Toxic Metals Research Articles

A Brief Meta-analysis and Health Risk Assessment of Lead and Cadmium in Meat, Liver, and Kidney of Livestock in Iran

Background: Red meat from livestock is an excellent source of high-quality protein, vitamins, and minerals Objective: This meta-analysis aimed to investigate the levels of two of the most toxic heavy metals; lead (Pb) and cadmium (Cd) in meat and edible offal (liver and kidney) of livestock (sheep, buffalo, and cow) in Iran with assessing their health risk of developing cancer. Methods: A systematic search was conducted covering ISI Web of Science, PubMed, and Google Scholar. Finally, data from 4 articles including 624 samples were analysed. Results: Pooled results show that the mean concentrations of Pb and Cd were 0.18 mg/kg and 0.13 mg/kg respectively which were both higher than their eligible maximum limits by FAO/WHO. The Estimated Daily Intake (EDI) of Pb and Cd in meat, liver, and kidney for adults and children was lower than the Total Daily Intake (TDI) limits. The consumers' non-carcinogenic risk (THQ) for meat consumption was generally safe in terms of Cd and Pb in all cities except for Pb in Hamadan which was greater than one (unsafe) for both adults and children. Carcinogenic Risk (CR) for meat consumption was generally safe or within the acceptable range in terms of Cd and Pb in all cities except for Pb in Hamadan which had a Pb-CR greater than safe/permissible level for children. Conclusion: It can be concluded that the dangerous levels of CR and THQ of meat in terms of Pb in Hamadan warrant concern and further study.

Study on the new slow-release carbon source biochemistry and its improvement of SRB on the acid mine drainage treatment

The content of sulfate and heavy metals in acidic mine drainage (AMD) exceeds the standard severely, and the acidity is extremely high, causing serious harm to the environment. SRB can efficiently remove sulfates through its own metabolism. The treatment of AMD by SRB faces problems such as carbon source scarcity and heavy metal ion toxicity to SRB. In this study, corn cob and polycaprolactone were embedded to prepare a novel slow-release carbon source (PSCL), which simultaneously achieves carbon source supply and metal ion removal. Through adsorption isotherms, kinetics, thermodynamics studies, and various characterization analyses, it is known that PSCL removes Cu2+ and Zn2+ through ion exchange, physical and chemical adsorption, electrostatic attraction, and surface complexation. PSCL carbon release experiments and characterization results confirm that its surface carbon distribution is dense, the molecular weight of DOM in the leachate is small, the degree of humification is low, and it has a porous structure, making it a good carbon release material and biological attachment. The experimental results of PSCL enhanced SRB treatment of AMD showed that the removal rates of SO42−, Cu2+ and Zn2+ could be increased to 97.48%, 98.11% and 90.42%, respectively, with a effluent pH of 7.05, effectively improving the water quality of AMD. This study provides new materials and methods to address the limitations of SRB in treating actual AMD.

Potencial bioindicador de mudas de Cedrela fissilis em áreas contaminadas por cobre

ABSTRACT Soil contamination with toxic metals brings along severe environmental issues. Among these metals, copper (Cu) is harmful to plant development when it reaches high contamination levels in the soil. Thus, identifying species capable of resisting this contamination type helps these sites’ revegetation and decontamination processes. Therefore, the present study aimed to investigate the tolerance of Cedrela fissilis plants to excess Cu through morphophysiological and biochemical variables. C. fissilis seedlings were subjected to five concentrations of Cu (0, 2, 4, 6, and 8 mg L-1). The experimental design was completely randomized, with five treatments and four repetitions. Morphophysiological (number of leaves, shoot height, root length, dry weight, morphological variables of the root system, and leaf area) and biochemical (antioxidant enzymes, lipid peroxidation, hydrogen peroxide concentration, and photosynthetic pigments) traits and Cu accumulated in roots and shoot were evaluated. High concentrations of Cu had a negative effect on the shoot and root dry weight, photosynthetic rate, stomatal conductance, and transpiration rate. Overall, Cu increased the activity of the antioxidant enzymes and lipid peroxidation. Therefore, Cu incidence in the nutrient solution has negatively influenced the biochemical and physiological traits of C. fissilis seedlings to the detriment of their growth. Thus, it was possible to identify sensitive behavior by the investigated species. Because of these features, C. fissilis seedlings can be used as markers for copper-contaminated areas.

Formation mechanism of Fe oxyhydroxides and behavior of metals during the oxidation of submarine sulfides at the Wocan-1 hydrothermal field, Carlsberg Ridge

Hydrothermal sulfides undergo complex oxidation process under seawater conditions, which has the potential to impact resource values and marine environments. However, the oxidation process is not fully explored, particularly regarding the transformation of minerals and the behavior of metals. In this paper, we conducted detailed mineralogical and geochemical analyses on a series of samples with varying degrees of oxidation, collected from the Wocan-1 hydrothermal field, Carlsberg Ridge, Northwest Indian Ocean. The principal purpose is to illuminate the formation and transformation of Fe (oxyhydr)oxides, and further to reveal the migration and redistribution of key metals throughout the oxidation process. We identified four types of Fe(−Si) (oxyhydr)oxides with two distinct formation mechanisms. Three Fe (oxyhydr)oxides are the direct oxidation products of pyrite and marcasite, while Fe-Si (oxyhydr)oxide precipitates from low-temperature hydrothermal fluids. Thin Fe (oxyhydr)oxide forms as the secondary product of euhedral pyrite at the early stage of oxidation. Pseudomorphic Fe (oxyhydr)oxide with low Fe contents, occurs as the replacement of euhedral marcasite. Filamentous Fe (oxyhydr)oxide, enriched in trace metals, is attributed to the uniform oxidation of subhedral pyrite-marcasite intergrowth. Moreover, major and trace elements occur multiple migrations and redistributions among primary sulfides, secondary products, and seawater. Notably, Fe (oxyhydr)oxides, through the sequestration mechanism, not only retain Cu and Zn released by the oxidation of primary sulfide minerals, but also scavenge Cu from seawater. However, the dissolution of Pb, As, Mo, and Co exceeds the amount retained during the oxidation, indicating that the potential release of toxic metals into the environment could pose a threat to the local ecosystem. These new insights can provide an initial foundation for the effect of submarine oxidation on economic values of sulfides and ecological environments of deep sea.

Comparative Study of Biosorption and Traditional Methods for Heavy Metal Removal from Industrial Wastewater in Panipat

In this research paper, I have thoroughy described about the topic Comparative Study of Biosorption and Traditional Methods for Heavy Metal Removal from Industrial Wastewater in Panipat.” Industrial wastewater contamination by toxic heavy metals poses a significant environmental threat globally, especially in rapidly industrializing regions like Panipat District in Haryana, India. Panipat, renowned for its extensive textile and chemical industries, generates substantial volumes of wastewater laden with heavy metals such as lead (Pb), cadmium (Cd), and mercury (Hg). Recent studies have revealed that the concentrations of these metals in Panipat's industrial effluents frequently surpass the permissible limits set by environmental regulations. Traditional methods for heavy metal removal, including chemical precipitation and ion exchange, are widely utilized but often entail high operational costs and the generation of secondary pollutants like sludge. Biosorption, an emerging and sustainable technology, offers a promising alternative by utilizing biological materials such as algae, bacteria, and agricultural waste to adsorb heavy metals from wastewater. This study aims to investigate the effectiveness, cost-effectiveness, and environmental impact of biosorption compared to traditional methods in Panipat District. By examining heavy metal removal efficiencies, conducting cost analysis, and assessing environmental implications, this research seeks to provide valuable insights into sustainable wastewater treatment practices.

Visible Light-Driven Metal- and Photocatalyst-Free Synthesis of β-Trifluoromethylated Enamines via Trifluoromethyl Thianthrenium Salts.

A novel protocol for the visible-light-driven synthesis of β-trifluoromethylated enamines has been developed, which operates without the use of transition metals or any photocatalysts, utilizing trifluoromethylthiosulfonium salts as the source of trifluoromethyl groups under mild conditions. According to this new protocol, more than 40 products have been prepared in moderate to good yields. In addition to eliminating the need for expensive or toxic transition metals and photocatalysts, this new methodology proves its potential scalability through air-stability, the use of safe and readily available reagents, a two-step one-pot procedure, and effective gram-scale reactions. This innovative approach not only demonstrates promise for green chemical synthesis but also offers a new pathway for the advancement of fluorine chemistry in sustainable organic synthesis.

Nymphaea lotus Distribution in Oguta Lake: Implications for Heavy Metal Pollution in Surface Water and Sediments

Water quality is increasingly deteriorating and has affected lakes, which are important sources of freshwater. Heavy metals are of great concern because they are mostly toxic and resistant to decomposition. Aquatic macrophytes serve as stable biological filters that purify water bodies by accumulating dissolved metals and toxins in their tissues. Given their ability to trap various toxic heavy metals, the macrophyte Nymphaea lotus, which is observed on the surface waters of Oguta Lake, was studied to estimate the concentrations of six heavy metals in the water, sediment, and macrophytes. This was achieved by studying the spatial and temporal distribution of Nymphaea lotus in the lake and analysing the concentrations of heavy metals in the surface water, macrophytes, and sediment samples. Descriptive statistics, exploratory data analysis, and correlation analysis were used to analyse data obtained. Results revealed that the population of Nymphaea lotus declines over time from June to November in all regions. Upstream had the highest concentration of macrophytes (64%), while the downstream area has the lowest (2%). The heavy metal concentrations in the three samples ranges from 0.16 mg/kg to 2.96 mg/kg in sediments and Nymphaea lotus, and from 0.16 mg/L to 2.16 mg/L in water, with lead showing the highest concentration across all sample type. This highlights heavy metal contamination in the lake. The sparsely populated Nymphaea lotus exhibits selective bioaccumulation of lead, mercury, and zinc, while it seems to exclude or inefficiently absorb arsenic and chromium. Correlation analysis suggests a close interdependence between the concentrations of metals in sediments, water, and macrophytes, with sediments playing a key role in both water contamination and macrophyte metal absorption. Corrective and preventive measures should be taken to restore the lake.

Capacity of an aquatic macrophyte, Pistia stratiotes L., for removing heavy metals from water in the Oued Fez River and their accumulation in its tissues.

Water resources, particularly rivers, are increasingly exposed to pollutants, especially heavy metals of chemical origin, which are difficult to monitor and can pose risks to both ecosystems and human health. This study assesses heavy metal contamination in the Oued Fez River, focusing on the bioaccumulation by the invasive plant Pistia stratiotes. The methodology involves measuring and comparing metal concentrations in water and plant tissues. Results revealed that while aluminium (Al) slightly exceeded recommended levels at 0.2978 mg L-1, other metals like zinc (Zn), iron (Fe), copper (Cu), lead (Pb) and cadmium (Cd) remained within acceptable limits. The study demonstrates P. stratiotes' effectiveness in heavy metal phytoremediation, with its roots showing high bioaccumulation up to 19,726 mg kg-1 for Fe and 15,128 mg kg-1 for Al, indicating its potential for water decontamination. Eco-toxicological assessments, including bioconcentration and translocation factors, confirm the plant's capacity to mobilize toxic metals. Statistical analysis also points to possible industrial, urban, or agricultural contamination sources based on correlations between Al, Fe and Zn. The study underscores P. stratiotes' role in phytoremediation while emphasizing the need for monitoring and controlling contamination sources and managing the spread of this invasive species to ensure sustainable water resources.

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

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

EDTA-treated fibrillated cellulose bio-adsorbents from okra plant biomass and their performance on toxic divalent metal ions attenuation from aqueous solution

EDTA-treated fibrillated cellulose bio-adsorbents from okra plant biomass and their performance on toxic divalent metal ions attenuation from aqueous solution

8-Anilino-1-naphthalenesulfonate-Conjugated Carbon-Coated Ferrite Nanodots for Fluoromagnetic Imaging, Smart Drug Delivery, and Biomolecular Sensing

Background: Superparamagnetic properties and excitation independence have been incorporated into carbon-decorated manganese ferrite nanodots (MnFe@C) to introduce an economical and safer multimodal agent for use in both T1-T2 MRI and fluorescence-based imaging to replace the conventional highly toxic heavy metal contrast agents. Methods: The surface conjugation of 8-anilino-1-naphthalenesulfonate (ANS) to MnFe@C nanodots (ANS-MnFe@C) enhances both longitudinal and transverse MRI relaxation, improves fluorescence for optical imaging, and increases protein detection sensitivity, showing higher multimodal efficacy in terms of molar relaxivity, radiant efficiencies, and fluorescence sensitivity compared to MnFe@C. Results: The band gap energy was determined using Tauc’s equation to be 3.32 eV, while a 72% quantum yield demonstrated that ANS-MnFe@C was highly fluorescent, with the linear range and association constant calculated using the Stern–Volmer relation. The synthesized ANS-MnFe@C demonstrated excellent selectivity and sensitivity for bovine serum albumin (BSA), with a nanomolar detection limit of 367.09 nM and a broad linear range from 0.015 to 0.225 mM. Conclusions: In conclusion, ANS-MnFe@C holds ease of fabrication, good biocompatibility, as assessed in A375 cells, and an effective pH-sensitive doxorubicin release profile to establish anticancer activity in lung cancer cell line (A549), highlighting its potential as an affordable therapeutic agent for multimodal imaging, drug delivery, and protein sensing.

Monitoring of urinary nickel and chromium in metal industries workers in Alborz, Iran

Heavy metal contamination from occupational sources is a cause for concern due to its potential accumulation in the environment and the body of living organisms, which leads to long-term toxic effects. There is limited evidence on the concentration of heavy metals in the body fluids of welding workers. This study aimed to measure the concentration of nickel (Ni) and chromium (Cr) as two main toxic heavy metals in the urine samples of welders and determine the potential relationship of various environmental factors on their concentration levels. This study was conducted in Iran in 2022–2023. Eighty-five urine samples were collected from the studied welding workers. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to measure the concentration of Ni and Cr. Data related to socio-demographic characteristics (education level, income, work experience, age, and body mass index (BMI)), lifestyle profile (consumption of seafood and canned food, smoking, physical activity), type of ventilation and preventive devices at work, and suffering from underlying diseases (cardiovascular and high blood pressure) were collected using valid questionnaires. Ni and Cr were present in 100% of urine samples with mean concentrations of (1.09 ± 0.294) and (11.45 ± 16.751) µg/g creatinine, respectively. A significant correlation was observed between the mean concentration of Ni and Cr with the level of education, income, work experience, age, consumption of seafood and canned food, smoking, type of ventilation and preventive devices, and underlying diseases (p-value < 0.05). Also, there was no significant difference between Ni concentration and physical activity and Cr concentration with BMI. Lifestyle determinants and not using preventive devices are important predictors of urinary heavy metals in welding workers. Therefore, more research is required to determine the adverse effects of long-term exposure to these heavy metals.

Simple solution and paper-based fluorescent aptasensors for toxic metal ions, thallium(l) and lead(ll).

Heavy metal ions, such as thallium(I) and lead(II) are environmental toxicants known to cause a severe threat to human and ecosystem health. This work investigates aptamers and intercalating chromophore-based complexes for the detection of these toxic species. In one method, a selective label-free "turn-on" biosensor was developed using a G-quadruplex-intercalating agent, berberine. Fluorescence, melting temperature (Tm), and circular dichroism analysis confirmed the affinity and selectivity results, illustrating the potential of these aptasensor methods for improving detection limits. These fluorescence assays were found to perform with a detection limit of 3.4 μM for Tl(I) and 0.84 nM for Pb(II). Furthermore, the assays were challenged successfully with Tl(I) and Pb(II) spiked into river water samples. We next developed paper-based fluorescent assays for Tl(I) and Pb(II), where the aptamer/berberine complex was spotted onto the paper test zone. When Tl(I) or Pb(II) ions solutions were spotted onto the top of the test zone and the spot was illuminated with a portable UV light (365 nm), a strong green fluorescence could be easily visualized with the naked eye. The lowest detection limits achieved with these fluorescent paper-based assays for Tl(I) and Pb(II) were 1.1 nM and 1.6 nM, respectively. The two fluorescent approaches presented here have the potential to be the basis of rapid, fast, and cost-efficient screening assays for these toxic species.

Assessment of Water Status, Bottom Sediments, Macrophytes in the Light of Index Analysis and Geochemical Parameters of Selected Dam Reservoirs of Kielce Upland (Poland)

Concentrations of trace elements such as Cr, Zn, Cd, Co, Mn, Cu, Ni, Pb, and Fe were investigated in water, bottom sediments, and macrophytes (Phragmites australis and Typha latifolia L.) collected from the Borków, Wilków, and Rejów water reservoirs in the Kielce Upland (Poland). The main objective of this study was to investigate the condition of water, bottom sediments, and macrophytes in selected three sedimentary basins of the Kielce Upland and to identify natural and anthropogenic factors influencing this condition. The secondary objectives were (i) to determine the contents of trace metals in water, bottom sediments, and macrophytes, (ii) to assess the quality of abiotic and biotic elements of the ecosystem based on selected criteria, (iii) to compare reservoirs in terms of pollution, and (iv) to determine the ability of macrophytes to be used as a bioindicator of water/sediment pollution. Field tests were conducted in 2021. The trace metals in water were determined by ETAAS (Cr, Cd, Mn, Cu, Ni, Pb) and FAAS (Zn), and spectrophotometry method (Fe). The trace metals in sediments and macrophytes, including Cr, Zn, Cd, Co, Mn, Cu, Ni, Pb, and Fe, were detected using ICP-OES method. Contamination of bottom sediments with potentially toxic metals was determined based on the geo-accumulation index (Igeo), contamination factor (CF), and pollutant load index (PLI). Statistical analyses were performed using the Statistica PL 13.1. The analyses showed that the accumulation of trace elements in the surface layer of the reservoir sediments increases as follows: in Borków, Cd &lt; Co &lt; Ni &lt; Cu &lt; Pb &lt; Cr &lt; Zn &lt; Mn &lt; Fe; in Wilków, Cd &lt; Co &lt; Cu &lt; Ni &lt; Pb &lt; Cr &lt; Zn &lt; Mn &lt; Fe; and in Rejow, Cd &lt; Co = Cu = Ni = Pb &lt; Zn &lt; Cr &lt; Mn &lt; Fe. It was shown that the average distribution of metals in the bottom sediments of the studied reservoirs was as follows: Borków &gt; Wilków &gt; Rejów. Research has shown that the degree of trace metal accumulation increases as follows: water &lt; sediments &lt; macrophytes (except Pb from the reservoir in Borków).

Microbial remediation of heavy metal-polluted water

Heavy metal pollution in water has become a global environmental problem, threatening aquatic ecosystems and human health. Physical and chemical methods can effectively remove heavy metal pollutants, while their applications are limited due to the high costs, complex operation, and susceptibility to secondary pollution. Bioremediation is the most promising method for eliminating toxic pollutants. Microorganisms including bacteria, fungi, and algae can convert toxic heavy metals into less toxic forms, which has become an effective and environmentally friendly solution for the remediation of heavy metal pollution in water environments. This paper expounds the toxicity and mechanism of heavy metal pollution, microbial remediation mechanisms, and primary microbial remediation strategies, providing a reference for the removal or reduction of metal pollutants in water environments as well as the development of related technologies.

Invasive Seaweed Rugulopteryx okamurae: A Potential Source of Bioactive Compounds with Antioxidant Activity

Rugulopteryx okamurae (RO) is a species of brown seaweed that has invaded several shorelines worldwide, including the Spanish Mediterranean and the Strait of Gibraltar coasts, causing serious environmental and economic problems. This work aimed to characterize the bioactive composition of RO. A high content of carbohydrates (58.7 ± 2.6 wt%), fats (17.1 ± 0.4 wt%), and ashes (14.3 ± 0.2 wt%) were found, together with lower protein content (5.5 ± 1.8 wt%). Holocellulose was the most abundant polysaccharide fraction (49.2 ± 1.3 wt%), showing 43.4 ± 2.0 wt% of cellulose and 5.8 ± 0.7 wt% of hemicellulose, followed by lignin (18.9 ± 2.5 wt%). The monosaccharides composition showed a high level of glucose (13.2 ± 1 wt%) and glucuronic acid (9.3 ± 0.5 wt%). RO contained high levels of essential nutrients (Ca, K, Na, S, Mg), trace minerals (Mn, Mo, Se, and Cu), and some toxic heavy metals (Ni, Cd, As). The main fatty acid present in RO was palmitic acid (C16:0, 30.8 ± 3.0 mg/100 g), followed by myristic acid (C14:0, 19.3 ± 2.4 mg/100 g) and eicosatetraenoic acid (C20:4, 19.2 ± 1.3 mg/100 g). The extract obtained by microwave-assisted extraction (MAE) presented significant contents of polyphenols (2.7 ± 0.2 mg GAE/g) and antioxidant activity (3.0 ± 0.4 mg TE/g DPPH, 4.5 ± 0.3 mg TE/g ABTS, 4.7 ± 0.3 mg TE/g FRAP). Six main polyphenols were identified by HPLC-MS/MS, showing higher contents of gallic acid (20.7 ± 1.5 mg/g) and chlorogenic acid (9.7 ± 0.5 mg/g). These results highlight the possibilities offered in the valorization of RO to obtain bioactive compounds with antioxidant performance in several applications.

Evaluating the Potential of Marine Algae as Sustainable Ingredients in Poultry Feed

Algae are a complex source of crucial nutrients, including proteins, minerals, vitamins, and carbohydrates. The use of marine algae, specifically Sargassum species, Gracilaria species, and Spirulina species, as feed ingredients in poultry feed was examined in the current research. This study’s aims were to carry out lipid profiling, proximate analysis, and heavy metal toxicity testing, as well as to evaluate the presence of hazardous hydrocarbons in the algae and investigate the effect of the fatty acid profile of Sargassum species on broilers. The proximate analysis was conducted on the algae types containing considerable quantities of fats and proteins and a sizable quantity of omega-3 fatty acids. This research assessed the productive effectiveness of broilers with 2.5%, 6%, and 10% algal additions in their diet. Fatty acid profiling of Sargassum species was performed at 1% and 2% levels in the bursa, fat pads, heart, liver, spleen, thymus, thighs, and breast. The findings showed no significant differences in the development performance or feed utilization efficiency of broilers with 2.5%, 6%, and 10% algae supplementation in their diet. The results of fatty acid profiling showed changes in the heart, liver, and spleen at 1% and 2% supplementations levels. However, this research concludes that if algae partially replaces the imported feed proteins used in animal feed, then these can achieve maximum beneficial effects on poultry health and performance. Algae are sustainable, easy to produce, and cost-effective sources of nutrients and contain numerous bioactive compounds, which will contribute to sustainability and food safety.

Metal contamination in mangrove tissues, seeds, and associated sediments from the Vattanam mangrove forest of Palk Bay, southeastern India: An ecological risk assessment

In the present work, the concentrations of toxic heavy metals in mangrove sediments, mangrove leaves, and seeds collected from five stations in the Vattanam mangrove of Palk Bay, southeastern India, as well as the effects of the monsoon season on toxic heavy metals concentrations were determined. The concentrations were 17.5 μg/g for zinc (Zn), 9.11 μg/g for copper (Cu), and 6.03 μg/g for lead (Pb) in sediments; 10.71 μg/g (Zn) and 8.94 μg/g (Cu) in mangrove leaves; and 26.24 μg/g (Zn) and 17.01 μg/g (Cu) in mangrove seeds. At all sampling stations, the Cd concentration was below the limit of detection. These mangroves seem to have adapted successfully to their environment given their selective intake of only essential metals (Cu and Zn) and the restricted movement of non-essential metals (Cd and Pb). The concentrations of metals were below the maximum residual limits regulated by national and international standard limits.

Endophytic Bacteria Improve Bio- and Phytoremediation of Heavy Metals

Currently, the problem of heavy metal pollution in China is becoming increasingly serious, which poses grave threats to the environment and human health. Owing to the non-biodegradability and toxicity of heavy metals, a more sustainable and ecological approach to remediate heavy metal pollution has always been a focus of attention for environmental researchers. In recent years, many scientists have found that phytoremediation aided by endophytes has high potential to remediate heavy metals owing to its low cost, effectiveness, environmental friendliness, and sustainability compared with physical and chemical methods. Indeed, the mechanism of interaction between endophytes, plants, and heavy metals in the soil is pivotal for plants to tolerate metal toxicity and thrive. In this review, we focus on the mechanism of how endophytic bacteria resist heavy metals, and the direct and indirect mechanisms employed by endophytic bacteria to promote the growth of plants and enhance phytoextraction and phytostabilization. Moreover, we also discuss the application of combinations of endophytic bacteria and plants that have been used to remediate heavy metal pollution. Finally, it is pointed out that although there have been many studies on phytoremediation systems that have been assisted by endophytes, large-scale field trials are important to deliver “real” results to evaluate and improve phytoremediation assisted with microorganisms in polluted natural environments.

Plant membrane transporters function under abiotic stresses: a review.

In the present review, we discussed the detailed signaling cascades via membrane transporters that confer plant tolerance to abiotic stresses and possible significant use in plant development for climate-resilient crops. Plant transporters play significant roles in nutrient uptake, cellular balance, and stress responses. They facilitate the exchange of chemicals and signals across the plant's membrane by signal transduction, osmotic adjustment, and ion homeostasis. Therefore, research into plant transporters is crucial for understanding the mechanics of plant stress tolerance. Transporters have potential applications in crop breeding for increased stress resistance. We discuss new results about various transporter families (ABC, MATE, NRAMP, NRT, PHT, ZIP), including their functions in abiotic stress tolerance and plant development. Furthermore, we emphasize the importance of transporters in plant responses to abiotic stresses such as drought, cold, salt, and heavy metal toxicity, low light, flooding, and nutrient deficiencies. We discuss the transporter pathways and processes involved in diverse plant stress responses. This review discusses recent advances in the role of membrane transporters in abiotic stress tolerance in Arabidopsis and other crops. The review contains the genes discovered in recent years and associated molecular mechanisms that improve plants' ability to survive abiotic stress and their possible future applications by integrating membrane transporters with other technologies.