Heavy metal pollution in the aquatic environment: efficient and low-cost removal approaches to eliminate their toxicity: a review

Rhodamine 6G-PAH probes for heavy metal: Fluorescence detection, bioimaging, and solid-phase sensing application

Four rhodamine 6G-PAH probes with pyrene (R6G-Pyr), anthracene (R6G-Ant), acenaphthene (R6G-Acp) or phenanthrene (R6G-PA) as fluorophore were designed and synthesized for Hg(II) detection. Probe R6G-PA, which had the lowest detection limit of 0.84 nmol/L, displayed the best fluorescence performance as compared to the other three probes. This type of probe had good anti-interference properties against most common metal ions except Cu(II). Metal Cu(II) had a certain quenching effect on the fluorescence generated by Hg(II), with a minimum detection limit of 0.31 nmol/L (for R6G-Acp), indicating its potential practicability for Cu(II) detection. The structure-fluorescence relationship was discussed based on density functional theory (DFT) calculations, and R6G-PA + Hg(II), which had the minimum dihedral angle between polycyclic aromatic rings and rhodamine spiro ring, produced the strongest π-π accumulation and provided the brightest fluorescence. Probe R6G-PA was successfully employed for fluorescence detection of Hg(II) in biological samples. Its solid-phase sensor PS@R6G-PA was developed by immobilizing R6G-PA on PS microspheres for the determination of Hg(II) in water and food samples, with excellent reproducibility and fluorescence "on/off" response. The relative error of the spiked recovery rate was less than 10 %.

Design of aggregation-induced emission materials for biosensing of molecules and cells

In recent years, aggregation-induced emission (AIE) materials have gained significant attention and have been developed for various applications in different fields including biomedical research, chemical analysis, optoelectronic devices, materials science, and nanotechnology. AIE is a unique luminescence phenomenon, and AIEgens are fluorescent moieties with relatively twisted structures that can overcome the aggregation-caused quenching (ACQ) effect. Additionally, AIEgens offer advantages such as non-washing properties, deep tissue penetration, minimal damage to biological structures, high signal-to-noise ratio, and excellent photostability. Fluorescent probes with AIE characteristics exhibit high sensitivity, short response time, simple operation, real-time detection capability, high selectivity, and excellent biocompatibility. As a result, they have been widely applied in cellular imaging, luminescent sensing, detection of physiological abnormalities in the human body, as well as early diagnosis and treatment of diseases. This review provides a comprehensive summary and discussion of the progress over the past four years regarding the detection of metal ions, small chemical molecules, biomacromolecules, microbes, and cells based on AIE materials, along with discussing their potential applications and future development prospects.

Selective synergistic effects of oxalic acid and salicylic acid in enhancing amino acid levels and alleviating lead stress in Zea mays L

Lead is one of the major environmental pollutants which is highly toxic to plants and living beings. The current investigation thoroughly evaluated the synergistic effects of oxalic acid (OA) and salicylic acid (SA) on Zea mays L. plants subjected to varying durations (15, 30, 30, and 45 days) of lead (Pb) stress. Besides, the effects of oxalic acid (OA) combined with salicylic acid (SA) for different amino acids at various periods of Pb stress were also investigated on Zea mays L. The soil was treated with lead nitrate Pb (NO3)2 (0.5 mM) to induce Pb stress while the stressed plants were further treated using oxalic acid (25 mg/L), salicylic acid (25 mg/L), and their combination OA + SA (25 mg/L each). Measurements of protein content, malondialdehyde (MDA) levels, guaiacol peroxidase (GPOX) activity, catalase (CAT) activity, GSH content, and Pb concentration in maize leaves were done during this study. MDA levels increased by 71% under Pb stress, while protein content decreased by 56%, GSH content by 35%, and CAT activity by 46%. After treatment with SA, OA, and OA+SA, there was a significant reversal of these damages, with the OA+SA combination showing the highest improvement. Specifically, OA+SA treatment led to a 45% increase in protein content and a 39% reduction in MDA levels compared to Pb treatment alone. Moreover, amino acid concentrations increased by 68% under the Pb+OA+SA treatment, reflecting the most significant recovery (p < 0.0001).

Harnessing microalgae for metal nanoparticles biogenesis using heavy metal ions from wastewater as a metal precursor: A review

Heavy metal contamination of water sources has long been a silent yet potent threat, endangering environmental and human health. Conventional wastewater treatments are costly due to high infrastructure expenses, energy consumption, and chemical usage. These treatments lead to secondary environmental pollution, such as producing toxic sludge, greenhouse gaseous emissions, and residual pollutants discharges. Therefore, more sustainable and cost-effective wastewater treatment alternatives are needed to overcome these challenges. Microalgae biosorption and bioaccumulation can bioremediate wastewater by effectively removing heavy metals and other contaminants, such as nitrate and phosphate. By utilizing sunlight and CO2 for growth, microalgae cultivation reduces the need for expensive chemicals and energy-intensive operations in wastewater treatment. Additionally, microalgae can potentially convert heavy metal ions from wastewater into metal nanoparticles, providing a dual benefit of bioremediation and resource recovery. The primary objectives of this review are to assess the effectiveness of microalgae in heavy metal bioremediation and nanoparticle synthesis while also identifying critical research gaps and future directions for optimizing this biotechnology. Heavy metal ions in wastewater can be used as a metal precursor, and metal nanoparticles can be synthesized from wastewater. A review methodology was carried out to assess the availability of literature for readers to identify the research trends and gaps. Mechanisms of microalgae for the biogenesis of metal nanoparticles, including activation, growth, and termination phases, were elucidated. Various chemical interactions between metal ions and functional groups of microalgae, including amine (-NH2), carboxyl (-COOH), phosphate (-PO4), and hydroxyl (-OH) groups were evaluated. Nonetheless, this review also identifies the current challenges and future research directions for optimizing microalgae biotechnology in heavy metal bioremediation and nanoparticle biogenesis.

Charge-switchable zwitterionic nanomagnets for wastewater remediation

Enormous amounts of toxic synthetic dyes and inorganic contaminants, such as heavy metals, are regularly discharged into local water bodies unregulated and untreated through effluents from a wide range of industries. Designing industrial methodologies that limit or eliminate the unloading of harmful substances in the surrounding environment has become a requisite for sustainable growth. Although the magnetic separation-based adsorption technique seems quite promising, the functional moieties on the nanoparticle surface often restrict the choice of target pollutants, limiting their universal applicability. Here, we explore the utility of a zwitterion-coated magnetic adsorbent for the easy separation of both positively and negatively charged contaminants from water. Water-dispersible monodispersed nitrilotriacetic acid-functionalized superparamagnetic iron oxide nanoparticles (NTA@SPIONs) were prepared on a large scale following a simple one-pot route. The zwitterionic nanoparticles exhibit surface charge reversibility with a change in pH. The charge-switching property of the nanomaterial was exploited for the removal of cationic and anionic contaminants, such as dyes and heavy metal ions. By proper tuning of the medium pH, methylene blue (MB), a cationic dye, and Congo red (CR), a benzidine-based anionic azo dye, were separated from the aqueous dispersion with the help of the NTA@SPIONs. Under the same working principle, chromium, a highly toxic heavy metal both in cationic and anionic form, was successfully separated from the contaminated water. Low-gradient magnetic separation makes the process rapid, easy, and efficient, and also avoids the chances of secondary pollution.

Effects on lethal concentration 50 % hematological parameters and plasma components of Starry flounder, Platichthys stellatus exposed to hexavalent chromium

Starry flounders (Platichthys stellatus, mean weight 105 ± 14 g, mean total length 20.2 ± 0.7 cm) were exposed to hexavalent chromium concentrations of 0, 5, 10, 20, 40, and 80 mg Cr6 +/L for 96 hours. The half-lethal concentration (LC50) of P. stellatus induced by acute exposure to waterborne hexavalent chromium for 96 hours was found to be 58.84 mg Cr6+/L. In hematological parameters, red blood cell counts (RBCs), hemoglobin and hematocrit were significantly increased (P < 0.05). Major plasma components also changed significantly due to exposure to waterborne hexavalent chromium. Calcium in plasma inorganic components significantly increased, and glucose and cholesterol in plasma organic components also showed significant increases (P < 0.05). Plasma enzyme components such as AST, ALT and ALP were significantly increased (P < 0.05) at high levels of waterborne hexavalent chromium exposure. The results of this study suggest that acute exposure to waterborne hexavalent chromium in P. stellatus affects survival rates, hematological properties and plasma components.

Facile Synthesis of Natural Kaolin-Based CuO Catalyst: An Efficient Heterogeneous Catalyst for the Catalytic Reduction of 4-Nitrophenol

Water contamination by nitro compounds from various industrial processes has significantly contributed to environmental pollution and severely threatened aquatic ecosystems. Inexpensive, efficient, and environmentally benign catalysts are required for the catalytic reduction of such nitro compounds. This study reports the fabrication of various nanocomposites (NCs) of copper oxide nanoparticles (CuO NPs) supported on a kaolin sheet using straightforward and simple one-pot synthesis procedures that control the metal precursor to kaolin ratios. The selected as-synthesized CuO/kaolin NC was characterized using a range of advanced spectroscopic and microscopic methods, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV-vis) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), high-angle annular dark-field scanning TEM (HAADF-STEM), and N2 adsorption/desorption analysis. The characterization results confirmed the successful incorporation of CuO NPs into the kaolin sheets, which had an average size of about 18.7 nm. The fabricated CuO/kaolin NC was used as a heterogeneous catalyst for the efficient reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of sodium borohydride (NaBH4) in an aqueous system at room temperature. The catalyst demonstrated superior catalytic performance with high 4-NP conversion into 4-AP (>99%) in the aqueous phase (50 mL, 20 mg L-1) within 6 min. In addition, the reaction kinetics of 4-NP reduction was also investigated, and the reaction followed the pseudo-first-order kinetics equation with the apparent rate constant of 1.76 min-1. Furthermore, the Arrhenius and Eyring parameters for the catalytic hydrogenation reaction of 4-NP were calculated in order to investigate the catalytic reaction process in more detail. Moreover, the catalyst exhibited excellent reusability and stability over seven repeated catalytic test cycles without any noticeable decline in catalytic activity. Therefore, this paper could provide a novel, efficient, and environmentally promising clay-based non-noble metal oxide nanocatalyst to reduce nitro compounds in the aqueous system.

Heavy metals concentration and human health risk assessment in selected shrimp species of Pakistan

Heavy metal pollution in marine organisms poses a significant threat to both ecosystems and human health. Dumping untreated sewage into the sea pollutes coastal waters with toxic metals. This study examined the levels of chromium (Cr), lead (Pb), nickel (Ni), mercury (Hg), arsenic (As) and copper (Cu) in three shrimp species of genus Penaeus i.e. Penaeus merguiensis, Penaeus monodon, and Penaeus indicus. The findings revealed that the average levels of arsenic, lead, and mercury were considerably higher than the legislative limits. Furthermore, chromium and lead levels remained consistent across shrimp species, while other metals exhibited significant variation. Additionally, THQ and HI values were below the limit of 1, indicating low health risks from consuming shrimp species from this area. However, sustained monitoring and research are essential to protect consumer health and ensure long-term sustainability of seafood resources.

Fluorescent polymers for environmental monitoring: Targeting pathogens and metal contaminants with naphthalimide derivatives

Monitoring Hg2+ levels in aqueous environments is crucial to assess the potential methylmercury contamination via bacterial conversion, however, existing methods often require extensive sample treatment and expensive equipment. To mitigate this issue, this study examines the synthesis and application of three naphthalimide-based compounds, with significant fluorescent and solvatochromic behavior (C1, C2, and C3). Compounds C1 and C2 demonstrated a strong affinity for Hg2+ metal ions, with C2 showing selectivity and a strong antibacterial profile, particularly against S. aureus (MIC50 (C2) = 0.01 µg/mL). Moreover, these compounds were incorporated into three polymeric matrices, namely polyvinyl chloride (PVC), poly (methyl methacrylate-co-methacrylic acid) (PMMMA), and Starch, allowing for the development of solid-support sensors/surfaces with a strong antibacterial profile, highlighting the inherent dual-functionality of the compounds. Interestingly, the C2-doped Starch biopolymer detected low concentrations of Hg2+ ions, such as 23 nM in tap water (value within the WHO standards for drinking water), through a rapid spectroscopic evaluation without sample treatment. This biopolymer was generated via a sustainable, green-chemistry-oriented, temperature-dependent water/Starch synthetic route, without the addition of plasticizers and any associated ecotoxicity. The study used sustainable methods for environmental monitoring and antibacterial applications, advancing material science to offer effective, accessible, and eco-friendly solutions for detecting and mitigating mercury pollution and bacterial contaminations, enhancing environmental and health safety.

Emerging hazardous chemicals and biological pollutants in Canadian aquatic systems and remediation approaches: A comprehensive status report

Emerging contaminants can be natural or synthetic materials, as well as materials of a chemical, or biological origin; these materials are typically not controlled or monitored in the environment. Canada is home to nearly 7 % of the world's renewable water supply and a wide range of different kinds of water systems, including the Great Lake, rivers, canals, gulfs, and estuaries. Although the majority of these pollutants are present in trace amounts (μg/L - ng/L concentrations), several studies have reported their detrimental impact on both human health and the biota. In Canadian aquatic environments, concentrations of pharmaceuticals (as high as 115 μg/L), pesticides (as high as 1.95 μg/L), bioavailable heavy metals like dissolved mercury (as high as 135 ng/L), and hydrocarbon/crude oil spills (as high as 4.5 million liters) have been documented. Biological threats such as genetic materials of the contagious SARS-CoV-2 virus have been reported in the provinces of Québec, Ontario, Saskatchewan and Manitoba provinces, as well as in the Nunavut territory, with a need for more holistic research. These toxins and emerging pollutants are associated with nefarious short and long-term health effects, with the potential for bioaccumulation in the environment. Hence, this Canadian-focused report provides the footprints for water and environmental sustainability, in light of this emerging threat to the environment and society. Several remediation pathways/tools that have been explored by Canadian researchers, existing challenges and prospects are also discussed. The review concludes with preventive measures and strategies for managing the inventory of emerging contaminants in the environment.

3D printing of antimicrobial adsorbents using Mercapto-graphene oxide / chitosan / ε-Polylysine: Elucidating adsorption mechanisms and antimicrobial performance

Cu2+ in wastewater is hazardous to human health, and adsorption technology can effectively remove heavy metal ions. In this study, sulfhydryl graphene oxide/chitosan/ε-polylysine (SGCS-E) polymeric antimicrobial materials were prepared using 3D printing technology. These materials were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and XPS. The effects of temperature and other influencing factors on the adsorption performance were systematically investigated. The adsorption process followed pseudo-second-order kinetics and the Langmuir model. The maximum adsorption capacity of the adsorbent was 313 mg/g at an initial Cu2+ concentration of 20 mg/L, pH 5, and a temperature of 303.15 K. The study on the adsorption mechanism showed that the adsorption of Cu2+ by SGCS-E was mainly controlled by chemical interactions. Antibacterial experiments showed that SGCS-E has a good growth inhibition effect on E. coli and S. aureus. The antibacterial process of SGCS-E is mainly achieved by interfering with the synthesis of proteins and DNA in bacterial cells. Therefore, SGCS-E can not only adsorb and remove Cu2+ from wastewater but also inhibit the overgrowth of microorganisms in the porous adsorbent and improve its reusability, making it a dual-functional adsorbent-antibacterial material with high stability.

Toxicodynamics of cadmium in the green mussel Perna viridis (Linnaeus, 1758) using bioenergetic and physiological biomarkers

This study evaluated the toxicity of cadmium (Cd) on the green mussel Perna viridis, aiming to identify toxicological endpoints and investigate its responses across physiological, bioenergetic, and biochemical parameters. The 96-hour LC50 value for Cd in P. viridis was 3.03 ± 0.12 mg L-1, with a 95% confidence interval of 2.35-3.91 mg L-1. Chronic toxicity tests revealed a No Observable Effect Concentration (NOEC), Lowest Observable Effect Concentration (LOEC), and chronic toxicity values of 0.20, 0.37, and 0.29 mg L-1, respectively. Cadmium accumulation in treated mussels increased 46- to 215-fold compared to the control group. Superoxide dismutase, catalase, glutathione S-transferase, and glutathione peroxidase levels in exposed mussels exhibited a significant increase compared to the control group. The redox index ratio, acetylcholinesterase activity, and lysosomal membrane stability decreased with increasing exposure concentrations. Levels of reduced and oxidized glutathione, glutathione reductase, lipid peroxidation, and metallothionein-like proteins increased in exposed mussels. Clearance rate, respiration rate, and excretion rate decreased in a dose-dependent manner. Protein, carbohydrate, and lipid levels decreased with increasing exposure concentration (p < 0.001). Mitochondrial electron transport system activity increased, while cellular energy allocation (p < 0.001) and scope for growth decreased in a dose-dependent manner (p < 0.01). The significant increase in antioxidants suggests heightened oxidative stress in mussels under Cd exposure. The physiological activities of the mussels were severely affected, ultimately leading to a reduced scope for growth. The toxicological data generated in this study contribute to the development of seawater quality criteria for the metal Cd.

Aquifer pollution by metal-antibiotic complexes: Origins, transport dynamics, and ecological impacts

Aquifer pollution by metal-antibiotic complexes is a rising environmental and public health concern owing to their enhanced mobility and persistence in groundwater. The purpose of this review is to examine the origins, transport dynamics, and ecological impacts of complexes formed through interactions between metal ions and antibiotics in agricultural runoff, pharmaceutical effluents, and wastewater discharge. Metal-antibiotic complexes are more resistant to degradation and are more soluble than their components. This complicates the conventional water purification efforts. These complexes disrupt microbial ecosystems, facilitate the spread of antibiotic-resistance genes, and negatively affect aquatic organisms. The entry of pollutants into drinking water sources poses notable health risks, including chronic exposure to contaminants and the emergence of antibiotic-resistant pathogens. This review emphasizes both preventative and remedial strategies to mitigate these impacts. Preventative measures emphasize the regulation of antibiotic and metal use in agriculture and industry and promote green chemistry alternatives. Remediation approaches include advanced treatment technologies such as membrane filtration, oxidation, and bioremediation. Integrated management practices and ongoing monitoring were discussed to address this complex issue. To protect water quality and public health, metal-antibiotic complexes in aquifers require stringent regulatory measures, innovative treatment solutions, and heightened public awareness. This review highlights the importance of coordinated efforts to prevent and remediate the emerging pollution problem.

Designing a Simple Quinoline-Based Chromo-Fluorogenic Receptor for Highly Specific Quantification of Copper (II) Ions: Environmental and Bioimaging Applications

Many industries use copper metal ions (Cu2+ ions), and their salts are utilized as supplemental materials in both agriculture and medicine. Identifying and monitoring these Cu2+ ions in biological and environmental specimens is crucial due to their association with several health issues. In this investigation, we have designed a simple quinoline-based receptor (E)-3-(((2,4-di-tert-butyl-5-hydroxyphenyl)imino)methyl)-6-methoxyquinolin-2(1H)-one (QAP) containing imine functional groups to inspect its capability to identify metal ions in a semi-aqueous medium. The photophysical characteristics and structural confirmation of the receptor QAP were investigated using various spectroscopic techniques. Among various metal ions, the receptor QAP displayed an intense color shift from slightly yellow to strong yellow in the existence of Cu2+ ions, as visualized by the nude eye. Furthermore, the fluorescence spectral maximum wavelength at 485 nm and the strong cyan fluorescence color were quenched upon introducing Cu2+ ions. The alteration in the spectral and colorimetric features of QAP with Cu2+ ions is due to coordination complex formation. The present sensor shows the linear range from 3 to 69 μM, subsequent in a computed limit of detection as 3.16 nM, which is much lower than that of the maximum threshold of Cu2+ ions in drinking water set by WHO. Therefore, the receptor can respond to Cu2+ ions sensing in two ways: by changing color and by quenching fluorescence. The binding mode of the Cu2+ ions to the functional groups of the receptor QAP is a 1:1 stoichiometry, according to ESI-mass, Job's plot analysis, and density functional theory (DFT) computations. The practical utility of the fluorescent receptor QAP was applied for Cu2+ ions determination in environmental samples (drinking, tap, and dam water) and cancer cells (HeLa cells).

Assessment of reproductive, genotoxic, and cytotoxic effects of leachate-contaminated water in male mice

Leachate-contaminated water (LCS) poses significant health risks due to its heavy metal content and altered physicochemical properties. This study examined the physicochemical parameters and heavy metal levels in LCS and assessed its reproductive toxicity, genotoxicity, and cytotoxic effects in exposed mice. Groups of mice (n = 5) were orally administered 100 μL of 30 % and 70 % LCS (v/v) twice daily for 35 days. Drinking water served as a negative control, and cyclophosphamide (Cyp) (20 mg/kg bw) as a positive control. On day 36, the mice were weighed, sacrificed, and their testicular weight, sperm count, sperm morphology, viability, acrosome integrity, and serum testosterone were examined. Oxidative stress in the testes, histopathological changes, and serum markers for liver and kidney function (SGOT, SGPT, and creatinine) were also assessed. Genotoxic effects were evaluated using a micronuclei (MN) assay. Analysis of the leachate showed altered physicochemical parameters and elevated heavy metal levels. Exposure to LCS led to a significant decrease in relative testis weight, sperm count, normal sperm morphology, viability, acrosome integrity, and serum testosterone levels. It also caused a notable increase in MDA levels and a decrease in catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) levels, along with histological changes in the testes of LCS-treated mice compared to controls. Additionally, there was a significant rise in MN formation in RBCs and elevated levels of liver enzymes and creatinine, indicating liver and renal toxicity. Histological alterations in the liver and kidneys were also observed in LCS-exposed mice. These findings suggest that LCS induces reproductive toxicity, genotoxicity, and cytotoxicity in male subjects.

Comprehensive insights into the application of graphene-based aerogels for metals removal from aqueous media: Surface chemistry, mechanisms, and key features

Efficient removal of heavy metals and other toxic metal pollutants from wastewater is essential to protect human health and the surrounding vulnerable ecosystems. Therefore, significant efforts have been invested in developing practical and sustainable tools to address this issue, including high-performance adsorbents. In this respect, within the last few years, graphene-based aerogels/xerogels/cryogels (GBAs) have emerged and drawn significant attention as excellent materials for removing and recovering harmful and valuable metals from different aqueous media. Such an upward trend is mainly due to the features of the aerogel materials combined with the properties of the graphene derivatives within the aerogel's network, including the GBAs' unique three-dimensional (3D) porous structure, high porosity, low density, large specific surface area, exceptional electron mobility, adjustable and rich surface chemistry, remarkable mechanical features, and tremendous stability. This review offers a comprehensive analysis of the fundamental and practical aspects and phenomena related to the application of GBAs for metals removal. Herein, we cover all types of (bottom-up) synthesized GBAs, including true microporous graphene-based aerogels as well as other 3D graphene-based open-cell interconnected mesoporous and macroporous aerogels, foams, and sponges. Indeed, we provide insights into the fundamental understanding of the GBAs' suitability for such an important application by revealing the mechanisms involved in metals removal and the factors inducing and controlling the highly selective behavior of these distinctive adsorbents. Besides conventional adsorptive pathways, we critically analyzed the ability of GBAs to electrochemically capture metal pollutants (i.e., electrosorption) as well as their efficiency in metals detoxification through reductive mechanisms (i.e., adsorption-reduction-readsorption). We also covered the reusability aspect of graphene aerogels (GAs)-based adsorbents, which is strongly linked to the GBAs' outstanding stability and efficient desorption of captured metals. Furthermore, in view of their numerous practical and environmental benefits, the development and application of magnetically recoverable GAs for metals removal is also highlighted. Moreover, we shed light on the potential practical and scalable implementation of GBAs by evaluating their performance in continuous metals removal processes while highlighting the GBAs' versatility demonstrated by their ability to remove multiple contaminants along with metal pollutants from wastewater media. Finally, this review provides readers with an accessible overview and critical discussion of major recent achievements regarding the development and applications of GAs-based adsorbents for metal ions removal. Along with our recommendations and suggestions for potential future work and new research directions and opportunities, this review aims to serve as a valuable resource for researchers in the field of wastewater treatment and inspire further progress towards developing next-generation high-performance GBAs and expanding their application.

Role of SiO2, TiO2, and Fe3O4 adsorbed on glycine for remediation of heavy metals and antibacterial activity in water

Metals have a tendency to accumulate in the environment and can have carcinogenic effects. Accordingly, this study used density functional theory (DFT) calculations to investigate the adsorption of different metal ions on the glycine surface. Glycine has attracted a lot of research interest because of its remarkable metal-binding properties and cost effectiveness. Accordingly, to improve glycine's adsorption capacity, it has been combined with SiO2, TiO2, and Fe3O4, creating a glycine-metal oxide nanocomposite through hydrogen bonding. After optimizing the structures at their energy minima at the B3LYP/6-31G(d, p) level of theory, the following analyses were carried out: total dipole moment (TDM), frontier molecular orbitals (FMOs), reactivity indexes, and molecular electrostatic potential (MESPs). The study of TDM, FMOs, reactivity indexes, density of states (DOS), and UV-Vis absorption analysis demonstrated the improved reactivity of glycine due to functionalization with SiO2. Additionally, the results showed that, compared to the glycine, the glycine/SiO2 surface experiences a greater degree of charge redistribution as a result of more hydrogen bonds being formed with adsorbate molecules. Thus, the study successfully extracted Cr, Fe, Co, Ni, Cu, As, Cd, and Pb from wastewater by demonstrating their selectivity for the glycine/SiO2 nanocomposite. The findings show that Ni had a stronger adsorption for glycine/SiO2 than the others as TDM increased (34.040 Debye), band gap energy decreased significantly (0.249 eV), and reactivity indices got improved. Additionally, the IR spectra were calculated and compared to the experimental data, which revealed remarkable frequency changes due to intermolecular interactions. HR-TEM scans validated the dispersion of SiO2 NP on the glycine surface with minimal aggregation. Furthermore, the antibacterial activity of glycine-amino acid-based surfactants was assessed, and the results show that glycine/SiO2 nanocomposites exhibited antibacterial efficacy against Gram-positive and Gram-negative microorganisms. These findings highlight the glycine/SiO2 nanocomposites for remediation of heavy metals and have antibacterial activity for treating pathogenic bacteria.

Constructed wetlands and hyperaccumulators for the removal of heavy metal and metalloids: A review

Water pollutions of heavy metal and metalloids (HMMs), typically including As, Cd, Cu, Cr, Mn, Ni, Pb, and Zn, are becoming a severe environmental problem to be controlled. Constructed wetlands (CWs) have been intensively investigated and applied for the removal of HMMs. By analyzing a mass of data from the existing literatures, this review found that the HMM removals in CWs varied from 12.35 % to 91.01 %, depending upon the HMM species and CW conditions. Nonetheless, 88.50 % of the influent HMMs were eventually immobilized in the CW sediments, while the common wetland plants are inefficient (i.e., accounting for 4.64 %) to uptake and accumulate the HMMs. It was also found that the concentrations of certain HMMs in the CW sediments have already exceeded up to 100 % of various environmental standards, indicating the urgency of introducing HMM hyperaccumulators in the systems. Through comparison, both the aboveground and belowground HMM accumulating capacities of reported hyperaccumulators were higher by magnitudes than common wetland plants. Following this, the efficacies and mechanisms of candidate hyperaccumulators were provided for the various scenarios of HMM control in CWs. Further, the selection principals, culture methods, and harvest strategies of hyperaccumulator in CWs were discussed. Finally, several perspectives were suggested for the future research. Overall, this review provided guiding information for the utilization of hyperaccumulators in CWs, which can improve the efficiency and sustainability of HMM removal in the CW systems.

Bioaccumulation of polycyclic aromatic hydrocarbons and microbiota dynamics across developmental stages of the Asian tiger mosquito, Aedes albopictus exposed to urban pollutants

Aedes albopictus mosquitoes face numerous anthropic stressors in urban areas. These xenobiotics not only impact mosquito physiology but also shape the composition of their microbiota, which play important roles in host physiological traits. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants known to alter mosquito metabolism, but no studies have yet investigated their impact on microbiota. Using a bespoke indoor mesocosm tailored for Ae. albopictus mosquitoes, we investigated the dynamics of bacterial communities in both mosquitoes and their larval breeding sites following chronic exposure to a cocktail of PAHs consisting of benzo[a]pyrene, benz[a]anthracene, chrysene and benzo[b]fluoranthene. Our findings showed that PAHs have a stage-specific effect on mosquito microbiota, with a higher impact in larvae than in adults, contributing to 12.5 % and 4.5 % of the PAHs-induced variations, respectively. The presence of PAHs in the treated mesocosm led to the enrichment of bacterial families and genera known for their ability to catabolize PAHs, such as Comamonadaceae and Raoultella (increasing from 19 % to 30 % and from 1.2 % to 5.6 %, respectively). Conversely, prevalent taxa found in mosquito microbiota like Wolbachia and Cedecea exhibited a reduction (decreasing from 4 % to 0.8 % and from 12.8 % to 6.4 %, respectively). This reduction could be attributed to the competitive advantage gained by PAH-degrading taxa, or it could reflect a direct sensitivity to PAH exposure. Overall, this indicates a shift in microbiota composition favoring bacteria that can thrive in a PAH-contaminated environment. PAHs persisted in the water of breeding sites only the first 45 days of the experiment. Benzo[a]pyrene and benzo[b]fluoranthene were more susceptible to bioaccumulation in larval tissues over time. Overall, this study enhances our understanding of the impact of pollution on mosquitoes and could facilitate future research on the importance of symbiosis in urban-dwelling insect disease vectors. Given the recent advancements in the generation of axenic (microbe-free) and gnotobiotic (mosquitoes with a defined or specific microbiota) mosquitoes, further studies are needed to explore how changes in microbiota composition could influence mosquito responses to pollution, particularly in relation to host fitness, immunity, and vector competence.

Recent and sustainable advances in phytoremediation of heavy metals from wastewater using aquatic plant species: Green approach

A key component in a nation's economic progress is industrialization, however, hazardous heavy metals that are detrimental to living things are typically present in the wastewater produced from various industries. Therefore, before wastewater is released into the environment, it must be treated to reduce the concentrations of the various heavy metals to maximum acceptable levels. Even though several biological, physical, and chemical remediation techniques are found to be efficient for the removal of heavy metals from wastewater, these techniques are costly and create more toxic secondary pollutants. However, phytoremediation is inexpensive, environmentally friendly, and simple to be applied as a green technology for heavy metal detoxification in wastewater. The present study provides a thorough comprehensive review of the mechanisms of phytoremediation, with an emphasis on the possible utilization of plant species for the treatment of wastewater containing heavy metals. We have discussed the concept, its applications, advantages, challenges, and independent variables that determine how successful and efficient phytoremediation could be in the decontamination of heavy metals from wastewater. Additionally, we argue that the standards for choosing aquatic plant species for target heavy metal removal ought to be taken into account, as they influence various aspects of phytoremediation efficiency. Following the comprehensive and critical analysis of relevant literature, aquatic plant species are promising for sustainable remediation of heavy metals. However, several knowledge gaps identified from the review need to be taken into consideration and possibly addressed. Therefore, the review provides perspectives that indicate research needs and future directions on the application of plant species in heavy metal remediation.

Silica-Based Composite Sorbents for Heavy Metal Ions Removal from Aqueous Solutions

Weak polyelectrolyte chains are versatile polymeric materials due to the large number of functional groups that can be used in different environmental applications. Herein, one weak polycation (polyethyleneimine, PEI) and two polyanions (poly(acrylic acid), PAA, and poly(sodium methacrylate), PMAA) were directly deposited through precipitation of an inter-polyelectrolyte coacervate onto the silica surface (IS), followed by glutaraldehyde (GA) crosslinking and extraction of polyanions chains. Four core-shell composites based on silica were synthesized and tested for adsorption of lead (Pb2+) and nickel (Ni2+) as model pollutants in batch sorption experiments on the laboratory scale. The sorbed/desorbed amounts depended on the crosslinking degree of the composite shell, as well as on the type of anionic polyelectrolyte. After multiple loading/release cycles of the heavy metal ions, the maximum sorption capacities were situated between 5-10 mg Pb2+/g composite and 1-6 mg Ni2+/g composite. The strong crosslinked composites (r = 1.0) exhibited higher amounts of heavy metal ions (Me2+) sorbed than the less crosslinked ones, with less PEI on the surface but with more flexible chains being more efficient than more PEI with less flexible chains. Core-shell composites based on silica and weak polyelectrolytes could act as sorbent materials, which may be used in water or wastewater treatment.

Multiple-Integrated Biomarker Indexes to Assess the Responses of the Flatfish Achirus lineatus during Exposure to Light Crude Oil Water Accommodated Fraction

In the present study, we evaluated the biological response of Achirus lineatus to water accommodated fraction (WAF) of light crude oil (American Petroleum Institute gravity 35°) during a sub-chronic bioassay (14 and 28 days) at two different concentrations: 5% v/v (1.20 µg∙L- 1 expressed as total polycyclic aromatic hydrocarbons [∑25 PAH]) and 10% v/v (6.61 µg∙L- 1 [∑25 PAH]). The responses were evaluated through the biomarker response index (BRI), the integrated biomarker response (IBRv2) and the bioconcentration factor (BCF). The results showed an increase in biological response in relation to WAF concentration and exposure time, which resulted in a slight and moderate disturbance in the basal condition and bioconcentration level of metals (Pb > Ni > V > Cd) in fish tissue. Results in the present study denote that flatfish such as A. lineatus may be negatively influenced by spilled light crude oil.

Effect of co-exposure to multiple metals (Pb, Cd, Cr, Hg, Fe, Mn and Ni) and metalloid (As) on liver function in Swiss albino mice

The study examined the cumulative toxic effect of multiple elements, As, Pb, Cd, Cr, Hg, Fe, Mn and Ni on the liver function and their association with inflammation and apoptosis. To explore the health consequence of simultaneous exposure to multiple metals and metalloid, male and female Swiss Albino mice were randomly divided into 14 groups and subjected to different doses [MPL (maximum permissible limit), 1×, 5×, 10×, 50× or 100×] of metal(loid)s mixture via drinking water for 8 weeks. Data showed that combined effect of multiple elements impaired the liver function. This was associated with significant decrease in the antioxidant enzymes and the elevation in lipid peroxidation for high exposure dose of 50× and 100× (p < 0.05). The metal(loid)s mixture exposure led to significant increase (p < 0.05) in cytokines, TNF-α, IL-6 and effector caspases (3 and 6) in exposure groups above 10× dose. Histopathological observation also revealed significant damage in the hepatic tissue on exposure to high dose. Dose dependent accumulation of respective elements (As, Cd, Cr, and Pb) in the liver was observed in each of the exposure groups. However, similar dose related increment was not observed for essential metals such as Ni, Fe and Mn. Differential accumulation of metals in the liver may be attributed to the effect of co-contaminant exposure, which could affect the divalent cation absorption due to antagonism and competitive transport process. Overall findings in this study manifest the complexity of possible joint effect of co-exposure to multiple metals and metalloid on the liver function.

Highly efficient recovery of Zn (II) from zinc-containing wastewater by tourmaline tailings geopolymers to in-situ construct nanoscale ZnS for the photodegradation of tetracycline hydrochloride

While treating zinc-containing wastewater, recovering zinc for reuse as a secondary resource has significant environmental and economic benefits. Herein, based on the alkali-activated tourmaline tailings geopolymers (TTG) after adsorption of zinc ions (Zn (II)), a series of new composites with in-situ construction ZnS nanoparticles on TTG (ZnS/TTG) were synthesized, and used as photocatalysts for the photodegradation of tetracycline hydrochloride (TCH) in solution. Specifically, ZnS nanoparticles were uniformly and stably distributed in the layered structure of TTG, interweaving with each other to generate an interfacial electric field, which could induce more photocarrier generation. Meanwhile, TTG acted as an electron acceptor to accelerate the electron transfer at the interface, thus enhancing the photodegradation activity for TCH. The active radical quenching experiments combined with the ESR indicated that the active species produced during the photocatalytic degradation of TCH by ZnS/TTG composites were •O2- and photogenerated h+. When the initial concentration of Zn (II) was 60 mg/L, the synthesized 60-ZnS/TTG composites (0.5 g/L) reached 91.53% degradation efficiency of TCH (10 mg/L) at pH = 6. Furthermore, the possible pathways and mechanism of 60-ZnS/TTG composites photodegraded TCH were revealed with the aid of degraded intermediates. This report not only proposed valuable references for reusing heavy metal ions and removing TCH from wastewater, but also provided promising ideas for realizing the conversion of used adsorbents into high-efficiency photocatalysts.

The molecular insights of cyanobacterial bioremediations of heavy metals: the current and the future challenges

In recent years, overexplorations of ore and the growth of industries are the prime factors in the release of heavy metals in environments. As a result, the food crops and water bodies are contaminated with metals which may have several adverse effects on the health of humans and other living species. These metals and metalloids, such as Zn, Cu, Mn, Ni, Cr, Pb, Cd, and As, upset the biochemical pathways of metabolite synthesis in living organisms and contribute to the etiology of different diseases. Microorganisms include bacteria, archaea, viruses, and many unicellular eukaryotes, which can span three domains of life-Archaea, Bacteria, and Eukarya-and some microorganisms, such as cyanobacteria, have shown high efficiency in the biosorption rate of heavy metals. Cyanobacteria are suitable for bioremediation as they can grow in adverse environments, have a less negative impact on the surrounding environment, and are relatively cheaper to manage. The structure of cyanobacteria has shown no extensive internal-bound membranes, so it can directly employ the physiological mechanisms to uptake heavy metals from contamination sites. Such biochemical makeups are suitable for managing and bioremediating heavy metal concentrations in polluted environments. This review aims to explore the potential of cyanobacteria in the bioremediation of heavy metals and metalloids in water bodies. Additionally, we have identified the prospects for enhancing bioremediation effectiveness.

Manganese(IV) reduction coupled with ammonium oxidation mediated by a single strain Aromatoleum evansii MAY27: Performance, metabolomics, and mechanism

Manganese(IV) (Mn(IV)) reduction coupled to anaerobic ammonium (NH4+-N) oxidation (Mnammox) is a recently identified metal oxide-mediated nitrogen (N) loss pathway, holding potential value for the efficient removal of NH4+-N from wastewater. However, little is known about the application of Mnammox in wastewater treatment. Here, a novel Mnammox bacterium Aromatoleum evansii (strain MAY27) was screened. Strain MAY27 can utilize MnO2 as an electron acceptor to achieve NH4+-N removal under a low C/N condition (C/N = 0.5). The influencing factors in the Mnammox process and the Mn(IV) reduction driving effect on NH4+-N oxidation were investigated. The physiological characteristics of strain MAY27 and differential metabolic pathways were identified through whole-genome sequencing and metabolomic analyses. A significant up-regulation of several key pathways upon the addition of MnO2, including glycolysis/gluconeogenesis, transmembrane transporter activity, and oxidoreductase activity. This study contributes to the advancement of biotechnological approaches for treating N-containing wastewater.

The phenotypic and demographic response to the combination of copper and thermal stressors strongly varies within the ciliate species, Tetrahymena thermophila

Copper pollution can alter biological and trophic functions. Organisms can utilise different tolerance strategies, including accumulation mechanisms (intracellular vacuoles, external chelation, etc.) to maintain themselves in copper-polluted environments. Accumulation mechanisms can influence the expression of other phenotypic traits, allowing organisms to deal with copper stress. Whether copper effects on accumulation strategies interact with other environmental stressors such as temperature and how this may differ within species are still unsolved questions. Here, we tested experimentally whether the combined effect of copper and temperature modulates traits linked to demography, morphology, movement and accumulation in six strains of the ciliate Tetrahymena thermophila. We also explored whether copper accumulation might modulate environmental copper concentration effects on phenotypic and demographic traits. Results showed high intraspecific variability in the phenotypic and demographic response to copper, with interactive effects between temperature and copper. In addition, they suggested an attenuation effect of copper accumulation on the sensitivity of traits to copper, but with great variation between strains, temperatures and copper concentrations. Diversity of responses among strains and their thermal dependencies pleads for the integration of intraspecific variability and multiple stressors approaches in ecotoxicological studies, thus improving the reliability of assessments of the effects of pollutants on biodiversity.

Bioinspired, Carbohydrate-Containing Polymers Efficiently and Reversibly Sequester Heavy Metals

Water scarcity and heavy metal pollution are significant challenges in today's industrialized world. Conventional heavy metal remediation methods are often inefficient and energy-intensive, and produce chemical sludge. To address these issues, we developed a bioinspired, carbohydrate-containing polymer system for efficient and selective heavy metal removal. Using ring opening metathesis polymerization, we synthesized polymers bearing amphiphilic glucuronate side chains capable of selectively binding heavy metal cations in mixed media. In samples containing high concentrations of heavy metals (>550 ppb), these polymers rapidly form a filterable precipitate upon metal capture, reducing the concentration of cation to <1.5 ppb within 3 min, as measured by inductively coupled plasma mass spectrometry. This system effectively removes cadmium ions from highly contaminated solutions to levels below the Agency for Toxic Substances and Disease Registry limit for Cd2+ in drinking water and selectively removes both Cd2+ and Pb2+ from lake water spiked with trace amounts of metal. Acidification triggers protonation of the glucuronate groups, releasing the heavy metals and resolubilizing the polymer. This capture-and-release process can be repeated over multiple cycles without loss of binding capacity. As such, this study introduces a novel class of recyclable materials with pH-responsive properties, offering potential for applications in water remediation and beyond.

β-Lactoglobulin Enhances Clay and Activated Carbon Binding and Protection Properties for Cadmium and Lead

The removal of heavy metals from wastewater remains a challenge due to the limitations of current remediation methods. This study aims to develop multicomponent composites as inexpensive and environmentally friendly sorbents with enhanced capture of cadmium (Cd) and lead (Pb). The composites are based on calcium montmorillonite (CM) and activated carbon (AC) because of their proven effectiveness as sorbents for diverse toxins in environmental settings. In this study, we used a combination of computational and experimental methods to delineate that β-lactoglobulin enhances CM and AC binding and protection properties for Cd and Pb. Modeling and molecular dynamics simulations investigated the formation of material systems formed by CM and AC in complex with β-lactoglobulin and predicted their capacity to bind heavy metal ions at neutral pH conditions. Our simulations suggest that the enhanced binding properties of the material systems are attributed to the presence of several binding pockets formed by β-lactoglobulin for the two heavy metal ions. At neutral pH conditions, divalent Cd and Pb shared comparable binding propensities in all material systems, with the former being consistently higher than the latter. To validate the interactions depicted in simulations, two ecotoxicological models (L. minor and H. vulgaris) were exposed to Cd, Pb, and a mixture of the two. The inclusion of CM-lactoglobulin (β-lactoglobulin amended CM) and AC-lactoglobulin (β-lactoglobulin amended AC) at 0.05-0.2% efficiently and dose-dependently reduced the severe toxicity of metals and increased the growth parameters. This high efficacy of protection shown in the ecotoxicological models may result from the numerous possible interaction pockets of the β-lactoglobulin-amended materials depicted in simulations. The ecotoxicological models support the agreement with computations. This study serves as a proof of concept on how computations in tandem with experiments can be used in the design of multicomponent clay- and carbon-based sorbent amended systems with augmented functionalities for particular toxins.

Spatiotemporal distribution of cyanobacteria in relation to water chemistry of Sutlej River, Punjab (India)

In this investigation, the spatiotemporal distribution of cyanobacteria and their relationships with variations in water chemistry (physico-chemical parameters and heavy metal) of Sutlej River, Punjab (India) has been analyzed by employing multivariate statistical methods. Sutlej River exhibits a rich array of cyanobacterial diversity, comprising 28 species across 15 genera, distributed among 11 families and spanning 5 orders within the class Cyanophyceae. In terms of relative abundance, Microcystis aeruginosa (17.47%) was documented as the most abundant taxa followed by Microcystis robusta (16.55%), Merismopedia punctata (11.03%), Arthrospira fusiformis (6.67%) and Pseudanabaena galeata (3.68%). Significant variations were observed among sampling sites in most of the physico-chemical parameters. Principal Component Analysis delineated sampling sites into two discernible groups according to variations in water chemistry. River Pollution Index (RPI) showed that river water is under the unpolluted (RPI 1.5) to negligibly polluted category in the upstream sites, while moderately polluted (RPI 5.5) in the downstream sites. Heavy metal Pollution Index (HPI) revealed consistent heavy metal contamination at sites RWS7 and RWS8 across all seasons. Conversely, site RWS1 consistently exhibited lower HPI values throughout the three studied seasons. Further, Canonical Correspondence Analysis identified that pH, TDS, TA, NO3, Na, and NH4 are the key physicochemical parameters which affect the spatiotemporal distribution of cyanobacteria in the studied river system. Overall, this study will offer significant information for hydrologists, ecologists, and taxonomists to develop future holistic strategies for further monitoring of the Sutlej River and other similar habitats.

Biochar and biosorbents derived from biomass for arsenic remediation

Global groundwater contamination by Arsenic (As) presents a grave danger to the health of living beings and wildlife, demanding comprehensive remediation strategies. This review delves into the complex landscape of arsenic remediation, encompassing its chemical forms, occurrences, sources, and associated health risks. Advanced techniques, notably biomass-derived adsorbents, emerge as promising and cost-effective solutions. The exploration spans preparing and modifying biomass-derived adsorbents, unraveling their adsorption capacity, influencing factors, isotherms, kinetics, and thermodynamics. Noteworthy attention is given to plant-agricultural waste, algal-fungal-bacterial, and iron-modified biomass-derived adsorbents. The comprehensive discussion of the adsorption mechanism highlights the efficacy of low-cost biomass, particularly from plant, animal, and agricultural residues, offering a sustainable remedy for arsenic removal. This insightful review contributes to the understanding of evolving technologies essential for addressing arsenic contamination in wastewater, emphasizing the potential of renewable biomaterials in advancing efficient remediation practices.

On the Strong Binding Affinity of Gold-Graphene Heterostructures with Heavy Metal Ions in Water: A Theoretical and Experimental Investigation

Minimum energy configurations in 2D material-based heterostructures can enable interactions with external chemical species that are not observable for their monolithic counterparts. Density functional theory (DFT) calculations reveal that the binding energy of divalent toxic metal ions of Cd, Pb, and Hg on graphene-gold heterointerfaces is negative, in contrast to the positive value associated with free-standing graphene. The theoretical predictions are confirmed experimentally by Surface Plasmon Resonance (SPR) spectroscopy, where a strong binding affinity is measured for all the heavy metal ions in water. The results indicate the formation of a film of heavy metal ions on the graphene-gold (Gr/Au) heterointerfaces, where the adsorption of the ions follows a Langmuir isotherm model. The highest thermodynamic affinity constant K = 3.1 × 107 L mol-1 is observed for Hg2+@Gr/Au heterostructures, compared to 1.1 × 107 L mol-1 and 8.5 × 106 L mol-1 for Pb2+@Gr/Au and Cd2+@Gr/Au, respectively. In the case of Hg2+ ions, it was observed a sensitivity of about 0.01°/ppb and a detection limit of 0.7 ppb (∼3 nmol L-1). The combined X-ray photoelectron spectroscopy (XPS) and SPR analysis suggests a permanent interaction of all of the HMIs with the Gr/Au heterointerfaces. The correlation between the theoretical and experimental results indicates that the electron transfer from the graphene-gold heterostructures to the heavy metal ions is the key for correct interpretation of the enhanced sensitivity of the SPR sensors in water.

A comprehensive review of enhanced CO2 capture using activated carbon derived from biomass feedstock

The increasing level of atmospheric CO2 requires the urgent development of effective capture technologies. This comprehensive review thoroughly examines various methods for the synthesis of carbon materials, modification techniques for converting biomass feedstock into carbon materials and pivotal factors impacting their properties. The novel aspect of this review is its in-depth comparison of how these modifications specifically affect the pore structure and surface area together with the exploration of the mechanism underlying the enhancement of CO2 adsorption performance. Additionally, this review addresses research gaps and provides recommendations for future studies concerning the advantages and drawbacks of CO2 adsorbents and their prospects for commercialization and economic feasibility. This article revealed that among the various strategies, template carbonization offers a viable option for providing control of the material pore diameter and structure without additional modification treatments. Optimizing the pore structure of activated carbons, particularly those activated with agents such as KOH and ZnCl2, together with synthesizing hybrid activated carbons using multiple activating agents, is crucial for enhancing their CO2 capture performance. Cost-benefit analysis suggests that biomass-derived activated carbons can significantly meet the escalating demand for CO2 capture materials, offering economic advantages and supporting sustainable waste management.

Spatiotemporal variations, source identification, and risk assessment of potentially toxic elements in the surface water of Felent Stream impacted by the silver mine

The silver deposits located in the upper basin of the Felent Stream are currently the largest producing mine in the Türkiye. It is also significantly impacted by industrial, agricultural, and thermal spring-related waste in Kütahya Province. The main objectives of this study were to examine the spatiotemporal variations of 12 dissolved potentially toxic elements (PTEs) in the surface water of Felent Stream, to identify their possible sources, and to assess their probable risks. As a result of this study, among investigated PTEs, the highest mean concentrations of 3592-14,388 µg/L for Mg and the lowest of 0.15-0.19 µg/L for Cd were noted in Felent Stream water. The average concentrations of PTEs were found in the order of Mg > Ca > Na > As > Mn > B > Zn > Ni > Cu > Pb > Cr > Cd. Remarkably, during the dry season, there was a conspicuous escalation in the average PTEs contents of water, with an approximately multifold amplification. PTEs in stream water were evaluated for their potential ecotoxicological risks and possible sources. Based on ecological risk assessment indices, the stream exhibited low pollution levels during the wet season but displayed elevated pollution levels during the dry season, indicating a general shift towards heightened pollution conditions. The hazard index (HI) data for As exhibited significant potential noncarcinogenic risks across all monitoring stations. Conversely, the carcinogenic risk (CR) data underscored the imperative nature of addressing the health risks associated with As in the waters of the studied region. Mining activities were identified as the primary origin of PTEs based on principal component analysis (PCA). Moreover, upstream regions, proximal to the mining site, emerged as the most heavily contaminated areas according to cluster analysis (CA).

Plants' molecular behavior to heavy metals: from criticality to toxicity

The contamination of soil and water with high levels of heavy metals (HMs) has emerged as a significant obstacle to agricultural productivity and overall crop quality. Certain HMs, although serving as essential micronutrients, are required in smaller quantities for plant growth. However, when present in higher concentrations, they become very toxic. Several studies have shown that to balance out the harmful effects of HMs, complex systems are needed at the molecular, physiological, biochemical, cellular, tissue, and whole plant levels. This could lead to more crops being grown. Our review focused on HMs' resources, occurrences, and agricultural implications. This review will also look at how plants react to HMs and how they affect seed performance as well as the benefits that HMs provide for plants. Furthermore, the review examines HMs' transport genes in plants and their molecular, biochemical, and metabolic responses to HMs. We have also examined the obstacles and potential for HMs in plants and their management strategies.

Biomonitoring of Heavy Metal Toxicity in Freshwater Canals in Egypt Using Creeping Water Bugs (Ilyocoris cimicoides): Oxidative Stress, Histopathological, and Ultrastructural Investigations

The abundance of metal pollutants in freshwater habitats poses serious threats to the survival and biodiversity of aquatic organisms and human beings. This study intends for the first time to assess the pernicious influences of heavy metals in Al Marioteya canal freshwater in Egypt, compared to Al Mansoureya canal as a reference site utilizing the creeping water bug (Ilyocoris cimicoides) as an ecotoxicological model. The elemental analysis of the water showed a significantly higher incidence of heavy metals, including cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni), and lead (Pb), in addition to the calcium (Ca) element than the World Health Organization's (WHO) permitted levels. The Ca element was measured in the water samples to determine whether exposure to heavy metals-induced oxidative stress engendered Ca deregulation in the midgut tissues of the creeping water bug. Remarkably, increased levels of these heavy metals were linked to an increase in chemical oxygen demand (COD) at the polluted site. Notably, the accumulation of these heavy metals in the midgut tissues resulted in a substantial reduction in antioxidant parameters, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and ascorbate peroxidase (APOX), along with a marked rise in malondialdehyde (MDA), cytochrome P450, and protein carbonyl levels. These results clearly indicate a noticeable disturbance in the antioxidant defense system due to uncontrollable reactive oxygen species (ROS). Notably, the results demonstrated that oxidative stress caused disturbances in Ca levels in the midgut tissue of I. cimicoides from polluted sites. Furthermore, the comet and flow cytometry analyses showed considerable proliferations of comet cells and apoptotic cells in midgut tissues, respectively, exhibiting prominent correlations, with pathophysiological deregulation. Interestingly, histopathological and ultrastructural examinations exposed noticeable anomalies in the midgut, Malpighian tubules, and ovarioles of I. cimicoides, emphasizing our findings. Overall, our findings emphasize the potential use of I. cimicoides as a bioindicator of heavy metal pollution in freshwater to improve sustainable water management in Egypt.

Biochemical study of the effect of lead exposure in nonobese gasoline station workers and risk of hyperglycemia: A retrospective case-control study

Evaluate the relationship between blood lead (Pb) levels and other biomedical markers and the risk of diabetes in gasoline station workers. The participants were separated into 2 groups: group A consisted of 26 workers from gasoline filling stations, while group B comprised 26 healthy individuals. Serum levels of malondialdehyde, IL-1β, visfatin, insulin, fasting blood sugar, and vitamin D were assessed. Mean Pb level was significantly higher in group A compared to group B (almost 2.9 times higher levels) (14.43 ± 1.01 vs 5.01 ± 1.41, µg/dL). The levels of visfatin (23.19 ± 0.96 vs 3.88 ± 0.58, ng/mL), insulin (22.14 ± 1.31 vs 11.26 ± 0.75, mU/L), fasting blood sugar (118.4 ± 26.1 vs 82.7 ± 9.2, gm/dL), malondialdehyde (6.40 ± 0.27 vs 1.62 ± 0.21, nmol/mL), and IL-1β (330.25 ± 10.34 vs 12.35 ± 1.43, pg/mL) were significantly higher in group A, meanwhile; vitamin D (11.99 ± 1.55 vs 35.41 ± 3.16, ng/mL) were significantly lower in group A. A positive association exists between blood Pb levels and increased inflammatory markers. Lead exposure increases serum insulin and fasting blood sugar, which suggests that it is diabetogenic and that increased inflammation is a possible cause.

Adsorption of Bichromate and Arsenate Anions by a Sorbent Based on Bentonite Clay Modified with Polyhydroxocations of Iron and Aluminum by the "Co-Precipitation" Method

The physicochemical properties of natural bentonite and its sorbents were studied. It has been established the modification of natural bentonites using polyhydroxoxides of iron (III) (mod.1_Fe_5-c) and aluminum (III) (mod.1_Al_5-c) by the "co-precipitation" method led to changes in their chemical composition, structure, and sorption properties. It was shown that modified sorbents based on natural bentonite are finely porous (nanostructured) objects with a predominance of pores of 1.5-8.0 nm in size. The modification of bentonite with iron (III) and aluminum compounds by the "co-precipitation" method also leads to an increase in the sorption capacity of the obtained sorbents with respect to bichromate and arsenate anions. A kinetic analysis showed that, at the initial stage, the sorption process was controlled by an external diffusion factor, that is, the diffusion of the sorbent from the solution to the liquid film on the surface of the sorbent. The sorption process then began to proceed in a mixed diffusion mode when it limited both the external diffusion factor and the intra-diffusion factor (diffusion of the sorbent to the active centers through the system of pores and capillaries). To clarify the contribution of the chemical stage to the rate of adsorption of bichromate and arsenate anions by the sorbents under study, kinetic curves were processed using equations of chemical kinetics (pseudo-first-order, pseudo-second-order, and Elovich models). It was found that the adsorption of the studied anions by the modified sorbents based on natural bentonite was best described by a pseudo-second-order kinetic model. The high value of the correlation coefficient for the Elovich model (R2 > 0.9) allows us to conclude that there are structural disorders in the porous system of the studied sorbents, and their surfaces can be considered heterogeneous. Considering that heterogeneous processes occur on the surface of the sorbent, it is natural that all surface properties (structure, chemical composition of the surface layer, etc.) play an important role in anion adsorption.

Development of a flow system for decentralized electrochemical analysis of heavy metals using screen-printed electrodes: the importance of sensor stability

Year after year, the need for decentralized tools to tackle the monitoring of heavy metal levels in the environment gradually increases. In this context, suitable electrochemical methodologies are widely established and particularly attractive for the production of low-cost miniaturized field-deployable analytical platforms. This work focused on the development of an automatable portable system based on square-wave anodic stripping voltammetry (SWASV) for the on-line detection of heavy metals. The surface of the sensors is appropriately modified and coupled with a fluidic system equipped with an ad-hoc designed flow cell. A custom software tool was introduced to handle the remote-controlled potentiostat and automate the various steps of the procedure, including stirring operations, cleaning phases, SWASV measurements, and data collection. After studying technical and analytical challenges, the final system developed was applied to the simultaneous detection of Cd(II), Pb(II), and Cu(II) in solution, achieving sub-ppb detection limits. Additionally, the practical applicability of the method was successfully applied to river water samples collected from the Loire basin in France.

Advanced protein nanobiosensors to in-situ detect hazardous material in the environment

Determining hazardous substances in the environment is vital to maintaining the safety and health of all components of society, including the ecosystem and humans. Recently, protein-based nanobiosensors have emerged as effective tools for monitoring potentially hazardous substances in situ. Nanobiosensor detection mode is a combination of particular plasmonic nanomaterials (e.g., nanoparticles, nanotubes, quantum dots, etc.), and specific bioreceptors (e.g., aptamers, antibodies, DNA, etc.), which has the benefits of high selectivity, sensitivity, and compatibility with biological systems. The role of these nanobiosensors in identifying dangerous substances (e.g., heavy metals, organic pollutants, pathogens, toxins, etc.) is discussed along with different detection mechanisms and various transduction methods (e.g., electrical, optical, mechanical, electrochemical, etc.). In addition, topics discussed include the design and construction of these sensors, the selection of proteins, the integration of nanoparticles, and their development processes. A discussion of the challenges and prospects of this technology is also included. As a result, protein nanobiosensors are introduced as a powerful tool for monitoring and improving environmental quality and community safety.

ZIF-8 functionalized S-tapered fiber-optic sensor for polystyrene nanoplastics detection by electrostatic adsorption

Microplastic (MP) residues in marine have become an increasingly serious environmental pollution issue, and in recent years the detection of MPs in marine started to attract worldwide research interests. Optical-fiber-based environmental sensors have been extensively employed for their several merits such as high sensitivity, pressure resistance, compactness and ease of constructing communication networks. However, fiber-optic refractive index sensors are not specifically developed for distinguishing MPs from other inorganic particles suspended in water. In this paper, an metal-organic framework (MOF) ZIF-8 functionalized S-tapered fiber (STF) sensor is proposed for specific detection of polystyrene nanoplastics (PSNPs) in aqueous environment. ZIF-8 coordination nanoporous polymers with different film thickness were immobilized over the surface of the fabricated STF structure based on self-growth technique and yielding a large surface area over the sensor surface. High sensitivity detection can be achieved by converting the concentration perturbation of PSNPs into evanescent waves over the ZIF-8 functionalized STF surface through the strong electrostatic adsorption effect and π-π stacking, while the fabricated sensor is insensitive to gravels with silica as the primary component in water. It is found that the proposed detector with 18 film layers achieves a sensitivity up to 114.1353nm/%(w/v) for the PSNPs concentration range of 0.01 %(w/v) to 0.08 %(w/v).

Synthesis of bis(2-aminoethyl)amine functionalized mesoporous silica (SBA-15) adsorbent for selective adsorption of Pb2+ ions from wastewater

Rapid growth in the industry has released large quantities of contaminants, particularly metal discharges into the environment. Heavy metal poisoning in water bodies has become a major problem due to its toxicity to living organisms. In this study, we developed a 3-chloropropyl triethoxysilane incorporated mesoporous silica nanoparticle (SBA-15) based adsorbent utilizing the sol-gel process and Pluronic 123 (P123) as a structure-directing surfactant. Furthermore, the produced SBA-15 NPs were functionalized with bis(2-aminoethyl)amine (BDA) using the surface grafting approach. The physical and chemical properties of the prepared SBA-15@BDA NPs were determined using a variety of instruments, including small-angle X-ray diffraction (SAXS), Fourier-transform infrared (FTIR), scanning electron microscope (SEM), N2 adsorption-desorption, thermogravimetric, particle size distribution, and zeta potential analysis. The MSN has a large surface area of up to 574 m2/g, a pore volume of 0.57 cm3/g, and a well-ordered mesoporous nanostructure with an average pore size of 3.6 nm. The produced SBA-15@BDA NPs were used to adsorb selectively to lead (Pd2+) ions from an aqueous solution. The adsorption study was performed under various conditions, including the influence of solution pH, adsorbent dose, adsorption kinetics, adsorption selectivity in the presence of competing metal ions, and reusability. The results of the kinetic study demonstrated that SBA-15@BDA NPs absorb selectively Pb2+ ions via chemisorption. The SBA-15@BDA NPs show Pb2+ ions with a maximum adsorption capacity of ~ 88% and an adsorbed quantity of approximately ~ 112 mg/g from the studied aqueous solution. The adsorption mechanism relies on coordination bonding between Pb2+ ions and surface-functionalized amine groups on SBA-15@BDA NPs. Furthermore, the proposed SBA-15@BDA NPs adsorbent demonstrated excellent reusability over five cycles without significantly reducing adsorption performance. As a consequence, SBA-15@BDA NPs might serve as an effective adsorbent for the selective removal of Pb2+ ions from aqueous effluent.

Metal distribution in three organs and edibility assessment on Coptodon rendalli from the Umgeni River impacted by metallurgic industrial activities

Fish is among the most affordable and readily available protein sources for communities residing near water bodies. However, the recent pollution status of aquatic ecosystems has rendered fish consumption risky for human health. The study evaluated metal levels in the liver, gill, and muscle tissues of Redbreast tilapia (Coptodon rendalli) from Inanda and Nagle dams in the uMgeni River system. Metals, Al, Sb, Cd, Cr, Fe, Mn, Mo, Pb, and Zn were analysed using ICP-OES. Fish size showed no significant difference between the two dams (p > 0.05) whereas a descending trend liver > gill > muscle was observed for most metal levels at both dams. Moreover, there was a clear separation for metal levels in the liver, gill, and muscle between the two dams (p < 0.001) and a similar trend was observed for organs in each dam (p < 0.001). No relationship was observed between fish length and metal levels and no definite trend was observed for inter-metal relationships. Antimony, Cr, and Pb showed THQs greater than 1 at both dams which suggests health risks for consumers. Molybdenum has also shown a concerning THQs with some individuals exhibiting values ranging from 0.5 - 0.9. These findings suggest that consuming C. rendalli from the Inanda and Nagle dams could result in adverse health effects from Sb, Cr and Pb.

Investigating the efficiency of electrocoagulation using similar/dissimilar electrodes for the detoxification of Coralene Rubine dye: a cost effective approach

Efficient treatment of textile dyeing wastewater can be achieved through electrocoagulation (EC) with minimal sludge production; however, the selection of the appropriate electrode is essential in lowering overall costs. Also, the reuse of the treated aqueous azo dye solution from this process has not been explored in detail. With these objectives, this study aims to treat synthetic azo dye solutions and achieve high colour removal efficiency (CRE%) using similar (Ti-Ti) and dissimilar (Ti-Cu) metal electrodes through EC with an attempt to reduce the cost. The aqueous Coralene Rubine GFL azo dye was used to examine the efficiency and cost of the EC process. X-Ray Photoelectron Spectroscopy was used to study the EC mechanism, while High Performance Liquid Chromatography was used to analyse the degradation of the dye and the formation of intermediate compounds. The concentration of metal ions in the treated dye solution was quantified using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), with Ti-Ti treated solution having 14.20 mg/L concentration of Ti and Ti-Cu treated solution having 0.078 mg/L of Ti and 0.001 mg/L of Cu, respectively. Colour removal efficiency of 99.49% was obtained for both electrode sets, with a lower operating time and voltage for dissimilar metal combination. Ecotoxicity studies showed negligible toxicity of Ti-Cu treated dye samples compared to untreated solutions. Survival rate, protein estimation, and catalase activity was used to validate the treatment method's efficacy. The study found that the dissimilar electrode material exhibited reduced toxicity due to the presence of heavy metals below the permissible limit.

Comprehensive review on toxic heavy metals in the aquatic system: sources, identification, treatment strategies, and health risk assessment

Heavy metal pollution in water sources has become a major worldwide environmental issue, posing a threat to aquatic ecosystems and human health. The pollution of the aquatic environment is increasing as a result of industrialization, climate change, and urban development. The sources of heavy metal pollution in water include mining waste, leachates from landfills, municipal and industrial wastewater, urban runoff, and natural events such as volcanism, weathering, and rock abrasion. Heavy metal ions are toxic and potentially carcinogenic. They can also buildup in biological systems and cause bioaccumulation even at low levels of exposure, heavy metals can cause harm to organs such as the nervous system, liver and lungs, kidneys and stomach, skin, and reproductive systems. There were various approaches tried to purify water and maintain water quality. The main purpose of this article was to investigate the occurrence and fate of the dangerous contaminants (Heavy metal and metalloids) found in domestic and industrial effluents. This effluent mixes with other water streams and is used for agricultural activities and other domestic activities further complicating the issue. It also discussed conventional and non-conventional treatment methods for heavy metals from aquatic environments. Conclusively, a pollution assessment of heavy metals and a human health risk assessment of heavy metals in water resources have been explained. In addition, there have been efforts to focus on heavy metal sequestration from industrial waste streams and to create a scientific framework for reducing heavy metal discharges into the aquatic environment.

Coastal aquatic pollutants degradation using ZnCo2O4 nanorods

Water pollution has caused problems in coastal areas, rivers, lakes, and other important water sources around the world as a result of inappropriate waste management. Meanwhile, these pollutants are harmful to humans and aquatic life. Textile dye effluent methyl orange (MO) was used in this work for dye degradation studies employing nanocomposites. As a result, the importance of synthesizing pure ZnO and Co3O4 nanoparticles with composites of ZnCo2O4 (zinc cobaltite) nanorods in three various proportions (90:10, 75:25, and 50:50) is emphasized in this study. Many advanced approaches were used to assess the various features of these materials, including size and shape. Fourier transform infrared (FT-IR) spectroscopy was used to determine the vibrational modes of the materials. The absorption measurements were then carried out using UV-vis spectroscopic techniques, and the photocatalytic breakdown of MO was done under visible light irradiation. The findings revealed that pure materials were inadequate for visible light activity, resulting in decreased degradation efficiencies. Spinel cobaltite structures have potential degradation efficiency under visible light, while ZnCo2O4 (50:50) catalyst has superior degradation efficiency of 59.8% over MO. The crystallite size, morphology, functional group, absorption wavelength, and band gap all play important roles in enhancing the material's photocatalytic activity under visible light. Meanwhile, ZnCo2O4 spinel structures are crucial for increasing charge carriers and reducing electron-hole recombination. As a result, zinc cobaltite minerals are widely used in industrial dye degradation applications.

Strength and functionalized borage biochar for effective elimination of nickel contamination: Insight into batch and dynamic flow mode treatment applications

A silica gel-modified borage biochar (BB@Si) was first produced and used as a binding agent for potentially hazardous Ni2+ ions in aqueous systems. The recommended biochar was more effective in eliminating Ni2+ than pristine biochar (BB). Its maximum qm could reach up to 1.39 × 10-3 mol/g at 30 °C, and sorption isotherms showed that the Langmuir model could more accurately define its sorption behavior. The Dubinin-Radushkevich isotherm also revealed that the average sorption energy ranged from 11.00 to 11.14 kJ/mol. Zeta potential tests, SEM images, and FT-IR scans confirmed the interactions between BB@Si and Ni2+ ions. Dynamic flow treatment studies showed high uptake effectiveness when the flow rate and amount of BB@Si were suitable. Nickel desorption yield of around 80% from BB@Si was noted with 0.01 M HCl. The BB@Si column's breakthrough and exhausted points were identified to be 45 and 352 min, respectively. Its maximum exhaustion capacity value was determined to be 52.73 mg/g. Ni2+ removal from the actual wastewater sample exceeded 75%. The resulting outcomes imply the immense potential of employing BB@Si in the treatment of Ni2+- contaminated aqueous systems.

Advances in the integration of microalgal communities for biomonitoring of metal pollution in aquatic ecosystems of sub-Saharan Africa

This review elucidated the recent advances in integrating microalgal communities in monitoring metal pollution in aquatic ecosystems of sub-Saharan Africa (SSA). It also highlighted the potential of incorporating microalgae as bioindicators in emerging technologies, identified research gaps, and suggested directions for further research in biomonitoring of metal pollution. Reputable online scholarly databases were used to identify research articles published between January 2000 and June 2023 for synthesis. Results indicated that microalgae were integrated either individually or combined with other bioindicators, mainly macroinvertebrates, macrophytes, and fish, alongside physicochemical monitoring. There was a significantly low level of integration (< 1%) of microalgae for biomonitoring aquatic metal pollution in SSA compared to other geographical regions. Microalgal communities were employed to assess compliance (76%), in diagnosis (38%), and as early-warning systems (38%) of aquatic ecological health status. About 14% of biomonitoring studies integrated microalgal eDNA, while other technologies, such as remote sensing, artificial intelligence, and biosensors, are yet to be significantly incorporated. Nevertheless, there is potential for the aforementioned emerging technologies for monitoring aquatic metal pollution in SSA. Future monitoring in the region should also consider the standardisation and synchronisation of integrative biomonitoring and embrace the "Citizen Science" concept at national and regional scales.

Metal pollution assessment in the surface sediments of a river system in Türkiye: Integrating toxicological risk assessment and source identification

This study investigates potentially toxic elements (PTEs) in the surface sediments of the Abdal River system, a critical water source for Samsun province, Türkiye, due to the presence of the Çakmak Dam. PTE concentrations, measured in mg/kg, show significant variability: Hg (0.03) < Cd (0.26) < As (10.98) < Pb (13.88) < Cu (48.61) < Ni (62.45) < Zn (70.97) < Cr (96.28) < Mn (1015) < Fe (38357). Seasonal variations were observed, in particular increased concentrations of As, Cd and Pb in summer (p < 0.05). Contamination and ecological risk indices (mHQ, EF, Igeo, CF, PLI, Eri, mCd, NPI, PERI, MPI, and TRI) indicate moderate to low levels of contamination, suggesting potential ecological effects. Health risk assessments suggest minimal risks to human health from sediment PTEs. Statistical analyses (PCC, PCA and HCA) improve the understanding of the sediment environment and contamination sources, while the coefficient of variation assists in source identification.

Equilibrium, Kinetic, and Diffusion Mechanism of lead(II) and cadmium(II) Adsorption onto Commercial Activated Carbons

The adsorption of Pb(II) and Cd(II) on three commercial microporous activated carbons was analysed. Adsorption kinetics and statistics were investigated, and the results were described with different models. The highest values of the correlation coefficient R2 were obtained for the pseudo-second-order kinetics model for all ions tested and all sorbents used. The adsorption process was found to be determined by both diffusion in the liquid layer and intraparticle diffusion. The adsorption equilibrium is very well described by Langmuir, Temkin, Thoth or Jovanovic isotherm models. Based on the values of n from the Freundlich isotherm and KL from the Langmuir isotherm, the adsorption of cadmium and lead ions was found to be favourable. The highest monolayer capacities were obtained during the adsorption of lead ions (162.19 mg/g) and for cadmium (126.34 mg/g) for activated carbon WG-12. This carbon is characterised by the highest amount of acid functional groups and the largest specific surface area. The adsorption efficiency of the tested ions from natural water is lower than that from a model solution made from deionised water. The lowest efficiencies are obtained when the process occurs from highly mineralised water.