Phytoextraction of heavy metals by potential native plants and their microscopic observation of root growing on stabilised distillery sludge as a prospective tool for in situ phytoremediation of industrial waste

Enhancing the Phytoremediation of Heavy Metals by Plant Growth Promoting Rhizobacteria (PGPR) Consortium: A Narrative Review

Heavy metal pollution has become a significant concern as the world continues to industrialize, urbanize, and modernize. Heavy metal pollutants impede the growth and metabolism of plants. The bioaccumulation of heavy metals in plants may create chlorophyll antagonism, oxidative stress, underdeveloped plant growth, and reduced photosynthetic system. Finding practical solutions to protect the environment and plants from the toxic effects of heavy metals is essential for long-term sustainable development. The direct use of suitable living plants for eliminating and degrading metal pollutants from ecosystems is known as phytoremediation. Phytoremediation is a novel and promising way to remove toxic heavy metals. Plant growth-promoting rhizobacteria (PGPR) can colonize plant roots and help promote their growth. Numerous variables, such as plant biomass yield, resistance to metal toxicity, and heavy metal solubility in the soil, affect the rate of phytoremediation. Phytoremediation using the PGPR consortium can speed up the process and increase the rate of heavy metal detoxification. The PGPR consortium has significantly increased the biological accumulation of various nutrients and heavy metals. This review sheds light on the mechanisms that allow plants to uptake and sequester toxic heavy metals to improve soil detoxification. The present review aids the understanding of eco-physiological mechanisms that drive plant-microbe interactions in the heavy metal-stressed environment.

Biosorption potential of basella Alba (Malabar spinach) for removal of fluoride in aqueous solutions based on its phytoremediation applications; a review

This review article explores the applications of Basella alba (Malabar spinach), a fast-growing vine plant known for its numerous health benefits, culinary uses, and potential in dye and oil production. Fluoride contamination in water poses a significant global health and environmental challenge, particularly in regions where natural and industrial activities lead to elevated fluoride levels. Among its varied applications, B. alba has shown significant promise in the phytoremediation of contaminants in both water and soil, owing to its hyper accumulating capacities. The plant has a transfer factor value of more than 1 which means that there is higher accumulation of contaminants in parts of the plant than in soil. The objective of this review is to assess the feasibility of B. alba in contributing to sustainable water management solutions for fluoride contamination, while offering a comprehensive evaluation of its environmental remediation potential. The article examines the biosorption capabilities of B. alba based on its established use in phytoremediation, offering insights into its suitability for addressing fluoride contamination in water. This article is organized into sections starting with an introduction, which brings explains the global challenge of fluoride, and different treatment techniques justifying why biosorption needs to be considered, cases of application of phytoremediation using B. Alba, and finally exploring the success factors for plants that have been applied for both biosorption and phytoremediation.

Plant diversity value of informal green spaces in tropical coastal urban areas: An empirical study of species, functional, and phylogenetic diversity

Informal green spaces (IGS) are a hot topic in urban biodiversity studies, but overlooked in urban biodiversity conservation or management, especially in tropical coastal cities, where comprehensive assessments remain scarce. Most existing research has been limited to species diversity (α-diversity), with few studies addressing functional and phylogenetic diversity as aspects of α-diversity, and species turnover (β-diversity) across multiple IGS types. This study bridges these gap by conducting a detailed vegetation survey in Jiangdong New Area of Haikou City, establishing 213 sites. Within these sites, we examined 343 IGS sample plots and 274 formal green spaces (FGS) sample plots. We assessed species, functional, and phylogenetic diversity using α and β diversity metrics and analyzed the influence of environmental factors with generalized linear mixed models (GLMMs). The results recorded 235 species of herbaceous plants from 179 genera and 54 families in IGS, including 215 spontaneous species, compared to 154 spontaneous species in FGS. Our findings indicate that IGS exhibited higher species richness and functional richness compared to FGS, though differences in phylogenetic diversity were less pronounced. Key environmental factors like relative humidity, trampling intensity, and proximity to urban areas significantly influenced species richness and abundance in IGS. These findings underscore the critical role of IGS in enhancing biodiversity and resilience in tropical coastal cities, emphasizing the need to integrate IGS into urban planning strategies for sustainable urban ecosystems.

Environmental risks and agronomic benefits of industrial sewage sludge-derived biochar

The main objective of the present work was to assess the ecotoxicological safety of the use of thermochemically treated sewage sludge from the wastewater treatment plant (WWTP) of a distillery plant as a soil additive in agricultural soils based on its physicochemical characteristics and the bioaccumulation of selected elements in the plant tissues of maize (Zea mays). We have carried out physicochemical characterization (pH, EC, Corg, Cinorg, CEC, N, H, ash content, PAHs) of sewage sludge feedstock (SS) and sludge-derived biochar (BC) produced by slow pyrolysis at a temperature of 400 °C. The effect of 1% (w/w) amendment of SS and BC on soil physicochemical properties (pH, EC, Cinorg), germination of ryegrass, soil rhizobacteria and microorganisms, as well as on the accumulation and translocation of selected elements in maize (Zea mays) was studied. The results show that pyrolysis treatment of distillery WWTP sludge at 400 °C increases pH (from 7.3 to 7.7), Corg(from 28.86% to 36.83%), N (from 6.19% to 7.53%), ash content (from 23.59% to 50.99%) and decreases EC (from 2.35 mS/cm to 1.06 mS/cm), CEC (from 118.66 cmol/kg to 55.66 cmol/kg), H (from 6.76% to 1.98%) and Σ18 PAHs content (from 4.03 mg/kg to 3.38 mg/kg). RFA analysis of SS and BC showed that pyrolysis treatment multiplies chromium (Cr) (2.2 times), nickel (Ni) (2.96 times), lead (Pb) (2.13 times), zinc (Zn) (2.79 times), iron (Fe) (1.26 times) in the obtained BC, but based on an ecotoxicological test with earthworms Eisenia fetida, we conclude that pyrolysis treatment reduced the amount of available forms of heavy metals in BC compared to SS. We demonstrated by a pot experiment with a maize that a 1% addition of BC increased soil pH, decreased EC and Cinorg and had no significant effect on heavy metal accumulation in plant tissues. According to the results of the three-level germination test, it also does not affect the germination of cress seeds (Lepidium sativum). There was a significant effect of 1% BC addition on soil microbial community, and we observed a decrease in total microbial biomass and an increase in fungal species variability in the soil. Based on these results, we conclude that BC represents a promising material that can serve as a soil additive and source of nutritionally important elements after optimization of the pyrolysis process.

Phytoremediation mechanism and role of plant growth promoting rhizobacteria in weed plants for eco-restoration of hazardous industrial waste polluted site: a review

Plants have numerous strategies for phytoremediation depending upon the characteristic of pollutants. Plant growth promoting rhizobacteria (PGPR) are essential to the process of phytoremediation and play a key part in it. The mechanism of PGPR for phytoremediation is mediated by two methods; under the direct method there is phytohormone production, nitrogen fixation, nutrient mineral solubilization, and siderophore production while the indirect method includes quorum quenching, antibiosis, production of lytic enzyme, biofilm formation, and hydrogen cyanide production. Due to their economic and environmental viability, most researchers have recently concentrated on the potential of weed plants for phytoremediation. Although weed plants are considered unwanted and noxious, they have a high growth rate and adaptability which opens a high scope for its role in phytoremediation of contaminated site. The interaction of plant with rhizobacteria starts from root exudates containing various organic acids and peptides which act as nutrients essential for colonization and siderophore production by the rhizospheric bacteria. The rhizobacteria, while colonizing, tend to promote plant growth and health either directly by providing phytohormones and minerals or indirectly by suppressing growth of possible phytopathogens. Recently, several weed plants have been reported for phytoextraction of heavy metals (Ni, Pb, Zn, Hg, Cd, Cu, As, Fe, and Cr) contaminants from various agro-based industries. These potential native weed plants have high prospect of eco-restoration of polluted site with complex organo-metallic waste for sustainable development.

Optimisation of Manganese Peroxidase (MnP) Activity of Enterobacter wuhouensis Using Response Surface Method and Evaluation of Its Maillard Reaction Products Along with Lignin Degradation Ability

Manganese peroxidase (MnP), a microbial ligninolytic enzyme which plays significant role in lignin and melanoidin degradation has gained much attention in the field of industry. In the present study, 15 ligninolytic bacteria were isolated from the soil sample of Similipal Biosphere Reserve (SBR) and screened for MnP activity. The most efficient MnP-producing bacterium HNB5 was evaluated for alkali lignin and maillard reaction products (MRPs) degradation and identified as Enterobacter wuhouensis using 16S rRNA sequencing. This bacterium exhibited the highest MnP activity of 2.6 U mL-1 min-1 in un-optimized conditions. Further, optimization using response surface methodology E. wuhouensis showed increased MnP activity of 4.11 U mL-1 min-1 at pH 6.3, temperature 37 °C, substrate concentration 1.05%, and time 144 h. In both FT-IR and UV-Vis spectrophotometry analyses of control and bacterium degraded MRPs, the reduction in Maillard product colour was correlated with shifting absorption peaks. Also, the GC-MS analysis data showing a change in functional group revealed the rise of novel peaks caused due to the degradation of MRPs complex. The phytotoxicity study was conducted for bacterial degraded MRPs medium revealed that toxicity of the medium decreased after bacterial treatment. The findings of the current study suggest that the manganese MnP produced by E. wuhouensis isolated from SBR soil sample may be employed for bioremediation purposes to degrade MRPs.

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Dynamic crosstalk between silicon nanomaterials and potentially toxic trace elements in plant-soil systems

Agricultural soil pollution with potentially toxic trace elements (PTEs) has emerged as a significant environmental concern, jeopardizing food safety and human health. Although, conventional remediation approaches have been used for PTEs-contaminated soils treatment; however, these techniques are toxic, expensive, harmful to human health, and can lead to environmental contamination. Nano-enabled agriculture has gained significant attention as a sustainable approach to improve crop production and food security. Silicon nanomaterials (SiNMs) have emerged as a promising alternative for PTEs-contaminated soils remediation. SiNMs have unique characteristics, such as higher chemical reactivity, higher stability, greater surface area to volume ratio and smaller size that make them effective in removing PTEs from the environment. The review discusses the recent advancements and developments in SiNMs for the sustainable remediation of PTEs in agricultural soils. The article covers various synthesis methods, characterization techniques, and the potential mechanisms of SiNMs to alleviate PTEs toxicity in plant-soil systems. Additionally, we highlight the potential benefits and limitations of SiNMs and discusses future directions for research and development. Overall, the use of SiNMs for PTEs remediation offers a sustainable platform for the protection of agricultural soils and the environment.

Roles and significance of chelating agents for potentially toxic elements (PTEs) phytoremediation in soil: A review

Phytoremediation is a biological remediation technique known for low-cost technology and environmentally friendly approach, which employs plants to extract, stabilise, and transform various compounds, such as potentially toxic elements (PTEs), in the soil or water. Recent developments in utilising chelating agents soil remediation have led to a renewed interest in chelate-induced phytoremediation. This review article summarises the roles of various chelating agents and the mechanisms of chelate-induced phytoremediation. This paper also discusses the recent findings on the impacts of chelating agents on PTEs uptake and plant growth and development in phytoremediation. It was found that the chelating agents have increased the rate of metal absorption and translocation up to 45% from roots to the aboveground plant parts during PTEs phytoremediation. Besides, it was also explored that the plants may experience some phytotoxicity after adding chelating agents to the soil. However, due to the leaching potential of synthetic chelating agents, the use of organic chelants have been explored to be used in PTEs phytoremediation. Finally, this paper also presents comprehensive insights on the significance of using chelating agents through SWOT analysis to discuss the advantages and limitations of chelate-induced phytoremediation.

Phytoextraction of per- and polyfluoroalkyl substances (PFAS) by weeds: Effect of PFAS physicochemical properties and plant physiological traits

Phytoextraction is a promising technology that uses plants to remediate contaminated soil. However, its feasibility for per- and polyfluoroalkyl substances (PFAS) and the impact of PFAS properties and plant traits on phytoextraction efficacy remains unknown. In this study, we conducted greenhouse experiment and evaluated the potential of weeds for phytoextraction of PFAS from soil and assessed the effects of PFAS properties and plant traits on PFAS uptake via systematic correlation analyses and electron probe microanalyzer with energy dispersive spectroscopy (FE-EPMA-EDS) imaging. The results showed that 1) phytoextraction can remove 0.04%- 41.4%wt of PFAS from soil, with extracted PFAS primarily stored in plant shoots; 2) Weeds preferentially extracted short-chain PFAS over long-chain homologues from soil. 3) PFAS molecular size and hydrophilicity determined plant uptake behavior, while plant morphological traits, particularly root protein and lipid content, influenced PFAS accumulation and translocation. Although plants with thin roots and small leaf areas exhibited greater PFAS uptake and storage ability, the impact of PFAS physicochemical properties was more significant. 4) Finally, short-chain PFAS were transported quickly upwards in the plant, while uptake of long-chain PFOS was restricted.

Functional genomic analysis of an efficient indole degrading bacteria strain Alcaligenes faecalis IITR89 and its biodegradation characteristics

Indole is a nitrogenous heterocyclic aromatic pollutant often detected in various environments. An efficient indole degrading bacterium strain IITR89 was isolated from River Cauvery, India, and identified as Alcaligenes faecalis subsp. phenolicus. The bacterium was found to degrade ~ 95% of 2.5 mM (293.75 mg/L) of indole within 18 h utilizing it as a sole carbon and energy source. Based on metabolite identification, the metabolic route of indole degradation is indole → (indoxyl) → isatin → (anthranilate) → salicylic acid → (catechol) → (Acetyl-CoA) → and further entering into TCA cycle. Genome sequencing of IITR89 revealed the presence of gene cluster dmpKLMNOP, encoding multicomponent phenol hydroxylase; andAbcd gene cluster, encoding anthranilate 1,2-dioxygenase ferredoxin subunit (andAb), anthranilate 1,2-dioxygenase large subunit (andAc), and anthranilate 1,2-dioxygenase small subunit (andAd); nahG, salicylate hydroxylase; catA, catechol 1,2-dioxygenase; catB, cis, cis-muconate cycloisomerase; and catC, muconolactone D-isomerase which play an active role in indole degradation. The findings strongly support the degradation potential of strain IITR89 and its possible application for indole biodegradation.

Bioaccumulation of Per- and Polyfluoroalkyl Substances (PFAS) in Ferns: Effect of PFAS Molecular Structure and Plant Root Characteristics

The present study assessed the bioaccumulation potential of per- and polyfluoroalkyl substances (PFAS) in ferns and linked root uptake behaviors to root characteristics and PFAS molecular structure. Tissue and subcellular-level behavioral differences between alternative and legacy PFAS were compared via an electron probe microanalyzer with energy dispersive spectroscopy (EPMA-EDS) and differential centrifugation. Our results show that ferns can accumulate PFAS from water, immobilize them in roots, and store them in harvestable tissue. The PFAS loading in roots was dominated by PFOS; however, a substantial amount of associated PFOS could be rinsed off by methanol. Correlation analyses indicated that root length, surface and project area, surface area per unit length of the root system, and molecular size and hydrophobicity of PFAS were the most significant factors affecting the magnitude of root uptake and upward translocation. EPMA-EDS images together with exposure experiments suggested that long-chain hydrophobic compounds tend to be adsorbed and retained on the root epidermis, while short-chain compounds are absorbed and quickly translocated upward. Our findings demonstrated the feasibility of using ferns in phytostabilization and phytoextraction initiatives of PFAS in the future.

Comparative assessment of the heavy metal phytoextraction potential of vegetables from agricultural soils: A field experiment

A field study was established to determine the phytoextraction potential of six vegetable species, namely Amaranthus viridis L., Basella alba L., Brassica chinensis var. Parachinensis, Brassica rapa L., Capsicum frutescens L., and Ocimum tenuiflorum L.. These edible plants were selected for their short growth cycles and high biomass production, which are some traits for efficient phytoremediation. Following acid digestion of the soil and vegetable samples using the USEPA 3050B acid digestion method, the extracts were analyzed for Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn using ICP-OES. Results in soil samples showed that the concentrations of both beneficial and essential heavy metals, and non-essential heavy metals are below the WHO, USEPA, and CCME soil quality guidelines. Al is one of the highest concentrations found in the soil samples but it tends to accumulate in the root part of all vegetable species compared to the aboveground parts. In general, B. rapa L. accumulated the highest level of Cd (0.4 mg/kg) and Pb (5.71 mg/kg), while B. alba L. accumulated the highest Cr (2.62 mg/kg) in all plant parts. The findings in this study indicated that Co, Cu, Fe, Mn and Zn were mostly accumulated in leaves of A. viridis L. (Co, Cu, Fe, Mn and Zn), B. alba L. (Co, Fe and Mn), B. chinensis (Mn and Zn) and O. tenuiflorum L. (Mn), and roots of C. frutescens L. (Co, Cu, Fe and Mn), B. alba L. (Co, Cu and Zn), A. viridis L. and B. chinensis (Cu and Fe) and B. rapa L. (Fe). Cr, Pb and Ni were significantly greater in B. alba L. (Cr) And B. rapa L. (Ni and Pb) roots. MTF >1 was observed in the roots of all species for Co, Cd, Zn, and Ni. BTC values varied between the different vegetable species with A. viridis L. having the greatest heavy metal mobility between its plant parts and the best heavy metal phytoextraction potential among other species. The PCA biplots showed that heavy metals were partitioned differently between various plant parts of the vegetable species and can be explained by the first two components (PC1 and PC2) which were associated with the root and/or leaf parts for most vegetable species.

Copper, lead and zinc interactions during phytoextraction using Acer platanoides L.-a pot trial

Of the many environmental factors that modulate the phytoextraction of elements, little has been learnt about the role of metal interactions. The study aimed to show how different concentrations of Cu, Pb and Zn in the cultivation medium influenced the biomass, plant development and phytoextraction abilities of Acer platanoides L. seedlings. Additionally, the impact on the content and distribution of Ca, K, Mg and Na in plant parts was studied with an analysis of phenols. Plants treated with a mixture of two metals were characterised by lower biomass of leaves and higher major elements content jointly than those grown in the salt of one element. Leaves of A. platanoides cultivated in Pb5 + Zn1, Pb1 + Zn1 and Pb1 + Zn5 experimental systems were characterised by specific browning of their edges. The obtained results suggest higher toxicity to leaves of Pb and Zn present simultaneously in Knop solution than Cu and Pb or Cu and Zn, irrespective of the mutual ratio of the concentrations of these elements. Antagonism of Cu and Zn concerning Pb was clearly shown in whole plant biomass when one of these elements was in higher concentration (5 mmol L-1) in solution. In the lowest concentrations (1 mmol L-1), there was a synergism between Cu and Zn in plant roots. Plants exposed to Zn5, Cu1 + Pb5, Pb5 + Zn1 and Cu1 + Zn1 were characterised by higher total phenolic content than the rest plants. Both the presence and the concentration of other elements in the soil are significant factors that modulate element uptake, total phenolic content, and plant development.

Phytoextraction of Cu, Cd, Zn and As in four shrubs and trees growing on soil contaminated with mining waste

Mining activity has degraded large extensions of soil and its waste is composed of metals, anthropogenic chemicals, and sterile rocks. The use of native species in the recovery of polluted soils improves the conditions for the emergence of other species, tending to a process of ecosystem restoration. The objective of this study was to evaluate the bioaccumulation of metal(loid)s in four species of native plants and the effect of their distribution and bioavailability in soil with waste from an abandoned gold mine. Soil samples were taken from two sites in La Planta, San Juan, Argentina: Site 1 and Site 2 (mining waste and reference soil, respectively). In Site 1, vegetative organ samples were taken from Larrea cuneifolia, Bulnesia retama, Plectrocarpa tetracantha, and Prosopis flexuosa. The concentration of metal(loid)s in soil from Site 1 were Zn > As > Cu > Cd, reaching values of 7123, 6516, 240 and 76 mg kg^-1, respectively. The contamination indices were among the highest categories of contamination for all four metal(loid)s. The spatial interpolation analysis showed the effect of the vegetation as the lowest concentration of metal(loid)s were found in rhizospheric soil. The maximum concentrations of As, Cu, Cd and Zn found in vegetative organs were 371, 461, 28, and 1331 mg kg^-1, respectively. L. cuneifolia and B. retama presented high concentrations of Cu and Zn. The most concentrated metal(loid)s in P. tetracantha and P. flexuosa were Zn, As and Cu. Cd was the least concentrated metal in all four species. The values of BAF and TF were greater than one for all four species. In conclusion, the different phytoextraction capacities and the adaptations to arid environments of these four species are an advantage for future phytoremediation strategies. Their application contributes to the ecological restoration and risk reduction, allowing the recovery of ecosystem services.

Effect of biochar amendment on metal mobility, phytotoxicity, soil enzymes, and metal-uptakes by wheat (Triticum aestivum) in contaminated soils

The use of low-cost substances such as biochar could be a sustainable approach to reduce the mobility, accumulation, and toxic impact of heavy metals in crop systems. This study investigates the effect of biochar amendment on heavy metal (Cr, Cd, Cu, Pb, Ni, Zn, Mg and Fe) mobility, bioaccumulation factor (BAF), plant (wheat) metal-uptake, plant oxidative stress, and soil enzymatic profile in contaminated industrial soil. Biochar was obtained from slow pyrolysis of Lantana (LBC), and Parthenium (PBC) biomass, and applied at 3% rates in contaminated soils for wheat crop study under a greenhouse experimental setup. Results show in comparison with control setups, low mobility of Cr (14.15-16.35%), Cd (7.17-15.24%), Cu (9.81-12.97%), Pb (7.99-15.23%), Ni (1.52-2.38%), Zn (10.47-14.42%), Mg (48.85-52.89%), and Fe (19.13-19.90%) contents in soils. The heavy metal uptake rates were 63.08% (Cr), 78.07% (Cd), 74.61% (Cu), 78.11% (Pb), 75.73% (Ni), 69.71% (Zn), 28.78% (Mg), and 49.26% (Fe) lower in biochar amendments, compared with the control treatments. Similarly, the biochar amended treatments exhibited low oxidative stress in wheat plants than control setups. In addition, soil enzymes (dehydrogenase, β-glucosidase, alkaline phosphatase, and urease) alleviated in biochar amended soils indicating reduced toxicity of metals in experimental soils. In summary, this study indicates that biochar amendment in contaminated soils not only improves plant growth but also lowers the rates of soil and plant toxicity and metal bioavailability as well.

The Alleviation of Metal Stress Nuisance for Plants—A Review of Promising Solutions in the Face of Environmental Challenges

Environmental changes are inevitable with time, but their intensification and diversification, occurring in the last several decades due to the combination of both natural and human-made causes, are really a matter of great apprehension. As a consequence, plants are exposed to a variety of abiotic stressors that contribute to their morpho-physiological, biochemical, and molecular alterations, which affects plant growth and development as well as the quality and productivity of crops. Thus, novel strategies are still being developed to meet the challenges of the modern world related to climate changes and natural ecosystem degradation. Innovative methods that have recently received special attention include eco-friendly, easily available, inexpensive, and, very often, plant-based methods. However, such approaches require better cognition and understanding of plant adaptations and acclimation mechanisms in response to adverse conditions. In this succinct review, we have highlighted defense mechanisms against external stimuli (mainly exposure to elevated levels of metal elements) which can be activated through permanent microevolutionary changes in metal-tolerant species or through exogenously applied priming agents that may ensure plant acclimation and thereby elevated stress resistance.

Degradation and decolourization potential of ligninolytic enzyme producing Bacillus paramycoides BL2 and Micrococcus luteus BL3 for pulp paper industrial effluent and its toxicity evaluation

Aim of this study was to optimize the production of Ligninolytic enzyme for the degradation of complex pollutants present in pulp paper industrial effluent (PPIE). Two ligninolytic enzyme-producing bacterial strains were isolated from PPIE and identified as Bacillus paramycoides strain BL2 (MZ676667) and Micrococcus luteus strains BL3 (MZ676668). The identified bacterial strain Bacillus paramycoides strain BL2 showed optimum production of LiP (4.30 U/ml), MnP (3.38 U/ml) at 72 h of incubation, while laccase (4.43 U/ml) at 96 h of incubation. While, Micrococcus luteus strains BL3 produced maximum LiP (3.98) and MnP (3.85 U/ml) at 96 h of incubation and maximum laccase (3.85 U/ml) at 72 h of incubation, pH 7-8, and temperatures of 30-35 °C. Furthermore, in the presence of glucose (1.0%) and peptone (0.5%) as nutrient sources, the enzyme activity of consortium leads to reduction of lignin (70%), colour (63%) along with COD (71%) and BOD (58%). The pollutants detected in control i.e. 3.6-Dioxa-2,7-disilaoctane, 2-Heptnoic acid,trimethylsilyl ester, 7-Methyldinaphtho [2,1-b,1',2'-d] silole, Hexadeconoic acid, trimethylysilyl ester, Methyl1(Z)-3,3-dipheny.1-4-hexenoale, 2,6,10,14,18,22-Tetracosahexane,2,2-dimethylpropyl(2Z,6E)-10,11epoxy5,6 Dihyrostigmasterol, acetate were completely diminished. The toxicity of PPIE was reduced up to 75%. Hence, knowledge of this study will be very useful for industrial sector for treatment of complex wastewater.

Phytoremediation of heavy metals in soil and water: An eco-friendly, sustainable and multidisciplinary approach

Rapid industrialization, increased waste production and surge in agricultural activities, mining, contaminated irrigation water and industrial effluents contribute to the contamination of water resources due to heavy metal (HM) accumulation. Humans employ HM-contaminated resources to produce food, which eventually accumulates in the food chain. Decontamination of these valuable resources, as well as avoidance of additional contamination has long been needed to avoid detrimental health impacts. Phytoremediation is a realistic and promising strategy for heavy metal removal from polluted areas, based on the employment of hyper-accumulator plant species that are extremely tolerant to HMs present in the environment/soil. Green plants are used to remove, decompose, or detoxify hazardous metals in this technique. For soil decontamination, five types of phytoremediation methods have been used viz. phytostabilization, phytodegradation, rhizofiltration, phytoextraction and phytovolatilization. Traditional phytoremediation methods, on the other hand, have significant limits in terms of large-scale application, thus biotechnological efforts to modify plants for HM phytoremediation ways are being explored to improve the efficacy of plants as HM decontamination candidates. It is relatively a new technology that is widely regarded as economic, efficient and unique besides being environment friendly. New metal hyperaccumulators with high efficiency are being explored and employed for their use in phytoremediation and phytomining. Therefore, this review comprehensively discusses different strategies and biotechnological approaches for the removal of various HM containments from the environment, with emphasis on the advancements and implications of phytoremediation, along with their applications in cleaning up various toxic pollutants. Moreover, sources, effects of HMs and factors affecting phytoremediation of HMs metals have also been discussed.

Rhizosphere microbial community composition and survival strategies in oligotrophic and metal(loid) contaminated iron tailings areas

In this study, the metal(loid) fractions in two alkaline iron tailings areas with similar physico-chemical properties and the enrichment ability of dominant plants in these areas were investigated. Additionally, high-throughput sequencing and metagenome analysis were used to examine the rhizosphere microbial community structures and their strategies and potential for carbon fixation, nitrogen metabolism, and metal(loid) resistance in mining areas. Results showed that Salsola collina, Setaria viridis, and Xanthium sibiricum have strong enrichment capacity for As, and the maximum transport factor for Mn can reach 4.01. The richness and diversity of bacteria were the highest in rhizosphere tailings, and the dominant phyla were Proteobacteria, Actinobacteria, Ascomycota, and Thaumarchaeota. The key taxa present in rhizosphere tailings were generally metal(loid) resistant, especially Sphingomonas, Pseudomonas, Nocardioides, and Microbacterium. The reductive citrate cycle was the main carbon fixation pathway of microorganisms in tailings. Rhizosphere microorganisms have evolved a series of survival strategies and can adapt to oligotrophic and metal(loid) polluted mining environments. The results of this study provide a basis for the potential application of plant-microbial in situ remediation of alkaline tailings.

Thermochemical conversion of heavy metal contaminated biomass: Fate of the metals and their impact on products

With the rapid depletion of fossil energy and increasingly severe environmental pollution, the development of biomass resources for biorefineries has become a new research focus. However, heavy metals may be released during the thermochemical treatment when the biomass materials used in biomass conversion are contaminated by heavy metals. This can cause secondary environmental pollution or transference to the target products, reducing product quality. Therefore, having a systematic understanding of the fate of heavy metals in biomass conversion is necessary for alleviating potential risks. This study presents the current status of contaminated biomass and conversion products involving thermochemical processes, the migration, transformation, and impact of heavy metals in biomass conversion was investigated, and the utilization of heavy metals in contaminated biomass was briefly outlined. This review aims to link biomass conversion to the fate of heavy metals, avoid existing risks as much as possible to produce cleaner products efficiently, and promote the sustainable development of heavy metal contaminated biomass resources.

Phytoremediation of soils contaminated by lead and cadmium in Ethiopia, using Endod (Phytolacca dodecandra L)

Phytoremediation is a cost effective and environmentally sustainable green technology for remediation of metal contaminated sites. In Addis Ababa, the capital of Ethiopia, large vegetable farms are grown on contaminated sites. This study evaluates the potential of Phytolacca dodecandra L to remediate Pb and Cd from contaminated sites in Addis Ababa. Pb and Cd in soil samples and different plant parts were determined using AAS. Phytoremediation potential of P. dodecandra in different seasons was estimated by calculating the Bioconcentration factor (BCF) and translocation factor (TF). The average BCF recorded for plant shoot in dry season samples varied from 0.87 to 1.74 for Pb and 1.06 to 2.00 for Cd, while in wet season it was within the range of 1.1-1.53 for Pb and 0.93-3.89 for Cd. The TF values for P. dodecandra ranged from 0.84 to 3.49 for Pb and 1.81 to 4.11 for Cd in dry season, whereas for wet season it varied between 1.34 and 2.01 for Pb and 1.78 and 2.97 for Cd. Since the mean values of BCF and TF were >1, it was concluded that P. dodecandra has considerable potential for phytoextraction of Pb and Cd in contaminated sites.

Increase in Phytoextraction Potential by Genome Editing and Transformation: A Review

Soil metal contamination associated with productive activities is a global issue. Metals are not biodegradable and tend to accumulate in soils, posing potential risks to surrounding ecosystems and human health. Plant-based techniques (phytotechnologies) for the in situ remediation of metal-polluted soils have been developed, but these have some limitations. Phytotechnologies are a group of technologies that take advantage of the ability of certain plants to remediate soil, water, and air resources to rehabilitate ecosystem services in managed landscapes. Regarding soil metal pollution, the main objectives are in situ stabilization (phytostabilization) and the removal of contaminants (phytoextraction). Genetic engineering strategies such as gene editing, stacking genes, and transformation, among others, may improve the phytoextraction potential of plants by enhancing their ability to accumulate and tolerate metals and metalloids. This review discusses proven strategies to enhance phytoextraction efficiency and future perspectives on phytotechnologies.

Rhizosphere Bacteria in Plant Growth Promotion, Biocontrol, and Bioremediation of Contaminated Sites: A Comprehensive Review of Effects and Mechanisms

Agriculture in the 21st century is facing multiple challenges, such as those related to soil fertility, climatic fluctuations, environmental degradation, urbanization, and the increase in food demand for the increasing world population. In the meanwhile, the scientific community is facing key challenges in increasing crop production from the existing land base. In this regard, traditional farming has witnessed enhanced per acre crop yields due to irregular and injudicious use of agrochemicals, including pesticides and synthetic fertilizers, but at a substantial environmental cost. Another major concern in modern agriculture is that crop pests are developing pesticide resistance. Therefore, the future of sustainable crop production requires the use of alternative strategies that can enhance crop yields in an environmentally sound manner. The application of rhizobacteria, specifically, plant growth-promoting rhizobacteria (PGPR), as an alternative to chemical pesticides has gained much attention from the scientific community. These rhizobacteria harbor a number of mechanisms through which they promote plant growth, control plant pests, and induce resistance to various abiotic stresses. This review presents a comprehensive overview of the mechanisms of rhizobacteria involved in plant growth promotion, biocontrol of pests, and bioremediation of contaminated soils. It also focuses on the effects of PGPR inoculation on plant growth survival under environmental stress. Furthermore, the pros and cons of rhizobacterial application along with future directions for the sustainable use of rhizobacteria in agriculture are discussed in depth.

Current trends for distillery wastewater management and its emerging applications for sustainable environment

Ethanol distillation generates a huge volume of unwanted chemical liquid known as distillery wastewater. Distillery wastewater is acidic, dark brown having high biological oxygen demand, chemical oxygen demand, contains various salt contents, and heavy metals. Inadequate and indiscriminate disposal of distillery wastewater deteriorates the quality of the soil, water, and ultimately groundwater. Its direct exposure via food web shows toxic, carcinogenic, and mutagenic effects on aquatic-terrestrial organisms including humans. So, there is an urgent need for its proper management. For this purpose, a group of researchers applied distillery wastewater for fertigation while others focused on its physico-chemical, biological treatment approaches. But until now no cutting-edge technology has been proposed for its effective management. So, it becomes imperative to comprehend its toxicity, treatment methods, and implication for environmental sustainability. This paper reviews the last decade's research data on advanced physico-chemical, biological, and combined (physico-chemical and biological) methods to treat distillery wastewater and its reuse aspects. Finally, it revealed that the combined methods along with the production of value-added products are one of the best options for distillery wastewater management.

Phytoremediation potentials of Eichhornia crassipes for nutrients and organic pollutants from textile wastewater

We used live water hyacinth (WH, Eichornnia crassipes) to purify effluents from textile factories and monitored changes in the physicochemical properties, organic pollutants, and WH biomass. Although the water plant could not thrive in the highly polluted effluents after eight weeks, it achieved 55, 91, 53, 84, 96, 53, and 55% removal efficiency for total Kjeldahl-N (tK-N), NH₃-N, organic-N, PO₄^3-, SO₄^2-, Cl^-, and hardness, respectively. Likewise, the biomass growth showed a positive and strong correlation with NH₃-N (0.998), tK-N (0.956), organic-N (0.923), pH (0.853), and EC (0.712). In contrast, chemical oxygen demand and total oil and grease (TOG) evinced negative and strong correlations of -0.994 and -0.807, respectively. Further, Cl^- correlated mildly (-0.38), while alkalinity (0.154) and water hardness (-0.296) were less influential on the biomass growth. From the removal models, an average of 312 ± 7.7 g of WH would ensure 100% remediation of the nutrients in 29.2 ± 2.5 days. Except for organic-N, the removal kinetics generally favors pseudo-first-order, suggesting the sorbates' concentration and contact time as the limiting factors. Conclusively, WH is a phytoremediator of high potentials for industrial textile effluents, provided the effluents are conditioned at optimum concentration before contact with mature WH of sufficient biomass weight. Novelty statement Eichhornia crassipes was used for simultaneous removal of nutrients and organics from textile effluents. The influence of the macrophte's biomass weight and maturity on the remediation process were examined. Also, the limiting parameters that govern the remediation process were investigated via statistical correlation and kinetic study.

Decontamination potential of five native plants in Maharlu Wetland, Iran

This study investigates the level of toxic trace elements (TTE) in the rhizosphere soil and tissues of five native plants and their phytoextraction/phytostabilization potential growing in Maharlu Lake wetland, in Southern Iran. The study anticipated by determination of 11 potentially TTE concentrations (As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn) in the soil, soil extract, and the plants' dry matter (root and shoot). Pollution index (PI), pollution load index (PLI), bioconcentration factor (BCF), bioaccumulation coefficient (BAC), and translocation factor (TF) were applied in the study. Two main results were pointed out in this study. Firstly, the result of pollution indexing and total and phyto-availability concentrations of TTE showed that some of them in the rhizosphere soil are problematic in the Maharlu wetland, in particular for Mo, Pb, Zn, and As. Secondly, the result of the correlation coefficients and phytoremediation indexing revealed that TTE accumulation in the plant tissues, not only depends on the concentration in the soil extract but is also plant-specific. Moreover, the results suggested that Halopeplis sp. has the potential for phytoextraction of Cd and Mo in the contaminated wetlands. Novelty statement: This manuscript addresses the toxic trace elements concentration in rhizosphere soil and tissues of five native plants and their phytoextraction/phytostabilization potential: Maharlu wetland in southern Iran.

Bioremedial approach of Pseudomonas stutzeri SPM-1 for textile azo dye degradation

The optimization of the bacterium Pseudomonas stutzeri SPM-1, obtained from textile wastewater dumping sites of Surat, Gujarat was studied for the degradation of the textile azo dye Procion Red-H3B. The strain showed significant activities of azoreductase (95%), laccase (76%) and NADH-DCIP reductase (88%) at 12, 10 and 8 h of growth, respectively, indicating the evidence for reductive cleavage of the dye. The optimization was carried on phenanthrene enrichment medium followed by exposing it to variable environmental factors and nutritional sources. The complete decolourization of dye (50 mg/L) happened within 20 h of incubation at pH 8 and temperature 32 ± 0.2 °C under microaerophilic condition. Decolourization was monitored with the shifting of absorbance peak in UV-Vis spectrophotometry and HPLC analysis. The changes in the functional groups were confirmed by the presence of new peaks in FT-IR data. GC-MS analysis helped in recognizing the degraded dye compounds thus elucidating the proposed pathway for Procion Red-H3B. The potential of bioremediation process was completed by phytotoxicity test using two plants Vigna radiata and Cicer arietinum. Our study concludes that the strain Pseudomonas stutzeri SPM-1, with its rapid decolourization efficiency holds noteworthy prospective in industrial application for textile wastewater treatment.

Effect of the direct use of biomass in agricultural soil on heavy metals __ activation or immobilization?

In recent years, the biomass was directly used extensively in agriculture due to its low cost and convenience. Increasingly serious soil pollution of heavy metals may pose threats and risks to human health. Directly addition of biomass to soil may affect the bioavailability and content of heavy metals. Here, we reviewed the impact of direct application of oil cake, manure, sewage sludge, straw and municipal waste to soil on the form and concentration of heavy metals in soil, and also emphasized the role of biomass in soil heavy metals remediation. Heavy metals can be activated in a short term by the content of heavy metals in biomass, the production of low-molecular-weight organic acids by biomass application, and the oxidation of sulfides (except for ammoniation). However, heavy metals in soil can be immobilized by humic substances. These can be produced by biomass during a long-term application to soil. Moreover, the degree of immobilization depended on the kind of biomass. Biomass contaminated by heavy metals cannot be returned to the field directly. Therefore, Mitigating the activation of heavy metals in the early stage of biomass application is meaningful, especially for application of these biomass such as straw, sewage sludge and municipal waste. Future researches should focus on the heavy metal control on direct use of biomass in agricultural.

Microbial degradation of Procion Red by Pseudomonas stutzeri

The bacterium Pseudomonas stutzeri SPM-1, obtained from textile wastewater dumping sites of Surat, Gujarat was studied for the degradation of the textile azo dye Procion Red-H3B. The optimization was carried on the phenanthrene enrichment medium followed by exposing it to variable environmental factors and nutritional sources. The complete decolorization of dye (50 mg/L) happened within 20 h of incubation at pH 8 and temperature 32 ± 0.2 °C under microaerophilic conditions. Decolourization was monitored with the shifting of absorbance peak in UV-Vis spectrophotometry and HPLC analysis. The physicochemical studies of effluent before and after the treatment revealed 85%, 90%, and 65% decline in BOD, COD, and TOC levels. The strain showed significant activities of azoreductase (95%), laccase (76%), and NADH-DCIP reductase (88%) at 12 h, 10 h, and 8 h of growth respectively indicating evidence for reductive cleavage of the dye. The changes in the functional groups were confirmed by the presence of new peaks in FT-IR data. GC-MS analysis helped in recognizing the degraded dye compounds thus elucidating the proposed pathway for degradation of Procion Red-H3B. The potential of the bioremediation process was concluded by a phytotoxicity test using two plants, Vigna radiata and Cicer arietinum. Our study demonstrates that the strain Pseudomonas stutzeri SPM-1 has rapid decolorization efficiency and holds a noteworthy perspective in industrial application for textile wastewater treatment.

Screening of seaweeds for sustainable biofuel recovery through sequential biodiesel and bioethanol production

The present study evaluated the sequential biodiesel-bioethanol production from seaweeds. A total of 22 macroalgal species were collected at different seasons and screened based on lipid and carbohydrate contents as well as biomass production. The promising species was selected, based on the relative increase in energy compounds (REEC, %), for further energy conversion. Seasonal and annual biomass yields of the studied species showed significant variations. The rhodophyte Amphiroa compressa and the chlorophyte Ulva intestinalis showed the highest annual biomass yield of 75.2 and 61.5 g m-2 year-1, respectively. However, the highest annual carbohydrate productivity (ACP) and annual lipid productivity (ALP) were recorded for Ulva fasciata and Ulva intestinalis (17.0 and 3.0 g m-2 year-1, respectively). The later was selected for further studies because it showed 14.8% higher REEC value than Ulva fasciata. Saturated fatty acids (SAFs) showed 73.4%, with palmitic acid as a dominant fatty acid (43.8%). Therefore, biodiesel showed high saturation degree, with average degree of unsaturation (ADU) of 0.508. All the measured biodiesel characteristics complied the international standards. The first route of biodiesel production (R1) from Ulva intestinalis showed biodiesel recovery of 32.3 mg g-1 dw. The hydrolysate obtained after saccharification of the whole biomass (R2) and lipid-free biomass (R3) contained 1.22 and 1.15 g L-1, respectively, reducing sugars. However, bioethanol yield from R3 was 0.081 g g-1 dw, which represented 14.1% higher than that of R2. Therefore, application of sequential biofuel production using R3 resulted in gross energy output of 3.44 GJ ton-1 dw, which was 170.9% and 82.0% higher than R1 and R2, respectively. The present study recommended the naturally-grown Ulva intestinalis as a potential feedstock for enhanced energy recovery through sequential biodiesel-bioethanol production.

Metagenomics analysis of rhizospheric bacterial communities of Saccharum arundinaceum growing on organometallic sludge of sugarcane molasses-based distillery

The present paper aims to explore the rhizospheric bacterial communities associated with Saccharum arundinaceum grown on organometallic pollutants-rich hazardous distillery sludge. The sequence analysis of 16S rRNA V3-V4 hypervariable region with Illumina MiSeq platform showed 621,897 OTUs derived from rhizospheric and non-rhizospheric distillery sludge samples out of 1,191,014 and 901,757 sequences read, respectively. The major phyla detected in rhizospheric sludge sample were Proteobacteria (50%), Bacteriodetes (33%), Firmicutes (5%) Gemmatimonadetes (2%), Chloroflexi (2%), and Tenericutes (2%). The dominant three genera were detected as Rheinheimera (21%), Sphingobacterium (17%), and Idiomarina (8%). In addition, other minor genera such as uncultured Bacillus (4%), Acidothermus (4%), Bacillus (3%), Pseudomonas (2%), Flavobacterium (2%), uncultured bacterium (2%), Parapedobacter (2%), Alcanivorax (2%), Acholeplasma (2%), Hyphomonas (1%), and Aquamicrobium were also detected (1%) in rhizospheric sludge. Our results suggested that rhizospheric bacterial communities associated with S. arundinaceum were substantially different in richness, diversity, and relative abundance of taxa compared to non-rhizospheric sludge. Further, the comparative organic pollutant analysis from non-rhizospheric and rhizospheric sludge samples through GC-MS analysis revealed the disappearance of few compounds and generation of some compounds as new metabolic products by the activity of rhizospheric bacterial communities. The results of this study will be helpful in understanding the role of rhizospheric bacterial communities responsible for degradation and detoxification of complex organometallic waste and, thus, can help in designing appropriate phytoremediation studies for eco-restoration of polluted sites.

Phytoremediation potential of heavy metal accumulator plants for waste management in the pulp and paper industry

The present manuscript has focused on the heavy metal; accumulation potential by common native plants i.e. Chenopodium album L., Ricinus communis, Ranunculus sceleratus, and Rumex dentatus growing on the disposed of pulp and paper mill effluent sludge. The sludge showed the abundance of benzene propanoic acid tert- butyldimethylsilyl ester, Octadecanoic acid, TMS, Hexadecanoic acid, TMS, cinnamic acid-α-phenyl-TMS ester, β-sitosterol TMS, 4-mercaptobenzoic acid as residual complex organic compounds along with heavy metals Fe (98.30 mg/L-1), Zn (51.00 mg/L-1), Cu (3.21 mg/L-1), Cd (9.11 mg/L-1), Mn (18.27 mg/L-1), Ni (5.21 mg/L-1), (Hg 0.014 mg/L-1) which were above the prescribed limit of environmental standard. The complexation of organic compounds with heavy metal restricts the bioavailability of metals to plants. But the metal analysis in various parts of the plant showed a significant amount of metal accumulation. Further, histological observations of root tissue through TEM showed apparent deposition of metal granules near the cell wall and vacuole as adoption features of plants. But the variable concentration of metal accumulation in different parts by various plants indicated the variable potential of tested plants with various metals. This also indicated their metal bio-availability and movement to plant tissue. Further, their bioconcentration factor (BCF) and translocation factor (TF) > 1.0 indicated the hyperaccumulation tendency of plants Mn was accumulated maximum in leaves C. album (69.38 mg/kg-1) followed by Cu (25.75 mg/kg -1), As (23.20 mg/kg -1), Fe (20.90 mg/kg -1) and Pb was maximum accumulated (22.41 mg/kg -1) in R. cummunis leaves. The result revealed that arsenic has been accumulated in higher amount root, shoot and leaves of all tested plants. The metal accumulator plants showed phytoremediation potential also by reducing various pollution parameters after growth on sludge. These potential plants may be used as biotechnological tools for the eco-restoration of polluted sites.

Hemp-Based Phytoaccumulation of Heavy Metals from Municipal Sewage Sludge and Phosphogypsum Under Field Conditions

The aim of this study was to evaluate the ability of three hemp cultivars to accumulate heavy metals under sewage sludge (SS) and phosphogypsum (PG) application. The field study was carried out from 2014 to 2016 on Luvisol (loamy sand) in Poland. The experiment scheme included five treatments—T0: the control without fertilization, T1: 170 kg N (nitrogen) ha−1 from sewage sludge, T2: 170 kg N ha−1 from sewage sludge and 100 kg ha−1 of phosphogypsum, T3: 170 kg N ha−1 from sewage sludge and 500 kg ha−1 of phosphogypsum, and T4: 170 kg N ha−1 from sewage sludge and 1000 kg ha−1 of phosphogypsum. It was found that the application of municipal sewage sludge enriched the soil with the bioavailable forms of heavy metals to the greatest extent and contributed to the highest increase in their contents in vegetative and generative organs of hemp plants. These parameters showed a phosphogypsum dose-dependent decline, which could hinder the phytoextraction process. The greatest extractions of heavy metal(loid)s (HMs) from the soil treated with SS and PG were achieved by the Tygra variety, which had the highest bioconcentration factor (BCF) and biomass yield.

Evaluating phytotoxicity of bare and starch-stabilized zero-valent iron nanoparticles in mung bean

Zero-valent iron nanoparticles (nZVI) are among the most widely used nanoparticles in nanoremediation of various environmental pollutants. Environmental fate and impact of nZVI has attracted increasing concerns due to their potential risks. However, phytotoxicity of nZVI still remains poorly understood. Here, the phytotoxic effects of bare nZVI (B-nZVI) and starch-stabilized nZVI (S-nZVI) were evaluated on the germination of mung bean seeds exposed to suspensions with different doses of 0-1000 mg/L and the growth of hydroponically cultured seedling at 600 mg/L. In most cases, B-nZVI had no inhibition on seed germination, and even promotion on shoot and root elongation. However, S-nZVI displayed dose-dependent effects, with a decreased germination rate at 600-750 mg/L. B-nZVI at 600 mg/L showed no obvious phytotoxic but even stimulatory effects on seedling growth. Comparatively, S-nZVI at 600 mg/L produced significant phytotoxicity on mung bean plants, leading to decreased seedling growth, altered nutritional balance, and excess Fe accumulation in roots (>400 mg/kg). S-nZVI were observed to form a coating of insoluble Fe(III) compounds on root surface. Simultaneously, some nZVI penetrated and accumulated into root cells, but did not move to shoots. In conclusion, B-nZVI easily aggregate into larger particles in solution, leading to decreased adhesion to root surface and lower uptake by roots, whereas the higher dispersity and hydrophilicity of S-nZVI makes them more readily be adhered to root surface forming a coating, and penetrated into roots, resulting in excess Fe accumulation, consequently interfering with root functions such as the adsorption and transport of water and nutrients.

Phytoremediation of Three Herbaceous Plants to Remove Metals from Urban Runoff

Phytoremediation experiments were carried out to assess the ability of different herbaceous buffer strips to absorb metals. Results revealed the Medicago sativa buffer strip had the best removal capacity for copper, lead, and cadmium in the runoff and seepage flow. Copper and lead content in M. sativa were significantly higher than in Lolium perenne and Poa pratensis (p < 0.05). Cadmium content in P. pratensis was significantly higher than in L. perenne and M. sativa(p < 0.05). Total accumulation of copper and lead in M. sativa buffer strips was 13.45 mg kg^-1 and 1.01 mg kg^-1, respectively. Total cadmium accumulation was approximately 0.50 mg kg^-1 in both M. sativa and P. pratensis. Overall, results indicated that using M. sativa in the buffer strips was optimal for the remediation of copper, lead, and cadmium in sewage water.

Dual Role of Metallic Trace Elements in Stress Biology-From Negative to Beneficial Impact on Plants

Heavy metals are an interesting group of trace elements (TEs). Some of them are minutely required for normal plant growth and development, while others have unknown biological actions. They may cause injury when they are applied in an elevated concentration, regardless of the importance for the plant functioning. On the other hand, their application may help to alleviate various abiotic stresses. In this review, both the deleterious and beneficial effects of metallic trace elements from their uptake by roots and leaves, through toxicity, up to the regulation of physiological and molecular mechanisms that are associated with plant protection against stress conditions have been briefly discussed. We have highlighted the involvement of metallic ions in mitigating oxidative stress by the activation of various antioxidant enzymes and emphasized the phenomenon of low-dose stimulation that is caused by non-essential, potentially poisonous elements called hormesis, which is recently one of the most studied issues. Finally, we have described the evolutionary consequences of long-term exposure to metallic elements, resulting in the development of unique assemblages of vegetation, classified as metallophytes, which constitute excellent model systems for research on metal accumulation and tolerance. Taken together, the paper can provide a novel insight into the toxicity concept, since both dose- and genotype-dependent response to the presence of metallic trace elements has been comprehensively explained.

Heavy metals in food crops: Health risks, fate, mechanisms, and management

Food security is a high-priority issue for sustainable global development both quantitatively and qualitatively. In recent decades, adverse effects of unexpected contaminants on crop quality have threatened both food security and human health. Heavy metals and metalloids (e.g., Hg, As, Pb, Cd, and Cr) can disturb human metabolomics, contributing to morbidity and even mortality. Therefore, this review focuses on and describes heavy metal contamination in soil-food crop subsystems with respect to human health risks. It also explores the possible geographical pathways of heavy metals in such subsystems. In-depth discussion is further offered on physiological/molecular translocation mechanisms involved in the uptake of metallic contaminants inside food crops. Finally, management strategies are proposed to regain sustainability in soil-food subsystems.

Heavy metal tolerance in contrasting ecotypes of Alyssum montanum

The response of metallicolous (M) and nonmetallicolous (NM) Alyssum montanum ecotypes to multi-metal stress was investigated under in vitro condition and compared in this study. Shoot cultures were simultaneously treated with 0.7 mM ZnSO₄, 3.0 μM Pb(NO₃)₂ and 16.4 μM CdCl₂ for 8 weeks and evaluated for their morphogenetic and ultrastructural reaction, growth tolerance as well as ability to Zn, Pb, and Cd uptake. Moreover, tissue localization and concentrations of antioxidant compounds were determined in order to elucidate the potential role of ROS-scavenging machinery in plant tolerance to metal toxicity. The results clearly demonstrated that M specimens treated with heavy metals showed less phytotoxic symptoms and low level of lipid peroxidation than reference NM one. The enhanced tolerance of M ecotype resulted from heavy metals detoxification in trichomes and intracellular leaf compartments as well as balanced ROS accumulation. The inactivation of ROS in M plants was based on peroxidase-flavonoid system, while in NM plants such relationship was not detected and amounts of antioxidant enzymes or phenolic compounds was comparable to untreated specimens or decreased significantly. Considering the procumbent growth of such hemicryptophyte which reproduce effectively in the presence of heavy metals but is characterized by low biomass production, it is proposed to exploit M ecotype of A. montanum in revegetation schemes of polluted calamine wastes to provide the prompt stabilization of areas prone to erosion.

Environmental pollution and health hazards from distillery wastewater and treatment approaches to combat the environmental threats: A review

Distillery industries are the key contributor to the world's economy, but these are also one of the major sources of environmental pollution due to the discharge of a huge volume of dark colored wastewater. This dark colored wastewater contains very high biological oxygen demand, chemical oxygen demand, total solids, sulfate, phosphate, phenolics and various toxic metals. Distillery wastewater also contains a mixture of organic and inorganic pollutants such as melanoidins, di-n-octyl phthalate, di-butyl phthalate, benzenepropanoic acid and 2-hydroxysocaproic acid and toxic metals, which are well reported as genotoxic, carcinogenic, mutagenic and endocrine disrupting in nature. In aquatic resources, it causes serious environmental problems by reducing the penetration power of sunlight, photosynthetic activities and dissolved oxygen content. On other hand, in agricultural land, it causes inhibition of seed germination and depletion of vegetation by reducing the soil alkalinity and manganese availability, if discharged without adequate treatment. Thus, this review article provides a comprehensive knowledge on the distillery wastewater pollutants, various techniques used for their analysis as well as its toxicological effects on environments, human and animal health. In addition, various physico-chemicals, biological as well as emerging treatment methods have been also discussed for the protection of environment, human and animal health.

Detection of Androgenic-Mutagenic Compounds and Potential Autochthonous Bacterial Communities during In Situ Bioremediation of Post-methanated Distillery Sludge

Sugarcane-molasses-based post-methanated distillery waste is well known for its toxicity, causing adverse effects on aquatic flora and fauna. Here, it has been demonstrated that there is an abundant mixture of androgenic and mutagenic compounds both in distillery sludge and leachate. Gas chromatography-mass spectrometry (GC-MS) analysis showed dodecanoic acid, octadecanoic acid, n-pentadecanoic acid, hexadecanoic acid, β-sitosterol, stigmasterol, β-sitosterol trimethyl ether, heptacosane, dotriacontane, lanosta-8, 24-dien-3-one, 1-methylene-3-methyl butanol, 1-phenyl-1-propanol, 5-methyl-2-(1-methylethyl) cyclohexanol, and 2-ethylthio-10-hydroxy-9-methoxy-1,4 anthraquinone as major organic pollutants along with heavy metals (all mg kg^-1): Fe (2403), Zn (210.15), Mn (126.30, Cu (73.62), Cr (21.825), Pb (16.33) and Ni (13.425). In a simultaneous analysis of bacterial communities using the restriction fragment length polymorphism (RFLP) method the dominance of Bacillus sp. followed by Enterococcus sp. as autochthonous bacterial communities growing in this extremely toxic environment was shown, indicating a primary community for bioremediation. A toxicity evaluation showed a reduction of toxicity in degraded samples of sludge and leachate, confirming the role of autochthonous bacterial communities in the bioremediation of distillery waste in situ.

Ricinus communis L. (Castor bean), a potential multi-purpose environmental crop for improved and integrated phytoremediation

Phytoremediation is a plant based environmental cleanup technology to contain (rendering less toxic), sequester and degrade contaminated susbtrates. As can be seen from data metrics, it is gaining cosiderable importance globally. Phytoremediation approach is being applied for cleanup of inorganic (potentially toxic metals), organic (persistent, emergent, poly-acromatic hydrocarbons and crude oil etc.) and co-contaminated (mixture of inorganic and organic) and/or polluted sites globally. Recently new approaches of utilizing abundantly available natural organic amendments have yielded significant results. Ricinus communis L. (Castor bean) is an important multipurpose crop viz., Agricultural, Energy, Environmental and Industrial crop. The current status of knowledge is abundant but scattered which need to be exploited for sustainable development. This review collates and evaluates all the scattered information and provides a critical view on the possible options for exploiting its potential as follows: 1. Origin and distribution, 2. Lead toxicity bioassays, 3. Progress in arbuscular mycorrhizal fungi-assisted phytoremediation, 4. Promising bioenergy crop that can be linked to pytoremediation, 5. A renewable source for many bioproducts with rich chemical diversity, 6. It is a good biomonitor and bioindicator of atmospheric pollution in urban areas, 7. Enhanced chelate aided remediation, 8. Its rhizospheric processes accelerate natural attenuation, 9. It is suitable for remediation of crude oil contaminated soil, 10. It is an ideal candidate for aided phytostabilization, 11. Castor bean is a wizard for phytoremediation and 12. Its use in combined phytoextraction and ecocatalysis. Further, the knowledge gaps and scope for future research on sustainable co-generation of value chain and value addition biobased products for sustainable circular economy and environmental security are described in this paper.