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

Potential of pigeon pea [Cajanus cajan (L.) Millsp.] associated with endophytic bacterium Bacillus cereus PEB-9 to remediate cadmium-contaminated soil

Phytoremediation associated with plant-beneficial bacteria has gained considerable attention for its efficiency in remediating cadmium (Cd)-contaminated soil. In this study, we isolated an endophytic bacterium, PEB-9, from pigeon pea, which was identified as Bacillus cereus and exhibited strong plant growth-promoting traits along with high Cd resistance in vitro. Pot experiments demonstrated that PEB-9 inoculation increased in pigeon pea biomass (11.45-19.29 %), Cd accumulation (43.89-69.90 %), and the Cd transfer factor (4.17-16.89 %) in Cd-stress soil (2-10 mg/kg), with soil remediation efficiency improving by 11.1-15.4 %. Under Cd stress, PEB-9-treated pigeon pea exhibited significant improvement in the activities of superoxide dismutase, peroxidase, and catalase, while a notable decrease in malondialdehyde content, indicating a reduction in Cd cytotoxicity. Additionally, the chlorophyll content in PEB-9-treated plants was significantly higher than that in the control group. Furthermore, PEB-9 inoculation enhanced bioavailable Cd, soil enzymes activity and nutrient content, including available nitrogen, phosphorus, and organic matter, while also boosting the relative abundance of stress-resistant bacterial groups, such as Proteobacteria and Actinobacteria. Correlation analysis indicated that soil nutrient changes induced by PEB-9 significantly influenced bacterial community structure, thereby regulating plant physiological responses, and improving Cd remediation efficacy of pigeon pea. These findings offer a valuable basis for the practical implementation of PEB-9 in remediating Cd-contaminated soils.

Impact of heavy metal toxicity on the human health and environment

Heavy metals are among the major categories of pollutants that are widespread and have enormous potential to affect the environment and public health. Today, the toxicity of heavy metals has become a challenge since it is highly toxic and can accumulate in the body system. Heavy metal contamination results from various natural and anthropogenic activities that release these elements into the environment. Consequently, heavy metals contribute to multiple forms of environmental pollution and pose serious health risks to humans. This review seeks to give an understanding of the characteristics and toxicity of several heavy metals. Some of the physicochemical properties of heavy metals that give them their toxicity as well as the many ways that they can be introduced into the environment are described in the review. Other factors including the type of heavy metals, dose of exposure, route of exposure, duration of exposure, interaction with other chemicals, and environmental factors are further examined to establish the effects on the toxicity of heavy metals. In addition, the reviews also point to the impacts of these pollutants on water, plants, and human beings as regards ecotoxicological consequences. Last but not least, prospects to justify the novelty of diverse assessment and monitoring techniques for handling these contaminants have been presented. Thus, there are several opportunities to design strategies for mitigating the removal of such contaminants by combining the understanding of the toxicity of heavy metals. Overall, this review gives adequate information to researchers and academicians on the toxicity of heavy metals that can be used to design ways of opposing these pollutants and thus protecting the environment towards the development of a sustainable future.

Phosphate-solubilizing bacteria facilitate rhizospheric processes of Bidens pilosa L. in the phytoremediation of cadmium-contaminated soil: Link between phosphorus availability and cadmium accumulation

Although cadmium (Cd) hyperaccumulators have been widely used in phytoremediation of Cd-contaminated soils, the relationship between soil phosphorus (P) uptake and Cd accumulation during phytoremediation remains unclear. In this study, a phosphate-solubilizing bacterium (PSB), Enterobacter sp., and the Cd hyperaccumulator B. pilosa L. were selected to address this knowledge gap. Our results show that Enterobacter sp. inoculation enhances P cycling processes in the rhizosphere of B. pilosa L., resulting in an increase in soil available phosphorus (AP), by 16.2-84.3 % in low-contaminated soil and by 17.6-64.8 % in high-contaminated soil. Inorganic P solubilization was the primary process driving the increase in AP content, contributing the most to soil P cycling. Moreover, Enterobacter sp. inoculation significantly promoted the growth of B. pilosa L., boosting total phosphorus, phospholipids, primary metabolic phosphorus, and Cd concentrations in plant tissues. Notably, a strong positive correlation was observed between soil AP and Cd concentrations in plant tissues. P-functional microbes in the rhizosphere, encoding genes such as gcd, ppa, and ppx-gppA, predominantly enhance P bioavailability in soils. Furthermore, in P-deficient and heavily contaminated soils, Proteobacteria replaced Actinobacteria as the predominant hosts for key genes involved in soil P cycling. This study provides valuable insights into the critical link between P availability and Cd accumulation, emphasizing the role of P cycling in enhancing Cd accumulation during phytoremediation mediated by PSB.

Cleaner horizons: Exploring advanced technologies for pollution remediation

Soil pollution causes many harmful effects by its contaminants or pollutants, which are known as soil pollutants. They are causing serious problems in plants as well as in humans. By entering into plants, harmful chemicals become part of the food chain. When humans consume contaminated food, it has harmful effects on human health. Pollutants are making soil unfit for living. Many techniques are being used for the remediation of soil pollution. Some are traditional techniques; some are innovative and effective as emerging science and technology are going on. In this review, we have discussed some significant methods, their aspects, and how they are playing their role in the remediation. Biological methods such as living organisms, chemical, and genetic manipulation are modern techniques that are being used for soil pollution remediation. Genetic manipulations sometimes change the enzyme processes, which enhance the whole activity by changing some of the proteins of organisms related to enzymes. Pollution remediation can be done by the process of bio-augmentation, which uses different types of strains of microbes for treatment. As there is an increase in the formation of OH compounds, advanced oxidation technologies are being introduced to treat them. Trace metals and heavy metals are also a big problem for soil pollution, which can be treated by phytoremediation techniques that use many different strategies. Nanoparticles are also being used for the treatment of compounds like nitrates, manganese, arsenic, etc. This review will guide you through the different technologies for soil pollution remediation.

A critical review about phytoremediation of heavy metals and radionuclides: from mechanisms to post-remediation strategies

Phytoremediation has emerged as an environmentally friendly and cost-effective solution for mitigating heavy metal and radionuclide contamination in soil and water. While extensive research has been conducted on phytoremediation mechanisms and the effectiveness of various plant species in pollutant uptake, limited attention has been given to the crucial aspect of post-remediation biomass management, particularly for biomass containing heavy metals and radionuclides. This review provides a pioneering perspective by integrating phytoremediation mechanisms with a comprehensive discussion of post-remediation biomass treatment methods, such as incineration, solidification, gasification, and pyrolysis, which are essential for reducing environmental risks. This study's output highlights that solidification is more suitable for radioactive biomass management for safe long-term storage and sustainable radioactive waste management; however, it does not produce value-added products. Meanwhile, gasification offers relatively low-emission biomass treatment compared to incineration and enables superior energy conversion efficiency and lower costs on a large scale compared to pyrolysis. The findings contribute to improving the overall efficiency of phytoremediation and provide insights into post-remediation biomass handling methods, reinforcing the feasibility of phytoremediation as a sustainable large-scale remediation solution. By identifying research gaps and proposing future directions to enhance the sustainability of phytoremediation, this review serves as an advantageous reference for policymakers, researchers, and environmental practitioners in designing effective phytoremediation strategies and post-remediation biomass management policies.

Prospects of phytoremediation in degradation of environmental contaminants: recent advances, challenges and way forward

Phytoremediation has gained recognition as an environmentally friendly, cost-efficient, and sustainable solution for addressing pollution in soil and water. This review provides an in-depth analysis of how this technique is applied to treat contaminants such as heavy metals, antibiotics, plastics, and radioactive substances. It emphasizes the effectiveness of plants like Brassica juncea, Pteris vittata, and Eichhornia crassipes, which have demonstrated significant pollutant uptake-removing arsenic concentrations as high as 20,000 mg/kg and reducing lead in wastewater by up to 75%. Innovations in genetic modification and nanotechnology have further enhanced the capabilities of these plants by boosting their tolerance and pollutant degradation potential. The review also explores the role of soil microbes, rhizosphere-based degradation, and the integration of nanomaterials in advancing phytoremediation. However, several challenges persist, such as limited pollutant availability to plants, slow breakdown of plastic waste, and low absorption rates for pharmaceutical residues. This work outlines existing research gaps, highlights regulatory and technical limitations, and proposes forward-looking approaches, including CRISPR-based gene editing, microbial partnerships, and hybrid remediation models. Although still developing, phytoremediation holds considerable promise as a comprehensive approach for restoring polluted environments.

Season-based phytoremediation potential of brown mustard for lead decontamination: effect of EDTA chelation and antioxidant enzyme activity

Phytoremediation technology is an environmentally benign, potent, and cost-effective approach for treating contaminated ecological sites. To yield a worthwhile remediation performance, phytoremediation technology involves amalgamating multifarious techniques and strategies. The primary objective of this research was to look into the effects of seasonal changes, contamination level, and EDTA chelation on Brown mustard's potential to extract Lead (Pb) from synthetically contaminated soil and its response to antioxidant enzyme activity. Soil samples containing 5 mg kg-1 of EDTA were spiked with 200, 500, and 1000 mg kg-1 of Pb, while the control group (unspiked) without EDTA addition was used. The results indicated that adding EDTA in winter (winter + EDTA) significantly increased (p < 0.05) plant growth by 18.83%. Observing the seasonal variation, the removal efficiency of Pb was achieved in this order: summer + EDTA > winter + EDTA > summer + No EDTA > winter + No EDTA. The results also showed that the removal rate had improved up to 52.53% as the concentration of Pb rose from 67 to 500 mg kg-1 but showed a decline after reaching 1000 mg kg-1, indicating a maximum Pb stress level. Additionally, the EDTA chelation during winter demonstrated a significant effect on the ability of Brown mustard to accumulate higher levels of Pb in both roots and leaves, with 500 mg kg-1 as the optimal level taken by the plant throughout the experiment. Except for CAT, the increased enzyme activities were observed under EDTA chelation while Pb-stress (1000 mg kg-1) reduced the enzyme activities by over 4%. The findings suggest that having 143 U/g CAT, 285 U/g SOD, and 14.9 U/g MDA in the summer season with EDTA amendments were the most suitable recourse for decontamination of Pb-polluted soil compared to a single-factor treatment.

Role of reactive oxygen species (ROS) on biochar enhanced chromium phytoremediation in the soil-plant system: Exploration on detoxification mechanism

Biochar, as an amendment to enhance phytoremediation of heavy metal contamination, can mediate reactive oxygen species (ROS) generation. However, the role of biochar-mediated ROS (BMR) during soil-plant phytoremediation remains inadequately understood. In this study, a combination of pot experiments, chemical extraction, and partial least squares path modeling (PLS-PM) was employed to investigate BMR dynamics and their influence on chromium (Cr) accumulation and detoxification in plants. Biochar addition promoted Cr removal efficiency and decreased ROS concentrations in soil, notably reaching the largest removal efficiency of 80.60 % and the lowest ROS concentration of 37.53 μmol/kg in BC-3 group at 90d. Decreased ROS concentrations in soil facilitated the plant absorbing water-soluble Cr (VI), adsorbed Cr (VI), and chromate-precipitated Cr (VI) in soil, and enhanced Cr accumulation in metabolically inactive compartments (cell walls and vacuoles). When biochar was added at concentrations of 2 % and 3 % (w/w), ROS concentrations in plant tissues decreased to signaling molecule thresholds. This reduction further stimulated antioxidant enzyme activity, promoted the reduction of Cr (VI) within subcellular organelles, and enhanced Cr cell wall fixation and vacuolar compartmentation, ultimately achieving their synergistic integration with Cr detoxification with accumulation. This study provides an in-depth understanding of BMR-related mechanisms during phytoremediation and valuable insights into strategies for enhancing mitigation of variable valence heavy metals in soils.

Medicinal plant ashwagandha in hydroponics: Pioneering greywater remediation using response surface methodology along with plants' physiological and phytochemical attributes for sustainable resource recovery

This study aimed to investigate greywater treatment through hydroponically growing ashwagandha, often referred to as "Indian Ginseng," which is rich in secondary metabolites and bioactive compounds that enhance its medicinal properties. The research examines the effect of input parameters, such as initial chemical oxygen demand (300-1500 mg/L), phosphate (0-120 mg/L), and nitrate (15-75 mg/L) and their optimization utilizing response surface methodology (RSM) with central composite design (CCD). The interactive effects are analysed with model fit through analysis of variance. The optimized parameters are investigated as 600 mg/L chemical oxygen demand (COD), 37 mg/L phosphate, and 35 mg/L nitrate, with maximum removal efficiencies of 97.74% COD, 93.62% total phosphorus, and 89.68% nitrate-nitrogen while preserving ashwagandha's medicinal qualities. The study assesses growth improvements through physiological traits, showing increase of 72.2% in wet biomass, 20% in plant height, 60% in leaf number, and total chlorophyll content of 45.45 μmol m-2. It also examines phytochemical characteristics, including fourier transform infrared spectroscopy analysis (-OH peaks within 3500-3000 cm-1) and total phenolic content of leaf and root extracts, measuring 7.14 mg gallic acid equivalents for leaves and 2.155 mg GAE for roots. Additionally, the extracts demonstrated radical scavenging activities of 73.26% for leaves and 83.74% for roots after treatment, highlighting ashwagandha's adaptability and resilience in greywater conditions. Lastly, scanning electron microscopy analysis to assess the impact of wastewater on the root structure. This research presents significant economic potential of the greywater treatment within 6 days by cultivating ashwagandha with the preservation of its medicinal properties.

Intercropping Pteris cretica and Spinacia oleracea L. with peanut enhances arsenic removal and soil remediation

Arsenic (As) exposure through agricultural soil contamination poses significant health risks and threatens food security. This study explored the efficacy of hyperaccumulator plant diversity and intercropping systems in enhancing As removal from contaminated soil while simultaneously reducing As uptake in peanuts (Arachis hypogaea L.). Thus, a pot experiment was conducted using As-contaminated soil, peanut plants, and hyperaccumulator species as the experimental materials. The experimental treatments included monocultured peanuts (Ck) and peanuts intercropped with Pteris cretica. (P*Pc), intercropped peanut with Spinacia oleracea L. (P*So), and intercropped peanut with P. cretica and S. oleracea L. (P*Pc*So). Our findings revealed that the intercropping system significantly reduced soil As levels compared to monocropping. In addition, peanut As uptake was significantly decreased in hyperaccumulator plants, with enhanced effects under hyperaccumulator plant diversity, minimizing the risk of As transfer to the food chain. Moreover, the As removal rate was higher under intercropping than under monocropping, with the highest removal rate of 88% under intercropped peanut/P. cretica/S. oleracea L., followed by peanut/S. oleracea L. (81%) and peanut/P. cretica (80%). The results demonstrate the potential of using diverse hyperaccumulator plants and intercropping systems as sustainable and effective methods for remediating As-contaminated soils, while simultaneously ensuring food safety. However, further research is needed to elucidate the underlying mechanisms driving these effects and to optimize the phytoremediation of As-contaminated soil and crop production.

Assessment the impact of palygorskite modified by chlorides on speciation and environmental risk of heavy metals in soil contaminated

This study aims to evaluate the effectiveness of palygorskite (PAL) modified with various chlorides (PMNaCl), (PMCaCl2), (PMMgCl2), (PMFeCl3) and (PMAlCl3) in stabilizing Cu and Ni in contaminated soils. Characterization methods involving Scanning Electron Microscopy (SEM), X-ray deflection (XRD and Fourier Transform Infrared Spectroscopy (FT-IR) were used to characterize the effects of palygorskite on the chemical functional groups of chloride stick and the construction of stabilizers. The Diethylene Triamine Pentaacetic Acid ("DTPA extraction") and Toxicity Characteristic Leaching Procedure (TCLP) were conducted to assess the bioavailability and mobility of Cu and Ni in soil with PAL-modified chlorides. The germinated index (GI) was employed to examine and analyze the microstructure and physico-chemical properties of the contaminated soil. The residue speciation concentration enhanced substantially, illustrating that the heavy metal speciation had stabilized after being with PAL-modified chloride. After the amendment of the PAL-modified chlorides the soil pH was enhanced by 1.33 units, whereas Electrical Conductivity (EC) increased significantly (P < 0.05) from 2.61 to 4.95 µS cm-1, Cation Exchange Capacity (CEC) increased significantly (P < 0.05) from 11.50 to 13.00 cmol/kg, while the available potassium (K) was significantly (P < 0.05) increased from 51.67 to 69.30, and the available phosphate (P) was significantly (P < 0.05) increased from 0.38 to 0.63. The most significant Sequential Extraction Procedure (BCR) in residual fraction for Cu and Ni in soil treated by PMFC and PMMC were significantly (P < 0.05) increased by 37.37% and 39.33%, respectively. Our findings indicate that PAL-modified chlorides significantly stabilize heavy metals in soil, making them promising candidates for soil remediation.

Environmental effects of the Kakhovka Dam destruction by warfare in Ukraine

The use of water as a weapon in highly industrialized areas in the Russo-Ukrainian war has resulted in catastrophic economic and environmental damages. We analyze environmental effects caused by the military destruction of the Kakhovka Dam. We link field, remote sensing, and modeling data to demarcate the disaster's spatial-temporal scales and outline trends in reestablishment of damaged ecosystems. Although media attention has focused on the immediate impacts of flooding on society, politics, and the economy, our results show that toxic contamination within newly exposed sediments of the former reservoir bed poses a largely overlooked long-term threat to freshwater, estuarine, and marine ecosystems. The continued use of water as a weapon may lead to even greater risks for people and the environment.

Cadmium accumulation potential and detoxication mechanism of Koenigia tortuosa: A novel extremely hardy plant from high altitude lead-zinc mine in Qinghai-Tibet Plateau

Hardy plants play a crucial role in restoring high-altitude tailings ponds, but the accumulation of potentially toxic elements (PTEs) and detoxification mechanisms in alpine plants are understudied. This study first investigated the cadmium (Cd) accumulation capacity and detoxification mechanisms by comparative transcriptomics with different Cd stress (0, 5, 10, 20 and 40 mg L-1 Cd2+) of Koenigia tortuosa from a lead-zinc mine (4950 m above sea level) in Qinghai-Tibet Plateau. The findings revealed that, despite elevated Cd concentrations suppressed the growth of Koenigia tortuosa, the plant retained a notable ability to accumulate Cd. The content of soluble protein and antioxidant enzyme activities increased with the concentration of Cd from 5 mg L-1 to 20 mg L-1, and then decreased when the concentration of Cd increased to 40 mg L-1. The maximum Cd accumulation in roots was 269.44 mg kg-1 at the 20 mg L-1 Cd concentration, with 61.83% of Cd extracted by NaCl. In addition, transcriptome analysis showed that differentially expressed genes (DEGs) were mainly distributed in the nucleotide metabolism, oxidative phosphorylation pathway, glutathione metabolism and plant signaling, which were significantly up-regulated in ribosomal protein genes, translational factor genes and glutathione-related genes. These results will contribute to revealing the physiological response and molecular mechanism of Cd tolerance in Koenigia tortuosa, supporting the ecological remediation of Cd contaminated sites in high-altitude mining areas.

Remediating contaminated environmental systems: the role of plants in cadmium removal

Cadmium (Cd) is one of the most harmful heavy metals in the environment, negatively impacting plant growth and development. However, phytoremediation which is an environmentally friendly and cost-effective technique can be used to treat Cd contaminated environments. It effectively removes Cd from polluted soil and water through processes, such as phytoextraction, phytostabilization, phytostimulation, phytofiltration, and phytotransformation. Numerous research has shown evidences that biological, physical, chemical, agronomic, and genetic methods are being utilized to improve phytoremediation. A special group of plants known as hyperaccumulator plants further enhance Cd removal, turning polluted areas into productive land. These plants accumulate Cd in root cell vacuoles and aerial parts. Despite the morphological and genetic variations, different plant species remediate Cd at different rates using either one or multiple mechanisms. To improve the effectiveness of phytoremediation, it is essential to thoroughly understand the mechanisms that control the accumulation and persistence of Cd in plants, including absorption, translocation, and elimination processes. However, what missing in understanding is in depth of idea on how the limitations of phytoremediation can be overcome. The limitations of phytoremediation can be addressed through various strategies, including natural and chemical amendments, genetic engineering, and natural microbial stimulation, broadly categorized into soil amelioration and plant capacity enhancement approaches. This review presents a concise overview of the latest research on various plants utilized in Cd phytoremediation and the different methods employed to enhance this process. Moreover, this review also underscores the creditability of phytoremediation technique to remediate Cd pollution as it offers a promising approach for eliminating Cd from contaminated sites and restoring their productivity. Additionally, we recommend directing future research toward enhancing the biochemical capabilities of plants for remediation purposes, elucidating the molecular mechanisms underlying the damage caused by Cd in plants, and understanding the fundamental principles regulating the enrichment of Cd in plants.

Microbe-assisted phytoremediation for sustainable management of heavy metal in wastewater - A green approach to escalate the remediation of heavy metals

Water pollution from Heavy metal (HM) contamination poses a critical threat to environmental sustainability and public health. Industrial activities have increased the presence of HMs in wastewater, necessitating effective remediation strategies. Conventional methods like chemical precipitation, ion exchange, adsorption, and membrane filtration are widely used but possess various limitations. These include high costs, environmental impacts, and the potential for generating secondary pollutants, highlighting the need for sustainable alternatives. Phytoremediation, enhanced by microbial interactions, offers an eco-friendly solution to this issue. The unique physiological and biochemical traits of plants, combined with microbial metabolic capabilities, enable efficient uptake and detoxification of HMs. Microbial enzymes play a crucial role in these processes by breaking down complex compounds, enhancing HM bioavailability, and facilitating their conversion into less toxic forms. Synergistic interactions between root-associated microbes and plants further improves metal absorption and stabilization, boosting phytoremediation efficiency. However, challenges remain, including the limited bioavailability of contaminants and plant resilience in highly polluted environments. Recent advancements focus on improving microbial-assisted phytoremediation through mechanisms like bioavailability facilitation, phytoextraction, and phytostabilization. Genetic engineering facilitates the altering of genes that control plant immune responses and growth which improves the ability of plants to interact beneficially with microbes to thrive in HM rich environments while efficiently cleaning contaminated wastewater. This review examines these strategies and highlights future research directions to enhance wastewater remediation using phytoremediation technologies.

Magnetic Carbon Porous Polymer Prepared from a New Suspended Emulsion for the Absorption of Heavy Metal Ions

In this study, magnetic carbon nanopolymers (Fe3O4/C@PM) were synthesized by suspension polymerization using magnetic carbon nanoparticles as the matrix, 2-thiophene formaldehyde and acrylamide as the monomers, and ethylene glycol dimethacrylate (EGDMA) as the crosslinking agent. The obtained material was characterized using multiple techniques, including scanning electron microscopy (SEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), N2 adsorption-desorption, and thermogravimetric analysis (TGA). The adsorption effects of Zn2+, Cd2+, and Pb2+ in the mixed solution were evaluated using magnetic carbon nanoparticles (Fe3O4/C) and Fe3O4/C@PM as adsorbents. The adsorption isotherms, kinetic models, and cyclic regeneration of various metal ions, including Zn2+, Cd2+ and Pb2+, were studied. The results showed that the Fe3O4/C@PM maintained a slightly aggregated spherical morphology similar to Fe3O4/C and exhibited excellent adsorption capacity for all of Zn2+, Cd2+, and Pb2+, with maximum adsorption capacities of 343.3, 250.7, and 177.6 mg·g-1, respectively. The adsorption mechanisms were mainly based on the chemical interactions between metal ions and functional groups on the surface of polymers. The kinetic study revealed that the adsorption process followed a pseudo-second-order kinetic model. When Fe3O4/C@PM was reused five times, its adsorption rates for Zn2+, Cd2+, and Pb2+ remained above 81%, indicating its great potential for the treatment of wastewater containing Zn2+, Cd2+, and Pb2+.

Megoura crassicauda promote the ability of Vicia faba L. to remediate cadmium pollution of water and soil

With the increasing severity of heavy metal pollution in soil and water, phytoremediation is becoming increasingly popular because of its low cost, high returns, and environmental friendliness. The use of leguminous plants such as the broad bean for heavy metal remediation is becoming a research hotspot because of their symbiotic relationship with rhizobia. This study investigated the cadmium (Cd) remediation ability of fava beans by M. crassicauda feeding on or not using both hydroponic and soil cultures containing varying concentrations of Cd. Under hydroponic conditions, the Cd content in fava beans increased significantly following aphid invasion. while the Cd content decreased after aphid infestation under soil cultivation conditions. Aphid infestation significantly decreased the Cd content in both soil and hydroponic solution. However, there were no significant changes in germination rate and phenotype. We also found that prolonged Cd treatment increased the activities of stress-related antioxidant enzymes in fava beans, including superoxide dismutase, peroxidase, and malondialdehyde. After consumption by M. crassicauda, the levels of total sugar content underwent varying changes. These results demonstrate that fava beans not only exhibit high Cd tolerance but can also effectively absorb Cd ions from soil and water. Moreover, pest infestation can enhance broad bean remediation efficiency, making them potential targets for use in the phytoremediation of heavy metal pollution.

Application risk and value of Cd-enriched poplar wood: Wood properties, leaching characteristics and brown rot resistance

This study investigated the application risk and value of Cd-enriched poplar wood, focusing on its wood properties, leaching characteristics, and brown rot resistance. The results indicated that Cd deposition in cell walls significantly inhibited brown rot fungi, thereby enhancing decay resistance. Furthermore, the extent of improvement in brown rot resistance was linked to wood density: the higher the density of Cd-enriched poplar wood, the stronger its resistance to brown rot. As the Cd concentration increased, the Cd distribution abundance and the wood crystallinity gradually increased. Structural changes were observed, including fluctuating microfibril angle and double wall thickness of fibers and vessels. Cd concentrations exceeding 50 mg/kg altered the chemical composition of the cell walls. The binding form of Cd in wood cell wall showed a trend of bound Cd ＞ free Cd ＞ residual Cd. Cd leaching occurred under cyclic soaking in water, which may lead to secondary contamination. However, under the condition of 75 % relative humidity, Cd leaching was negligible, suggesting potential for safer use in controlled environments. These findings provide valuable insights into the management and application of Cd-enriched wood, especially in contexts where decay resistance is critical or in water-exposed environments.

Physiological and transcriptome analysis of sex-specific responses to cadmium stress in poplars

Soil cadmium (Cd) pollution is a serious ecological problem worldwide. Understanding Cd-detoxification mechanisms in woody plants will help to evaluate their tolerance ability and phytoremediation potential to Cd-polluted soils. This study investigated the growth, physiochemistry, Cd distribution, and transcriptome sequencing of male and female poplars under three Cd levels (0, 50, and 100 mg·kg-1). The results showed that Cd stress significantly inhibited the growth of aboveground parts. Over 70 % of the Cd was distributed in the cell wall fraction of roots, stems, and leaves, with the majority accumulating in the roots. Poplars can conjugate Cd with phytochelatins to reduce Cd damage, which is more evident in males than females. The antioxidant defense system of females is more effective than that of males at reducing the damage from Cd. Females demonstrated a stronger Cd-regulation ability than males under the 100 mg·kg-1 Cd treatment. Sex-specific responses to Cd were associated with differential gene expression. Under Cd stress, the genes related to oxidation-reduction processes, antioxidant enzyme activity and defense mechanisms, cell wall synthesis, and glutathione metabolism were mainly enriched and upregulated in females, whereas in males, genes related to photosynthesis and photosynthetic pigment biosynthesis were mainly enriched and downregulated, indicating greater damage to the photosynthetic system than in females. Our study provides novel insights into the mechanisms responding to Cd tolerance in poplars. Further studies should be carried out to assess the impact of soil Cd pollution on the wood quality of poplars.

Unlocking plant resilience: Advanced epigenetic strategies against heavy metal and metalloid stress

The escalating threat of heavy metal and metalloid stress on plant ecosystems requires innovative strategies to strengthen plant resilience and ensure agricultural sustainability. This review provides important insights into the advanced epigenetic pathways to improve plant tolerance to toxic heavy metals and metalloid stress. Epigenetic modifications, including deoxyribonucleic acid (DNA) methylation, histone modifications, and small ribonucleic acid (RNA) engineering, offer innovative avenues for tailoring plant responses to mitigate the impact of heavy metal and metalloid stress. Technological advancements in high-throughput genome sequencing and functional genomics have unraveled the complexities of epigenetic regulation in response to heavy metal and metalloid contamination. Recent strides in this field encompass identifying specific epigenetic markers associated with stress resilience, developing tools for editing the epigenome, and integrating epigenetic data into breeding programs for stress-resistant crops. Understanding the dynamic interaction between epigenetics and stress responses holds immense potential to engineer resilient crops that thrive in environments contaminated with heavy metals and metalloids. Eventually, harnessing epigenetic strategies presents a promising trajectory toward sustainable agriculture in the face of escalating environmental challenges. Plant epigenomics expands, the potential for sustainable agriculture by implementing advanced epigenetic approaches becomes increasingly evident. These developments lay the foundation for understanding the growing significance of epigenetics in plant stress biology and its potential to mitigate the detrimental effects of heavy metal and metalloid pollution on global agriculture.

Claroideglomus etunicatum enhances Pteris vittata L. arsenic resistance and accumulation by mediating the rapid reduction and transport of arsenic in roots

Arbuscular mycorrhizal fungi (AMF) have been widely shown to significantly promote the growth and recovery of Pteris vittata L. growth and repair under arsenic stress; however, little is known about the molecular mechanisms by which AMF mediate the efficient uptake of arsenic in this species. To understand how AMF mediate P. vittata arsenic metabolism under arsenic stress, we performed P. vittata root transcriptome analysis before and after Claroideglomus etunicatum (C. etunicatum) colonization. The results showed that after C. etunicatum colonization, P. vittata showed greater arsenic resistance and enrichment, and its dry weight and arsenic accumulation increased by 2.01-3.36 times. This response is attributed to the rapid reduction and upward translocation of arsenic. C. etunicatum enhances arsenic uptake by mediating the MIP, PHT, and NRT transporter families, while also increasing arsenic reduction (PvACR2 direct reduction and vesicular PvGSTF1 reduction). In addition, it downregulates the expression of ABC and P-type ATPase protein families, which inhibits the compartmentalization of arsenic in the roots and promotes its translocation to the leaves. This study revealed the mechanism of C. etunicatum-mediated arsenic hyperaccumulation in P. vittata, providing guidance for understanding the regulatory mechanism of P. vittata.

Non-phytoremediation and phytoremediation technologies of integrated remediation for water and soil heavy metal pollution: A comprehensive review

Since the 1980s, there has been increasing concern over heavy metal pollution remediation. However, most research focused on the individual remediation technologies for heavy metal pollutants in either soil or water. Considering the potential migration of these pollutants, it is necessary to explore effective integrated remediation technologies for soil and water heavy metals. This review thoroughly examines non-phytoremediation technologies likes physical, chemical, and microbial remediation, as well as green remediation approaches involving terrestrial and aquatic phytoremediation. Non-phytoremediation technologies suffer from disadvantages like high costs, secondary pollution risks, and susceptibility to environmental factors. Conversely, phytoremediation technologies have gained significant attention due to their sustainable and environmentally friendly nature. Enhancements through chelating agents, biochar, microorganisms, and genetic engineering have demonstrated improved phytoremediation remediation efficiency. However, it is essential to address the environmental and ecological risks that may arise from the prolonged utilization of these materials and technologies. Lastly, this paper presents an overview of integrated remediation approaches for addressing heavy metal contamination in groundwater-soil-surface water systems and discusses the reasons for the research gaps and future directions. This paper offers valuable insights for comprehensive solutions to heavy metal pollution in water and soil, promoting integrated remediation and sustainable development.

Morphophysiological Adaptations of Aquatic Macrophytes in Wetland-Based Sewage Treatment Systems: Strategies for Resilience and Efficiency under Environmental Stress

There is a common misconception that aquatic macrophytes face significant challenges in wetland-based sewage treatment systems. This study aims to correct this perception by focusing on the crucial morphophysiological adaptations of aquatic macrophytes that enable them to thrive in wetland-based sewage treatment systems, particularly under environmental stress. These adaptations are vital for improving the efficiency and resilience of wastewater treatment processes, offering sustainable solutions in the face of variable environmental conditions and complex contaminant mixtures. The review emphasizes the role of macrophytes as natural engineers, capable of enhancing pollutant removal and system stability through their unique structural and functional traits. By understanding these adaptations, the review aims to guide the optimization of wetland design and management, ultimately contributing to more sustainable and effective wastewater treatment practices. The findings underscore the importance of species selection and the integration of nature-based solutions in environmental management, advocating for policies that support the use of macrophytes in modern wastewater management.

Phytoremediation of molybdenum (Mo)-contaminated soil using plant and humic substance

The severity of soil molybdenum (Mo) pollution is increasing, and effective management of contaminated soil is essential for the sustainable development of soil. To investigate this, a pot experiment was carried out to assess the impact of different rates of humic acid (HA) and fulvic acid (FA) on the mobility of Mo in soil solution and its uptake by alfalfa, wheat and green bristlegrass. The concentration of Mo in Plants and soil was determined using an Atomic Absorption Spectrophotometer. The findings revealed that the application of HA led to an increase in Mo accumulation in the shoot and root of green bristlegrass and wheat, ranging from 10.56 % to 28.73 % and 62.15-115.79 % (shoot), and 17.52-46.53 % and 6.29-81.25 % (root), respectively. Nonetheless, the use of HA resulted in a slight inhibition of plant Mo uptake, leading to reduced Mo accumulation in alfalfa roots compared to the control treatment (from 3284.49 mg/kg to 2140.78-2813.54 mg/kg). On the other hand, the application of FA decreased Mo accumulation in the wheat shoot (from 909.92 mg/kg to 338.54-837.45 mg/kg). Furthermore, the bioavailability of green bristlegrass (with HA) and wheat (with FA) decreased, and the percentage of residual fraction of Mo increased (from 0.39 % to 0.78-0.96 %, from 3.95 % to 3.97∼ 4.34 %). This study aims to elucidate the ternary interaction among Mo, humic substances, and plants (alfalfa, wheat, and green bristlegrass), to enhance both the activation and hyperaccumulation of Mo simultaneously.

Assessing Lettuce Exposure to a Multi-Pharmaceutical Mixture in Soil: Insights from LC-ESI-TQ Analysis and the Impact of Biochar on Pharmaceutical Bioavailability

Agricultural practices introduce pharmaceutical (PhAC) residues into the terrestrial environment, potentially endangering agricultural crops and human health. This study aimed to evaluate various aspects related to the presence of pharmaceuticals in the lettuce-soil system, including bioconcentration factors (BCFs), translocation factors (TFs), ecotoxicological effects, the influence of biochar on the PhAC bioavailability, persistence in soil, and associated environmental and health risks. Lettuce (Lactuca sativa L.) was exposed to a mixture of 25 PhACs in two scenarios: initially contaminated soil (ranging from 0 to 10,000 ng·g-1) and soil irrigated with contaminated water (ranging from 0 to 1000 μg·L-1) over a 28-day period. The findings revealed a diverse range of BCFs (0.068-3.7) and TFs (0.032-0.58), indicating the uptake and translocation potential of pharmaceuticals by lettuce. Significant ecotoxicological effects on L. sativa, including weight change and increased mortality, were observed (p < 0.05). Interestingly, biochar did not significantly affect PhAC uptake by L. sativa (p > 0.05), while it significantly influenced the soil degradation kinetics of 12 PhACs (p < 0.05). Additionally, the estimated daily intake of PhACs through the consumption of L. sativa suggested negligible health risks, although concerns arose regarding the potential health risks if other vegetable sources were similarly contaminated with trace residues. Furthermore, this study evaluated the environmental risk associated with the emergence of antimicrobial resistance (AMR) in soil, as medium to high. In conclusion, these findings highlight the multifaceted challenges posed by pharmaceutical contamination in agricultural environments and emphasize the importance of proactive measures to mitigate the associated risks to both environmental and human health.

A combined bibliometric and sustainable approach of phytostabilization towards eco-restoration of coal mine overburden dumps

Extraction of coal through opencast mining leads to the buildup of heaps of overburden (OB) material, which poses a significant risk to production safety and environmental stability. A systematic bibliometric analysis to identify research trends and gaps, and evaluate the impact of studies and authors in the field related to coal OB phytostabilization was conducted. Key issues associated with coal extraction include land degradation, surface and groundwater contamination, slope instability, erosion and biodiversity loss. Handling coal OB material intensifies such issues, initiating additional environmental and physical challenges. The conventional approach such as topsoiling for OB restoration fails to restore essential soil properties crucial for sustainable vegetation cover. Phytostabilization approach involves establishing a self-sustaining plant cover over OB dump surfaces emerges as a viable strategy for OB restoration. This method enhanced by the supplement of organic amendments boosts the restoration of OB dumps by improving rhizosphere properties conducive to plant growth and contaminant uptake. Criteria essential for plant selection in phytostabilization are critically evaluated. Native plant species adapted to local climatic and ecological conditions are identified as key agents in stabilizing contaminants, reducing soil erosion, and enhancing ecosystem functions. Applicable case studies of successful phytostabilization of coal mines using native plants, offering practical recommendations for species selection in coal mine reclamation projects are provided. This review contributes to sustainable approaches for mitigating the environmental consequences of coal mining and facilitates the ecological recovery of degraded landscapes.

IAA is more effective than EDTA in enhancing phytoremediation potential for cadmium and copper contaminated soils

Enhanced phytoremediation offers a rapid and eco-friendly approach for cleaning agricultural soil contaminated with copper and cadmium which pose a direct threat to food scarcity and security. The current study aimed to compare the effectiveness of the two commonly used additives, IAA and EDTA, for the remediation of copper (Cu) and cadmium (Cd) contaminated soils using sunflower and maize. The plants were cultivated in pots under controlled conditions with four sets of treatments: control (0), Cu50/Cd50, Cu50/Cd50 + EDTA, and Cu50/Cd50 + IAA. The results showed that Cu50/Cd50 mg/kg drastically compromised the phytoremediation potential of both plants, as evident by reduced shoot and root length, and lower biomass. However, the augmentation of Cu50/Cd50 with EDTA or IAA improved the tested parameters. In sunflower, EDTA enhanced the accumulation of Cu and Cd by 58% and 21%, respectively, and improved plant biomass by 41%, compared to control treatment. However, IAA exhibited higher accumulation of Cu and Cd by 64% and 25%, respectively, and enhanced plant biomass by 43%. In case of maize, IAA was superior to EDTA which enhanced the accumulation of Cu and Cd by 87% and 32% respectively, and increased the plant biomass by 57%, compared to control treatment. Our findings demonstrate that foliar IAA is more effective than EDTA in enhancing the phytoremediation potential of sunflower and maize for Cu and Cd.

Biochar Amendments and Phytoremediation: A Combined Approach for Effective Lead Removal in Shooting Range Soils

The increasing contamination of soil with heavy metals poses a problem to environmental sustainability. Among these pollutants, lead is particularly concerning due to its persistence in the environment, with harmful effects on human health and ecosystems. Various strategies that combine phytoremediation techniques with soil amendments have emerged to mitigate lead contamination. In this context, biochar has gained significant attention for its potential to enhance soil quality and remediate metal-contaminated environments. This study aims to investigate the combined effect of biochar amendments on the phytoremediation of lead-contaminated shooting range soils. A series of experiments were conducted to determine the impact of the amount and distribution of biochar on lead removal from soil. Soil samples were incubated with biochar for one week, after which two types of seeds (Brassica rapa and Lolium perenne) were planted. Plant and root lengths, as well as the number of germinated seeds, were measured, and a statistical analysis was conducted to determine the influence of the amendments. After one month, the Pb concentration decreased by more than 70%. Our results demonstrate that seed germination and plant growth were significantly better in soil samples where biochar was mixed rather than applied superficially, with the optimal performance observed at a 10% wt. biochar amendment. Additionally, the combined use of biochar and phytoremediation proved highly effective in immobilizing lead and reducing its bioavailability. These findings suggest that the combination of biochar, particularly when mixed at appropriate concentrations, and Brassica rapa significantly improved lead removal efficiency.

Transcriptome and metabolome analysis reveal key genes and metabolic pathway responses in Leersia hexandra Swartz under Cr and Ni co-stress

Phytoremediation, an eco-friendly approach for mitigating heavy metal contamination, is reliant on hyperaccumulators. This study focused on Leersia hexandra Swart, a known chromium (Cr) hyperaccumulator with demonstrated tolerance to multiple heavy metals. Our objective was to investigate its response to simultaneous Cr and nickel (Ni) stress over 12 days. Results from physiological experiments demonstrated a significant increase in the activities of antioxidant enzymes (APX, SOD, CAT) and glutathione (GSH) content under Cr and Ni stress, indicating enhanced antioxidant mechanisms. Transcriptome analysis revealed that stress resulted in the differential expression of 27 genes associated with antioxidant activity and metal binding, including APX, SOD, CAT, GSH, metallothionein (MT), and nicotinamide (NA). Among them, twenty differentially expressed genes (DEGs) related to GSH metabolic cycle were identified. Notably, GSTU6, GND1, and PGD were the top three related genes, showing upregulation with fold changes of 4.57, 6.07, and 3.76, respectively, indicating their crucial role in metal tolerance. The expression of selected DEGs was validated by quantitative real-time PCR, confirming the reliability of RNA-Seq data. Metabolomic analysis revealed changes in 1121 metabolites, with amino acids, flavonoids, and carbohydrates being the most affected. Furthermore, glucosinolate biosynthesis and amino acid biosynthesis pathways were represented in the KEGG pathway of differentially expressed metabolites (DEMs). This study provides insights into the tolerance mechanisms of L. hexandra under the co-stress of Cr and Ni, offering a new perspective for enhancing its remediation performance.

Hyperaccumulators' Diversity Enhances Cd-Contaminated Soil Restoration and Reduces Rice Cd Uptake under an Intercropping System

Cd accumulation in rice-cultivated soils across China is a major problem that needs to be tackled. A plot experiment was carried out using heavy metal (HM) hyperaccumulators Amaranthus hypochondriacus L. and Perilla frutescens (L.) Britt. intercropped with low-accumulation rice to obtain safe edible rice while reducing the soil Cd concentration. It was found that Cd concentration in soil was decreased by 7.43 and 2.86% under rice intercropped with Amaranthus hypochondriacus L. and Perilla frutescens (L.) Britt., respectively, compared to single cropped rice. In addition, enhanced effects were noted under the combination of Amaranthus hypochondriacus L., Perilla frutescens (L.) Britt, and rice in which a 20.35% decrease in soil Cd content was recorded compared to single-cultivated rice soil. In addition, the available Cd in soil was reduced by 4.00 and 5.00% under rice/Amaranthus and rice/Perilla, respectively, and 12.00% under rice/Amaranthus/Perilla mixed culture. Moreover, the concentration of Cd in various parts of rice was under permissible limits. However, rice biomass was decreased by the presence of hyperaccumulators. This study suggests that combining HM hyperaccumulator plants and low-accumulation rice provides efficient Cd extraction results and could be a crucial option for restoring Cd-contaminated soil without reducing rice production.

Bioremediation potential of microalgae for sustainable soil treatment in India: A comprehensive review on heavy metal and pesticide contaminant removal

The escalating environmental concerns arising from soils contamination with heavy metals (HMs) and pesticides (PSTs) necessitate the development of sustainable and effective remediation strategies. These contaminants, known for their carcinogenic properties and toxicity even at small amounts, pose significant threats to both environmental ecology and human health. While various chemical and physical treatments are employed globally, their acceptance is often hindered by prolonged remediation times, high costs, and inefficacy in areas with exceptionally high pollutant concentrations. A promising emerging trend in addressing this issue is the utilization of microalgae for bioremediation. Bioremediation, particularly through microalgae, presents numerous benefits such as high efficiency, low cost, easy accessibility and an eco-friendly nature. This approach has gained widespread use in remediating HM and PST pollution, especially in large areas. This comprehensive review systematically explores the bioremediation potential of microalgae, shedding light on their application in mitigating soil pollutants. The paper summarizes the mechanisms by which microalgae remediate HMs and PSTs and considers various factors influencing the process, such as pH, temperature, pollutant concentration, co-existing pollutants, time of exposure, nutrient availability, and light intensity. Additionally, the review delves into the response and tolerance of various microalgae strains to these contaminants, along with their bioaccumulation capabilities. Challenges and future prospects in the microalgal bioremediation of pollutants are also discussed. Overall, the aim is to offer valuable insights to facilitate the future development of commercially viable and efficient microalgae-based solutions for pollutant bioremediation.

Physiological and transcriptomic analyses reveal the cadmium tolerance mechanism of Miscanthus lutarioriparia

Miscanthus lutarioriparia is a promising energy crop that is used for abandoned mine soil phytoremediation because of its high biomass yield and strong tolerance to heavy metals. However, the biological mechanism of heavy metal resistance is limited, especially for applications in the soil restoration of mining areas. Here, through the investigation of soil cadmium(Cd) in different mining areas and soil potted under Cd stress, the adsorption capacity of Miscanthus lutarioriparia was analyzed. The physiological and transcriptional effects of Cd stress on M. lutarioriparia leaves and roots under hydroponic conditions were analyzed. The results showed that M. lutarioriparia could reduce the Cd content in mining soil by 29.82%. Moreover, different Cd varieties have different Cd adsorption capacities in soils with higher Cd concentration. The highest cadmium concentrations in the aboveground and belowground parts of the plants were 185.65 mg/kg and 186.8 mg/kg, respectively. The total chlorophyll content, superoxide dismutase and catalase activities all showed a trend of increasing first and then decreasing. In total, 24,372 differentially expressed genes were obtained, including 7735 unique to leaves, 7725 unique to roots, and 8912 unique to leaves and roots, which showed differences in gene expression between leaves and roots. These genes were predominantly involved in plant hormone signal transduction, glutathione metabolism, flavonoid biosynthesis, ABC transporters, photosynthesis and the metal ion transport pathway. In addition, the number of upregulated genes was greater than the number of downregulated genes at different stress intervals, which indicated that M. lutarioriparia adapted to Cd stress mainly through positive regulation. These results lay a solid foundation for breeding excellent Cd resistant M. lutarioriparia and other plants. The results also have an important theoretical significance for further understanding the detoxification mechanism of Cd stress and the remediation of heavy metal pollution in mining soil.

Alterations in the Anatomy and Ultrastructure of Leaf Blade in Norway Maple (Acer platanoides L.) Growing on Mining Sludge: Prospects of Using This Tree Species for Phytoremediation

Alterations in leaf architecture can be used as an indicator of the substrate toxicity level as well as the potential of a given plant species in the phytoremediation of polluted areas, e.g., mining sludge. In this work, we demonstrated, for the first time, the nature and scale of alterations in leaf architecture at the tissue and cellular levels occurring in Norway maple growing on mining sludge originating from a copper mine in Lubin (Poland). The substrate differs from other mine wastes, e.g., calamine or serpentine soils, due to an extremely high level of arsenic (As). Alterations in leaf anatomy predominantly included the following: (1) a significant increase in upper epidermis thickness; (2) a significant decrease in palisade parenchyma width; (3) more compact leaf tissue organization; (4) the occurrence of two to three cell layers in palisade parenchyma in contrast to one in the control; (5) a significantly smaller size of cells building palisade parenchyma. At the cellular level, the alterations included mainly the occurrence of local cell wall thickenings-predominantly in the upper and lower epidermis-and the symptoms of accelerated leaf senescence. Nevertheless, many chloroplasts showed almost intact chloroplast ultrastructure. Modifications in leaf anatomy could be a symptom of alterations in morphogenesis but may also be related to plant adaptation to water deficit stress. The occurrence of local cell wall thickenings can be considered as a symptom of a defence strategy involved in the enlargement of apoplast volume for toxic elements (TE) sequestration and the alleviation of oxidative stress. Importantly, the ultrastructure of leaf cells was not markedly disturbed. The results suggested that Norway maple may have good phytoremediation potential. However, the general shape of the plant, the significantly smaller size of leaves, and accelerated senescence indicated the high toxicity of the mining sludge used in this experiment. Hence, the phytoremediation of such a substrate, specifically including use of Norway maple, should be preceded by some amendments-which are highly recommended.

Potential strategies for phytoremediation of heavy metals from wastewater with circular bioeconomy approach

Water pollution is an inextricable problem that stems from natural and human-related factors. Unfortunately, with rapid industrialization, the problem has escalated to alarming levels. The pollutants that contribute to water pollution include heavy metals (HMs), chemicals, pesticides, pharmaceuticals, and other industrial byproducts. Numerous methods are used for treating HMs in wastewater, like ion exchange, membrane filtration, chemical precipitation, adsorption, and electrochemical treatment. But the remediation through the plant, i.e., phytoremediation is the most sustainable approach to remove the contaminants from wastewater. Aquatic plants illustrate the capacity to absorb excess pollutants including organic and inorganic compounds, HMs, and pharmaceutical residues present in agricultural, residential, and industrial discharges. The extensive exploitation of these hyperaccumulator plants can be attributed to their abundance, invasive mechanisms, potential for bioaccumulation, and biomass production. Post-phytoremediation, plant biomass can be toxic to both water bodies and soil. Therefore, the circular bioeconomy approach can be applied to reuse and repurpose the toxic plant biomass into different circular bioeconomy byproducts such as biochar, biogas, bioethanol, and biodiesel is essential. In this regard, the current review highlights the potential strategies for the phytoremediation of HMs in wastewater and various strategies to efficiently reuse metal-enriched biomass material and produce commercially valuable products. The implementation of circular bioeconomy practices can help overcome significant obstacles and build a new platform for an eco-friendlier lifestyle.

Biphasic pretreatment excels over conventional sulfuric acid in pinewood biorefinery: An environmental analysis

This study assesses the environmental impact of pine chip-based biorefinery processes, focusing on bioethanol, xylonic acid, and lignin production. A cradle-to-gate Life Cycle Assessment (LCA) is employed, comparing a novel biphasic pretreatment method (p-toluenesulfonic acid (TsOH)/pentanol, Sc-1) with conventional sulfuric acid pretreatment (H2SO4, Sc-2). The analysis spans biomass handling, pretreatment, enzymatic hydrolysis, yeast fermentation, and distillation. Sc-1 yielded an environmental impact of 1.45E+01 kPt, predominantly affecting human health (96.55%), followed by ecosystems (3.07%) and resources (0.38%). Bioethanol, xylonic acid, and lignin contributed 32.61%, 29.28%, and 38.11% to the total environmental burdens, respectively. Sc-2 resulted in an environmental burden of 1.64E+01 kPt, with a primary impact on human health (96.56%) and smaller roles for ecosystems (3.07%) and resources (0.38%). Bioethanol, xylonic acid, and lignin contributed differently at 22.59%, 12.5%, and 64.91%, respectively. Electricity generation was predominant in both scenarios, accounting for 99.05% of the environmental impact, primarily driven by its extensive usage in biomass handling and pretreatment processes. Sc-1 demonstrated a 13.05% lower environmental impact than Sc-2 due to decreased electricity consumption and increased bioethanol and xylonic acid outputs. This study highlights the pivotal role of pretreatment methods in wood-based biorefineries and underscores the urgency of sustainable alternatives like TsOH/pentanol. Additionally, adopting greener electricity generation, advanced technologies, and process optimization are crucial for reducing the environmental footprint of waste-based biorefineries while preserving valuable bioproduct production.

Revolutionizing soil heavy metal remediation: Cutting-edge innovations in plant disposal technology

Soil contamination with heavy metals has emerged as a global environmental threat, compromising agricultural productivity, ecosystem integrity, and human health. Conventional remediation techniques often fall short due to high costs, operational complexities, and environmental drawbacks. Plant-based disposal technologies, including biochar, phytometallurgy, and phrolysis, have emerged as promising solutions in this regard. Grounded in a novel experimental framework, biochar is studied for its dual role as soil amendment and metal adsorbent, while phytometallurgy is explored for its potential in resource recovery and economic benefits derived from harvested metal-rich plant biomass. Pyrolysis, in turn, is assessed for transforming contaminated biomass into value-added products, thereby minimizing waste. These plant disposal technologies create a circular model of remediation and resource utilization that holds the potential for application in large-scale soil recovery projects, development of environmentally friendly agro-industries, and advancement in sustainable waste management practices. This review mainly discussed cutting-edge plant disposal technologies-biochar application, phytometallurgy, and pyrolysis-as revolutionary approaches to soil heavy metal remediation. The efficacy, cost-effectiveness, and environmental impact of these innovative technologies are especially evaluated in comparison with traditional methods. The success of these applications could signal a paradigm shift in how we approach both environmental remediation and resource recovery, with profound implications for sustainable development and circular economy strategies.

Synergistic interactions of assorted ameliorating agents to enhance the potential of heavy metal phytoremediation

Pollution by toxic heavy metals creates a significant impact on the biotic community of the ecosystem. Nowadays, a solution to this problem is an eco-friendly approach like phytoremediation, in which plants are used to ameliorate heavy metals. In addition, various amendments are used to enhance the potential of heavy metal phytoremediation. Symbiotic microorganisms such as phosphate-solubilizing bacteria (PSB), endophytes, mycorrhiza and plant growth-promoting rhizobacteria (PGPR) play a significant role in the improvement of heavy metal phytoremediation potential along with promoting the growth of plants that are grown in contaminated environments. Various chemical chelators (Indole 3-acetic acid, ethylene diamine tetra acetic acid, ethylene glycol tetra acetic acid, ethylenediamine-N, N-disuccinic acid and nitrilotri-acetic acid) and their combined action with other agents also contribute to heavy metal phytoremediation enhancement. With modern techniques, transgenic plants and microorganisms are developed to open up an alternative strategy for phytoremediation. Genomics, proteomics, transcriptomics and metabolomics are widely used novel approaches to develop competent phytoremediators. This review accounts for the synergistic interactions of the ameliorating agent's role in enhancing heavy metal phytoremediation, intending to highlight the importance of these various approaches in reducing heavy metal pollution.

Characterization of a uranium-tolerant green microalga of the genus Coelastrella with high potential for the remediation of metal-polluted waters

Uranium (U) contamination of terrestrial and aquatic ecosystems poses a significant threat to the environment and human health due to the chemotoxicity of this actinide. The characterization of organisms that tolerate and accumulate U is crucial to decipher the mechanisms evolved to cope with the radionuclide and to propose new effective strategies for the bioremediation of U-contaminated environments. Here, we isolated a unicellular green microalga of the genus Coelastrella from U-contaminated wastewater. We showed that Coelastrella sp. PCV is much more tolerant to U than Chlamydomonas reinhardtii and Chlorella vulgaris. Coelastrella sp. PCV is able to accumulate U very rapidly and then gradually release it into the medium, behaving as an excluder to limit the toxic effects of U. The ability of Coelastrella sp. PCV to accumulate U is remarkably high, with up to 240 mg of tightly bound U per g of dry biomass. Coelastrella sp. PCV is able to grow and maintain high photosynthesis in natural metal-contaminated waters from a wetland near a reclaimed U mine. In a single one-week growth cycle, Coelastrella sp. PCV is able to capture 25-55 % of the U from the contaminated waters and shows lipid droplet accumulation. Coelastrella sp. PCV is a very promising microalga for the remediation of polluted waters with valorization of algal biomass that accumulates lipids.

Piriformospora indica colonization enhances remediation of cadmium and chromium co-contaminated soils by king grass through plant growth promotion and rhizosphere microecological regulation

Poor plant growth and low pollutant bioavailability in contaminated soils limit phytoremediation efficiency. Pot experiments were conducted to investigate the effects and mechanisms of Piriformospora indica inoculation on the phytoremediation of Cd-Cr co-contaminated soils from farmland using king grass. P. indica colonization increased plant biomass by 20.4-24.6% and enhanced Cd/Cr accumulation in root, stem and leave tissues. Root vascular cylinder and cortex were the major structures for Cd/Cr transportation in plants. The amounts of Cd and Cr extracted by king grass considerably increased in the presence of P. indica (by 31.5-88.9% and 22.4-38.4%, respectively), as did the removal efficiency of both metals from soils (by 13.2-32.2% and 23.2-33.5%, respectively). Cd/Cr phytoextraction was closely related to the contents of alkanes, lipids and acids in root exudates. Following inoculation, the respiration of microbial sulfur compounds was promoted in soils at low and medium pollution levels, whereas nitrogen fixation and nitrification were reduced at high pollution level. This study demonstrates that P. indica inoculation enhances the phytoremediation efficiency of king grass for Cd-Cr co-contaminated soils through multiple regulation of plant growth, rhizosphere environment, root exudation and soil microbial function.

Prevalence of antibiotic and metal resistance genes in phytoremediated cadmium and zinc contaminated soil assisted by chitosan and Trichoderma harzianum

Heavy metal in soil have been shown to be toxic with high concentrations and acts as selective pressure on both bacterial metal and antibiotic resistance determinants, posing a serious risk to public health. In cadmium (Cd) and zinc (Zn) contaminated soil, chitosan (Chi) and Trichoderma harzianum (Tri) were applied alone and in combination to assist phytoremediation by Amaranthus hypochondriacus L. Prevalence of antibiotic and metal resistance genes (ARGs and MRGs) in the soil was also evaluated using metagenomic approach. Results indicated that the phytoremediation of Cd and Zn contaminated soil was promoted by Chi, and Tri further reinforced this effect, along with the increased availability of Cd and Zn in soil. Meanwhile, combination of Chi and Tri enhanced the prevalence of ARGs (e.g., multidrug and β-lactam resistance genes) and maintained a high level of MRGs (e.g., chromium, copper) in soil. Soil available Zn and Cd fractions were the main factors contributing to ARGs profile by co-selection, while boosted bacterial hosts (e.g., Mitsuaria, Solirubrobacter, Ramlibacter) contributed to prevalence of most MRGs (e.g., Cd). These findings indicate the potential risk of ARGs and MRGs propagation in phytoremediation of metal contaminated soils assisted by organic and biological agents.

A WRKY transcription factor, PyWRKY71, increased the activities of antioxidant enzymes and promoted the accumulation of cadmium in poplar

Cadmium (Cd) pollution poses significant threats to the ecological environment and human health. Currently, phytoremediation is recognized as an environmentally friendly approach for mitigating Cd pollution, with increasing attention on the utilization of transgenic plants in Cd-contaminated soil remediation. In this study, we isolated and cloned PyWRKY71 from Populus yunnanensis and conducted a pot experiment to validate its enhanced functionality in conferring Cd tolerance to woody plants (poplar). During the experiment, the increase in plant height of the OE-87 line (overexpression poplar) was 1.46 times than that of the wild type (WT). Moreover, PyWRKY71 significantly promoted the accumulation of Cd in poplar, especially in the roots, where the Cd content in the OE-45 and OE-87 lines was 1.42 times than that in the WT. The chlorophyll content of transgenic poplar leaves was higher than that of the WT, reflecting a protective mechanism of PyWRKY71. Additionally, the activities of other antioxidants, including POD, SOD, CAT, and MDA, were elevated in transgenic poplars, bolstering their tolerance to Cd stress. In summary, PyWRKY71 exhibits substantial potential in regulating plant tolerance to Cd stress. This study not only provides a solid scientific foundation but also introduces a novel modified poplar variety for the remediation of Cd pollution.

Transcriptome Analysis Reveals the Stress Tolerance Mechanisms of Cadmium in Zoysia japonica

Cadmium (Cd) is a severe heavy metal pollutant globally. Zoysia japonica is an important perennial warm-season turf grass that potentially plays a role in phytoremediation in Cd-polluted soil areas; however, the molecular mechanisms underlying its Cd stress response are unknown. To further investigate the early gene response pattern in Z. japonica under Cd stress, plant leaves were harvested 0, 6, 12, and 24 h after Cd stress (400 μM CdCl2) treatment and used for a time-course RNA-sequencing analysis. Twelve cDNA libraries were constructed and sequenced, and high-quality data were obtained, whose mapped rates were all higher than 94%, and more than 601 million bp of sequence were generated. A total of 5321, 6526, and 4016 differentially expressed genes were identified 6, 12, and 24 h after Cd stress treatment, respectively. A total of 1660 genes were differentially expressed at the three time points, and their gene expression profiles over time were elucidated. Based on the analysis of these genes, the important mechanisms for the Cd stress response in Z. japonica were identified. Specific genes participating in glutathione metabolism, plant hormone signal and transduction, members of protein processing in the endoplasmic reticulum, transporter proteins, transcription factors, and carbohydrate metabolism pathways were further analyzed in detail. These genes may contribute to the improvement of Cd tolerance in Z. japonica. In addition, some candidate genes were highlighted for future studies on Cd stress resistance in Z. japonica and other plants. Our results illustrate the early gene expression response of Z. japonica leaves to Cd and provide some new understanding of the molecular mechanisms of Cd stress in Zosia and Gramineae species.

Current Status of Biotechnological Approaches to Enhance the Phytoremediation of Heavy Metals in India-A Review

Rising waste construction, agricultural actions, and manufacturing sewages all contribute to heavy metal accumulation in water resources. Humans consume heavy metals-contaminated substances to make sustenance, which equally ends up in the food circle. Cleaning of these vital properties, along with the prevention of new pollution, has long been required to evade negative strength consequences. Most wastewater treatment techniques are widely acknowledged to be costly and out of the grasp of governments and small pollution mitigation businesses. Utilizing hyper-accumulator plants that are extremely resilient to heavy metals in the environment/soil, phytoremediation is a practical and promising method for eliminating heavy metals from contaminated environments. This method extracts, degrades, or detoxifies harmful metals using green plants. The three phytoremediation techniques of phytostabilization, phytoextraction, and phytovolatilization have been used extensively for soil remediation. Regarding their ability to be used on a wide scale, conventional phytoremediation methods have significant limitations. Hence, biotechnological attempts to change plants for heavy metal phytoremediation methods are extensively investigated in order to increase plant effectiveness and possible use of improved phytoremediation approaches in the country of India. This review focuses on the advances and significance of phytoremediation accompanied by the removal of various harmful heavy metal contaminants. Similarly, sources, heavy metals status in India, impacts on nature and human health, and variables influencing the phytoremediation of heavy metals have all been covered.

Zinc and nano zinc mediated alleviation of heavy metals and metalloids in plants: an overview

Heavy metals and metalloids (HMs) contamination in the environment has heightened recently due to increasing global concern for food safety and human livability. Zinc (Zn2+ ) is an important nutrient required for the normal development of plants. It is an essential cofactor for the vital enzymes involved in various biological mechanisms of plants. Interestingly, Zn2+ has an additional role in the detoxification of HMs in plants due to its unique biochemical-mediating role in several soil and plant processes. During any exposure to high levels of HMs, the application of Zn2+ would confer greater plant resilience by decreasing oxidative stress, maintaining uptake of nutrients, photosynthesis productivity and optimising osmolytes concentration. Zn2+ also has an important role in ameliorating HMs toxicity by regulating metal uptake through the expression of certain metal transporter genes, targeted chelation and translocation from roots to shoots. This review examined the vital roles of Zn2+ and nano Zn in plants and described their involvement in alleviating HMs toxicity in plants. Moving forward, a broad understanding of uptake, transport, signalling and tolerance mechanisms of Zn2+ /zinc and its nanoparticles in alleviating HMs toxicity of plants will be the first step towards a wider incorporation of Zn2+ into agricultural practices.

Exploring the role of microbes for the management of persistent organic pollutants

Persistent organic pollutants (POPs) are chemicals which have been persisting in the environment for many years due to their longer half-lives. POPs have gained attention over the last few decades due to the unsustainable management of chemicals which led to their widespread and massive contamination of biota from different strata and environments. Due to the widespread distribution, bio-accumulation and toxic behavior, POPs have become a risk for organisms and environment. Therefore, a focus is required to eliminate these chemicals from the environment or transform into non-toxic forms. Among the available techniques for the removal of POPs, most of them are inefficient or incur high operational costs. As an alternative to this, microbial bioremediation of POPs such as pesticides, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, pharmaceuticals and personal care products is much more efficient and cost-effective. Additionally, bacteria play a vital role in the biotransformation and solubilization of POPs, which reduces their toxicity. This review specifies the Stockholm Convention that evaluates the risk profile for the management of existing as well as emerging POPs. The sources, types and persistence of POPs along with the comparison of conventional elimination and bioremediation methods of POPs are discussed comprehensively. This study demonstrates the existing bioremediation techniques of POPs and summaries the potential of microbes which serve as enhanced, cost-effective, and eco-friendly approach for POPs elimination.

Phytoremediation strategies for heavy metal-contaminated soil by selecting native plants near mining areas in Inner Mongolia

Phytoremediation technology, as an eco-friendly and cost-effective approach, is widely used to restore soil contaminated by heavy metal(loid)s. However, the adaptability and absorption capacity of plants to multiple elements are the crucial factors affecting the application of phytoremediation in mining areas. In this study, dominant native plant species and their paired soils were collected near a lead-zinc mine in Inner Mongolia, to assess the ecological risk of heavy metal(loid)s and phytoremediation potential. The results showed that Cd and As were the dominant soil pollutants, with levels of 90.91% and 100%, respectively, exceeding the risk intervention values for soil contamination of agricultural land. The rates of Pb, Cu, and Zn exceeding the risk screening values were 69.70%, 60.61%, and 96.97%, respectively. Extremely high ecological risk of heavy metal(loid)s was observed in this area. The ability of native plants accumulating heavy metals varied among species. The bioconcentration factor (BCF) varied from 0.14 to 2.59 for Cd, 0.02 to 0.45 for As, 0.06 to 0.76 for Pb, 0.05 to 2.69 for Cr, 0.15 to 1.00 for Cu, and 0.22 to 4.10 for Zn. Chinese Cinquefoil Herb (Potentilla chinensis Ser.) showed the potential to accumulate multiple toxic elements based on the biomass, shoot content, translocation factor (TF), BCF, and metal extraction rate (MER), while, other species showed the potential to accumulate single toxic element: goosefoot (Chenopodium album L.), Lespedeza daurica (Laxm.) Schindl. and peashrubs (Caragana korshinskii Kom.), Herba Artemisiae Scopariae (Artemisia capillaris Thunb.), alfalfa (Medicago sativa L.), and Moldavian Dragonhead (Dracocephalum moldavica L.) for Cd, As, Cr, Cu, and Zn, respectively. Furthermore, wild leek (Allium ramosum L.), cogongrass (Imperata cylindrica (L.) Beauv.), fringed sagebrush (Artemisia frigida Willd.), and field bindweed (Convolvulus arvensis L.) were selected for phytostabilization of specific elements, considering the heavy metal contents in the roots and low TF values. This study provides a reference for selecting appropriate species for the remediation of heavy metal-contaminated soils in certain mining areas.

Does phytoextraction with Sedum plumbizincicola increase cadmium leaching from polluted agricultural soil?

Sedum plumbizincicola is a cadmium (Cd) and zinc hyperaccumulator that can activate Cd by rhizosphere acidification. However, there is little understanding of the Cd leaching risk from polluted soil during phytoextraction process. Here, pot and column experiments were conducted to monitor soil Cd leaching characteristics under different rainfall simulation conditions during S. plumbizincicola phytoextraction. Soil Cd leaching increased significantly with increasing simulated rainfall intensity. Compared with normal rainfall (NR), weak rainfall (WR) resulted in a 34.3% decrease in Cd uptake by S. plumbizincicola and also led to a 68.7% decline in Cd leaching. In contrast, Cd leaching under heavy rainfall (HR) was 2.12 times that of NR in the presence of S. plumbizincicola. After two successive growing periods, phytoextraction resulted in a 53.5-66.4% decline in the amount of soil Cd leached compared with controls in which S. plumbizincicola was absent. Even compared with maize cropping as a control, S. plumbizincicola did not instigate a significant increase in Cd leaching. The contribution of Cd leaching loss to the decline in soil total Cd concentration was negligible after phytoextraction in the pot experiment. Overall, the results contribute to our understanding of soil Cd leaching risk by phytoextraction with S. plumbizincicola.

Investigating the pollution of irrigated plants (Rosmarinus officinalis) with polluted water in different growth stages using spectrometer and K-means method

Rosmarinus officinalis is a widely cultivated plant with various medicinal and culinary uses. However, irrigation with contaminated water can lead to the accumulation of heavy elements in the tissues of this plant. Therefore, the purpose of this study was to investigate the contamination of Rosmarinus officinalis with heavy elements during irrigation with polluted water (wastewater). To achieve this, 39 seedlings were uniformly planted in pots and irrigated with water contaminated with zinc, lead, nickel, and cadmium. The level of contamination in the plant was measured at three vegetative stages using target hazard quotient (THQ), hazard index (HI), and bioconcentration factor (BCF) indicators. In addition, a spectrometer in the range of 400-1030 nm was used to measure the amount of reflection of plants to electromagnetic waves. The K-means method was then applied to investigate the relationship between the morphological characteristics of the plants and heavy metal pollution. The results showed that the highest THQ values were observed in the third vegetative stage (THQPb = 113, THQNi = 0.08, THQZn = 0.25, THQCd = 0.1). Furthermore, the BCFCd and BCFPb indices indicated that the highest contamination levels occurred in the third vegetative stage. The regression analysis identified the spectral bands of 880, 580, 1030, 400, 760, 570, 650, 1050, 560, and 910 nm as the most important for identifying heavy element-contaminated plants. Finally, the K-means method showed high accuracy (R2 = 0.89) for identifying and classifying plant organs affected by pollution from healthy parts. It is worth noting that the investigation of the contamination of Rosmarinus officinalis with heavy elements using electromagnetic waves represents a novel contribution to the field, particularly given the importance of this plant in the pharmaceutical and food industries.

Valorised polypropylene waste based reversible sensor for copper ion detection in blood and water

Heavy metals and plastic pollutants are the two most disastrous challenges to the environment requiring immediate actions. In this work, a techno-commercially feasible approach to address both challenges is presented, where a waste polypropylene (PP) based reversible sensor is produced to selectively detect copper ions (Cu2+) in blood and water from different sources. The waste PP-based sensor was fabricated in the form of an emulsion-templated porous scaffold decorated with benzothiazolinium spiropyran (BTS), which produced a reddish colour upon exposure to Cu2+. The presence of Cu2+ was checked by naked eye, UV-Vis spectroscopy, and DC (Direct Current) probe station by measuring the current where the sensor's performance remained unaffected while analysing blood, water from different sources, and acidic or basic environment. The sensor exhibited 1.3 ppm as the limit of detection value in agreement with the WHO recommendations. The reversible nature of the sensor was determined by cyclic exposure of the sensor towards visible light turning it from coloured to colourless within 5 min and regenerated the sensor for the subsequent analysis. The reversibility of the sensor through exchange between Cu2+- Cu+ was confirmed by XPS analysis. A resettable and multi-readout INHIBIT logic gate was proposed for the sensor using Cu2+ and visible light as the inputs and colour change, reflectance band and current as the output. The cost-effective sensor enabled rapid detection of the presence of Cu2+ in both water and complex biological samples such as blood. While the approach developed in this study provides a unique opportunity to address the environmental burden of plastic waste management, it also allows for the possible valorization of plastics for use in enormous value-added applications.