1; n=10) displayed that 92 to 100% of As was depleted despite in the presence of co-occurring competing anions (e.g., SO42-, CO32-, PO43-). This study shows that OW-BC has a great potential to remove As from solution and drinking (well) water. Overall, the combination of macroscopic sorption data and integrated spectroscopic and microscopic techniques highlight that the fate of As on biochar involves complex redox transformation and association with surface functional moieties in aquatic systems, thereby providing crucial information required for implication of biochar in environmental remediation programs.

Influence of groundwater and wastewater irrigation on lead accumulation in soil and vegetables: Implications for health risk assessment and phytoremediation

ABSTRACT The current study evaluated the effect of groundwater and wastewater irrigation on lead (Pb) accumulation in soil and vegetables, and its associated health implications. A pot experiment was conducted in which spinach (Spinacia oleracea), radish (Raphanus sativus), and cauliflower (Brassica oleracea) were irrigated with groundwater and wastewaters containing varying concentrations of Pb. Lead contents were measured in wastewaters, soils and root and shoot of vegetables. We also measured health risk index (HRI) associated with the use of vegetables irrigated by wastewaters. Results revealed that Pb contents in groundwater and wastewater samples (range: 0.18–0.31 mg/L) were below the permissible limits (0.5 mg/L) set by the Food and Agriculture Organization (FAO). Application of Pb-containing groundwater and wastewater increased Pb concentration in soil and vegetables. Lead concentrations in all soils ranged from 10 to 31 mg/kg and were below the permissible limits of 300 mg/kg set by the European Union. Significant Pb enrichment was observed in the soils whereby all types of vegetables were grown and assessed for Pb risk. Our data showed that Pb contents, in all three vegetables (21–28 mg/kg DW), were higher than the permissible Pb limit of FAO (5 mg/kg Dry Weight (DW)). The HRI values were > 1.0 for radish and cauliflower. It is proposed that Vehari city wastewater/groundwater must be treated prior to its use for irrigation to avoid vegetable contamination by Pb, and as such for reducing Pb-induced human health risk.

A comparative study to evaluate efficiency of EDTA and calcium in alleviating arsenic toxicity to germinating and young Vicia faba L. seedlings

PurposeThis study delineated the effect of calcium (Ca) and ethylenediaminetetraacetic acid (EDTA) addition on arsenic (As) accumulation and physiological attributes of Vicia faba L.Materials and methodsTwo separate experiments were performed. In the first experiment, V. faba seedlings, grown under hydroponic conditions, were exposed to three levels of As (25, 125 and 250 μM) in the presence and absence of three levels of EDTA (25, 125, 250 μM) and calcium (CaCl2: 1, 5 and 10 mM). The effect of EDTA and Ca on As accumulation and physiological attributes of V. faba was assessed by determining As contents in roots and shoot, chlorophyll contents, H2O2 contents, and lipid peroxidation in young and old leaves. In the second experiment, V. faba seeds were grown in As-contaminated sand culture using the same treatment plan.Results and discussionThe accumulation and toxicity of As to V. faba plants increased with increasing As levels in nutrient solution. Arsenic exposure enhanced the production of reactive oxygen species (ROS) in both roots and leaves, which resulted in lipid peroxidation and decreased chlorophyll contents. The presence of both EDTA and Ca, in general, significantly decreased As accumulation by V. faba seedlings, Ca being more effective than EDTA. Both the amendments decreased As-induced reactive oxygen species (ROS) production and lipid peroxidation. In the case of chlorophyll contents, EDTA significantly decreased chlorophyll contents, while Ca significantly increased chlorophyll contents compared to As. The effect of all the treatments was more pronounced in roots than leaves and in young leaves compared to old leaves.ConclusionsIt is proposed that EDTA and Ca greatly affect As accumulation and toxicity to V. faba, and the effect varies greatly with their applied levels as well as type and age of plant organs. The germinating seedlings of V. faba may be preferred for risk assessment studies, while transplanting 1-week-old V. faba seedlings to As-contaminated soils can decrease its toxicity.

A critical review of selenium biogeochemical behavior in soil-plant system with an inference to human health

Selenium (Se) is an essential trace element for humans and animals, although controversial for different plant species. There exists a narrow line between essential, beneficial and toxic levels of Se to living organisms which greatly varies with Se speciation, as well as the type of living organisms. Therefore, it is crucial to monitor its solid- and solution-phase speciation, exposure levels and pathways to living organisms. Consumption of Se-laced food (cereals, vegetables, legumes and pulses) is the prime source of Se exposure to humans. Thus, it is imperative to assess the biogeochemical behavior of Se in soil-plant system with respect to applied levels and speciation, which ultimately affect Se status in humans. Based on available relevant literature, this review traces a plausible link among (i) Se levels, sources, speciation, bioavailability, and effect of soil chemical properties on selenium bioavailability/speciation in soil; (ii) role of different protein transporters in soil-root-shoot transfer of Se; and (iii) speciation, metabolism, phytotoxicity and detoxification of Se inside plants. The toxic and beneficial effects of Se to plants have been discussed with respect to speciation and toxic/deficient concentration of Se. We highlight the significance of various enzymatic (catalase, peroxidase, superoxide dismutase, ascorbate peroxidase, glutathione peroxidase) and non-enzymatic (phytochelatins and glutathione) antioxidants which help combat Se-induced overproduction of reactive oxygen species (ROS). The review also delineates Se accumulation in edible plant parts from soils containing low or high Se levels; elucidates associated health disorders or risks due to the consumption of Se-deficient or Se-rich foods; discusses the potential role of Se in different human disorders/diseases.

Biomedical applications of green synthesized Nobel metal nanoparticles

Synthesis of Nobel metal nanoparticles, play a key role in the field of medicine. Plants contain a substantial number of organic constituents, like phenolic compounds and various types of glycosides that help in synthesis of metal nanoparticles. Synthesis of metal nanoparticles by green method is one of the best and environment friendly methods. The major significance of the green synthesis is lack of toxic by-products produced during metal nanoparticle synthesis. The nanoparticles, synthesized by green method show various significant biological activities. Most of the research articles report the synthesized nanoparticles to be active against gram positive and gram negative bacteria. Some of these bacteria include Escherichia coli, Bacillus subtilis, Klebsiella pneumonia and Pseudomonas fluorescens. The synthesized nanoparticles also show significant antifungal activity against Trichophyton simii, Trichophyton mentagrophytes and Trichophyton rubrum as well as different types of cancer cells such as breast cancer cell line. They also exhibit significant antioxidant activity. The activities of these Nobel metal nano-particles mainly depend on the size and shape. The particles of small size with large surface area show good activity in the field of medicine. The synthesized nanoparticles are also active against leishmanial diseases. This research article explores in detail the green synthesis of the nanoparticles and their uses thereof.

Phytoremediation of Arsenic-Contaminated Soils Using Arsenic Hyperaccumulating Ferns

Arsenic contamination of soils is a global environmental, agricultural, and health issue given to the toxic and carcinogenic nature of As. Several anthropogenic activities, such as mining and smelting, coal combustion, wood preservation, leather tanning operations, and use of As-based pesticides in agriculture, have led to elevated concentrations of As in soil. Therefore, remediation and restoration of As-contaminated soils is imperative for providing safe food and healthy soils. In contrast to conventional (physicochemical) remediation methods, phytoremediation of As-contaminated soils using As-hyperaccumulating fern species has emerged as an eco-friendly, cost-effective, and efficient technology. Since the discovery of As-hyperaccumulator, Pteris vittata L., several other As-hyperaccumulating fern species have been identified in Pteris and Pityrogramma genera which demonstrated the ability to remove As from soil. This review will briefly discuss about the As dynamics and availability in soil; elucidate the mechanisms involved in As tolerance and (hyper)accumulation by ferns/plants for improving the phytoremediation efficiency; evaluate the capacity of As-hyperaccumulating fern species (e.g., P. vittata, Pityrogramma calomelanos) for phytoremediation of As-contaminated soils under pot and field conditions; and discuss how phosphate amendments, microbes, and agronomic practices can increase phytoremediation efficiency of the ferns.

Removal and recovery of metals by biosorbents and biochars derived from biowastes

The production of biosorbents and biochars from various biowastes (such as the agricultural and food industries and algal and fungal biomass) has received considerable attention because of their potential use in the removal and recovery of elements, such as precious metals and heavy metals from water and wastewater. Recovery of these metals from their aqueous solutions has emerged as an exciting area of research as a result of increasing or fluctuating prices of metals (eg, precious metals), limited availability of their deposits, and the ever-increasing demand and time- and energy-consuming processes needed to mine metal deposits. This review will summarize the various sources of metals, the available biowastes of the agricultural and food industries, and preparation methods for biosorbents and biochars from biowastes. We will focus on metal and heavy metal removal and recovery from waste and wastewater, methods for metal recovery, pretreatment and modification of biosorbents and biochars for enhanced metal sequestration, and strategies to provide stability to biosorbents and biochars to maximize resource recovery.