Copper environmental toxicology, recent advances, and future outlook: a review

Root development in Leucaena leucocephala (Lam.) de Wit enhances copper accumulation

Potentially toxic elements (PTE) in soil like copper (Cu) have been common in agricultural and mining areas worldwide. The sustainable remediation of these areas has been shown to have high socio-environmental relevance and phytoremediation is one of the green technologies to be considered. The challenge is to identify species that are tolerant to PTE, and to assess their phytoremediation potential. The objective of this study was to evaluate the physiological response of Leucaena leucocephala (Lam.) de Wit and to determine the species tolerance and phytoremediation potential to concentrations of Cu in the soil (100, 200, 300, 400 and 500 mg/dm3). The photosynthetic rate was not affected, while the content of chlorophylls decreased as Cu concentrations increased. There was an increased in stomatal conductance and water use efficiency from the treatment of 300. The root biomass and the length were bigger than the shoots, in the treatments above 300. Cu accumulation was greater in the roots than in the shoot of the plants, thus, the Cu translocation index to the shoot was lower. The ability to absorb and accumulate, mainly, Cu in the roots, allowed the development and growth of plants, since the parameters of photosynthesis and biomass accumulation were not affected by the Cu excess. This accumulation in the roots is characterized as a strategy for the phytostabilization of Cu. Therefore, L. leucocephala is tolerant to the Cu concentrations evaluated and has a potential phytoremediation of Cu in the soil.

Optimization of Paenibacillus sp. NMA1017 Application as a Biocontrol Agent for Phytophthora tropicalis and Moniliophthora roreri in Cacao-Growing Fields in Chiapas, Mexico

In Mexico, cacao production is endangered by pathogenic fungi, such as Phytophthora spp. and Moniliophthora rorei, that cause black pod rot and moniliasis, respectively. In this study the biocontrol agent Paenibacillus sp. NMA1017 was tested in cacao fields against the previous diseases. The treatments applied were shade management, inoculation of the bacterial strain with or without an adherent, and use of chemical control. The statistical analysis showed that the incidence of black pod rot in tagged cacao trees diminished when the bacterium was applied (reduction of 44.24 to 19.11%). The same result was observed with moniliasis when the pods were tagged (reduction of 66.6 to 27%). The use of Paenibacillus sp. NMA1017 with an integrated management might be a solution to cacao diseases and to having a sustainable production of cacao in Mexico.

Simple colorimetric copper(II) sensor - Spectral characterization and possible applications

New o-hydroxyazocompound L bearing pyrrole residue was obtained in the simple synthetic protocol. The structure of L was confirmed and analyzed by X-ray diffraction. It was found that new chemosensor can be successfully used as copper(II) selective spectrophotometric regent in solution and can be also applied for the preparation of sensing materials generating selective color signal upon interaction with copper(II). Selective colorimetric response towards copper(II) is manifested by a distinct color change from yellow to pink. Proposed systems were effectively used for copper(II) determination at concentration level 10^-8 M in model and real samples of water.

Physiological and Biochemical Properties of Cotton Seedlings in Response to Cu2+ Stress

Copper(II) (Cu²⁺) is essential for plant growth and development. However, high concentrations are extremely toxic to plants. We investigated the tolerance mechanism of cotton under Cu²⁺ stress in a hybrid cotton variety (Zhongmian 63) and two parent lines with different Cu²⁺ concentrations (0, 0.2, 50, and 100 μM). The stem height, root length, and leaf area of cotton seedlings had decreased growth rates in response to increasing Cu²⁺ concentrations. Increasing Cu²⁺ concentration promoted Cu²⁺ accumulation in all three cotton genotypes' roots, stems, and leaves. However, compared with the parent lines, the roots of Zhongmian 63 were richer in Cu²⁺ and had the least amount of Cu²⁺ transported to the shoots. Moreover, excess Cu²⁺ also induced changes in cellular redox homeostasis, causing accumulation of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA). Conversely, antioxidant enzyme activity increased, while photosynthetic pigment content decreased. Our findings indicated that the hybrid cotton variety fared well under Cu²⁺ stress. This creates a theoretical foundation for the further analysis of the molecular mechanism of cotton resistance to copper and suggests the potential of the large-scale planting of Zhongmian 63 in copper-contaminated soils.

Long-Term Copper Exposure Induced Excessive Autophagy of the Porcine Spleen

Copper (Cu) is one of the essential trace elements and is widespread in the environment. However, excessive exposure will induce toxicity in animals. To investigate the potential mechanisms of Cu-induced porcine spleen toxicity, sixty 30-day-old pigs were randomly divided into three groups. The control group was fed a basal diet and two treatment groups were separately fed the diet with 125 mg/kg and 250 mg/kg of Cu for 80 days. The result of immunohistochemical staining showed that the autophagy marker p62 was significantly increased under Cu exposure, and the immunofluorescence results showed the same trend as LC33-. Meanwhile, Cu intensified autophagy by increasing the expression levels of autophagy-related genes and proteins (LC3, p62, ATG5, Beclin1, and PINK1). These results suggested that long-term Cu exposure induced excessive autophagy in the porcine spleen, laying the groundwork for future studies on Cu-induced immunotoxicity in the spleen and increasing the public safety awareness of the excessive Cu-induced contamination in the environment.

How heavy metal stress affects the growth and development of pulse crops: insights into germination and physiological processes

The current work is an extensive review addressing the effects of heavy metals in major pulse crops such as Chickpea (Cicer arietinum L.), Pea (Pisum sativum L.), Pigeonpea (Cajanus cajan L.), Mung bean (Vigna radiata L.), Black gram (Vigna mungo L.) and Lentil (Lens culinaris Medik.). Pulses are important contributors to the global food supply in the world, due to their vast beneficial properties in providing protein, nutritional value and health benefits to the human population. Several studies have reported that heavy metals are injurious to plants causing inhibition in plant germination, a decrease in the root and shoot length, reduction in respiration rate and photosynthesis. Properly disposing of heavy metal wastes has become an increasingly difficult task to solve in developed countries. Heavy metals pose one of the substantial constraints to pulse crops growth and productivity even at low concentrations. This article attempts to present the morphological, biochemical and various physiological changes induced on the pulse crops grown under various heavy metal stress such as As, Cd, Cr, Cu, Pb, and Ni.

Single and combined genotoxicity of metals and fluoroquinolones to zebrafish embryos at environmentally relevant concentrations

Fluoroquinolones (FQs) are known to have genotoxicity to aquatic organisms. However, their genotoxicity mechanisms, individually and in combination with heavy metals, are poorly understood. Here, we investigated the single and joint genotoxicity of FQs, ciprofloxacin (CIP) and enrofloxacin (ENR), and metals (Cd and Cu) at environmentally relevant concentrations (0.2 µM) to zebrafish embryos. We found that FQs or/and metals induced genotoxicity (i.e., DNA damage and cell apoptosis) to zebrafish embryos. Compared with their single exposure, the combined exposure of FQs and metals elicited less ROS overproduction but higher genotoxicity, suggesting other toxicity mechanisms may also act in addition to oxidation stress. The upregulation of nucleic acid metabolites and the dysregulation of proteins confirmed the occurrence of DNA damage and apoptosis, and further revealed the inhibition of DNA repair by Cd and binding of DNA or DNA topoisomerase by FQs. This study deepens the knowledge on the responses of zebrafish embryos to exposure of multiple pollutants, and highlights the genotoxicity of FQs and heavy metals to aquatic organisms.

Metabolomic analysis reveals the molecular responses to copper toxicity in rice (Oryza sativa)

Copper (Cu) is one of the essential microelements and widely participates in various pathways in plants, but excess Cu in plant cells could induce oxidative stress and harm plant growth. Rice (Oryza sativa) is a main crop food worldwide. The molecular mechanisms of rice in response to copper toxicity are still not well understood. In this study, two-week-old seedlings of the rice cultivar Nipponbare were treated with 100 μM Cu²⁺ (CuSO₄) in the external solution for 10 days. Physiological analysis showed that excess Cu significantly inhibited the growth and biomass of rice seedlings. After Cu treatment, the contents of Mn and Zn were significantly reduced in the roots and shoots, while the Fe content was significantly increased in the roots. Meanwhile, the activities of antioxidant enzymes including SOD and POD were dramatically enhanced after Cu treatment. Based on metabolomic analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods, 695 metabolites were identified in rice roots. Among these metabolites, 123 metabolites were up-regulated and 297 were down-regulated, respectively. The differential metabolites (DMs) include carboxylic acids and derivatives, benzene and substituted derivatives, carbonyl compounds, cinnamic acids and derivatives, fatty acyls and organ nitrogen compounds. KEGG analysis showed that these DMs were mainly enriched in TCA cycle, purine metabolism and starch and sucrose metabolism pathways. Many intermediates in the TCA cycle and purine metabolism were down-regulated, indicating a perturbed carbohydrate and nucleic acid metabolism. Taken together, the present study provides new insights into the mechanism of rice roots to Cu toxicity.

Copper removal capability and genomic insight into the lifestyle of copper mine inhabiting Micrococcus yunnanensis GKSM13

Heavy metal pollution in mining areas is a serious environmental concern. The exploration of mine-inhabiting microbes, especially bacteria may use as an effective alternative for the remediation of mining hazards. A highly copper-tolerant strain GKSM13 was isolated from the soil of the Singhbhum copper mining area and characterized for significant copper (Cu) removal potential and tolerance to other heavy metals. The punctate, yellow-colored, coccoid strain GKSM13 was able to tolerate 500 mg L^-1 Cu²⁺. Whole-genome sequencing identified strain GKSM13 as Micrococcus yunnanensis, which has a 2.44 Mb genome with 2176 protein-coding genes. The presence of putative Cu homeostasis genes and other heavy metal transporters/response regulators or transcription factors may responsible for multi-metal resistance. The maximum Cu²⁺ removal of 89.2% was achieved at a pH of 7.5, a temperature of 35.5 °C, and an initial Cu²⁺ ion concentration of 31.5 mg L^-1. Alteration of the cell surface, deposition of Cu²⁺ in the bacterial cell, and the involvement of hydroxyl, carboxyl amide, and amine groups in Cu²⁺ removal were observed using microscopic and spectroscopic analysis. This study is the first to reveal a molecular-based approach for the multi-metal tolerance and copper homeostasis mechanism of M. yunnanensis GKSM13.

A Zinc(II) Schiff Base Complex as Fluorescent Chemosensor for the Selective and Sensitive Detection of Copper(II) in Aqueous Solution

The development of chemosensors able to detect analytes in a variety of sample matrices through a low-cost, fast, and direct approach is of current interest in food, health, industrial, and environmental fields. This contribution presents a simple approach for the selective and sensitive detection of Cu²⁺ ions in aqueous solution based on a transmetalation process of a fluorescent substituted Zn(salmal) complex. Transmetalation is accompanied by relevant optical absorption changes and quenching of the fluorescence emission, leading to high selectivity and sensitivity of the chemosensor, with the advantage of not requiring any sample pretreatment or pH adjustment. Competitive experiments demonstrate a high selectivity of the chemosensor towards Cu²⁺ with respect to the most common metal cations as potential interferents. A limit of detection down to 0.20 μM and a dynamic linear range up to 40 μM are achieved from fluorometric data. By exploiting the fluorescence quenching upon formation of the copper(II) complex, simple paper-based sensor strips, visible to naked eyes under UV light, are used for the rapid, qualitative, and quantitative in situ detection of Cu²⁺ ions in aqueous solution over a wide concentration range, up to 10.0 mM, in specific environments, such as in industrial wastewater, where higher concentrations of Cu²⁺ ions can occur.

Ion-Imprinted Polymeric Materials for Selective Adsorption of Heavy Metal Ions from Aqueous Solution

The introduction of selective recognition sites toward certain heavy metal ions (HMIs) is a great challenge, which has a major role when the separation of species with similar physicochemical features is considered. In this context, ion-imprinted polymers (IIPs) developed based on the principle of molecular imprinting methodology, have emerged as an innovative solution. Recent advances in IIPs have shown that they exhibit higher selectivity coefficients than non-imprinted ones, which could support a large range of environmental applications starting from extraction and monitoring of HMIs to their detection and quantification. This review will emphasize the application of IIPs for selective removal of transition metal ions (including HMIs, precious metal ions, radionuclides, and rare earth metal ions) from aqueous solution by critically analyzing the most relevant literature studies from the last decade. In the first part of this review, the chemical components of IIPs, the main ion-imprinting technologies as well as the characterization methods used to evaluate the binding properties are briefly presented. In the second part, synthesis parameters, adsorption performance, and a descriptive analysis of solid phase extraction of heavy metal ions by various IIPs are provided.

A contrast of Pb(II), Cd(II), and Cu(II) toxicities to Aspergillus niger through biochemical, morphological, and genetic investigations

The toxicity of metals to microorganisms is highly correlated with the type of metal used. However, the differences in the resistance mechanisms of filamentous fungi to multiple metals remain unclear. In this study, we investigated the responses of Aspergillus niger to three toxic metals, i.e., Pb²⁺, Cd²⁺, and Cu²⁺. Fungal growth and metabolism indices showed that A. niger had a higher tolerance to Pb²⁺ (>1000 mg L^-1) than to Cu²⁺ (300 mg L^-1) and Cd²⁺ (50 mg L^-1). An appropriate Pb²⁺ concentration (<500 mg L^-1) stimulated fungal growth and metabolic activity, whereas Cd²⁺ and Cu²⁺ stress showed continuously negative influences on fungal physiological parameters, such as biomass and secretion of oxalic acid. A. niger responded to Pb stress by constructing a new border layer around its cell wall. This pathway was also confirmed using RNA-seq analysis, i.e., the gene encoding cell wall α-1,3-glucan synthase was upregulated. This upregulation subsequently promoted the production of polysaccharides, which are the main components that support fungal cell walls. In contrast, the expression of genes encoding both AAA family ATPase and efflux pump antibiotic resistance proteins for Cd²⁺ and Cu²⁺ was significantly downregulated. Therefore, these findings elucidated the relatively complete fungal responses to different metal stresses.

Rescue effect of curcumin against copper toxicity

Turmeric has long been used not only as an indispensable part of Asian cuisine but as a medicinal herb for dressing wounds, bites, burns, treating eye infections and acne. Curcuminoids are the active substances and their synthetic derivatives (i.e. diacetylcurcumin (DAC) and metal-curcumin complexes) possess an incredibly wide range of medicinal properties that encompass chelation capacity for multiple heavy metals, antioxidant activity, anti-inflammatory properties, cytotoxicity against cancerous cells, antiviral and antibacterial effects, antihypertensive and insulin sensitizing role, and regulatory role on apoptosis. The aforementioned properties have put curcumin on spotlight as a potential treatment for ailments such as, hepatic diseases, neurodegenerative diseases, metabolic syndrome, dyslipidemia, cardiovascular disease, auto-immune diseases, malignancies and conditions associated with metal overload. Copper is essential for major biological functions, however, an excess causes chronic ailments including neurodegenerative disorders. The fascinating approach of curcumin could alleviate such effect by forming a complex. Thus, this review aims to present available data on the effect of copper-curcumin interaction in various in vitro, ex-vivo in vivo, and clinical studies.

Synthesis and characterization of copper oxide nanoparticles: its influence on corn (Z. mays) and wheat (Triticum aestivum) plants by inoculation of Bacillus subtilis

Nanotechnology is now playing an emerging role in green synthesis in agriculture as nanoparticles (NPs) are used for various applications in plant growth and development. Copper is a plant micronutrient; the amount of copper oxide nanoparticles (CuONPs) in the soil determines whether it has positive or adverse effects. CuONPs can be used to grow corn and wheat plants by combining Bacillus subtilis. In this research, CuONPs were synthesized by precipitation method using different precursors such as sodium hydroxide (0.1 M) and copper nitrate (Cu(NO₃)₂) having 0.1 M concentration with a post-annealing method. The NPs were characterized through X-ray diffraction (XRD), scanning electron microscope (SEM), and ultraviolet (UV) visible spectroscopy. Bacillus subtilis is used as a potential growth promoter for microbial inoculation due to its prototrophic nature. The JAR experiment was conducted, and the growth parameter of corn (Z. mays) and wheat (Triticum aestivum) was recorded after 5 days. The lab assay evaluated the germination in JARs with and without microbial inoculation under CuONP stress at different concentrations (25 and 50 mg). The present study aimed to synthesize CuONPs and systematically investigate the particle size effects of copper (II) oxide (CuONPs) (< 50 nm) on Triticum aestivum and Z. mays. In our results, the XRD pattern of CuONPs at 500 °C calcination temperature with monoclinic phase is observed, with XRD peak intensity slightly increasing. The XRD patterns showed that the prepared CuONPs were extremely natural, crystal-like, and nano-shaped. We used Scherrer's formula to calculate the average size of the particle, indicated as 23 nm. The X-ray diffraction spectrum of synthesized materials and SEM analysis show that the particles of CuONPs were spherical in nature. The results revealed that the synthesized CuONPs combined with Bacillus subtilis used in a field study provided an excellent result, where growth parameters of Z. Mays and Triticum aestivum such as root length, shoot length, and plant biomass was improved as compared to the control group.

Sewage-based surveillance shows presence of Klebsiella pneumoniae resistant against last resort antibiotics in the population in Bergen, Norway

The aim of this study was to understand the prevalence of antibiotic resistance in Klebsiella pneumoniae present in the population in Bergen city, Norway using city-scale sewage-based surveillance, as well as the potential spread of K. pneumoniae into the marine environment through treated sewage. From a total of 30 sewage samples collected from five different sewage treatment plants (STPs), 563 presumptive K. pneumoniae isolates were obtained on Simmons Citrate Agar with myo-Inositol (SCAI) plates, and 44 presumptive K. pneumoniae isolates on SCAI plates with cefotaxime. Colistin resistance was observed in 35 isolates, while cefotaxime resistance and tigecycline resistance was observed in only five isolates each, out of 563 presumptive K. pneumoniae isolates. All 44 isolates obtained on cefotaxime-containing plates were multidrug-resistant, with 25% (n = 11) showing resistance against tigecycline. Clinically important acquired antibiotic resistance genes (ARGs), like bla_CTX-M-14, bla_CTX-M-15, qnrS1, aac(3)-IIe, tet(A), and sul1, were detected in several sequenced Klebsiella spp. isolates (n = 53). All sequenced colistin-resistant isolates (n = 13) had a mutation in the mgrB gene with nucleotide substitution at position C88T creating a premature stop codon. All sequenced tigecycline-resistant isolates (n = 4) harbored a Tet(A) variant with 22 amino acid (aa) substitutions compared to the reference protein. The sequenced K. pneumoniae isolates (n = 44) belonged to 22 different sequence types (STs) with ST730 (29.5%) as most prevalent, followed by pathogenic ST307 (11.4%). Virulence factors, including aerobactin (iutA), enterobactin (entABCDEFS and fepABCDG), salmochelin (iro), and yersiniabactin (ybt) were detected in several sequenced K. pneumoniae isolates, suggesting pathogenicity potential. Heavy metal resistance genes were common in sequenced K. pneumoniae isolates (n = 44) with silver (silABCEFPRS) and copper (pcoABDRS) resistance genes present in 79.5% of the isolates. Sewage-based surveillance can be a useful tool for understanding antibiotic resistance in pathogens present within a population and to provide up-to date information on the current resistance situation. Our study presents a framework for population-based surveillance of resistance in K. pneumoniae.

In vitro and in vivo copper-treated Myrtus communis L.: terpene profiles and evidence for potential cultivation on metal-contaminated soils

The intensive application of agro-chemicals, and in particular of copper (Cu)-based compounds, causes increasing pollution of agricultural land, with serious risks for human health. Aromatic plants used for purposes other than food, can be considered for the exploitation and/or remediation of metal-polluted substrates, since contamination of the essential oils by these metals was not significant. Myrtle (Myrtus communis L.) is a Mediterranean evergreen shrub whose essential oil has many commercial applications. In this work, the effect of an excess of Cu in respect to control conditions was assessed on M. communis growth and foliar terpene composition. Metal accumulation in roots and shoots was also evaluated for the possible use of this species in phytoremediation. The amount of Cu applied in our experiments minimally affected the terpene profiles of in vitro grown plants, whereas no variations were detected in in vivo plants. The presence of the metal in the soil did not significantly impair plant growth, thus allowing its cultivation on polluted substrates. On the other hand, the amount of Cu in the plant was not enough to result in a significant reduction of Cu levels in the soil. Therefore, myrtle plants proved to be good candidates for the re-vegetation of Cu-contaminated lands.

Molecular Sieve, Halloysite, Sepiolite and Expanded Clay as a Tool in Reducing the Content of Trace Elements in Helianthus annuus L. on Copper-Contaminated Soil

The aim of this study was to determine the effect of copper soil contamination on the trace element content of sunflower aerial parts and in roots. Another aim was to assess whether the introduction of selected neutralizing substances (molecular sieve, halloysite, sepiolite and expanded clay) into the soil could reduce the impact of copper on the chemical composition of sunflower plants. Copper soil contamination with 150 mg Cu²⁺ kg^-1 of soil and 10 g of each adsorbent per kg of soil were used. Soil contamination with copper caused a significant increase in the content of this element in the aerial parts (by 37%) and roots (by 144%) of sunflower. Enriching the soil with the mineral substances reduced the amount of copper in the aerial parts of sunflower. Halloysite had the greatest effect (35%), while expanded clay had the smallest effect (10%). An opposite relationship was found in the roots of this plant. In copper-contaminated objects, a decrease in the content of cadmium and iron and an increase in the concentrations of nickel, lead and cobalt in the aerial parts and roots of sunflower were observed. The applied materials reduced the content of the remaining trace elements more strongly in the aerial organs than in the roots of sunflower. Molecular sieve had the greatest reducing effect on the content of trace elements in sunflower aerial organs, followed by sepiolite, while expanded clay had the least impact. The molecular sieve also reduced the content of iron, nickel, cadmium, chromium, zinc and, especially, manganese, whereas sepiolite reduced the content of zinc, iron, cobalt, manganese and chromium in sunflower aerial parts. Molecular sieve contributed to a slight increase in the content of cobalt, while sepiolite had the same effect on the content of nickel, lead and cadmium in the aerial parts of sunflower. All materials decreased the content of chromium in sunflower roots, molecular sieve-zinc, halloysite-manganese, and sepiolite-manganese and nickel. The materials used in the experiment, especially the molecular sieve and to a lesser extent sepiolite, can be used effectively to reduce the content of copper and some other trace elements, particularly in the aerial parts of sunflower.

Nano-biofertilizers as bio-emerging strategies for sustainable agriculture development: Potentiality and their limitations

Nanotechnology is a burgeoning revolutionary technology in the 21st century. Climate emergencies caused by natural or anthropogenic activities have tragically consequential repercussions on agricultural output worldwide. Modern cropping systems profoundly rely on synthetic fertilizers to deliver necessary nutrients, yet their prolonged and persistent administration is hazardous to the environment, soil fertility, and nutritional dynamics of the rhizospheric microbiome. By addressing the drawback of physico-chemically synthesized nano-dimensioned fertilizer, this review emphasizes on integrating nanoparticles and biofertilizers conjointly as nano-biofertilizers (NBF) which can safeguard global food security, in light of the population surge. Inoculation with nanoparticles and biofertilizers strengthens plant growth and stress tolerance. However, combined together (NBF), they have emerged as a more economically and environmentally sustainable, highly versatile, and long-lasting agriculture tool. Microbe-based green synthesis using the encapsulation of inorganic nanoparticles of Si, Zn, Cu, Fe, Ni, Ti, and Ag as well as organic materials, including chitosan, cellulose, and starch, to formulate NBFs can eliminate the constraints of conventional fertilizer contamination. The application of NBFs is in its infancy in agriculture, yet it has promising potential for transforming traditional farming techniques into smart agriculture, compared to any of the existing strategies. From this perspective, this review is an attempt to provide a comprehensive understanding of the formulations, fabrication, and characterization of NBFs while unraveling the underlying mechanisms of plant-NBF interactions along with their contribution to climate change-induced biotic and abiotic stress tolerance. We substantially summarize the latest advancements of field applications of NBFs for precision farming. Moreover, we critically revised their applications in agro-ecosystems according to the current literature, while also discussing the bottlenecks and future trends for developing potent NBFs.

Removing Mn, Cu and Fe from Real Wastewaters with Macrophytes: Reviewing the Relationship between Environmental Factors and Plants' Uptake Capacity

Heavy metal pollution creates environmental health concerns. Among these, iron (Fe), copper (Cu) and manganese (Mn) are commonly found in aquatic environments due to the release of wastewaters. Phytoremediation in hydroponics uses macrophytes to treat contaminated environments, and this is influenced by environmental factors. However, the relationship between these factors and the removal of Fe, Cu and Mn by macrophytes is not known. Therefore, a meta-analysis serves to determine the correlations between environmental factors and the removal of these metals in real wastewater by macrophytes, as well as to identify the role of different aquatic forms of macrophytes in phytoremediation. Emergent macrophytes had higher concentrations of manganese in their tissues, and higher bioconcentrations factor of iron and manganese than floating plants. Regardless of the biotope, higher concentrations of Fe and Cu decreased the ability of plants to bioconcentrate them. The correlations among exposure time, pH, dissolved oxygen, nitrogen, phosphorus, photoperiod and metal phytoremediation by plants were also found. It can be concluded that the emergent macrophytes showed better performance in terms of the removal of Fe, Cu and Mn, and that the significant correlations between environmental factors and removal vary with the type of metal and the environmental factor analyzed.

Accumulation of heavy metal(loid)s and polycyclic aromatic hydrocarbons in the sediment of the Prahovo Port (Danube) and associated risks

The current study investigated the concentrations, possible sources, toxicity, and ecological risk of eight heavy metal(loid)s (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) and sixteen priority polycyclic aromatic hydrocarbons (PAHs) in surface sediments in the port of Prahovo (Danube, Serbia). Among the examined HMs, the most abundant was Cu (38.3 mg/kg), followed by Zn. The Σ16PAHs concentrations ranged from 25 to 112.5 µg/kg, with 4-ring PAHs (17.3 µg/kg) being the most dominant in the study area. The mean and maximum values of HMs and PAHs obtained in this study were below the national regulatory limits and within environmental criteria. Particularly significant correlations between As, Cd, Cr, Ni, Pb, Zn, 5-, 6-ring PAHs, as well as between Pb and Hg, indicated their similar anthropogenic sources, pathways, and adsorption mechanisms. These findings were confirmed by cluster analysis and principal component analysis. Diagnostic ratios demonstrated that contamination in inner port stations was characterized by pyrogenic sources, while PAHs of petrogenic origin prevailed in samples near the port entrance. The mean ERM quotient (mERMq), toxic risk index (TRI), and toxic equivalent quotient (TEQ) were also calculated to assess the toxicity of the investigated HMs and PAHs in sediments. Positive matrix factorization suggested four potential sources as the main components of sediment contamination, whereas the risk assessment indicated a low or relatively insignificant risk of adverse biological effects from the combined toxicity of HMs and PAHs for the entire study area.

Single-Step Fabrication of a Dual-Sensitive Chitosan Hydrogel by C-Mannich Reaction: Synthesis, Physicochemical Properties, and Screening of its Cu2+ Uptake

Uncovering the value of waste materials is one of the keys to sustainability. In this current work, valorization of chitosan was pursued to fabricate a novel modified chitosan functional hydrogel using a process-efficient protocol. The fabrication proceeds by a one-pot and single-step C-Mannich condensation of chitosan (3% w/v), glutaraldehyde (20 eq.), and 4-hydroxycoumarin (40 eq.) at 22 °C in 3% v/v acetic acid. The Mannich base modified chitosan hydrogel (CS-MB) exhibits a dual-responsive swelling behavior in response to pH and temperature that has not been observed in any other hydrogel systems. Combining the pre-defined optimal swelling pH (pH = 4) and temperature (T = 22 °C), the CS-MB was screened for its Cu2+ adsorption capacity at this condition. The CS-MB achieved an optimal adsorption capacity of 12.0 mg/g with 1.2 g/L adsorbent dosage after 36 h with agitation. The adsorption of Cu2+ on the surface of CS-MB was verified by EDS, and an overview of the adsorption sites was exhibited by FT-IR. The simply fabricated novel CS-MB hydrogel under investigation presents a unique response to external stimuli that exhibits a promise in heavy metal removal from aqueous media.

Physiological and Ultrastructural Responses to Excessive-Copper-Induced Toxicity in Two Differentially Copper Tolerant Citrus Species

Over-applied copper (Cu)-based agrochemicals are toxic to citrus trees. However, less information is available discussing the ultrastructural alterations in Cu-stressed citrus species. In the present study, seedlings of Citrus sinensis and Citrus grandis that differed in Cu-tolerance were sandy-cultured with nutrient solution containing 0.5 µM Cu (as control) or 300 µM Cu (as Cu toxicity) for 18 weeks. At the end of the treatments, the physiological parameters and ultrastructural features of the citrus leaves and roots were analyzed. The results indicate that Cu toxicity significantly decreased the ratio of shoot biomass to dry weight, the Cu translocation factor and the total chlorophyll of two citrus species. The anatomical and ultrastructural alterations verified that excessive Cu resulted in starch granules accumulated in the leaves and roots of the two citrus species. Under Cu toxicity, increased root flocculent precipitate and thickened root cell wall might reduce the Cu translocation from citrus roots to the shoots. Compared with C. sinensis, C. grandis maintained a relatively integral root cellular structure under Cu toxicity, which provided a structural basis for a higher Cu tolerance than C. sinensis. The present results increase our understanding of the physiological and ultrastructural responses to Cu toxicity in citrus species.

Short and long-term phytoremediation capacity of aquatic plants in Cu-polluted environments

Freshwater ecosystems face numerous threats from human populations, including heavy metal contamination. Phytoremediation, the use of plants to remediate contaminated soils and sediments, is an effective and low-cost means of removing chemical contaminants, including heavy metals, from polluted environments. However, key questions remain unanswered in the application of this technology in aquatic environments, such as the long-term fate of pollutants following plant uptake. In this study, using two common wetland plant species (duckweed and tape grass), we first examined the capacity of plants to remove copper (Cu) from polluted water. Next, we evaluated the leaching potential of plant tissues following decomposition and how it is affected by a simulated freeze-thaw cycle. Using phytoremediated water and leachates from senesced plants we assessed phytoremediation success and Cu leaching potential by conducting standard toxicity assays using pond snails (Physa acuta), a species with known Cu sensitivity. We found that duckweed outperformed tape grass as a phytoremediator at low Cu concentrations. In addition, for plants grown in low concentrations of Cu, leaching from decaying plant material did not negatively impact snail survival, while at high concentrations of Cu, leaching did result in toxicity. Lastly, we found that a simulated freeze-thaw cycle increased the release of Cu from plant tissue in the presence of high Cu concentrations only, resulting in reduced snail survival. Our results indicate that in moderately Cu-polluted environments, some aquatic plants can remove contaminants without a long-term risk of leaching. In contrast, phytoremediation in highly polluted environments will likely require removal of plant tissue to prevent leaching of previously accumulated metals. Land managers must not only consider plant species and degree of contamination, but also geographic location, as freeze-thaw cycles may enhance plant decomposition and increase the likelihood of contaminant leaching following phytoremediation efforts in aquatic ecosystems.

Particelle nanostrutturate di idrossiapatite biomimetica come sistema di delivery di micro e macro elementi nelle colture biologiche

Nanoparticelle biomimetiche di idrossiapatite drogate con ioni metallici (Cu, Fe, Mg, Zn, K) sono state utilizzate in formulazioni contenenti basse concentrazioni di rame (Cu) e zolfo (S) per controllare la peronospora (plasmopara viticola) e l'oidio (erysiphe necator) della vite. I formulati sono stati testati in campo sulla varietà di vino "Dolcetto" coltivata secondo tecniche di agricoltura biologica, e la loro efficacia è stata confrontata con prodotti commerciali contenenti miscela bordolese e zolfo.

I dati indicano che le formulazioni contenenti bassi dosaggi di rame e zolfo possono essere trasportati in modo efficiente dalle nanoparticelle di idrossiapatite biomimetica e possono ridurre la presenza di micota sulle foglie della vite. Nessun residuo di rame e zolfo è stato rilevato in campioni di vino ottenuti da viti in cui è stata utilizzata l'idrossiapatite biomimetica. Il drogaggio di nanoparticelle di idrossiapatite biomimetica con metalli di transizione è un modo efficiente per fornire micro e macro-elementi alle piante a basso livello di dosaggio. Le formulazioni contenenti idrossiapatite funzionano anche come supporti a lento rilascio di macronutrienti come elementi di calcio e fosforo.

Acute Copper Toxicity Displays a Nonmonotonic Relationship with Age Across the Medaka (Oryzias latipes) Life Span

The ability of an organism to cope with environmental stressors varies across the life span because of developmental stage-specific responses and age-related functional declines. In the present study, we examined the effect of age on acute copper toxicity in Japanese medaka (Oryzias latipes). We first determined the median lethal concentration (LC50) at 96 h for embryos, 7-day-old fry, and 6-month-old medaka. Embryos were exposed to 0, 15, 30, 60, 125, 250, and 500 ppb CuSO₄ through hatching. Fry were exposed to 0, 20, 50, 75, 100, 150, 250, and 500 ppb CuSO₄ for 96 h. Adult fish were exposed to 0, 100, 150, 200, 250, and 300 ppb CuSO₄ for 96 h. The 96-h LC50 was 804 ppb for embryos, 262 ppb for embryonically exposed larvae, 60.3 ppb for 7-day-old fry, and 226 ppb for adults. We then challenged cohorts of fish aged 2, 3, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, and 16 months with a 225-ppb CuSO₄ exposure to determine the acute toxicity across the life span. The fish exhibited a bimodal tolerance to copper, with tolerance peaking in 2- and 3-month-old fish and again at 10 and 11 months of age. Our data demonstrate that copper sensitivity is dynamic throughout the medaka life span and may be influenced by trade-offs with reproduction. Environ Toxicol Chem 2022;41:2999-3006. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Effects of Heavy Metal Stress on Physiology, Hydraulics, and Anatomy of Three Desert Plants in the Jinchang Mining Area, China

The physiological mechanisms and phytoremediation effects of three kinds of native quinoa in a desert mining area were studied. We used two different types of local soils (native soil and tailing soil) to analyze the changes in the heavy metal content, leaf physiology, photosynthetic parameters, stem hydraulics, and anatomical characteristics of potted quinoa. The results show that the chlorophyll content, photosynthetic rate, stomatal conductance, and transpiration rate of Kochia scoparia were decreased, but intercellular CO₂ concentration (Ci) was increased under heavy metal stress, and the net photosynthetic rate (Pn) was decreased due to non-stomatal limitation. The gas exchange of Chenopodium glaucum and Atriplex centralasiatica showed a decrease in Pn, stomatal conductance (Gs), and transpiration rate (E) due to stomatal limitation. The three species showed a similar change in heavy metal content; they all showed elevated hydraulic parameters, decreased vessel density, and significantly thickened vessel walls under heavy metal stress. Physiological indicators such as proline content and activity of superoxide dismutase (SOD) and peroxidase (POD) increased, but the content of malondialdehyde (MDA) and glutathione (GSH), as well as catalase (CAT) activity, decreased in these three plants. Therefore, it can be concluded that these three species of quinoa, possibly the most dominant 30 desert plants in the region, showed a good adaptability and accumulation capacity under the pressure of heavy metal stress, and these plants can be good candidates for tailings remediation in the Jinchang desert mining area.

RETRACTED: The adaptive mechanism of halophilic Brachybacterium muris in response to salt stress and its mitigation of copper toxicity in hydroponic plants

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Authors who have indicated that there are significant errors with the scientific data upon which this study is based. Specifically, the authors have subsequently discovered that the 16S rDNA sequencing of Brachybacterium muris may not be reliable because of the limited identification methods from a few years ago. The authors are now repeating their experiments to reconfirm their data. The Authors take full responsibility for these errors and offer their sincere apologies.

Evaluating the Effects of Cu2+ on the Development and Reproduction of Spodoptera litura (Lepidoptera: Noctuidae) Based on the Age-Stage, Two-Sex Life Table

Copper (Cu2+) is a micronutrient that promotes the development and reproduction of organisms. However, with the rapid expansion of modern industry and agriculture, Cu2+ concentrations are increasing, which might have negative impacts on biological and ecological safety. Spodoptera litura is not only an intermittent outbreak pest but also can be used as a model organism to assess environmental and ecological risks. Therefore, the effects of the life history and population parameters of S. litura fed on artificial diets with different Cu2+ concentrations were analyzed using the age-stage, two-sex life table. Our results showed that not only the preadult survival rate but also the intrinsic rate of increase (r) and the finite rate of increase (λ) were significantly increased under exposure to low Cu2+ concentrations (2, 4, and 8 mg/kg). In addition, the population growth of S. litura was significantly faster, indicating that S. litura can adapt well to low concentrations and is likely to undergo outbreaks of damage. Whereas, in addition to a significant reduction in preadult survival rate, population growth rate, pupal weight, pupal length, adult body weight, and oviposition were also significantly reduced under exposure to high Cu2+ concentration (32 mg/kg). And when the concentration reached 64 mg/kg, the survival rate of adults was extremely low, suggesting a decrease in the adaptation of S. litura. These results can help to understand the population dynamics of S. litura and predict potential ecological risks.

Fruit Characteristics of Citrus Trees Grown under Different Soil Cu Levels

The effects of the increased soil copper (Cu) on fruit quality due to the overuse of Cu agents have been a hot social issue. Seven representative citrus orchards in Guangxi province, China, were investigated to explore the fruit quality characteristics under different soil Cu levels and the relationship between soil-tree Cu and fruit quality. These results showed that pericarp color a value, titratable acid (TA), and vitamin C (Vc) were higher by 90.0, 166.6, and 22.4% in high Cu orchards and by 50.5, 204.2, and 55.3% in excess Cu orchards, compared with optimum Cu orchards. However, the ratio of total soluble solids (TSS)/TA was lower by 68.7% in high Cu orchards and by 61.6% in excess Cu orchards. With the increase of soil Cu concentrations, pericarp color a value and Vc were improved, TA with a trend of rising first then falling, and TSS/TA with a trend of falling first then rising were recorded. As fruit Cu increased, pericarp color a value and TSS reduced and as leaf Cu increased, TSS/TA decreased while Vc was improved. Moreover, a rise in soil Cu enhanced leaf Cu accumulation, and a rise in leaf Cu improved fruit Cu accumulation. Fruit Cu accumulation reduced fruit quality by direct effects, leaf Cu improved fruit quality by direct and indirect effects. Soil Cu affected fruit quality by indirect effects by regulating leaf Cu and fruit Cu. Therefore, reasonable regulation and control of soil Cu concentrations can effectively increase pericarp color, sugar, and acid accumulation in citrus fruit.

UV-Cured Chitosan-Based Hydrogels Strengthened by Tannic Acid for the Removal of Copper Ions from Water

In this work, a new environmentally friendly material for the removal of heavy metal ions was developed to enhance the adsorption efficiency of photocurable chitosan-based hydrogels (CHg). The acknowledged affinity of tannic acid (TA) to metal ions was investigated to improve the properties of hydrogels obtained from natural and renewable sources (CHg-TA). The hydrogel preparation was performed via a simple two-step method consisting of the photocrosslinking of methacrylated chitosan and its subsequent swelling in the TA solution. The samples were characterized using ATR-FTIR, SEM, and Folin-Ciocalteu (F&C) assay. Moreover, the mechanical properties and the ζ potential of CHg and CHg-TA were tested. The copper ion was selected as a pollutant model. The adsorption capacity (Qe) of CHg and CHg-TA was assessed as a function of pH. Under acidic conditions, CHg-TA shows a higher Qe than CHg through the coordination of copper ions by TA. At an alkaline pH, the phenols convert into a quinone form, decreasing the Qe of CHg-TA, and the performance of CHg was found to be improved. A partial TA release can occur in the copper solution due to its high hydrophilicity and strong acidic pH conditions. Additionally, the reusability of hydrogels was assessed, and the high number of recycling cycles of CHg-TA was related to its high mechanical performance (compression tests). These findings suggest CHg-TA as a promising green candidate for heavy metal ion removal from acidic wastewater.

Multi-leveled insights into the response of the eelgrass Zostera marina L to Cu than Cd exposure

Seagrass beds are recognized as critical and among the most vulnerable habitats on the planet; seagrass colonize the coastal waters where heavy metal pollution is a serious problem. In this study, the toxic effects of copper and cadmium in the eelgrass Zostera marina L. were observed at the individual, subcellular, physiologically biochemical, and molecular levels. Both Cu and Cd stress significantly inhibited the growth and the maximal quantum yield of photosystem II (Fv/Fm); and high temperature increased the degree of heavy metal damage, while low temperatures inhibited damage. The half-effect concentration (EC₅₀) of eelgrass was 28.9 μM for Cu and 2246.8 μM for Cd, indicating Cu was much more toxic to eelgrass than Cd. The effect of Cu and Cd on photosynthesis was synergistic. After 14 days of enrichment, the concentration of Cu in leaves and roots of Z. marina was 48 and 37 times higher than that in leaf sheath, and 14 and 11 times higher than that in rhizome; and the order of Cd concentration in the organs was root > leaf > rhizome > sheath. Heavy metal uptake mainly occurred in the organelles, and Cd enrichment also occurred to a certain extent in the cytoplasm. Transcriptome results showed that a number of photosynthesis-related KEGG enrichment pathways and GO terms were significantly down-regulated under Cd stress, suggesting that the photosynthetic system of eelgrass was severely damaged at the transcriptome level, which was consistent with the significant inhibition of Fv/Fm and leaf yellowing. Under Cu stress, the genes related to glutathione metabolic pathway were significantly up-regulated, together with the increased autioxidant enzyme activity of GSH-PX. In addition, the results of recovery experiment indicated that the damage caused by short-term Cd and Cu stress under EC₅₀ was reversible. These results provide heavy metal toxic effects at multiple levels and information relating to the heavy metal resistance strategies evolved by Z. marina to absorb and isolate heavy metals, and highlight the phytoremediation potential of this species especially for Cd.

3-Aminopyridine Salicylidene: A Sensitive and Selective Chemosensor for the Detection of Cu(II), Al(III), and Fe(III) with Application to Real Samples

Interest in developing selective and sensitive metal sensors for environmental, biological, and industrial applications is mounting. The goal of this work was to develop a sensitive and selective sensor for certain metal ions in solution. The goal was achieved via (i) preparing the sensor ((E)-2-((pyridine-3-ylimino)methyl)phenol) (3APS) using microwave radiation in a short time and high yield and (ii) performing spectrophotometric titrations for 3APS with several metal ions. 3APS, a Schiff base, was prepared in 5 min and in a high yield (95%) using microwave-assisted synthesis. The compound was characterized by FTIR, XRD, NMR, and elemental analysis. Spectrophotometric titration of 3APS was performed with Al(III), Ba(II), Cd(II), Co(II), Cu(II), Fe(III), Mn(II), Ni(II), and Zn(II). 3APS showed good abilities to detect Al(III) and Fe(III) ions fluorescently and Cu(II) ion colorimetrically. The L/M stoichiometric ratio was 2:1 for Cu(II) and 1:1 for Al(III) and Fe(III). Low detection limits (μg/L) of 324, 20, and 45 were achieved for Cu(II), Al(III), and Fe(III), respectively. The detection of aluminum was also demonstrated in antiperspirant deodorants, test strips, and applications in secret writing. 3APS showed high fluorescent selectivity for Al(III) and Fe(III) and colorimetric selectivity towards Cu(II) with detection limits lower than corresponding safe drinking water guidelines.

Effects of Copper Exposure on Oxidative Stress, Apoptosis, Endoplasmic Reticulum Stress, Autophagy and Immune Response in Different Tissues of Chinese Mitten Crab (Eriocheir sinensis)

High concentrations of copper (Cu²⁺) pose a great threat to aquatic animals. However, the mechanisms underlying the response of crustaceans to Cu²⁺ exposure have not been well studied. Therefore, we investigated the alterations of physiological and molecular parameters in Chinese mitten crab (Eriocheir sinensis) after Cu²⁺ exposure. The crabs were exposed to 0 (control), 0.04, 0.18, and 0.70 mg/L of Cu²⁺ for 5 days, and the hemolymph, hepatopancreas, gills, and muscle were sampled. The results showed that Cu²⁺ exposure decreased the antioxidative capacity and promoted lipid peroxidation in different tissues. Apoptosis was induced by Cu²⁺ exposure, and this activation was associated with the mitochondrial and ERK pathways in the hepatopancreas. ER stress-related genes were upregulated in the hepatopancreas but downregulated in the gills at higher doses of Cu²⁺. Autophagy was considerably influenced by Cu²⁺ exposure, as evidenced by the upregulation of autophagy-related genes in the hepatopancreas and gills. Cu²⁺ exposure also caused an immune response in different tissues, especially the hepatopancreas, where the TLR2-MyD88-NF-κB pathway was initiated to mediate the inflammatory response. Overall, our results suggest that Cu²⁺ exposure induces oxidative stress, ER stress, apoptosis, autophagy, and immune response in E. sinensis, and the toxicity may be implicated following the activation of the ERK, AMPK, and TLR2-MyD88-NF-κB pathways.

Investigating the role of different maize (Zea mays L.) cultivars by studying morpho-physiological attributes in chromium-stressed environment

Because of global land surface warming, heavy metal toxicity is expected to occur more often and more intensely, affecting the growth and development of the major cereal crops such as maize (Zea mays L.) in several ways, thus affecting the production component of food security. Hence, it is important to know the best cultivars of Z. mays in abiotic stress environment to fulfill the market demand of this staple food. For this purpose, we investigate the present study to find the best Z. mays cultivar to be grown in chromium (Cr)-contaminated sand (200 µM). In this experiment, we have studied 10 cultivars (Malka, Sadaf, Pearl, CZP, YY, YH, MMRI-yellow, Sahiwal, EV-20, and EV-77) of Z. mays grown in plastic pots for 4 weeks (in addition with seed germination) under Cr - (0 µM) and Cr + (200 µM) in sand medium. Based on the findings of the current experiment, we illustrated that Cr toxicity induced a significant (P < 0.05) reduction in shoot length, root length, shoot fresh weight, root fresh weight, shoot dry weight and root dry weight, chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid content and induced oxidative damage to membrane-bounded organelles by increasing the malondialdehyde and hydrogen peroxide which were manifested by flavonoid and phenolic contents. Moreover, Cr uptake was also higher in the plants grown in the Cr-contaminated sand compared to the plants grown without the Cr-contaminated sand. We also noticed that Pearl, CZP, and Sahiwal cultivars are suggested to be Cr-tolerant cultivars as showed better growth and development in Cr-contaminated sand while Sadaf, MMRI, and EV-77 showed lower growth and composition in Cr-contaminated sand. The overall pattern of Z. mays cultivars grown in Cr-contaminated sand is as follows: Pearl > CZP > Sahiwal > YY > YH > EV-20 > Malka > EV-77 > MMRI-yellow > Sadaf. Conclusively, it can be identified that when grown in Cr-contaminated sand, Pearl, CZP, and Sahiwal have greater ability to grow in polluted soils. Overall, Z. mays cultivars showed better growth in Cr-stressed environment due to defense mechanism but further experiments needed to be conducted on molecular level.

Identifying contamination of heavy metals in soils of Peruvian Amazon plain: use of multivariate statistical techniques

The Peruvian Amazon plain has abundant natural resources and is home to great biodiversity, which makes it an area with high economic potential. However, the use of its resources through various activities has contributed to the release of heavy metals (HMs) into its soils, generating severe pollution problems which have mainly affected the health of local populations and their ecosystems. Currently, there are no comprehensive studies that have identified the specific sources of contamination by HMs in the soils of this part of the Peruvian territory. In this sense, this research aims to identify the possible sources of contamination by HMs in the soils of the Peruvian Amazon plain to focus efforts on the establishment of adequate measures for the protection of the health of people and the ecosystem. In the present study, samples of topsoils (0-20 cm depth) and subsoils (100-150 cm depth) were collected for the analysis of 11 HMs (Co, Cr, Cu, Fe, Mn, Ni, Pb, V, Zn, Be, and Hg) in 48 sites located in four regions of the Peruvian Amazon plain (Loreto, Amazonas, San Martín, and Ucayali), over the year 2019. The enrichment factor and geoaccumulation index were applied to assess contamination levels of HMs. The results indicated that topsoils and subsoils presented a greater enrichment by the elements Be and Pb, and were classified as moderately contaminated. Likewise, the integral analysis of these indexes together with principal component analysis, hierarchical cluster analysis, correlation analysis, and coefficient of variation allowed the identification of potential sources of contamination by HMs. As a result, Fe, Co, Zn, Ni, V, and Cr were associated with natural or lithogenic sources (parent material, crude oil deposits, and organic matter decomposition). Hg was attributed to anthropogenic sources (illegal gold mining, atmospheric deposition, and vehicle emissions). Be, Pb, Cu, and Mn originated from natural sources (parent material, crude oil deposits, decomposition of organic matter, and forest fires) and anthropogenic (areas degraded by solid waste, illegal gold mining, agriculture, and hydrocarbons). These findings provide essential information to establish regulations and prevent and control HM contamination in soils of the Peruvian Amazon plain.

Impact of Plantago ovata Forsk leaf extract on morpho-physio-biochemical attributes, ions uptake and drought resistance of wheat (Triticum aestivum L.) seedlings

The present study was conducted to examine the potential role of Plantago ovata Forsk leaf extract (POLE) which was applied at various concentration levels (control, hydropriming, 10, 20, 30, and 40% POLE) to the wheat (Triticum aestivum L.) seedlings. Drought stressed was applied at 60% osmotic potential (OM) to the T. aestivum seedlings to study various parameters such as growth and biomass, photosynthetic pigments and gas exchange characteristics, oxidative stress and response of various antioxidants and nutritional status of the plants. Various growth parameters such as gaseous exchange attributes, antioxidants and nutritional status of T. aestivum were investigated in this study. It was evident that drought-stressed condition had induced a negative impact on plant growth, photosynthetic pigment, gaseous exchange attributes, stomatal properties, and ion uptake by different organs (roots and shoots) of T. aestivum. The decrease in plant growth resulted from oxidative stress and overcome by the antioxidant (enzymatic and non-enzymatic) compounds, since their concentration increased in response to dehydration. Seed priming with POLE positively increased plant growth and photosynthesis, by decreasing oxidative stress indicators and increasing activities of antioxidant (enzymatic and non-enzymatic) compounds, compared to the plants which were grown without the application of POLE. Our results also depicted that optimum concentration of POLE for T. aestivum seedlings under drought condition was 20%, while further increase in POLE (30 and 40%) induced a non-significant (P < 0.05) effect on growth (shoot and root length) and biomass (fresh and dry weight) of T. aestivum seedling. Here we concluded that the understanding of the role of seed priming with POLE in the increment of growth profile, photosynthetic measurements and nutritional status introduces new possibilities for their effective use in drought-stressed condition and provides a promising strategy for T. aestivum tolerance against drought-stressed condition.

Multiwalled Carbon Nanotubes Alter the PSII Photochemistry, Photosystem-Related Gene Expressions, and Chloroplastic Antioxidant System in Zea mays under Copper Toxicity

A critical approach against copper (Cu) toxicity is the use of carbon nanomaterials (CNMs). However, the effect of CNMs on Cu toxicity-exposed chloroplasts is not clear. The photosynthetic, genetic, and biochemical effects of multiwalled carbon nanotubes (50-100-250 mg L^-1 CNT) were investigated under Cu stress (50-100 μM CuSO₄) in Zea mays chloroplasts. F_v/F_m and F_v/F_o were suppressed under stress. Stress altered the antioxidant system and the expression of psaA, psaB, psbA, and psbD. The chloroplastic activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione S-transferase (GST), and glutathione peroxidase (GPX) increased under CNT + stress, and those of hydrogen peroxide (H₂O₂) and lipid peroxidation decreased. CNTs were promoted to the maintenance of the redox state by regulating enzyme/non-enzyme activity/contents involved in the AsA-GSH cycle. Furthermore, CNTs inverted the negative effects of Cu by upregulating the transcriptions of photosystem-related genes. However, the high CNT concentration had adverse effects on the antioxidant capacity. CNT has great potential to confer tolerance by reducing Cu-induced damage and protecting the biochemical reactions of photosynthesis.

Copper-Binding Properties of Polyethylenimine-Silica Nanocomposite Particles

Increasing demand for copper resources, accompanied by increasing pollution, has resulted in an urgent need for effective materials for copper binding and extraction. Polyethylenimine (PEI) is one of the strongest copper-chelating agents but is not suitable directly (as is) for most applications due to its high solubility in water. PEI-based composite materials show potential as efficient and practical alternatives. In the present work, the interaction of copper ions with PEI-silica nanocomposite particles and precursor PEI microgels (as a reference) is investigated. It is hypothesized that the main driving force of the reaction is chelation of copper ions by amino groups in the PEI network. The presence of silica in the PEI-silica composites was shown to increase the copper-binding capacity in comparison with the parent microgel. The copper-binding behavior of etched (PEI-free "ghost") composite particles in comparison with the original composites and microgel particles shows that silica nanoparticles in the composite structure increase the number of copper-binding sites in the PEI network rather than adsorbing copper themselves. PEI-silica composites can be easily recycled after copper adsorption by simply washing in 1 M nitric acid, which results in complete copper extraction. Employing this recovery method, PEI-silica composite particles can be used for multiple, efficient cycles of copper removal and extraction.

Auxin regulates growth, photosynthetic efficiency and mitigates copper induced toxicity via modulation of nutrient status, sugar metabolism and antioxidant potential in Brassica juncea

The involvement of auxin (IAA) in growth and development of plants is well known, but its role in the mitigation of metal stress, especially copper (Cu), is not fully understood; therefore, it is time to explore its involvement in minimizing the stress. A pot experiment was conducted to assess the protective function of IAA, applied to the foliage, on photosynthetic machinery, carbohydrate metabolism, and growth of Brassica juncea, grown with Cu (30 or 60 mg kg^-1 of soil). Among the different concentrations (10^-10, 10^-8, or 10^-6 M), 10^-8 M of IAA alone enhanced the photosynthetic characteristics, sugar accumulation and vegetative growth with minimal cellular oxidative stress level. Moreover, the same concentration of auxin was most effective in decreasing the stress levels generated by Cu and maintained it nearly to that of the control in terms of photosynthetic attributes, gas exchange parameters, PSII activity, electron transport rate, and growth attributes. Auxin also maintained the membrane stability and ultrastructure of chloroplast, stomatal morphology with a reduction in malondialdehyde (MDA), electrolyte leakage (EL) and cell death in test plants even under Cu stress. IAA also improved the translocation of Cu from root to the aerial parts, thus enhanced the Cu-reclamation in metal contaminated soils. Our findings suggest that the application of 10^-8 M of IAA maintains the overall growth of plants and may be used as an effective agent to improve growth, photosynthesis and phyto-remediation potential of B. juncea in Cu contaminated soil.

Translocation and chronic effects of microplastics on pea plants (Pisum sativum) in copper-contaminated soil

Microplastics (MPs) released into soil environments, along with the existing pollutants in soil, may have adverse effects on plants. However, the chronic effects of MPs in soils contaminated with heavy metals on crop plants remain unidentified. This study aimed to investigate the chronic effects of MPs (polystyrene, 20 nm) on the reproductive and nutritional status of pea crop plant (Pisum sativum) grown in Cu- (40 mg/kg) and MP-contaminated soils (40, 20 mg/kg). The crop yield reduced in all groups, with an evident decrease in the complex exposure group (comprising MPs and Cu). Moreover, significant changes in plants were identified regarding the weight, color, amino acids, and protein content of peas. Nutrient content in beans increased by MP exposure in single and complex exposure groups. Cu accumulation did not differ in the presence and absence of MPs. Additionally, MPs that infiltrated into incomplete casparian strips during root formation translocated into aerial parts via the apoplast pathway along the cell walls of the vascular bundle. Therefore, long-term exposure to MPs in soil can significantly affect plants while collective application of Cu and MPs imposed severe damage. The changes in the crop quality and nutrient contents may in turn affect human health through the food chain.

Toxic metals that interact with thiol groups and alteration in insect behavior

Toxic metals, such as mercury (Hg), lead (Pb), cadmium (Cd), and copper (Cu), are widespread in the biosphere, and human activities have contributed to their continuous release into the ecosystems. Metal-induced toxicity has been extensively studied in mammals; however, the effects of these metals on insects' behavior have been explored to far lesser degree. As the main mechanism of toxicity, the cationic metals, explored in this review, have high affinity for thiol-containing molecules, disrupting the function of several proteins and low-molecular-weight thiol-containing molecules. Existing literature has corroborated that Hg, Pb, Cd, and Cu can disrupt locomotor and mating behaviors, but their effects on insects' memory and learning have yet to be fully characterized. Though field studies on metal-induced toxicity in insects are limited, results from Drosophila melanogaster as an experimental model suggest that insects living in contaminated environments can have behavioral foraging and reproductive deficits, which may cause population decline. In this review, we address the interaction between metals and endogenous thiol groups, with emphasis on alterations in insect behavior.

Posttranscriptional Regulation by Copper with a New Upstream Open Reading Frame

Copper is essential to most living beings but also highly toxic and as such is an important player at the host-pathogen interface. Bacteria have thus developed homeostatic mechanisms to tightly control its intracellular concentration. Known Cu export and import systems are under transcriptional control, whereas posttranscriptional regulatory mechanisms are yet to be characterized. We identified a three-gene operon, bp2923-bfrG-bp2921, downregulated by copper and notably encoding a TonB-dependent transporter in Bordetella pertussis. We show here that the protein encoded by the first gene, which is a member of the DUF2946 protein family, represents a new type of upstream Open Reading Frame (uORF) involved in posttranscriptional regulation of the downstream genes. In the absence of copper, the entire operon is transcribed and translated. Perception of copper by the nascent bp2923-coded protein via its conserved CXXC motif triggers Rho-dependent transcription termination between the first and second genes by relieving translation arrest on a conserved C-terminal RAPP motif. Homologs of bp2923 are widespread in bacterial genomes, where they head operons predicted to participate in copper homeostasis. This work has thus unveiled a new mode of genetic regulation by a transition metal and identified a regulatory function for a member of an uncharacterized family of bacterial proteins that we have named CruR, for copper-responsive upstream regulator.

Effect of foliar copper application on grain yield, 2-acetyl-1-Pyrroline and copper content in fragrant rice

Literature reporting the effects of application of exogenous copper (Cu) on the grain yield, 2-acetyl-1-pyrroline (2-AP) and Cu content of fragrant rice is scarce. Pot experiments were conducted in early and later season in 2020 with two fragrant rice cultivars, Meixiangzhan and Yuxiangyouzhan, at heading stage using four treatments, i.e.: 0 (CK), 20 (T1), 40 (T2), and 60 mM (T3) CuSO₄·5H₂O to assess the effects of foliar copper application on the yield, 2-AP and Cu content. Results showed that T2 treatment improved the yield of Meixiangzhan and Yuxiangyouzhan by 6.88% and 11.35% respectively, by increased seed-setting rate. Meanwhile, T2 treatment greatly increased the grains 2-AP content by 21.95% and 10.15% in early season, and by 5.40% and 27.25% in later season, respectively, which was significant associated with the contents of proline, pyrroline-5-carboxylic acid (P5C) and pyrroline, and the activities of proline dehydrogenase (PDH), ornithine aminotransferase (OAT) and pyrroline-5-carboxylic acid synthetase (P5CS). Foliar copper application increased the grain Cu content and showed the highest values in T3 treatment. Overall, foliar copper application at heading stage had a positive effect on yield and grain 2-AP and Cu content of fragrant rice. The results from this study show that T2 treatment (moderate CuSO₄ application) had the most desirable outcomes, synergistically improving the yield and aroma of fragrant rice as well as enriching the grain copper content.

Novel high capacity model for copper binary ion exchange on e-waste derived adsorbent resin

Heavy metal water pollution is a global concern in recent years. Copper is a toxic metal at higher concentrations (> 20 μg /g) and needs to be removed using ion exchanger systems. This study investigates the removal efficiencies of copper by the non-metallic fraction (NMF) waste printed circuit boards (PCBs). The high maximum adsorption capacity of copper by the PCB-derived material after activation with KOH was 2.65 mmol/g, and the experimental isotherm was best correlated by the Temkin model. Finally, this study presents a novel dual site adsorption/ion exchange mechanism, wherein the potassium (from the activation) and calcium (present in the structure) served as ion exchange sites for the copper in the solution. Therefore, this recycling study, focusing on cyclic environmental management, converts a major waste material to an activated ion exchange resin (high capacity) for the removal of copper from wastewater solutions and successfully regenerates the resin for re-use while producing an acidic copper solution for recovery by electrolysius or chemical salt precipitation.

Antidote or Trojan horse for submerged macrophytes: Role of microplastics in copper toxicity in aquatic environments

Due to their unique surface structures and physicochemical properties, microplastics (MPs) can adsorb other contaminants, thus impacting their toxicity and fate in aquatic ecosystems. In the present study, the adsorption and transportation of copper ions (Cu²⁺) in polyethylene (PE, 5 and 150 μm) and their combined effects on four submerged macrophyte species were assessed. Results demonstrated that the addition of PE reduced the Cu²⁺ concentration in copper sulfate (CuSO₄) solution and the adsorption of Cu²⁺ in PE (10 mg/L) increased with CuSO₄ concentration (100-600 μmol/L). PE alone exhibited no inhibitory effects on macrophytes, while Cu²⁺ showed fatal toxicity toward the macrophytes. However, the combination of PE and Cu²⁺ showed lower inhibitory effects on macrophytes and the toxicity attenuation varied among species. Additionally, PE may act as a carrier (like a Trojan horse) for the environmental transfer of Cu²⁺, thereby hosting Cu²⁺ toxicity against macrophytes in the imported environment. Our findings indicate that PE acts as both an antidote to and carrier of Cu²⁺ toxicity in macrophytes. This study should help in clarifying the combined effects and risk assessments of MPs and heavy metals in future studies.

Hydrogen sulphide and nitric oxide mitigate the negative impacts of waterlogging stress on wheat (Triticum aestivum L.)

Nitric oxide (NO) and hydrogen sulphide (H₂ S) are important gaseous signalling molecules that regulate key physiochemical mechanisms of plants under environmental stresses. A number of attempts have been made to improve waterlogging tolerance in plants, but with limited success. Having said that, NO and H₂ S are vital signalling molecules, but their role in mitigating waterlogging effects on crop plants is not well established. We investigated the efficacy of exogenous NO and H₂ S to alleviate waterlogging effects in two wheat cultivars (Galaxy-2013 and FSD-2008). Waterlogging produced a noticeable reduction in plant growth, yield, chlorophyll, soluble sugars and free amino acids. Besides, waterlogging induced severe oxidative damage seen as higher cellular TBARS and H₂ O₂ content. Antioxidant enzyme activity increased together with a notable rise in Fe²⁺ and Mn²⁺ content. Proline content was higher in waterlogged plants compared with non-waterlogged plants. In contrast, waterlogging caused a substantial decline in endogenous levels of essential nutrients (K⁺ , Ca²⁺ and Mg²⁺ ). Waterlogged conditions led to Fe²⁺ and Mn²⁺ toxicity due to rapid reduction of Fe³⁺ and Mn³⁺ in the soil. Exogenous NO and H₂ S significantly protected plants from waterlogging effects by enhancing the oxidative defence and regulating nutritional status. Besides, the protective effects of exogenous NO were more prominent as compared with effects of H₂ S. Further, we did not study the effect of H₂ S and NO on photosynthetic attributes and expression of stress-related genes. Therefore, future studies should examine the effects of H₂ S and NO on wheat physiology and gene expression under waterlogging.

Melatonin alleviates copper stress to promote rice seed germination and seedling growth via crosstalk among various defensive response pathways

Copper (Cu) contamination dramatically affects crop growth and thus threatens crop production; while applications of melatonin (MT) serve as an effective way to tolerate Cu stress for plant development, the underlying mechanism remains largely unknown in rice. Here, we found that Cu toxicity remarkably decreased germination rates and seedling growth compared to the untreated control (CK), while seed priming with a solution of 100 μM MT significantly alleviated the adverse effects on Cu-stressed seeds. In addition, the MT treatment decreased the accumulation of Cu in seedlings at 7 days after imbibition (DAI), possibly through enhanced Cu sequestration, and improved reserve mobilization through the promoted activity of α-amylase and protease in seeds under Cu stress. Interestingly, gibberellin (GA) synthesis was restored to or even exceeded the CK levels in the MT presoaking treatment, while the abscisic acid (ABA) content decreased compared to those of the Cu-stressed seeds, suggesting crosstalk between MT and other phytohormones, e.g., GA and ABA. More importantly, MT pretreatment also significantly promoted the growth of postgermination seedlings. This was largely ascribed to the MT-ameliorated antioxidant system, which consequently reduced the accumulation of Cu stress-induced oxidative products, e.g., hydrogen peroxide (H₂O₂), malondialdehyde (MDA), and superoxide (O₂·^_). Collectively, these results demonstrate that seed priming with MT could greatly mitigate the adverse effects of Cu stress on seed germination and subsequent postgermination growth through crosstalk among various defensive response pathways. This study provides vital guidance for applications of MT in agronomic production.

Essential (Cu, Zn) and nonessential (Pb, Cd) metals in the muscle of leopard groupers (Mycteroperca rosacea) from a mining port in the Gulf of California, Mexico: human health risk assessment

Mining activities are a current environmental issue due to heavy metal release and subsequent metal uptake by organisms. In this study, we quantified the concentrations of essential (Cu, Zn) and toxic (Cd, Pb) elements in the muscle of 248 leopard groupers, Mycteroperca rosacea, captured by spearfishing and free diving close to a mining district in the Gulf of California during 2014-2015. We analysed metals using high-resolution inductively coupled plasma source mass spectrometry (HR-ICP-MS). We analysed metal concentrations by fish size, sex, maturity, season, year and risk factor for human consumption. The results indicated common levels of essential elements (Cu: 11 ± 34.3 μg/g, Zn: 377 ± 1390 μg/g) in comparison with toxic elements (Cd: 0.06 ± 0.1 μg/g, Pb: 0.98 ± 1.5 μg/g). Cadmium was within the permissible limit of Mexican standards (0.5 μg/g), but lead content bordered its limit (1.0 μg/g). Heavy metal concentrations were comparable between males and females. Metal variations were not significantly correlated with sex, maturity, season or year (p > 0.05). The evaluation of benefits (daily mineral intake) and risks (target hazard quotients) to health indicated that these fish did not represent a risk of adverse effects to consumers within worldwide limits, while the nutritional benefits were high.

Analysis and Health Risk Assessment of Potentially Toxic Elements in Three Codonopsis Radix Varieties in China

As a valuable medicine food homology plant, Codonopsis Radix has been widely used in China. This study aimed to analyze the content of nine potentially toxic elements in three Codonopsis Radix varieties and evaluate their health risks to the human body. In this study, a total of 147 samples were collected from five provinces in China. The content of nine potentially toxic elements (Al, Mn, Cu, Cr, Ni, As, Pb, Cd, and Hg) were determined by ICP-MS. Results showed that the average contents of Al, Mn, Cu, Cr, Ni, Pb, As, Cd, and Hg were 486.81, 30.30, 5.59, 1.38, 1.24, 0.40, 0.20, 0.16, and 0.11 mg/kg, respectively. The Codonopsis tangshen Oliv. samples from Hubei showed the highest contents of eight elements (Al, Mn, Cr, Ni, Pb, As, Cd, and Hg) among three varieties, and the highest Cu level was found in Codonopsis pilosula (Franch.) Nannf. samples from Shanxi. The content of toxic elements in three Codonopsis Radix varieties showed significant differences (p < 0.05). LDA models facilitated the identification of three Codonopsis Radix varieties with a 91.2% classification score and 89.1% prediction score. Further, when Codonopsis Radix was used as food or medicine, both the hazard quotient values for single element and the hazard index values for nine elements (0.87 for food and 0.84 for medicine) were far below one. The carcinogenic risk values for Pb in Codonopsis Radix when used as food or medicine were 1.14 × 10^-6 and 5.51 × 10^-8; the values for As were 4.80 × 10^-5 and 4.98 × 10^-6, respectively. It indicated that under the current consumption of Codonopsis Radix, the non-carcinogenic and carcinogenic risks from these potentially toxic elements were acceptable for consumers.