Heavy Metal Pollution Research Articles

Fabrication of Hierarchically Porous “Fish Cage”‐like Carbonaceous Nanomaterials via Soft Template‐assisted Strategy for Cr Removal: Accelerated Stepped Adsorption and Enhanced Coordination Effect

The negative impact of heavy metal pollution, specifically chromium (VI), on human health is well‐documented. To solve this issue, hollow anisotropic hierarchically porous “Fish Cage”‐like carbonaceous nanomaterial (N,S‐HFC‐180) with multi‐active groups is synthesized. Hierarchically porous structure provides stepped adsorption effect. The addition of K2C2O4 leads to the specific surface area of N,S‐HFC‐180 increases to 1914.21 m2·g‐1 (an increase of ~552 times compared to HFC‐180). Thiourea introduces multi‐active groups act as “Barbs” in “Fish Cage” further reducing Cr(VI) to Cr(III) and sequestrating Cr(III) by coordination effect. Subsequent batch studies suggest that N,S‐HFC‐180 exhibits a high removal capacity of 164.29 mg·g‐1 for Cr(VI) at pH = 2. The kinetics and isotherm analyses display an outstanding maximum adsorption capacity of 393.88 mg·g‐1 at 298 K. In addition, even after seven cycles, the removal rate of Cr(VI) using N,S‐HFC‐180 remains > 85.00%, and it effectively reduces the concentration of electroplating wastewater from 55.82 to 0.14 mg·L‐1. Pore filling, chemical reduction and chelation, hydrogen bond and electrostatic attraction are the primary adsorption drivers. The results suggest that, the recoverable N,S‐HFC‐180 highlights its viability for practical applications in wastewater treatment processes.

Individual and combinatorial application of nanosilica and carbon nanoparticles alleviate nickel stress in barley (Hordeum vulgare L.): Impacts on gene expression, AsA − GSH cycle, cellular fractionation, and proline metabolism

Nanotechnology is grabbing great attention all over the world because of its stimulating use in numerous fields, and the nanosilica (nSi) and carbon nanoparticles (CNPs) application has been examined in various studies. Conversely, the nSi and CNPs combinatorial use is a new method and researched in limited literature. For this purpose, a pot experiment was conducted to examine various growth and biochemical parameters in barley (Hordeum vulgare L.) under the toxic concentration of nickel (Ni) i.e., 200 mg kg−1 which were primed with combined application of two NPs of nSi at 3 mM and CNPs i.e., 200 μM respectively. The results showed that the Ni toxicity in the soil showed a significantly (P < 0.05) declined in the growth, gas exchange attributes, sugars, AsA-GSH cycle, cellular fractionation, proline metabolism in H. vulgare. However, Ni toxicity significantly (P < 0.05) increased oxidative stress biomarkers, enzymatic and nonenzymatic antioxidants including their gene expression in H. vulgare. Although, the application of nSi and CNPs showed a significant (P < 0.05) increase in the plant growth and biomass, gas exchange characteristics, enzymatic and non-enzymatic compounds and their gene expression and also decreased the oxidative stress, and Ni uptake. In addition, individual or combined application of nSi and CNPs enhanced the cellular fractionation and decreases the proline metabolism and AsA−GSH cycle in H. vulgare. These results open new insights for sustainable agriculture practices and hold immense promise in addressing the pressing challenges of heavy metal contamination in agricultural soils.

An intelligent device with double fluorescent carbon dots based on smartphone for visual and point-of-care testing of Copper(II) in water and food samples

The excessive presence of Cu2+ could be harmful to human health. Therefore, a ratiometric fluorescence sensor based on multicolor fluorescent carbon dots (CDs) was developed for Cu2+ detection. The blue and yellow carbon dots (B-CDs/Y-CDs) were synthesized by one-step hydrothermal method. After adding Cu2+, it is captured by the amino groups of B-CDs to form complexes, resulting in a strong fluorescence quenching via photoinduced electron transfer (PET). Meanwhile, the amino groups from Y-CDs also binds with Cu2+ that inhibit the internal PET thus enhancing the fluorescence of Y-CDs. The sensor has the merits in rapid, visual, and selective with a low limit of detection (LOD) at 2.29 nM. Furthermore, an intelligent device composed of portable optical detector and smartphone is constructed, which realizes the visual point-of-care testing (POCT) of Cu2+ with a LOD of 7.51 nM. The strategy provides an accessible approach for monitoring heavy metal pollution and food safety.

Let the dust settle: Impact of enhanced rock weathering on soil biological, physical, and geochemical fertility

Terrestrial enhanced rock weathering (ERW) is a promising carbon dioxide removal technology that consists in applying ground silicate rock such as basalt on agricultural soils. On top of carbon sequestration, ERW has the potential to raise the soil pH and release nutrients, thereby improving soil fertility. Despite these possible co-benefits, concerns such as heavy metal pollution or soil structure damage have also been raised. To our knowledge, these contrasted potential effects of ERW on soil fertility have not yet been simultaneously investigated. This field trial aimed at assessing the impact of ERW on biological, physical, and chemical soil properties in a temperate agricultural context. To do so, three vineyard fields in Switzerland were selected for their distinct geochemical properties and were amended with basaltic rock powder at a dose of 20 tons per hectare (2 kg.m−2). On each field, basaltic rock powder was either applied one year before the sampling campaign, one month before the sampling campaign, or not applied (control) for a total of 27 plots with 9 repetitions of each level. Overall, basaltic rock powder addition had a predominantly positive to neutral effect on soil fertility. Most soil properties showed no significant change either 1 month or 1 year post application. Nevertheless, our study highlighted a significant increase in earthworm abundance (+71 % on average), soil respiration (+50 %) and extractable sodium concentration (+23 %) as early as 1 month post application. The higher soil respiration raises the question of CO2 losses from organic matter mineralization that could limit ERW's efficiency. The increase in sodium raises concerns about a sodification risk potentially damaging soil fertility. These elements now require further investigation before enhanced rock weathering can be considered a viable and secure carbon dioxide removal technology.

Detection and assessment of heavy metals concentration in wheat leaves collected from the vicinity of Sahiwal coal power plant, Pakistan, employing a modern data analysis approach

ABSTRACT Heavy metal pollution in food crops has become a global issue, especially in staple crops like wheat and rice. Electricity production utilising coal, ignites this issue in crops grown in the surrounding areas of coal power plants. Keeping this view in mind, the concentration of six heavy metals (HMs) Calcium (Ca), Cadmium (Cd), Chromium (Cr), Cobalt (Co), Lead (Pb) and Magnesium (Mg) in wheat leaves have been assessed in this study. Fifty samples of wheat leaves have been collected from the surrounding areas of the coal power plant in Sahiwal. The samples were prepared using the wet digestion method (WDM). Finally, these samples have been sent for analysis via atomic absorption spectroscopy (AAS). The limit of detection (LOD) and limit of Quantification (LOQ) of AAS were calculated with the help of blank samples. The concentration of Ca, Cd, Cr, Co, Pb and Mg in wheat leaves were 1.0187 ± 0.549 mg/kg, 0.00484 ± 0.00403 mg/kg 00,416 ± 0.00334 mg/kg, 0.0534 ± 0.0351 mg/kg, 0.035 ± 0.018 mg/kg, 0.464 ± 0.200 mg/kg respectively. The concentration of all understudy metals was below the Food and Agriculture Organization/World Health Organization (WHO/FAO) standards except for Co, in one sample. However, the concentration of heavy metals may increase, which may have profound repercussions. Therefore, preventive measures should be taken in this regard. The neutrosophic approach has been utilised to examine the variation of the heavy metals content in wheat leaves. This study provides a solid scientific foundation for future appropriate actions and management of heavy metals contamination in food crops near coal-fired power stations.

Insight into biochar as sustainable biomass: Production methods, characteristics, and environmental remediation

Industrialization has contributed significantly to the advancement and sustenance of human civilization. However, it has also posed serious challenges to environmental sustainability, notably through heavy metal pollution, which has severely impacted ecological systems. Recent studies have explored the use of biochar for the removal of heavy metals from aqueous solutions. This review underscores the diverse physicochemical and structural characteristics of biochar, derived from various biomass sources through different pyrolysis processes, and their varying adsorption efficiencies. The review aims to investigate current biochar production technologies, their unique properties, and their maximum removal efficiency and adsorption capacity for heavy metals. The primary adsorption mechanisms, adsorption isotherms, and kinetic models have been identified. Furthermore, the study confirms that optimal conditions—such as the choice of precursors, pyrolysis temperature, and an understanding of the advantages and limitations—are crucial for designing biochar with superior structural and physicochemical properties. This review provides an updated overview of biochar-based heavy metal treatment in aquatic systems, highlighting existing research gaps and suggesting future research directions.

One-Step-Modified Biochar by Natural Anatase for Eco-Friendly Cr (VI) Removal

The global serious pollution situation urgently needs green, efficient, and sustainable development methods to achieve heavy metal pollution control. The photocatalytic properties of anatase are sufficient to achieve pollution control by providing photoelectrons to harmful heavy metals. However, since natural anatase particles tend to agglomerate and deactivate in water, most studies have been conducted to prepare TiO2–biochar nanocomposites using chemical synthesis methods. In the present study, we utilized pyrolytic sintering to load natural anatase onto biochar to obtain natural anatase–biochar (TBC) composites. Characterization tests, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), showed that anatase was uniformly partitioned into the surface and pores of biochar without destroying the lattice structure. Due to its photocatalytic properties, TBC degraded Cr (VI) by 99.63% under light conditions. This is 1.58 times higher than the dark condition. Zeta potential showed that the surface of the TBC was positively charged under acidic conditions. The charge attraction between TBC and chromium salt was involved in the efficient degradation of Cr (VI). Different sacrificial agents as well as gas purge experiments demonstrated that photoelectrons (e−) and superoxide radicals (O2−) dominated the degradation of Cr (VI). TBC has the characteristics of high efficiency, stability, and sustainability. This may provide a new idea for the preparation of photocatalytic materials and the realization of environmental protection and sustainable development through heavy metal pollution control.

Recycled Jute Non-Woven Material Coated with Polyaniline/TiO2 Nanocomposite for Removal of Heavy Metal Ions from Water.

Growing volumes of textile waste and heavy metal pollution of water are emerging environmental challenges. In an attempt to tackle these issues, a non-woven sorbent based on jute fibers was fabricated by recycling the textile waste from the carpet industry. The influence of contact time, concentration, pH and temperature on the sorption of lead and copper ions from aqueous solutions was studied. In order to enhance the sorption capacity of the non-woven material, in situ synthesis of polyaniline (PANI) in the presence of TiO2 nanostructures was performed. The contribution of TiO2 nanoparticles and TiO2 nanotubes to the uniformity of PANI coating and overall sorption behavior was compared. Electrokinetic measurements indicated increased swelling of modified fibers. FTIR and Raman spectroscopy revealed the formation of the emeraldine base form of PANI. FESEM confirmed the creation of the uniform nanocomposite coating over jute fibers. The modification with PANI/TiO2 nanocomposite resulted in a more than 3-fold greater sorption capacity of the material for lead ions, and a 2-fold greater absorption capacity for copper ions independently of applied TiO2 nanostructure. The participation of both TiO2 nanostructures in PANI synthesis resulted in excellent cover of jute fibers, but the form of TiO2 had a negligible effect on metal ion uptake.

BioMOF@PAN Mixed Matrix Membranes as Fast and Efficient Adsorbing Materials for Multiple Heavy Metals' Removal.

Heavy metal ions are a common source of water pollution. In this study, two novel membranes with biobased metal-organic frameworks (BioMOFs) embedded in a polyacrylonitrile matrix with tailored porosity were prepared via nonsolvent induced phase separation methods and designed to efficiently adsorb heavy metal ions from oligomineral water. Under optimized preparation conditions, stable membranes with high MOF loading up to 50 wt % and a cocontinuous sponge-like morphology and a high water permeability of 50-60 L m-2 h-1 bar-1 were obtained. The tortuous flow path in combination with a low water flow rate guarantees maximum contact time between the fluid and the MOFs, and thus a high heavy metal capture efficiency in a single pass. The performances of these BioMOF@PAN membranes were investigated in the dynamic regime for the simultaneous removal of Pb2+, Cd2+, and Hg2+ heavy metals from aqueous environments in the presence of common interfering ions. The new composite adsorbing membranes are capable of reducing the concentration of heavy metal pollutants in a single pass and at much higher efficiency than previously reported membranes. The enhanced performance of the mixed matrix membranes is attributed to the presence of multiple recognition sites which densely decorate the BioMOF channels: (i) the thioether groups, deriving from the S-methyl-l-cysteine and (S)-methionine amino acid residues, able to recognize and capture Pb2+ and Hg2+ ions and (ii) the oxygen atoms of the oxamate moieties, which preferentially interact with Cd2+ ions, as revealed by single crystal X-ray diffraction. The flexibility of the pore environments allows these sites to work synergically for the simultaneous capture of different metal ions. The stability of the membranes for a potential regeneration process, a key-factor for the effective feasibility of the process in real life applications, was also evaluated and confirmed less than 1% capacity loss in each cycle.

Responses of Brassica napus to soil cadmium under elevated CO2 concentration based on rhizosphere microbiome, root transcriptome and metabolome

Rising atmospheric carbon dioxide (CO2) and soil heavy metal pollution affect crop safety and production. Exposure to elevated CO2 (ECO2) increases cadmium (Cd) uptake in some crops like wheat and rice, however, it remains unclear how ECO2 affects Cd uptake by Brassica napus. Here, we investigated the responses of B. napus seedlings exposed to ECO2 and Cd through analyses of physiology, transcriptome, metabolome, and rhizosphere microbes. Compared with Cd-stress alone (Cd50_ACO2), ECO2 boosted the uptake of Cd by B. napus roots by 38.78% under coupled stresses (Cd50_ECO2). The biomass and leaf chlorophyll a content increased by 38.49% and 79.66% respectively in Cd50_ECO2 relative to Cd50_ACO2. Activities of superoxide dismutase (SOD) and peroxidase (POD) enhanced by 8.42% and 185.01%, respectively, while glutathione (GSH) and ascorbic acid (AsA) contents increased by 16.44% and 52.48%, and abundances of rhizosphere microbes changed significantly under coupled stresses (Cd50_ECO2) relative to Cd-stress alone (Cd50_ACO2). Also, the upregulation of glutathione, glutathione transferase genes, and heavy metal ATPase expression promoted the detoxification effect of rapeseed on Cd. Changes in the expression of transcription factors like MAPK, WRKY, BAK1 and PR1, as well as changes in metabolic pathways like β-alanine, may be involved in the regulatory mechanism of stress response. These findings provide new insights for studying the regulatory mechanism of rapeseed under ECO2 on soil Cd stress, and also provide a basis for further research on Cd tolerant rapeseed varieties in the future climate context.

Distribution and ecological health risk assessment of heavy metals in damietta branch of Nile River, Egypt

ABSTRACT The Nile River is one of the longest rivers in the world, serving as the lifeline of many countries. The river is subjected to significant anthropogenic pressures, and thus, understanding the magnitude of contamination and its possible consequences is needed. This research aimed to evaluate the presence of heavy metals in the surface water of an understudied region within the Nile River. The distribution and level of 18 elements along the Damietta branch were assessed, and their potential sources were estimated. Additionally, pollution indices and health risks were calculated. The results showed that most metals were within the acceptable levels of USEPA and WHO. However, Na, Mg, and Ca were higher than the permissible level of WHO, and K was higher than the permissible levels for irrigation. Furthermore, heavy metal pollution indicators, degree of contamination indices, heavy metal evaluation indices, Nemerow pollution indices, and water quality indices all pointed to very high standards for water quality. Also, the noncarcinogenic health risk index indicated a safe limit for dermal and oral exposure for adults and children. Overall, this study recommends management focus on anthropogenic activities in the Damietta branch of the Nile River.

Facing Heavy Metal Stress, What Are the Positive Responses of Melatonin in Plants: A Review

With the growth of the population and the development of modern industry and the economy, the problem of heavy metal pollution in cultivated soil has become increasingly prominent. Moreover, heavy metal poses a serious threat to plant growth due to its characteristics of difficult degradation, high mobility, easy enrichment, and potential toxicity and has become a social topic. Melatonin is a new type of plant hormone widely present in animals, plants, fungi, and bacteria, and its biological role has begun investigated in the last dozen years. Facing heavy metal stress, melatonin can play a pleiotropic role in the physiological processes of plants, such as stress resistance and growth regulation, mitigate the damage caused by stress on plants, and provide a new research idea for alleviating heavy metal stress in plants. From the aspects of the plant phenotype, physiology, element absorption, and molecular structure, this paper, therefore, mainly reviews the effects of melatonin on plants subjected to heavy metal stress and the mechanism of melatonin alleviating heavy metal stress and then puts forward future research directions. This information may be of great significance to the normal growth of crops under heavy metal stress and will provide an important theoretical basis for the genetic improvement of crop resistance in the future.

Ferrous-driven efficient removal of nitrate and various heavy metals by Zoogloea sp. ZP7 under oligotrophic conditions: Kinetics and heavy metal stress responses

Denitrification in surface water is affected by its oligotrophic characteristics and heavy metal pollution. In this study, a heterotrophic denitrifying bacterium Zoogloea resiniphila ZP7, which can utilize ferrous (Fe2+) as an additional electron donor under oligotrophic conditions, was isolated. Strain ZP7 achieved a 98.5 % nitrate (NO3−-N) removal efficiency (NRE) within 12 h using sodium acetate as carbon sources, with a Fe2+ concentration of 10.0 mg L−1, pH of 7.0, carbon to nitrogen ratio of 2.0, and NO3−-N concentration of 5.01 mg L−1, and no nitrite residue was observed. The denitrification performance and the removing ability of heavy metal by strain ZP7 were studied when exposed to copper (Cu2+), zinc (Zn2+), and cadmium (Cd2+) alone or in combination. When 1.0 mg L−1 Cu2+, Zn2+, and Cd2+ were added simultaneously, the strain ZP7 could achieve 91.3 % NRE in 14 h, and the removal efficiencies of Cu2+, Zn2+, and Cd2+ were 68.1, 89.2, and 83.5 %, respectively. The results of fluorescence region integration showed that the response of strain ZP7 to different heavy metal system stresses was different. Moreover, the changes in the content of extracellular polymeric substances (EPS) and humic acids indicated that they contributed to the enhancement of the resistance of strain ZP7 to heavy metals. Various characterization results showed that EPS and bio‑iron oxides were beneficial to remove heavy metals. In future studies, strain ZP7 can be considered to be immobilized in biomaterials to treat contaminated oligotrophic water bodies to explore its application prospects in actual contaminated water bodies.

Root exudate–assisted phytoremediation of copper and lead contamination using Rumex acetosa L. and Rumex K-1

Heavy metal pollutants can be effectively removed from soil through phytoremediation using root exudates. Herein, experiments were conducted to assess the phytoremediation capabilities of Rumex acetosa L. and Rumex K-1 root exudates for copper (Cu) and lead (Pb) contamination. Results indicated that these root exudates effectively adsorbed Cu and Pb. Furthermore, the optimal adsorption conditions of Cu by the root exudates of both plants were as follows: light duration of 36 h, light intensity of 8000 Lx, temperature of 25 °C and CO(NH2)2 concentration of 0 %. Moreover, the optimal adsorption conditions of Pb by Rumex acetosa L. and Rumex K-1 root exudates were light duration of 48 h and 24 h, respectively, light intensity of 8000 Lx, temperature of 25 °C and CO(NH2)2 concentration of 0 %. In addition, the root exudates from both plants enhanced the enrichment and transport of Cu and Pb. Moreover, the root was found to be the main accumulation site of Pb, while the stems and leaves were the main accumulation sites of Cu. With the application of root exudates, plant growth increased, with growth indices in Rumex acetosa L. and Rumex K-1 groups treated with exudates being 1.08–1.81-fold and 1.06–1.9-fold higher, respectively, compared with the untreated ones; physiological indexes showed 1.14–2.62-fold and 1.14–2.71-fold improvements, respectively. Remediation efficiency indexes showed 1.05–1.62-fold and 1.10–1.89-fold improvements, respectively. Rumex acetosa L. and Rumex K-1 exhibited promising potential for the phytoremediation of Cu and Pb, with root exudates playing a critical role in metal adsorption and stabilisation, suggesting their potential for enhancing remediation capabilities. This study sheds light on the mechanisms of root exudate–assisted phytoremediation and provides insights into alleviating heavy metal pollution.

Interplay of heavy metal accumulation, physiological responses, and microbiome dynamics in lichens: insights and future directions.

Lichens are increasingly recognised as valuable bioindicators for environmental heavy metal pollution due to their sensitivity to spatial and temporal variations in pollution levels and their ability to adapt to diverse and often harsh habitats. This review initially examines the mechanisms of metal absorption in lichens, including particulate entrapment, ion exchange, and intracellular absorption, as well as their physiological responses to abiotic stressors such as heavy metal exposure and desiccation. In the latter part, we compile and synthesise evidence showing that secondary metabolites in lichens are significantly influenced by metal concentrations, with varying impacts across different species. Although extensive research has addressed the broader physiological effects of heavy metal hyperaccumulation in lichens, there remains a significant gap in understanding the direct or indirect influences of heavy metals on the lichen microbiome, possibly mediated by changes in secondary metabolite production. Our review integrates these aspects to propose new research directions aimed at elucidating the mechanisms underlying physiological responses such as resilience and adaptability in lichens. Overall, this review highlights the dynamic interplay between microbiome composition, secondary metabolite variation, and metal accumulation, suggesting that these factors collectively contribute to the physiological responses of lichens in polluted environments.

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.

The environmental capacity of rare heavy metal calculation in the Qinghai‒Tibet Plateau region via multifractal analysis.

Accurate assessments of the soil environmental capacity are important for evaluating heavy metal pollution levels, facilitating effective prevention and control measures against such pollution. However, due to the lack of risk screening values for certain key elements, such as Rb, Sn, and Th, the assessment of the soil environmental capacity is not comprehensive. Therefore, in this study, the Menyuan-Huangzhong area of Qinghai Province was selected as the research area, and local background and risk values were established via multifractal analysis, thereby systematically examining the environmental capacity. The findings indicated that within the study area, the static environmental capacity values of 15 elements could be ranked as follows: Ba, Cu, Zn, Cr, Rb, Ni, La, Pb, Th, As, U, Sn, Tl, Cd, and Hg. In general, the residual capacity distribution of the various elements varied across the study area, with lower values primarily found in the northern and central regions and higher values obtained in the northwestern and southwestern regions. Between 2018 and 2068, there was a notable and rapid decline in the dynamic environmental capacity of Hg, Cu, and Cd in the study area. In the Menyuan-Huangzhong area of Qinghai, the average comprehensive soil environmental capacity index reached 0.91, indicating a moderate environmental capacity and slight associated health risks. The findings of this study could serve as a valuable reference for soil heavy metal pollution assessment, early warning, and management in this area; enhance the study of soil environmental capacity methods; and provide a theoretical foundation for subsequent research.

Impact of Plant Growth-Promoting Rhizobacteria on Spinach Growth Concerned with Industrial Effluents Contaminated with Chromium

Heavy metal pollution in soil poses a significant threat to the environment and human health as it accumulates throughout the food chain. Remediation of soil contamination involves biological, chemical, and physical methods. Plant growth-promoting rhizobacteria inoculation helps some plants stabilize heavy metals in polluted soil by forming chelates with the metals. An experiment was conducted to examine the impact of Plant growth-promoting rhizobacteria on spinach growth and heavy metal stability in polluted soil with industrial effluents. The study found that Plant growth-promoting rhizobacteria (S1 and S2) enhanced growth and yield parameters, with fresh weights reaching 18% and 14%, highest dry weights at 10% and 40%, and longest roots at 11%. The treatment with Plant growth-promoting rhizobacteria S1 recorded the highest SPAD values (27%). Chemical parameters revealed that Cr levels in roots peaked in treatments without PGPR. The results concluded that PGPR can effectively remediate heavy metal-contaminated soils and industrial effluent-irrigated soils used for food crop growth.

Performance-complementary colorimetric/electrochemical bimodal detection of Hg2+ based on analyte-accelerated peroxidase-mimicking activity of GO-AuNPs

As a highly toxic heavy metal pollutant, mercury ions cause substantial risks to the environment and human health, and developing high-performance and convenient analytical approaches becomes quite important. Here we propose a performance-complementary colorimetric/electrochemical dual-mode Hg2+ sensing method based on the analyte accelerating the peroxidase-mimetic activity of gold nanoparticles (AuNPs) loaded on graphene oxide (GO). The GO-AuNPs composite was readily fabricated via mechanically mixing AuNPs and GO with controllable proportions, exhibiting a weak peroxidase-like activity in catalyzing the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB). Upon the introduction of Hg2+, it combined with AuNPs rapidly, significantly enhancing the peroxidase-mimicking activity of GO-AuNPs. By capturing the color signal of the generated blue oxTMB and the electro-oxidation response of residual TMB, a “turn-on” colorimetric and “turn-off” electrochemical bimodal method was established for Hg2+ measurement, providing a linear range of 10–60 μg/L in colorimetric detection and 0.001–20 μg/L in electrochemical analysis. Different from common bimodal assays mainly improving detecting reliability due to their cross-validation ability, our dual-mode sensor exhibits the unique feature of complementary sensitivity and detection range, thus enabling its flexible use in analyzing different levels of the target in a broad scope with no requirement for sample enrichment and dilution.

Macrophytes as Bioindicators of Heavy Metal Pollution in Belarusian Rivers

ABSTRACTMacrophytes are well‐known for accumulating a large number of various substances, including metals, and they may consequently serve as biogeochemical indicators of aquatic system pollution. In general, the sequence of analyzed metal accumulation in river macrophytes is as follows (mg/kg): Mn (141) &gt; Cu (2.53) &gt; V (0.89) &gt; Cr (0.70) &gt; Pb (0.68) &gt; Ni (0.23). Submersed species are conspicuous for their increased metal accumulation capacity, with statistically significant differences compared to other ecological groups. Among the aquatic plant genera examined (Potamogéton, Ceratophýllum, Elodea, Núphar, Butomus, Glycéria, and Spargánium), an increased capacity to accumulate Mn, Cu, and Pb is observed in all submersed macrophytes, while Cr, V, and Ni are particularly accumulated by Ceratophýllum and Elodea. Potamogéton has the largest range of V, Cr, Mn, Ni, and Cu variations. The overall bioaccumulation capability evaluated by the metal accumulation index was ordered as follows: Núphar (6.94) &gt; Potamogéton (5.53) &gt; Butomus (3.48) &gt; Glycéria (2.86) &gt; Spargánium (2.62) &gt; Elodea (2.33) &gt; Ceratophýllum (1.98). Bio‐accumulation factors (BAFs) (macrophytes/sediment) vary depending on the metal and macrophyte ecological groups. For submersed macrophytes, the sequence of BAFs is Mn &gt; Cu &gt; Ni &gt; Pb &gt; Cr &gt; V. In the submersed plants of watercourses taken at the anthropogenic impact sites, the accumulation of Ni, V, Mn, Pb, and Cu is statistically significantly higher compared to those in natural conditions. Compositional data analysis has revealed such biogeochemical signatures of the anthropogenic impact as the formation of the anthropogenic Cr–Ni association, which is associated with the identified multivariate anomalies, as well as an increase in Cu variability and a decrease in Mn.