Phytoremediation Of Heavy Metals Research Articles

Biotechnological approaches for enhancement of heavy metal phytoremediation capacity of plants.

Heavy metals are extremely hazardous for human health due to their toxic effects. They are non-biodegradable in nature, thus remain in the environment and enter and accumulate in the human body through biomagnification; hence, there is a serious need of their remediation. Phytoremediation has emerged as a green, sustainable, and effective solution for heavy metal removal and many plant species could be employed for this purpose. Plants are able to sequester substantial quantity of heavy metals, in some cases thousands of ppm, due to their robust physiology enabling high metal tolerance and anatomy supporting metal ion accumulation. Identification and modification of potential target genes involved in heavy metal accumulation have led to improved phytoremediation capacity of plants at the molecular level. The introduction of foreign genes through genetic engineering approaches has further enhanced phytoremediation capacity manifolds. This review gives an insight towards improving the phytoremediation efficiency through a better understanding of molecular mechanisms involved, expression of different proteins, genetic engineering approaches for transgenic production, and genetic modifications. It also comprehends novel omics tools such as genomics, metabolomics, proteomics, transcriptomics, and genome editing technologies for improvement of phytoremediation ability of plants.

Root-soil-microbiome interaction in the rhizosphere of Masson pine (Pinus massoniana) under different levels of heavy metal pollution

Heavy metal pollution of the soil affects the environment and human health. Masson pine is a good candidate for phytoremediation of heavy metal in mining areas. Microorganisms in the rhizosphere can help with the accumulation of heavy metal in host plants. However, studies on its rhizosphere bacterial communities under heavy metal pollution are still limited. Therefore, in this study, the chemical and bacterial characteristics of Masson pine rhizosphere under four different levels of heavy metal pollution were investigated using 16 S rRNA gene sequencing, soil chemistry and analysis of plant enzyme activities. The results showed that soil heavy metal content, plant oxidative stress and microbial diversity damage were lower the farther they were from the mine dump. The co-occurrence network relationship of slightly polluted soils (C1 and C2) was more complicated than that of highly polluted soils (C3 and C4). Relative abundance analysis indicated Sphingomonas and Pseudolabrys were more abundant in slightly polluted soils (C1 and C2), while Gaiella and Haliangium were more abundant in highly polluted soils (C3 and C4). LEfSe analysis indicated Burkholderiaceae, Xanthobacteraceae, Gemmatimonadaceae, Gaiellaceae were significantly enriched in C1 to C4 site, respectively. Mantel analysis showed that available cadmium (Cd) contents of soil was the most important factor influencing the bacterial community assembly. Correlation analysis showed that eight bacterial genus were significantly positively associated with soil available Cd content. To the best of our knowledge, this is the first study to investigate the rhizospheric bacterial community of Masson pine trees under different degrees of heavy metal contamination, which lays the foundation for beneficial bacteria-based phytoremediation using Masson pines in the future.

Harnessing plant-beneficial bacterial encapsulation: A sustainable strategy for facilitating cadmium bioaccumulation in Medicago sativa

Plant-beneficial bacteria (PBB) have emerged as a promising approach for assisting phytoremediation of heavy metal (HM)-contaminated soils. However, their colonization efficiency is often challenged by complex soil environments. In this study, we screened one rhizobacterium (Klebsiella variicola Y38) and one endophytic bacterium (Serratia surfactantfaciens Y15) isolated from HM-contaminated soils and plants for their high resistance to Cd and strong growth-promoting abilities. These strains were encapsulated individually or in combination with alginate and applied with Medicago sativa in Cd-contaminated soil pot experiments. The effectiveness of different bacterial formulations in promoting plant growth and enhancing Cd bioconcentration in M. sativa was evaluated. Results showed that PBB application enhanced plant growth and antioxidant capacity while reducing oxidative damage. Encapsulated formulations outperformed unencapsulated ones, with combined formulations yielding superior results to individual applications. Quantitative PCR indicated enhanced PBB colonization in Cd-contaminated soils with alginate encapsulation, potentially explaining the higher efficacy of alginate-encapsulated PBB. Additionally, the bacterial agents modified Cd speciation in soils, resulting in increased Cd bioaccumulation in M. sativa by 217–337 %. The alginate-encapsulated mixed bacterial agent demonstrated optimal effectiveness, increasing the Cd transfer coefficient by 3.2-fold. Structural equation modeling and correlation analysis elucidated that K. variicola Y38 promoted Cd bioaccumulation in M. sativa roots by reducing oxidative damage and enhancing root growth, while S. surfactantfaciens Y15 facilitated Cd translocation to shoots, promoting shoot growth. The combined application of these bacteria leveraged the benefits of both strains. These findings contribute to diversifying strategies for effectively and sustainably remediating Cd-contaminated soils, while laying a foundation for future investigations into bacteria-assisted phytoremediation.

Rapid assessment of heavy metal accumulation capability of Sedum alfredii using hyperspectral imaging and deep learning

Hyperaccumulators are the material basis and key to the phytoremediation of heavy metal contaminated soils. Conventional methods for screening hyperaccumulators are highly dependent on the time- and labor-consuming sampling and chemical analysis. In this study, a novel spectral approach assisted with multi-task deep learning was proposed to streamline accumulating ecotype screening, heavy metal stress discrimination, and heavy metals quantification in plants. The significant Cd/Zn co-hyperaccumulator Sedum alfredii and its non-accumulating ecotype were stressed by Cd, Zn, and Pb. Spectral images of leaves were rapidly acquired by hyperspectral imaging. The self-designed deep learning architecture was composed of a shallow network (ENet) for accumulating ecotype identification, and a multi-task network (HMNet) for heavy metal stress type and accumulation prediction simultaneously. To further assess the robustness of the networks, they were compared with conventional machine learning models (i.e., partial least squares (PLS) and support vector machine (SVM)) on a series of evaluation metrics of classification, multi-label classification, and regression. S. alfredii with heavy metals accumulation capability was identified by ENet with 100 % accuracy. HMNet reduced overfitting and outperformed machine learning models with the average exact match ratio (EMR) of heavy metal stress discrimination increased by 7.46 %, and residual prediction deviations (RPD) of heavy metal concentrations prediction increased by 53.59 %. The method succeeded in rapidly and accurately discriminating heavy metal stress with EMRs over 91 % and accuracies over 96 %, and in predicting heavy metals accumulation with an average RPD of 3.29 for Zn, 2.57 for Cd, and 2.53 for Pb, indicating the satisfactory practicability and potential for sensing heavy metals accumulation. This study provides a relatively novel spectral method to facilitate hyperaccumulator screening and heavy metals accumulation prediction in the phytoremediation process.

Potential of the plant growth-promoting rhizobacterium Rhodococcus qingshengii LMR356 in mitigating lead stress impact on Sulla spinosissima L.

Mining-related lead (Pb) pollution of the soil poses serious hazards to ecosystems and living organisms, including humans. Improved heavy metal phytoremediation efficacy, achieved by using phytostabilizing plants assisted by plant-growth-promoting (PGP) microorganisms, has been presented as an effective strategy for remediating polluted soils. The objective of this research was to examine the response and potential of the plant-growth-promoting bacterium LMR356, a Rhodococcus qingshengii strain isolated from an abandoned mining soil, under lead stress conditions. Compared to non-contaminated culture media, the presence of lead induced a significant decrease in auxin production (from 21.17 to 2.65 μg mL-1) and phosphate solubilization (from 33.60 to 8.22 mg L-1), whereas other PGP traits increased drastically, such as 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity (from 38.17 to 71.37 nmol mg-1 h-1 α-ketobutyrate), siderophore production (from 69 to 83%), exopolysaccharide production (from 1952.28 to 3637.72 mg mL-1), biofilm formation, and motility. We, therefore, investigated the behavior of Sulla spinosissima L. in the presence or absence of this strain under a variety of experimental conditions. Under hydroponic conditions, Sulla plants showed endurance to varying lead concentrations (500-1000 μM). Inoculation of plants with Rhodococcus qingshengii strain LMR356 enhanced plant tolerance, as demonstrated by the increase in plant biomass (ranging from 14.41 to 79.12%) compared to non-inoculated Pb-stressed and non-stressed control plants. Antioxidant enzyme activities (increasing by -42.71 to 126.8%) and chlorophyll (383.33%) and carotenoid (613.04%) content were also augmented. In addition to its impact on plant lead tolerance, strain LMR356 showed a growth-promoting effect on Sulla plants when cultivated in sterilized non-contaminated sand. Parameters such as plant biomass (16.57%), chlorophyll (24.14%), and carotenoid (30%) contents, as well as ascorbate peroxidase (APX), peroxidase (POD), and catalase (CAT) activities, were all elevated compared to non-inoculated plants. Furthermore, when the same plant species was cultivated in highly polluted soil, inoculation increased plant biomass and improved its physiological properties. These findings demonstrate that LMR356 is a phytobeneficial bacterial strain capable of enhancing Sulla growth under normal conditions and improving its heavy metal tolerance in multi-polluted soils. Thus, it can be considered a promising biofertilizer candidate for growing Sulla spinosissima L. or other selected plants intended for application in restoration and stabilization initiatives aimed at reviving and safeguarding environmentally compromised and polluted soils after mining activities.

Enhancing heavy metal phytoremediation in landfill soil by Chrysopogon zizanioides (L.) roberty through the application of bacterial-biochar pellets

This work investigated the performance of bacterial-biochar pellets (BBP) on promoting heavy metal phytoremediation by Chrysopogon zizanioides (L.) Roberty planted in landfill soil. Micrococcus sp. MU1, an indole-3-acetic acid (IAA)-producing bacterium, was incorporated into biochar pellets (MU1-BBP). MU1-BBP contained a high number of viable bacterial cells with 90 % viability after storage at 4°C for two months. In addition, it had a greater survival capability in heavy metals-contaminated landfill soil than MU1-free cells. The application of MU1-BBP significantly promoted the growth performance and chlorophyll synthesis of C. zizanioides planted in landfill soil. Cd, Cu, Pb and Zn were mostly retained in the roots relative to the shoots of C. zizanioides. The accumulation of Cd, Cu, Pb, and Zn in the roots of C. zizanioides were significantly boosted by MU1-BBP inoculation. Plants with MU1-BBP inoculation enhanced the accumulation coefficient (AC) of all four heavy metals. The values of AC values of Cd, Cu, and Zn in C. zizanioides with MU1-BBP inoculation were greater than 1.0. However, translocation factors of all four metals were low. The findings suggest C. zizanioides may be a good heavy metal phytostabilizer. The findings support the potential of bacterial-biochar pellets to enhance the efficiency of heavy metal phytostabilization of C. zizanioides in landfill sites.

Phytoextraction of Some Selected Heavy Metals in Contaminated Soil by Arabian Jasmine (Jasminum sambac)

Heavy metal contamination in soil is a significant environmental and health concern. This study investigates the potential of Arabian jasmine (Jasminum sambac) for phytoremediation of heavy metals in soil. The plants were grown in pots using soil samples collected from contaminated dumpsite soils of Dana Steel Limited in Katsina Metropolis; their ability to accumulate and remove heavy metals was assessed. An atomic absorption spectrophotometer (AAS) was used to measure the concentrations of metals in plants and soil. The statistical analysis of the data obtained was carried out using a t-test. The amounts of the metals under study in the polluted soil before planting were found to be higher than the values from the control soil: Cu (6.49±1.88 mg/kg), Ni (2.67±1.09 mg/kg), Cd (0.20±0.08 mg/kg), Pb (17.57±7.39 mg/kg), Zn (1.63±0.03 mg/kg), and Cr (8.01±2.68 mg/kg). The Bioaccumulation factor for Jasminum sambac was less than one (BAF<1) for all the studied heavy metals: Cu (0.10), Ni (0.32), Cd (0.87), Pb (0.30), Zn (0.02) and Cr (0.30), indicating a low bioaccumulation capacity. However, the transfer factor for Jasminum sambac was greater than 1 (TF>1) in Cu (3.35), Pb (3.00) and Cr (1.97), suggesting that the transfer rate of these heavy metals from soil into the plant's tissues was higher. These findings suggest that using this plant in phytoremediation can be a viable and sustainable approach to reducing heavy metals contamination in soil, thereby offering a potential solution to a significant environmental problem.

Microbial and Phytoremediation of Heavy Metals from Aquatic Ecosystem: An Initiative for Sustainable Environment

The amount of anthropogenic activity in the environment has significantly increased due to urbanization and industrialization. Toxic metals and other contaminants have become more concentrated as a result, appearing in wastewater released by many sectors. Aquatic animals suffer as a result of tainted wastewater entering water bodies. As a result, damage also occurs in the crops contaminating the agricultural ecology. Although several techniques have been used to detoxify contaminants in wastewater, the current situation necessitates environmentally acceptable and economically viable techniques for wastewater treatment. To fulfill this objective, this review is aimed at exploring the major sources of metals in wastewater. The traditional techniques for treating wastewater take a lot of time and are not environmentally or financially sustainable. Utilizing microorganisms, plants, and biomass leftovers to break down metal poisons is a proven biotechnology strategy that is environmentally friendly. Hence, the review highlights the drawbacks of conventional techniques with importance of bioremediation for sustainable ecosystem. Also, phytoremediation—the process of removing metals from the environment using plants is discussed as a successful strategy. Plants are thought to be the most effective option for wastewater remediation because they contain a variety of microorganisms and enzymes that aid in the detoxification of metals from wastewater. Overall, to gain a better understanding of environmentally friendly and sustainable ways, the buildup and detoxification of metals through the use of plants, microorganisms, and biomass residues in environmental remediation is highlighted.

Bioenergy crop rotation for phytoremediation of heavy metal contaminated soils at Mahd AD'Dahab mine, Kingdom of Saudi Arabia

Phytoremediation is a viable approach in order to mitigate toxic soil levels and, therefore, the associated impacts of HMs. This approach requires the assessment of contaminated sites and the selection of reportedly efficient phytoremediators, which might contribute to facilitating the practical implementation of phytoremediation in polluted soils. In a twelve-month microcosm experiment, Indian mustard (Brassica juncea) and rapeseed (Brassica napus) plants were planted over the winter season. Subsequently, maize (Zea maize) was planted after the harvest of these plants. Oil crop rotation systems might promote tested HM removal (Cu, Cd, Fe, Ni, Mn, Zn, and Pb) from the Mahd AD'Dahab mine-contaminated soil and provide higher biomass than single crops. The results indicated that both the rapeseed maize and Indian mustard maize rotation showed the highest phytoextraction efficiency compared to a single crop. The extraction of Zn, Pb, Ni, Mn, Fe, Cu, and Cd are 18, 27, 29, 24, 23, 24, and 28%, respectively, for Indian mustard-maize rotation, although 17, 27, 31, 24, 21, 23, and 26% respectively for rapeseed-maize rotation. The short rotation strategy could be helpful in landscaped and controlled access to the polluted sites. The utilization of short-rotation phytoremediation has the potential to emerge as a financially viable approach for the management of polluted areas. This method involves enhancing biomass yield through the implementation of phytomanagement techniques such as fertilization, irrigation, and coppicing, thereby capitalizing on the benefits associated with both biomass production and landscape management.

Effect of aluminosilicates on the release and form transformation of semi-volatile heavy metals during the combustion of hyperaccumulator plants

With the development of phytoremediation of heavy metals contaminated soils, the harmless disposal of hyperaccumulator plants has been imminent. In this study, the effects of typical aluminosilicates on the heavy metal migration during the combustion of ryegrass were compared. The addition of kaolin, montmorillonite, and γ-Al2O3 were all effective in solidifying Pb and Zn. As the combustion temperature increased, the toxicity of remaining Pb and Zn decreased. Compared to montmorillonite, kaolin was more effective in capturing Pb and Zn at 600–825 °C, and the remaining Pb and Zn were mainly in acid-soluble form. The large amount of alkali/alkaline earth metals will react with the Si/Al components to form various potassium feldspars and calcium silicates, thus inhibiting the solidification of heavy/alkali metals. However, the Si in montmorillonite was more effective in converting Pb and Zn into residual form than kaolin when faced with the competition solidification of alkali/alkaline earth metals, at which time the percentage of Pb and Zn in the residual form increased from 13.27% and 6.00% to 39.21% and 9.84%, respectively. This work provided a research perspective based on the solidification of heavy metals by Si component, which enables a more comprehensive analysis of the differences in heavy metals solidification by Si/Al-based minerals.

Responses of soil and rhizosphere microbial communities to Cd-hyperaccumulating willows and Cd contamination

BackgroundThe pollution of soil by heavy metals, particularly Cd, is constitutes a critical international environmental concern. Willow species are renowned for their efficacy in the phytoremediation of heavy metals owing to their high Cd absorption rate and rapid growth. However, the mechanisms underlying microbial regulation for high- and low-accumulating willow species remain poorly understood. Therefore, we investigated the responses of soil and rhizosphere microbial communities to high- and low-Cd-accumulating willows and Cd contamination. We analyzed soil properties were analyzed in bulk soil (SM) and rhizosphere soil (RM) planted with high-accumulating (H) and low-accumulating (L) willow species.ResultsRhizosphere soil for different willow species had more NH4+ than that of bulk soil, and RM-H soil had more than RM-L had. The available phosphorus content was greater in hyper-accumulated species than it was in lower-accumulated species, especially in RM-H. Genome sequencing of bacterial and fungal communities showed that RM-L exhibited the highest bacterial diversity, whereas RM-H displayed the greatest richness than the other groups. SM-L exhibited the highest diversity and richness of fungal communities. Ralstonia emerged as the predominant bacterium in RM-H, whereas Basidiomycota and Cercozoa were the most enriched fungi in SM-H. Annotation of the N and C metabolism pathways revealed differential patterns: expression levels of NRT2, NarB, nirA, nirD, nrfA, and nosZ were highest in RM-H, demonstrating the effects of NO3-and N on the high accumulation of Cd in RM-H. The annotated genes associated with C metabolism indicated a preference for the tricarboxylic pathway in RM-H, whereas the hydroxypropionate-hydroxybutyrate cycle was implicated in C sequestration in SM-L.ConclusionsThese contribute to elucidation of the mechanism underlying high Cd accumulation in willows, particularly in respect of the roles of microbes and N and C utilization. This will provide valuable insights for repairing polluted soil using N and employing organic acids to improve heavy metal remediation efficiency.

Pistia Stratiotes based heavy metals phytoremediation of a Himalayan river impacted by hydroelectric plant in an Indo Burma hotspot region

ABSTRACT Present study attempts to study the impact of Serlui-B hydroelectric dam on water quality (‘water-energy nexus’) of a Himalayan river and to devise possible phytotechnology for heavy metals remediation. Physico-chemical characteristics of water were analyzed using ‘American Public Health Association (APHA)’ methods while Atomic Absorption Spectrophotometer (AAS) was used for estimation of heavy metals. To this end, concentrations of Fe and Ni were recorded above permissible limit which can impose public health risks. Therefore, phytoremediation experiments were performed by using Pistia stratiotes L. (water lettuce) and effects of Fe and Ni concentrations (1.0, 2.0, and 5.0 mg/L) on photosynthetic pigments were observed. Phytoremediation investigations using 24 aquaria (of 40.5 L) revealed that P. stratiotes was an effective hyperaccumulator of Fe and Ni with maximum removal efficiency of 96.2% and 92%, respectively. In relation to bioaccumulation indices, the bioconcentration factor (BCF) values decreased with increase in Fe and Ni concentrations, whereas the translocation factor (TF) was noted higher at low concentrations and vice versa. Furthermore, the total chlorophyll content and carotenoid levels in P. stratiotes demonstrated negative significant correlation with the rise in Fe/Ni concentrations that may be considered as an adaptive biochemical strategy to mitigate metals induced oxidative stress. The present study can further be extrapolated to field phytoremediation for ameliorating both physico-chemical and metallic contaminants. Last, the role of microbial biodiversity associated with P. stratiotes should be elucidated in future to help achieve SDG 6 and environmental sustainability.

Heavy Metal Phytoremediation by Crop Species at Hebbal Industrial Area, Mysuru, India

Heavy metals are frequently added to the soil in the area of study as a result of industrialization. Removing this heavy metal from the soil is a difficult procedure, and phytoremediation is an essential and effective method for remediation. Heavy metals present in the study area include Fe, Cu, Cd, Pb, and Zn. Two plants namely Brassica juncea L. and Rapanus sativus L. were successfully grown on the polluted areas soil samples for phytoremediation. Brassica juncea L remediates the heavy metals Cu, Zn, Pb, and Cd, while Rapanus sativus L remediates Cd, Cu, Pb, and Fe. These two plants can uptake metal from roots to shoots, which means metal concentration is transferred from roots to shoots of the plant, indirectly decreasing concentration in the soil. Brassica juncea L was remediated for heavy metals Cd, Cu, Pb, and Zn at a rate of 25.47%, 38.74%, 31.60%, and 26.75%, respectively. The remediation percentages for Rapanus sativus L of Cd, Cu, Pb, and Fe were 21.01%, 37.08%, 23.77%, and 47.19%, respectively. Brassica juncea L remediate in the order of Cu>Pb>Zn>Cd, and Rapanus sativus L Fe>Cu>Pb>Cd were in decreasing order. Shoots of Brassica juncea L had a higher bioconcentration than the roots of Rapanus sativus L, which clearly explains the metal uptake capacity of the plant. This paper investigated the uptake of heavy metals from roots to shoots, as well as their bioconcentration.

Enhancing the phytoextraction efficiency of heavy metals in acidic and alkaline soils by Sedum alfredii Hance: A study on the synergistic effect of plant growth regulator and plant growth-promoting bacteria

Plant growth regulators (PGR) and plant growth-promoting bacteria (PGPB) have the potential in phytoremediation of heavy metals (HMs) contaminated soils. However, their sole application may not yield the optimal results, thus necessitating the combined application. The present study aimed to enhance the phytoremediation efficiency of Sedum alfredii Hance (S. alfredii) in acidic and alkaline soils through the combination of PGR (Brassinolide, BR) and PGPB (Pseudomonas fluorescens, P. fluorescens). The combination of BR and P. fluorescens (BRB treatment) effectively increased the removal efficiency of S. alfredii for Cd, Pb, and Zn by 355.2 and 155.3 %, 470.1 and 128.9 %, and 408.4 and 209.6 %, in acidic and alkaline soils, respectively. Moreover, BRB treatment led to a substantial increase in photosynthetic pigments contents and antioxidant enzymes activities, resulting in a remarkable increase in biomass (86.71 and 47.22 %) and dry mass (101.49 and 42.29 %) of plants grown in acidic and alkaline soils, respectively. Similarly, BRB treatment significantly elevated the Cd (109.4 and 71.36 %), Pb (174.9 and 48.03 %), and Zn levels (142.8 and 104.3 %) in S. alfredii shoots, along with cumulative accumulation of Cd (122.7 and 79.47 %), Pb (183.8 and 60.49 %), and Zn (150.7 and 117.9 %), respectively. In addition, the BRB treatment lowered the soil pH and DTPA-HMs contents, while augmenting soil enzymatic activities, thereby contributing soil microecology and facilitating the HMs absorption and translocation by S. alfredii to over-ground tissues. Furthermore, the evaluation of microbial community structure in phyllosphere and rhizosphere after remediation revealed the shift in microbial abundance. The combined treatment altered the principal effects on S. alfredii HMs accumulation from bacterial diversity to the soil HMs availability. In summary, our findings demonstrated that synergistic application of BR and P. fluorescens represents a viable approach to strengthen the phytoextraction efficacy of S. alfredii in varying soils.

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.

Screening of plant growth promoting and heavy metal tolerance of rhizospheric microorganisms in the mangrove ecosystem

Mangroves create a unique ecological niche with varied environmental conditions and diverse microbial communities, including nitrogen fixers and phosphate solubilizers, which have immense potential as plant growth promoting bacteria (PGPB) including heavy metal tolerance. To address this, the current study was undertaken to screen for the presence of lead and cadmium tolerant microorganisms from the mangrove rhizosphere in Sagar Vihar, Vashi and to evaluate their plant growth promoting (PGP) potential. Isolates were characterized and screened for various PGP properties. Four of the 17 isolates obtained showed the most promising PGP traits, with one isolate exhibiting the maximum PGP traits. Additionally, phyto-remediation of heavy metal by mangrove root or pneumatophores evaluated using Energy Dispersive X-ray Analysis (EDAX) showed absence of metal. The biocompatibility study of these isolates revealed that all lead tolerant isolates were compatible with each other. Through this investigation, we propose to use a consortia based on these microbes as a biofertilizer for the eco-restoration of mangrove forests.

Migration Behaviour of the Combined Pollutants of Cadmium and 2,2′,4,4′,5,5′-Hexabrominated Diphenyl Ether (BDE-153) in Amaranthus mangostanus L. and Their Toxicity to A. mangostanus

The effects of different concentrations of cadmium and 2,2′,4,4′,5,5′-hexabrominated diphenyl ether (BDE-153) on the growth and related physiological and biochemical indexes of Amaranthus mangostanus L. (amaranth) were studied. The results showed that the presence of BDE-153 promoted the absorption of Cd by the amaranth and inhibited the migration of Cd from the roots to the shoots. At the same time, 0.1 mg/L of Cd had a synergistic effect on the migration of BDE-153, but 5 mg/L Cd inhibited the accumulation of BDE-153 in the aboveground part of the amaranth. In addition, the kinetics of the uptake of pollutants by the amaranth showed that both Cd and BDE-153 could be transported by amaranth, but Cd and BDE-153 were mainly enriched in the roots, and the presence of Cd may cause a lag in the uptake of BDE-153 in the shoots. Compared with the control group, the biomass of the amaranth affected by BDE-153 and a high concentration of Cd (5 mg/L) decreased by 30.2–49.5%, the chlorophyll content decreased by 43.0–60.3%, the Evans blue increased, and the MDA content was higher. The activities of superoxide dismutase (SOD) and catalase (CAT) also decreased with an increase in the BDE-153 concentration. This indicates that the interaction between BDE-153 and a high concentration of Cd (5 mg/L) is more toxic to amaranth than single Cd pollution. This paper provides the necessary data support for phytoremediation of heavy metal and organic compound pollution.

Synergistic application of Pseudomonas strains and compost mitigates lead (Pb) stress in sunflower (Helianthus annuus L.) via improved nutrient uptake, antioxidant defense and physiology

Lead (Pb) is one of the most dreadful non-essential elements whose toxicity has been well reported worldwide due to its interference with the major plant functions and its overall yield. Bioremediation techniques comprising the application of beneficial microorganisms have gained attention in recent times owing to their ecofriendly nature. Addition of organic matter to soil has been reported to stimulate microbial activities. Compost application improves soil structure and binds toxic contaminants due to its larger surface area and presence of functional groups. Furthermore, it stimulates soil microbial activities by acting as C-source. So, in current study, we investigated the individual and synergistic potential of two lead (Pb)-tolerant Pseudomonas strains alongwith compost (1% w/w) in sustaining sunflower growth under Pb contaminated soil conditions. Lead chloride (PbCl2) salt was used for raising desired Pb concentration (500 mg kg−1). Results revealed that Pb stress drastically affected all the measured attributes of sunflower plant, however joint application of rhizobacteria and compost counteracted these adverse effects. Among them, co-application of str-1 and compost proved to be significantly better than str-2, as its inoculation significantly improved shoot and root lengths (64 and 76%), leaf area and leaves plant−1 (95 and 166%), 100-achene weight (200%), no. of flowers plant−1 (138%), chl ‘a’, ‘b’ and carotenoid (86, 159 and 33%) contents in sunflower as compared to control treatments. Furthermore, inoculation of Pseudomonas fluorescens along with compost increased the NPK in achene (139, 200 and 165%), flavonoid and phenolic contents (258 and 185%) along with transpiration and photosynthetic rates (54 and 72%) in leaves as compared to control treatment under Pb contamination. In addition, Pb entry to roots, shoots and achene were significantly suppressed under by 87, 90 and 91% respectively due to integrated application of compost and str-1 as evident by maximum Pb-immobilization efficiency (97%) obtained in this treatment. Similarly, bioconcentration factors for roots, shoots and achene were found to be 0.58, 0.18 and 0.0055 with associated translocation factor (0.30), which also revealed phytostabilization of Pb under combined application of PGPR and compost. Since, phytoremediation of heavy metals under current scenario of increasing global population is inevitable, results of the current study concluded that tolerant PGPR species along with organic amendments such as compost can inhibit Pb uptake by sunflower and confer Pb tolerance via improved nutrient uptake, physiology, antioxidative defense and gas exchange.

Bio-organic fertilizer facilitated phytoremediation of heavy metal(loid)s-contaminated saline soil by mediating the plant-soil-rhizomicrobiota interactions

Bio-organic fertilizer (BOF) was effective to promote the phytoremediation efficiency of heavy metal(loid)s-contaminated saline soil (HCSS) by improving rhizosphere soil properties, especially microbiome. However, there existed unclear impacts of BOF on plant metabolome and plant-driven manipulation on rhizosphere soil microbiota in HCSS, which were pivotal contributors to stress defense of plants trapped in adverse conditions. Here, a pot experiment was conducted to explore the mechanisms of BOF in improving alfalfa (Medicago sativa)-performing phytoremediation of HCSS. BOF application significantly increased the biomass (150.87–401.58 %) to support the augments of accumulation regarding heavy metal(loid)s (87.50 %–410.54 %) and salts (38.27 %–271.04 %) in alfalfa. BOF promoted nutrients and aggregates stability but declined pH of rhizosphere soil, accompanied by the boosts of rhizomicrobiota including increased activity, reshaped community structure, enriched plant growth promoting rhizobacteria (Blastococcus, Modestobacter, Actinophytocola, Bacillus, and Streptomyces), strengthened mycorrhizal symbiosis (Leohumicola, Funneliformis, and unclassified_f_Ceratobasidiaceae), optimized co-occurrence networks, and beneficial shift of keystones. The conjoint analysis of plant metabolome and physiological indices confirmed that BOF reprogrammed the metabolic processes (synthesis, catabolism, and long-distance transport of amino acid, lipid, carbohydrate, phytohormone, stress-resistant secondary metabolites, etc) and physiological functions (energy supply, photosynthesis, plant immunity, nutrients assimilation, etc) that are associated intimately. The consortium of root metabolome, soil metabolome, and soil microbiome revealed that BOF facilitated the exudation of metabolites correlated with rhizomicrobiota (structure, biomarker, and keystone) and rhizosphere oxidative status, e.g., fatty acyls, phenols, coumarins, phenylpropanoids, highlighting the plant-driven regulation on rhizosphere soil microbes and environment. By compiling various results and omics data, it was concluded that BOF favored the adaptation and phytoremediation efficiency of alfalfa by mediating the plant-soil-rhizomicrobiota interactions. The results would deepen understanding of the mechanisms by which BOF improved phytoremediation of HCSS, and provide theoretical guidance to soil amelioration and BOF application.

Phytorehzial Technique for Phytoremediation of Heavy Metals Using Ornamentals Plants

Plants and human health are both negatively impacted by the soil's heavy metal toxicity. By using excess amounts of fertilizers, sewage sludge, and pesticides, smelting, burning coal, and other methods, they are introduced into the soil. Among different heavy metals copper and arsenic are very important but their higher concentrations cause several morphological and biochemical in plants. They become part of the food chain when fruits and vegetables are grown in contaminated soil and can cause serious health issues to consumers. On the other hand, ornamental plants are used for aesthetic beautification and could be explored for the phytoremediation of soil heavy metals. A recent study was conducted to observe the phytoremediation potential of Gladiolus (Gladiolus grandifloras) and chrysanthemum against different levels of copper (80 and100µg/kg of soil) and arsenic (80 and 100 µg/kg) in the soil under completely randomized design. Data of accumulated quantity of heavy metals were noted after the flowering stage of both plants by dividing into four parts including roots, stem, leaves, and flowers. Both Gladiolus and chrysanthemum accumulated significant amounts of Cu and As in roots, stem, leaves, and flower. Gladiolus and chrysanthemum accumulated 367, 456, 796 and 1278ppm Co and 356, 571, 832 and 1478ppm As respectively. Chrysanthemums took up significant amounts of Cu in the stem and easily translocated from stem flowers. The translocation ability of chrysanthemum was higher for both metals compared to Gladiolus. The data were analyzed by mini tab statistics 8.1.