Phytodiversity on fly ash deposits: evaluation of naturally colonized species for sustainable phytorestoration

Assessment of medicinal plants colonizing abundantly on metal-enriched fly ash deposits: phytoremediation prospective

Heavy metal-enriched fly ash (FA) deposits are recognized as hazardous contaminated sites on the earth, which pollute our ecosystems. Consequently, the present investigation was carried out to explore the phytoremediation potential of naturally growing medicinal plants in the FA dumpsite. This present study chose two native medicinal plants i.e., Bacopa monnieri and Acmella oleracea found to be naturally colonizing abundantly on FA dumpsite to assess heavy metal accumulation. FA sample of B. monnieri thriving sites found to have metal content in order Mn (216.6)> Cr (39.27)> Zn (20.8)> Ni (16.1)> Cu (15.03)> Co (6.7)> Pb (5.43) whereas for A. oleracea FA dumpsites, the order of metal availability was Mn (750.3)> B (54.5)>Cr (37.2)>Zn (31.33)> Cu (18.7)> Ni (16.93)> Co (7.7)>Pb (4.23). In B. monnieri, higher concentrations of Cr and Mn were observed in the shoot in comparison to the root, indicative of its potential as a hyperaccumulator plant. Conversely, in A. oleracea, greater amounts of Pb were detected in the shoot relative to the root. Hence, it is recommended that B. monnieri and A. oleracea grow on such heavy metal-enriched substrates should be avoided for medicinal purposes; however, these plants can be used for phytoremediation purposes.

Investigating the recovery in ecosystem functions and multifunctionality after 10 years of natural revegetation on fly ash technosol

Technogenic soil (technosol) developed from coal fly ash (FA) landfilling has been considered a critical environmental problem worldwide. Drought-tolerant plants often naturally grow on FA technosol. However, the impact of these natural revegetations on the recovery of multiple ecosystem functions (multifunctionality) remains largely unexplored and poorly understood. Here we assessed the response of multifunctionality, including nutrient cycling (i.e., carbon, nitrogen, and phosphorus), carbon storage, glomalin-related soil protein (GRSP), plant productivity, microbial biomass carbon (MBC), microbial processes (soil enzyme activities), and soil chemical properties (pH and electrical conductivity; EC) to FA technosol ten years' natural revegetation with different multipurpose species in Indo-Gangetic plain, and identified the key factors regulating ecosystem multifunctionality during reclamation. We evaluated four dominant revegetated species: Prosopis juliflora, Saccharum spontaneum, Ipomoea carnea, and Cynodon dactylon. We found that natural revegetation initiated the recovery of ecosystem multifunctionality on technosol, with greater recovery under higher biomass-producing species (P. juliflora and S. spontaneum) than lower biomass-producing ones (I. carnea and C. dactylon). The individual functions (11 of the total 16 variables) at higher functionality (70 % threshold) also exhibited this pattern among revegetated stands. Multivariate analyses revealed that most of the variables (except EC) significantly correlated with multifunctionality, indicating the capability of multifunctionality to consider the tradeoff between individual functions. We further performed structural equation modeling (SEM) to detect the effect of vegetation, pH, nutrients, and microbial activity (MBC and microbial processes) on ecosystem multifunctionality. Our SEM model predicted 98 % of the variation in multifunctionality and confirmed that the indirect effect of vegetation mediated by microbial activity is more important for multifunctionality than their direct effect. Collectively, our results demonstrate that FA technosol revegetation with high biomass-producing multipurpose species promotes ecosystem multifunctionality and emphasizes the significance of microbial activity in the recovery and maintenance of ecosystem attributes.

Seasonal Variations in Bioaccumulation and Translocation of Toxic Heavy Metals in the Dominant Vegetables of East Kolkata Wetlands: a Case Study with Suggestive Ecorestorative Strategies

In recent times, East Kolkata Wetlands (EKW), a designated Ramsar site in the eastern part of megacity Kolkata, has been threatened by toxic heavy metal (HM) pollution. Besides being a natural wetland supporting biodiversity, EKW serves as a significant food basket for the city. For assessing the magnitude of HM pollution in this wetland, the three most cultivated food crops of EKW, namely Lagenaria siceraria (bottle gourd), Abelmoschus esculentus (ladies' fingers), and Zea mays (maize), as well as the ambient soil samples, were collected during premonsoon, monsoon, and postmonsoon for 2 consecutive years (2016 and 2017). Predominant HMs like cadmium (Cd), chromium (Cr), mercury (Hg), and lead (Pb) were analyzed in the roots and edible parts of these plants, as well as in the ambient soil to evaluate the bioaccumulation factor (BF) and translocation factor (TF) of each HM in the three vegetables. It was observed that the HM content in the food crop species followed the order Z. mays > L. siceraria > A. esculentus. HMs accumulated in all three vegetables as per the order Pb > Cd > Cr > Hg. Monsoon seems to be threatening in terms of bioaccumulation and translocation of HMs as both BF and TF were highest in this season irrespective of the plant species. Hence it demands critical monitoring of HM pollution levels in this wetland and subsequent ecorestoration through distinctive plant growth-promoting rhizobacteria (PGPR)-assisted co-cultivation of these food crops with low-metal-accumulating, deep-rooted, high-biomass-yielding, and bioenergy-producing perennial grass species for minimizing HM intake.

Sustainable amelioration of fly ash dumps linking bio-energy plantation, bioremediation and amendments: A review

Disposal of fly ash in dumps is posing serious environmental problem causing air pollution, groundwater contamination, and loss of valuable land making it unproductive dumpsites. Cultivation of plants using bioremediation technique is looked upon as one of the sustainable remedial solution to these fly ash dumpsites. In recent years, researches on the plantation of bio-energy crops over the fly ash dumpsites is creating renewed interest, as it serves remediation along with distinct energy outcomes creating a win-win situation. The issue of the slow growth of plants, due to lack of nutrients and microbial activities is being resolved through advances in bioremediation research done in conjunction with organic matter, microbial inoculants, and inclusion of wastewater. New researches are being done with different plants and microbes in the matrix combination and use wastewater to supplement nutrients requirement to find eco-friendly & sustainable solutions. The present paper critically reviews the research on bioremediation and amendments with specific to bio-energy plantation on fly ash dumps.

Ascorbate glutathione antioxidant system alleviates fly ash stress by modulating growth physiology and biochemical responses in Solanum lycopersicum

Tomato plants (Solanum lycopersicum L.) were developed in soils with different fly ash (FA) amendments (25, 50, 75, 100% FA) to measure the effects of FA on metal accumulation, chlorophyll pigments, chlorophyll fluorescence, growth, biomass, gas exchange parameters, and the ascorbate glutathione pathway (AsA-GSH). The metal concentration was much higher in FA compared to the garden soil/(control). The observed metal translocation was higher in roots than shoots. Plants raised in soils treated with 50% or more FA showed significant decreases in growth, biomass, gas exchange parameters, protein, chlorophyll pigments, and fluorescence parameters. Additionally, a significant increase in antioxidants under higher FA-amended soils were observed. Our results showed that the ability of Solanum lycopersicum plants to effectively synchronize the actions of antioxidant enzymes associated in reactive oxygen species (ROS) scavenging - notably superoxidase dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR) - with good maintenance of the AsA/DHA ratio, that could be connected to FA stress tolerance. The toxic metals present in FA caused oxidative stress in Solanum lycopersicum, as evident from the increase in electrolyte leakage (EL), lipid peroxidation (MDA), and ROS levels. Furthermore, the AsA-GSH cycle plays a key role in alleviating oxidative damage caused by FA application.

Understanding the Role of Litter Decomposition in Restoration of Fly Ash Ecosystem

Plant species possess a huge potential in restoration of fly ash ecosystem. Litter deposition and its decomposition in the ash deposited sites are two important processes of the fly ash ecosystem. In order to identify the biological potential of a plant species to aid restoration of fly ash deposited sites, it is needed to assess leaf litter decomposition as well as nutrient release pattern. In the present investigation, we studied the leaf litter decomposition of the plant species (Leucaena leucocephala, Pithecellobium dolce and Prosopis juliflora) and mix plantation in the fly ash ecosystem. The litter bag experiment was conducted in the area of plantation on the fly ash deposited site during a period of 365 days. Percentage of C and N was higher in L. leucocephala > P. dolce >Mix Plantation > P. juliflora while C/N ratio was higher in P. juliflora >Mix Plantation > L. leucocephala > P. dolce. L. leucocephala and P. dolce showed relatively fast decomposition rates (k = 1.27, 1.17), respectively while mix plantation (k = 0.82) and P. juliflora (k = 0.73) exhibited relatively slower decomposition rates. Thus, we noted that the decomposition rate of L. leucocephala was greater than the other selected species. This shows that the species having faster decomposition rate and nutrient release could be a factual choice for rehabilitation of fly ash deposited sites.

Adaptive Morphophysiological Features of Neottia ovata (Orchidaceae) Contributing to Its Natural Colonization on Fly Ash Deposits

In previous decades, some species of the Orchidaceae family have been found growing in man-made habitats. Neottia ovata is one of the most widespread orchids in Europe, however it is quite rare in Russia and is included in several regional Red Data Books. The purpose of this study was to compare the chemical composition and morphophysiological parameters of N. ovata from two forest communities of the Middle Urals, Russia: natural and transformed (fly ash dump of Verkhnetagil’skaya Thermal Power Station) for determining orchid adaptive features. The content of most of the studied metals in the underground parts (rhizome + roots) of N. ovata was considerably higher than in the leaves, which diminished the harmful effect of toxic metals on the aboveground organs. The adaptive changes in the leaf mesostructure of N. ovata such as an increase in epidermis thickness, the number of chloroplasts in the cell, and the internal assimilating surface were found for the first time. The orchids from the fly ash deposits were characterized by a higher content of chlorophyll b and carotenoids than plants from the natural forest community that evidenced the compensatory response on the decrease in chlorophyll a. The ability of N. ovata from the transformed habitat to maintain a relatively favorable water balance and stable assimilation indexes further contribute to its high viability. The study of orchid adaptive responses to unfavorable factors is necessary for their successful naturalization and introduction into a new environment.

Metal remediation potential of naturally occurring plants growing on barren fly ash dumps

The present study aimed to elucidate the remediation potential of visibly dominant, naturally growing plants obtained from an early colonized fly ash dump near a coal-based thermal power station. The vegetation comprised of grasses like Saccharum spontaneum L., Cynodon dactylon (L.) Pers., herbs such as Tephrosia purpurea (L.) Pers., Sida rhombifolia L., Dysphania ambrosioides (L.) Mosyakin & Clemants, Chromolaena odorata (L.) King & H.E. Robins along with tree saplings Butea monosperma (Lam.) Taub. The growth of the vegetation improved the N and P content of the ash. Average metal concentrations (mg kg^-1) in the ash samples and plants were in order Mn (345.1) > Zn (63.7) > Ni (29.3) > Cu (16.8) > Cr (9.9) > Pb (1.7) > Cd (0.41) and Cr (58.58) > Zn (52.74) > Mn (39.09) > Cu (10.71) > Ni (7.45) > Pb (5.52) > Cd (0.14), respectively. The plants showed fly ash dump phytostabilization potential and accumulated Cr (80.19-178.11 mg kg^-1) above maximum allowable concentrations for plant tissues. Positive correlations were also obtained for metal concentration in plant roots versus fly ash. Saccharum spontaneum showed highest biomass and is the most efficient plant which can be used for the restoration of ash dumps.

Functional response of Betula species to edaphic and nutrient stress during restoration of fly ash deposits in the Middle Urals (Russia)

We studied the impact of fly ash produced by the thermal power station in the Middle Urals (Russia) on functional traits of two Betula species naturally colonizing ash dump lagoons. The main limiting factors for tree growth on fly ash deposits were nitrogen deficiency, high alkalinity, and unfavorable mechanical composition of substrate. Leaf area ratio (LAR) and leaf mass ratio (LMR) per tree, leaf area (LA), leaf shape coefficient (LSh), leaf thickness (LT), leaf mass per area (LMA), photosynthesis (A_max) and transpiration rates, chlorophyll (Chl), carotenoid (Car), and nitrogen (N) content were measured in Betula pendula Roth and Betula pubescens Ehrh. growing on the ash dump and in the forest near the dump. Both Betula species showed similar functional response to adverse conditions of the fly ash. We found a 1.5-2-fold increase in LAR and LMR in trees growing on fly ash deposits compared with trees in the forest. In both species, the most significant differences across leaf morphological traits were shown for LT. Higher LT provided an increase in Chl and N content per leaf area that caused the rise in A_max and photosynthetic water use efficiency in the trees on the ash deposit. At the same time, Betula species preserved interspecific differences in values of LA and LT which were larger in B. pubescens whiles B. pendula differed by higher LSh. We concluded that the increase in assimilation activity at both whole-plant and leaf levels provides plant adjustment to edaphic and nutrient stress that allow Betula species to colonize technogenic substrates as fly ash deposits.

Ecological restoration of coal fly ash-dumped area through bamboo plantation

The present study entails the phytoremediation potential of different bamboo species on 5-year-old FA-dumped site near Koradi thermal power plant of Nagpur, Maharashtra, India. The selected FA-dumped site was treated with farmyard manure, press mud, and bio fertilizer followed by plantation of six promising species of bamboo namely Bambusa balcooa Roxb., Dendrocalamus stocksii (Munro.) M. Kumar, Remesh and Unnikrishnan, Bambusa bambos (L.) Voss, Bambusa wamin E.G. Camus, Bambusa vulgaris var. striata (Lodd. ex Lindl.) Gamble, and Bambusa vulgaris var. vittata Riviere and Riviere. The experimental results indicated that the organic input in the FA-dumped site nourished the soil by improving its physico-chemical, and biological characteristics. The results revealed the contamination of the site with different trace elements in varied quantity including Cr (89.29 mg kg-1), Zn (84.77 mg kg-1), Ni (28.84 mg kg-1), Cu (22.91 mg kg-1), Li (19.65 mg kg-1), Pb (13.47 mg kg-1), and Cd (2.35 mg kg-1). A drastic reduction in concentration of heavy metals in FA was observed after 1 year of bamboo plantation as compared to the initial condition. The results showed that bamboo species are good excluders of Ba, Co, Cr, Li, Ni, Mn, and Zn, whereas they are good accumulators of Cd, Pb, and Cu. The values of biochemical parameters, such as pH, total chlorophyll, ascorbic acid (AA), and relative water content of all the bamboo leaves ranged from 5.11-5.70, 1.56-6.33 mg g-1, 0.16-0.19 mg g-1, and 60.23-76.68%, respectively. It is thereby concluded that the bamboo plantation with biofertilizers and organic amendments may indicate adaptive response to environmental pollution on FA-dumped site.

Phytoremediation ability of naturally growing plant species on the electroplating wastewater-contaminated site

The presence of heavy metal in soil and water resources has serious impact on human health. The study was designed to examine the phytoremediation ability of plant species that are growing naturally on the Zn-contaminated site. For the study, six plant species and their rhizospheric soil as well as non-rhizospheric soil samples were collected from different parts of the industrial sites for chemical and biological characterization. Visual observations and highest importance value index (IVI) through biodiversity study revealed potential plants as effective ecological tools for the restoration of the contaminated site. Among the plants, almost all were the most efficient in accumulating Fe, Mn, Cu and Zn in its shoots and roots, while Cynodon dactylon, Chloris virgata and Desmostachya bipinnata were found to be stabilizing Cr, Pb and Cd (bioconcentration factor in root = 7.95, 6.28 and 1.98 as well as translocation factor = 0.48, 0.46 and 0.78), respectively. Thus, the results of this study showed that the naturally growing plant species have phytoremediation potential to remediate the electroplating wastewater-contaminated site. These plant species are successful phytoremediators with their efficient metal stabilizing and well-evolved tolerance to heavy metal toxicity.

Long-term willows phytoremediation treatment of soil contaminated by fly ash polycyclic aromatic hydrocarbons from straw combustion

A three-year experiment was conducted to investigate willows of Salix × smithiana Willd. (S. smithiana) phytoremediation of soil contaminated by polycyclic aromatic hydrocarbons (PAHs) derived by fly ash from biomass combustion. The total removal of ash PAHs in phytoremediation treatment was 50.9% after three consecutive years while the ash PAHs were decreased in natural attenuated soil by 9.9% in the end of the experiment. The ash and spiked PAHs with low and medium molecular weight were susceptible to be removed in higher rates than high molecular weight PAHs. Lower bioconcentration factors of individual PAHs were observed in willow shoots than in roots. The estimated relative direct removal of PAHs by S. smithiana in phytoremediation was significantly lower than 1% suggesting that the contribution of S. smithiana to take up PAHs from soil was negligible and the degradation of PAHs occurred mainly in soil. Phytoremediation using S. smithiana could be seen as a feasible and environmentally friendly approach of arable soils impacted by a PAH contaminated biomass fly ash.

Physiological response of metal tolerance and detoxification in castor (Ricinus communis L.) under fly ash-amended soil

Castor (Ricinus communis L.) is a metal tolerant plants and its ability to survive in highly polluted sites as well as its capacity for metal accumulation. There are very few reports on their physiological mechanism of metal tolerance and detoxification under fly ash. Therefore, an in-situ experiment was designed to study its biomass accumulation, photosynthetic response and antioxidative metabolism under different levels of fly ash amendments. Significant (P < 0.05) increase in plant biomass and metal tolerance index was observed in R. communis under 50 % fly ash in soil amendments in comparison to the control plants. In addition, photosynthetic activity was not significantly altered under fly ash amended soil in comparison to the garden soil, but these responses/activities were remarkable lowered under bare fly ash. The induction of antioxidant enzymes was also observed in different tissue over control under fly ash treatments. The bioconcentration factor (BCF) of Al, Fe, Zn, Mn, Cu and Cr in R. communis were recorded greater than one under fly ash (50%) with soil amendments. Therefore, it concluded that it can be used for phytoremediation of fly ash and fly ash (50%) with soil amendments enhanced phytoremediation ability.

Suitability of Brahmi (Bacopa monnieri L.) cultivation on fly ash-amended soil for better growth and oil content

Sustainable application of fly ash and its management in agriculture is a major challenge nowadays. A pot culture experiment was conducted to find out the most suitable level of fly ash application for soil amendments that can improve the plant growth and productivity of Brahmi (Bacopa monnieri L.). After growing seedlings of B. monnieri under different levels of fly ash for 90 days, a significant increase in plant biomass, essential oil content and tolerance index (more than 100%) was observed under 25% of fly ash amended soil in comparison to garden soil and higher fly ash treatments. Leaf chlorophyll content and photosynthetic parameters were remained unchanged under 25% of fly ash as compared to seedlings grown on garden soil. However, these parameters were significantly declined under higher concentrations of fly ash treatments. Higher levels of fly ash caused oxidative damage and the induction of some antioxidative enzymes activities in B. monnieri indicates its capability to endure oxidative stress tolerance. Overall, our study showed that 25% of fly ash can be used as soil amendment for cultivation of B. monnieri L. leading to enhance plant biomass and essential oil production.

Phytoremediation Potential, Photosynthetic and Antioxidant Response to Arsenic-Induced Stress of Dactylis glomerata L. Sown on Fly Ash Deposits

Arsenic (As) from coal fly ash can be released into soil/groundwater, presenting a global threat to the environment and human health. To overcome this environmental problem, phytoremediation represents an urgent need, providing ‘green’ cleanup of contaminated lands. The present study focused on As concentrations in fly ash and plants, evaluation of phytoremediation potential of Dactylis glomerata sown on fly ash deposits together with its photosynthetic activity, and oxidative and antioxidative response to As stress. Field research was carried out on fly ash deposits at the thermal power plant “Nikola Tesla”, Obrenovac (TENT-A, Serbia) and the control site. Fly ash is characterized by alkaline pH reactions, small amounts of organic matter, a large amount of available phosphate, and total and available As concentrations. Results in this study indicate that phosphate application can ameliorate As toxicity, uptake and root-shoot transport. Furthermore, D. glomerata can be considered as good As phytostabilizator, because it retains more As in roots than in leaves. Excess As in leaves decreases photosynthetic efficiency (Fv/Fm) and concentrations of chlorophylls, carotenoids, and anthocyanins, whereas high content of malondialdehyde (MDA) can be a signal for biosynthesis phenolics and ascorbic acid, providing cellular redox homeostasis and recovery of photosystem II (PSII) photochemistry. In the roots, low oxidative stress under high concentrations of As is related to intense antioxidant biosynthesis. Taken together, the results in this study indicate a high adaptive potential of D. glomerata to As stress. These findings may suggest that physiological and metabolic tools can be used as a way forward in the ‘real field’ scenario, phytomanagement of fly ash and ecosystem services providing sustainable phytoremediation of As-contaminated sites around the globe.

Fly-Ash Pollution Modulates Growth, Biochemical Attributes, Antioxidant Activity and Gene Expression in Pithecellobium Dulce (Roxb) Benth

This study investigates the effect of fly ash (FA) on the Pithecellobium dulce (Roxb) Benth. trees growing at three different locations. FA stress caused significant changes in different leaf attributes like sugar, protein contents, photosynthetic pigments, nitrate content and nitrate reductase activity in foliar tissues of plants growing at a highly contaminated site, as compared to a low-pollution site. Lower rates of stomatal conductance (SC) were observed in P. dulce leaves under fly ash stress conditions that drastically reduced net photosynthetic rate (P_N); however, intercellular carbon dioxide concentration and stomatal index (SI) showed an increase under the same stress conditions. On the other hand, significant increase was also observed in the proline, sulphur and nitrogen contents. A significant increase in oxidative stress and, consequently, in antioxidant enzymes such as ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), and superoxidase dismutase (SOD) and Air pollution tolerance index were discovered at three different sites. The transcriptional expression of antioxidant and stress responsive genes was higher at HPS as compared to two other two sites of the study. Taken together the results demonstrated that the P. dulce is best suited as a fly ash stress tolerant plant species with the potential to provide an alternative for the reclamation of fly ash affected soils.

Assessing the Bacterial Community Structure in the Rhizoplane of Wetland Plants

Plant-microorganism interaction in the rhizosphere is important for nutrient cycling, carbon sequestration in natural ecosystems, contaminant elimination and ecosystem functioning. Abundance of microbial communities and variation in species composition can be an imperative determinant of phytoremediation capability. In the present study we have assessed the bacterial community structure in the rhizoplane of wetland plants, Acorus calamus, Typha latifolia, and Phragmites karka using Terminal restriction fragment length polymorphism technique. The most dominant phylum, in the plants under study, was phylum Firmicutes, followed by Proteobacteria and Actinobacteria. Bacterial groups belonging to phylum Chloroflexi, Acidobacteria, Deferribacteres and Thermotogae also showed their presence in P. karka and T. latifolia but were absent in A. calamus. Diversity indices of bacterial community were assessed. The results of this study show the presence of bacterial phyla which play an important role in bioremediation of contaminants. Thus these plants can be used as potential candidates of phytoremediation.

Growth and physiological response of lemongrass (Cymbopogon citratus (D.C.) Stapf.) under different levels of fly ash-amended soil

Revegetation with metal tolerant plants for management of fly ash deposits is an important environmental perspective nowadays. Growth performance, photosynthesis, and antioxidant defense of lemongrass (Cymbopogon citratus (D.C.) Stapf.) were evaluated under various combination of fly ash amended with garden soil in order to assess its fly ash tolerance potential. Under low level of fly ash (25%) amended soil, the plant growth parameters such as shoot, root, and total plant biomass as well as metal tolerance index were increased compared to the control plants grown on garden soil, followed by decline under higher concentration of fly ash (50%, 75% and 100%). In addition, leaf photosynthetic rate, stomatal conductance, and photosystem (PS) II activity were not significantly changed under low level of fly ash (25%) amended soil compared to the garden soil but these parameters were significantly decreased further with increase of fly ash concentrations. Furthermore, increase of activities of some antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, and guaiacol peroxidase over control were noticed in lemongrass under all fly ash treatments. Taken together, the study suggests that lemongrass can be used for phytoremediation of fly ash at 25% amended soil.

Assessment of Ziziphus mauritiana grown on fly ash dumps: Prospects for phytoremediation but concerns with the use of edible fruit

A field study was carried out on fly ash (FA) dumps of Panki Thermal Power Station to assess the phytoaccumulation of elements in various plant parts of edible fruit tree Ziziphus mauritiana. Of the twelve analyzed elements, the highest concentration was found for Fe followed by Mn > Se > Zn > Mo > Cu > Cr > Pb > Cd >Ni > As > Co in rhizospheric substrate of Z. mauritiana grown on FA dumps. Metal accumulation, bioconcentration factor, and translocation factor for each metal were calculated in various parts of the edible fruit tree. Significant variations of metal accumulations were observed among various plant parts. Accumulation of toxic elements was higher in roots, and it gradually declined toward the aerial parts of the plant corresponding to its distance from the ground. The concentration of some elements in fruit tree was found to be above prescribed limits in edible parts. Therefore, the present study suggested that additional care should be undertaken, if edible fruit trees are considered for phytoremediation or afforestation programs of FA dumps.

Comparison of three types of oil crop rotation systems for effective use and remediation of heavy metal contaminated agricultural soil

Selecting suitable plants tolerant to heavy metals and producing products of economic value may be a key factor in promoting the practical application of phytoremediation polluted soils. The aim of this study is to further understand the utilization and remediation of seriously contaminated agricultural soil. In a one-year field experiment, we grew oilseed rape over the winter and then subsequently sunflowers, peanuts and sesame after the first harvest. This three rotation system produced high yields of dry biomass; the oilseed rape-sunflower, oilseed rape-peanut and oilseed rape-sesame rotation allowed us to extract 458.6, 285.7, and 134.5 g ha^-1 of cadmium, and 1264.7, 1006.1, and 831.1 g ha^-1 of lead from soil, respectively. The oilseed rape-sunflower rotation showed the highest phytoextraction efficiency (1.98%) for cadmium. Lead and cadmium in oils are consistent with standards after extraction with n-hexane. Following successive extractions with potassium tartrate, concentrations of lead and cadmium in oilseed rape and peanut seed meals were lower than levels currently permissible for feeds. Thus, this rotation system could be useful for local farmers as it would enable the generation of income during otherwise sparse phytoremediation periods.

An Evolutionary Perspective on Linoleic Acid Synthesis in Animals

The diet of organisms generally provides a sufficient supply of energy and building materials for healthy growth and development, but should also contain essential nutrients. Species differ in their exogenous requirements, but it is not clear why some species are able to synthesize essential nutrients, while others are not. The unsaturated fatty acid, linoleic acid (LA; 18:2n-6) plays an important role in functions such as cell physiology, immunity, and reproduction, and is an essential nutrient in diverse organisms. LA is readily synthesized in bacteria, protozoa and plants, but it was long thought that all animals lacked the ability to synthesize LA de novo and thus required a dietary source of this fatty acid. Over the years, however, an increasing number of studies have shown active LA synthesis in animals, including insects, nematodes and pulmonates. Despite continued interest in LA metabolism, it has remained unclear why some organisms can synthesize LA while others cannot. Here, we review the mechanisms by which LA is synthesized and which biological functions LA supports in different organisms to answer the question why LA synthesis was lost and repeatedly gained during the evolution of distinct invertebrate groups. We propose several hypotheses and compile data from the available literature to identify which factors promote LA synthesis within a phylogenetic framework. We have not found a clear link between our proposed hypotheses and LA synthesis; therefore we suggest that LA synthesis may be facilitated through bifunctionality of desaturase enzymes or evolved through a combination of different selective pressures.

Restoration of red mud deposits by naturally growing vegetation

Disposal of red mud (RM) poses serious environmental problems such as wind erosion, air and water pollution. To overcome these problems, effective restoration of the disposal land through naturally growing vegetation is a sustainable and economical approach. The present study involved estimation of frequency (F), density (D), abundance (Ab), and important value index (IVI) of natural flora on abandoned RM sites in order to assess their metal toxicity tolerance capacity. Based on visual observations and highest IVI, S. Asper and S. punicea were identified as effective ecological tools for the restoration of barren RM sites. From the study, remarkable differences were observed between non-rhizospheric and rhizospheric RM of both species. These rhizospheric RM analyses confirm the ability of S. asper and S. punicea for enhancing the biological activities of abandoned RM. Translocation factor (TF) of iron was maximum (2.58) in S. asper, and bioconcentration factor (BCF) was found maximum (1.25) in S. punicea, but both TF (2.58) and BCF (1.35) were high in S. asper. Therefore, this plant could be reported as an iron hyperaccumulator plant. These results suggest that these plant species can be exploited for effective restoration of RM deposited land without any inputs or maintenance.

Effects of different treatments of fly ash and mining soil on growth and antioxidant protection of Indian wild rice

The aim of the present study was investigation of the effects of fly ash and mining soil on growth and antioxidant protection of two cultivars of Indian wild rice (Oryza nivara and Oryza rufipogon) for possible phytoremediation and restoration of metal-contaminated site. In this study, Indian wild rice showed significant changes in germination, growth, and biochemical parameters after exposure to different ratio of fly ash and mining soil with garden soil. There was significant reduction of germination, fresh weight, dry weight, leaf chlorophyll content, leaf area, Special Analysis Device Chlorophyll (SPAD) Index, proteins, and activities of antioxidant enzymes in both cultivars of the wild rice grown in 100% fly ash and mining soil compared to the plants grown in 100% garden soil. Results from this study showed that in both cultivars of wild rice, all growth and antioxidant parameters increased when grown in 50% fly ash and mining soil. Taken together, Indian wild rice has the capacity to tolerate 50% of fly ash and mining soil, and can be considered as a good candidate for possible phytoremediation of contaminated soils.

Phytoremediation efficiency of Eichhornia crassipes in fly ash pond

The present study was focused on field research to examine the phytoremediation potential of naturally grown Eichhornia crassipes in fly ash (FA) pond. Field results indicate the efficiency of E. crassipes for remediation of heavy metals from FA pond. The bioconcentration factor trend was Cr (3.75) > Cu (2.62) > Cd (1.05), and Cu (1.35) in root and stem, respectively. The survival and abundance growth of E. crassipes in the circumstance of heavy metal enriched FA pond is another highlight of the present research that reveals its toxitolerant characteristics. Thus, this lesson on phytoremediation proved that E. crassipes is a potential accumulator of Cu, Cr, and Cd from FA ponds and is a promising species for FA pond's remediation globally.