Search Results (528)

The spatiotemporal regulatory mechanism underlying silicon (Si)-mediated cadmium (Cd) detoxification in rice (Oryza sativa L.) was investigated using non-invasive micro-test technology (NMT), combined with physiological and biochemical analyses. The results revealed the following: (1) Si significantly inhibited Cd²⁺ influx into rice roots, with the most pronounced reductions in ion flux observed under moderate Cd stress (Cd50, 50 μmol·L⁻¹), reaching 35.57% at 7 days and 42.30% at 14 days. Cd accumulation in roots decreased by 34.03%, more substantially than the 28.27% reduction observed in leaves. (2) Si application enhanced photosynthetic performance, as evidenced by a 14.21% increase in net photosynthetic rate (Pn), a 32.14% increase in stomatal conductance (Gs), and a marked restoration of Rubisco activity. (3) Si mitigated oxidative damage, with malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) levels reduced by 11.29–21.88%, through the upregulation of antioxidant enzyme activities (SOD, APX, CAT increased by 15.34–38.33%) and glutathione metabolism (GST activity and GSH content increased by 60.78% and 51.35%, respectively). (4) The mitigation effects of Si were found to be spatiotemporally specific, with stronger responses under Cd50 than Cd100 (100 μmol·L⁻¹), at 7 days (d) compared to 14 d, and in roots relative to leaves. Our study reveals a coordinated mechanism by which Si modulates Cd uptake, enhances photosynthetic capacity, and strengthens antioxidant defenses to alleviate Cd toxicity in rice. These findings provide a scientific basis for the application of Si in mitigating heavy metal stress in agricultural systems. Full article

This work employed peach stones as the precursor material for producing activated carbon (AC-PS). AC-PS was impregnated with H₃PO₄ and carbonized using a pyrolysis reactor under a reducing atmosphere. The surface area, average pore size, and total pore volume of AC-PS were determined using the BET method. Morphological characteristics of AC-PS were observed through scanning electron microscopy (SEM), the surface composition was identified by energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analyses were conducted to determine the crystalline structure of carbon. The thermal stability of AC-PS and its interactions with lead and cadmium were analyzed by thermogravimetric analyses (TGA/DTG) and infrared spectra (FTIR), respectively. The Elovich model described the adsorption kinetics of both lead and cadmium, and the Weber and Morris model indicated intraparticle diffusion as the controlling mechanism of the adsorption process. The equilibrium study showed that the Freundlich model was adequate for both ions, with adsorption capacities increasing with temperature, reaching around 150 mg g⁻¹ for lead and 80 mg g⁻¹ for cadmium at 45 °C. Economic analysis indicated costs of $0.25 g⁻¹ and $0.51 g⁻¹ for the removal of lead and cadmium from the contaminated water, respectively. Full article

Beyond sensing bitter-tasting compounds, bitter taste receptors (TAS2Rs) have been demonstrated to play a functional role in proton secretion as a key mechanism of gastric acid secretion (GAS) and the cellular uptake of the zinc metal ion. Given its chemical similarity and comparable effects in GAS, we focused this work on cadmium and hypothesized that gastric TAS2Rs are involved in (i) cadmium-induced inhibition of proton secretion and (ii) in its cellular uptake. To test this hypothesis, immortalized human parietal HGT-1 cells were exposed to 62.5–1000 µM CdCl₂ for 30 min to elucidate TAS2R-mediated proton secretory activity (PSA) using a fluorescence-based pH cell assay and to quantitate cellular cadmium uptake by ICP-MS. HGT-1 cells exposed to CdCl₂ exhibited a dose-dependent decrease in PSA, accompanied by a corresponding increase in intracellular cadmium concentrations. Following a TAS2R RT-qPCR screening, the functional roles of TAS2R8 and TAS2R10 were clarified using a siRNA knockdown approach, demonstrating that TAS2R8 promotes and TAS2R10 mediates protection against excessive cellular cadmium accumulation. An additional cDNA microarray screening revealed, via gene ontology analysis, a distinct gene association of TAS2R8 and TAS2R10 with several metal ion transporters. These results provide the first evidence for a specific role of individual TAS2Rs beyond taste perception, particularly in metal ion homeostasis and gastric physiology. Full article

Cadmium (Cd) contamination poses significant threats to aquatic ecosystems. Heavy metal-associated isoprenylated plant proteins (HIPPs) are plant-specific chaperones involved in metal ion homeostasis and stress adaptation. Lotus is an aquatic plant with high biomass and Cd accumulation capacity, showing great potential in water remediation. However, the functional characterization of HIPPs in lotus remains unexplored, limiting its application in phytoremediation. We conducted comprehensive characterization of NnHIPP genes in lotus, integrating comparative genomics, Cd-stress transcriptomics, and heterologous expression assays in transgenic yeast. This study identified 33 NnHIPP genes classified into five subfamilies with conserved motifs and structures. Synteny analysis revealed closer evolutionary relationships with dicots (Arabidopsis and Medicago sativa) than monocots. Abundant stress-responsive elements were found in NnHIPPs promoters. Tissue-specific expression profilings indicated functional diversification across organs and developmental stages. Our transcriptome analysis revealed that most NnHIPPs responded to Cd stress, with stronger induction in roots than leaves. Four Cd-induced NnHIPPs (NnHIPP10/14/21/33) showed both plasma membrane and nuclear localization. Notably, NnHIPP14, NnHIPP21, and NnHIPP33 conferred varying degrees of Cd tolerance when overexpressed in yeast. Our study demonstrates that NnHIPPs participate in Cd stress response. Three candidate NnHIPP genes are proposed for genetic engineering to enhance phytoremediation efficiency in lotus. Full article

Cadmium (Cd) pollution in rice crops is a global environmental challenge, endangering food security and sustainable agricultural development. Cd ions are highly dynamic and toxic and can easily accumulate in rice grains, resulting in adverse consequences on human health and ecological safety. With accelerated industrialization and abundant agricultural activities, Cd enters paddy soils through multiple pathways, leading to increasingly complex processes of migration and transformation of Cd in the soil–rice ecosystem. Although recent studies have substantially advanced our comprehension of the pathways promoting the uptake, transport, and accumulation of Cd in rice, this information is scattered and lacks systematic integration, leading to an incomplete understanding of the entire contamination process. This review adopts a rigorous perspective spanning from soil input to grain accumulation and comprehensively summarizes the absorption pathways, translocation mechanisms, and remediation strategies for Cd pollution in rice. The effects of phytotoxicity induced by Cd on rice growth are thoroughly analyzed, and recent advances in various mitigation strategies are highlighted, including agronomic management, cultivar improvement, bioremediation, and signal regulation. By integrating the findings of latest research, this review (i) proposes a mechanistic network of Cd contamination occurrence and control in rice; (ii) elucidates critical regulatory nodes; and (iii) offers a theoretical framework for growing rice cultivars with a low Cd content, remediating Cd-contaminated farmlands, and ensuring food safety. Full article

Heavy metal pollution is becoming increasingly severe, and cadmium (Cd) is one of the most threatening pollutants. The PCR (Plant cadmium resistance) gene encodes a class of small transmembrane proteins containing the PLAC8 motif, which confer cadmium tolerance to plants through multiple mechanisms such as efflux, compartmentalization, chelation, and antioxidant activity, and regulate fruit size and ion homeostasis. This study systematically integrated the PLAC8/PCR gene families from mosses, monocots, and dicots, revealing their structural and functional relationships, evolutionary trajectories, and functional diversification patterns through phylogenetic and motif analyses, providing a theoretical basis for cadmium-resistant breeding and environmental remediation. Future research should further integrate multi-omics and gene editing technologies to deeply elucidate the transport mechanism of the PCR protein pentamer and the functional differences of key motifs (CCXXXXCPC, CCXXCAL, and CCXXG), and conduct field trials to assess their ecological safety and crop application potential. Full article

Against the challenge of extreme lead (Pb) contamination (>15,000 ppm) in industrial polluted soils, where conventional agents fail to disrupt stable Pb–soil complexes—this study extends our prior cadmium (Cd) remediation research to validate amino acid ionic liquids (AAILs) for highly recalcitrant metals. Fifteen AAILs were screened via batch washing, with [Met][NO₃] (methionine-based) demonstrating the highest Pb removal efficiency. Single-factor optimization revealed that under the conditions of 0.8 mol/L, 6:1 liquid–soil ratio, 60 min, 85.4% Pb was removed from severely contaminated soil by [Met][NO₃]. Kinetic analysis using four common models showed that the second-order kinetic equation provided the best fit, indicating that Pb removal was predominantly driven by chemical reactions such as complexation or ion exchange. After washing, the contents of various Pb species were significantly reduced, thereby mitigating environmental risks. Notably, no substantial changes in soil texture were observed. However, a marked increase in organic matter content was detected, accompanied by decreases in soil pH and mineral element concentrations. Analysis of soil mineral composition, functional groups, and chemical speciation revealed that [Met][NO₃] primarily facilitated Pb removal through ion-exchange and coordination reactions. This study establishes [Met][NO₃] as a green agent with dual efficacy: it achieves high-efficiency remediation of severely Pb-contaminated soil while ensuring environmental sustainability, thus highlighting its potential for practical application. Full article

Despite increasing evidence that cigarette smoke is a significant source of indoor fine particulate matter (PM_2.5), quantitative emission factors (EFs) for PM_2.5 and its toxic chemical composition in mainstream (MS) and sidestream (SS) smoke are still not well defined. In this study, we employed a custom-designed chamber to separately collect MS (intermittent puff) and SS (continuous sampling) smoke from eleven cigarette models, representing six brands and two product types, under controlled conditions. PM_2.5 was collected on quartz-fiber filters and analyzed for carbon fractions (using the thermal–optical IMPROVE-A protocol), nine water-soluble inorganic ions (by ion chromatography), and twelve trace elements (via ICP-MS). SS smoke exhibited significantly higher mass fractions of total analyzed species (84.7% vs. 65.9%), carbon components (50.6% vs. 44.2%), water-soluble ions (17.1% vs. 13.7%), and elements (17.0% vs. 7.0%) compared to MS smoke. MS smoke is characterized by a high proportion of pyrolytic organic carbon fractions (OC₁–OC₃) and specific elements such as vanadium (V) and arsenic (As), while SS smoke shows elevated levels of elemental carbon (EC1), water-soluble ions (NH₄⁺, NO₃⁻), and certain elements like zinc (Zn) and cadmium (Cd). The toxicity-weighted distribution indicates that MS smoke primarily induces membrane disruption and pulmonary inflammation through semi-volatile organics and elements, whereas SS smoke enhances oxidative stress and cardiopulmonary impairment via EC-mediated reactions and secondary aerosol formation. The mean OC/EC ratio of 132.4 in SS smoke is an order of magnitude higher than values reported for biomass or fossil-fuel combustion, indicative of extensive incomplete combustion unique to cigarettes and suggesting a high potential for oxidative stress generation. Emission factors (µg/g cigarette) revealed marked differences: MS delivered higher absolute EFs for PM_2.5 (422.1), OC (8.8), EC (5.0), Na⁺ (32.6), and V (29.2), while SS emitted greater proportions of NH₄⁺, NO₃⁻, Cl⁻, and carcinogenic metals (As, Cd, Zn). These findings provide quantitative source profiles suitable for receptor-oriented indoor source-apportionment models and offer toxicological evidence to support the prioritization of comprehensive smoke-free regulations. Full article

The rational design of functional and sustainable polymers is central to addressing global environmental challenges. In this context, unmodified lignin derived from Sarkanda grass (Tripidium bengalense), an abundant agro-industrial lignocellulosic byproduct, was systematically investigated as a natural polymeric adsorbent for the remediation of aqueous media contaminated with heavy metals. The study evaluates lignin’s behavior toward nine metal(loid) ions: arsenic, cadmium, chromium, cobalt, copper, iron, nickel, lead, and zinc. Adsorption performance was systematically investigated under static batch conditions, optimizing key parameters, with equilibrium and kinetic data modeled using established isotherms and rate equations. Surface characterization and seed germination bioassays provided supporting evidence. Unmodified Sarkanda grass lignin demonstrated effective adsorption, exhibiting a clear preference for Cu(II) followed by other divalent cations, with lower capacities for As(III) and Cr(VI). Adsorption kinetics consistently followed a pseudo-second-order model, indicating chemisorption as the dominant mechanism. Thermodynamic studies revealed spontaneous and endothermic processes. Bioassays confirmed significant reduction in aqueous toxicity and strong metal sequestration. This work positions unmodified Sarkanda grass lignin as a bio-based, low-cost polymer platform for emerging water treatment technologies, contributing to circular bioeconomy goals and highlighting the potential of natural polymers in sustainable materials design. Full article

The excessive emission of cadmium (Cd²⁺) poses a serious threat to the aquatic environment due to its high toxicity and bioaccumulation potential. This study constructed three types of vertical-subsurface-flow constructed wetlands configured with iron–carbon–zeolite composite substrates, including an iron–carbon–zeolite constructed wetland (TF-CW), a zeolite–iron–carbon constructed wetland (FT-CW), and an iron–carbon–zeolite mixed constructed wetland (H-CW), to investigate the purification performance and mechanisms of constructed wetlands for cadmium-containing wastewater (0~6 mg/L). The results demonstrated that iron–carbon–zeolite composite substrates significantly enhanced Cd²⁺ removal efficiency (>99%) through synergistic redox-adsorption mechanisms, where the iron–carbon substrate layer dominated Fe-Cd co-precipitation, while the zeolite layer achieved short-term cadmium retention through ion-exchange adsorption. FT-CW exhibited superior NH₄⁺-N removal efficiency (77.66%~92.23%) compared with TF-CW (71.45%~88.05%), while iron–carbon micro-electrolysis effectively inhibited NO₃⁻-N accumulation (<0.1 mg/L). Under cadmium stress, Typha primarily accumulated cadmium through its root systems (>85%) and alleviated oxidative damage by dynamically regulating antioxidative enzyme activity, with the superoxide dismutase (SOD) peak occurring at 3 mg/L Cd²⁺ treatment. Microbial community analysis revealed that iron–carbon substrates promoted the relative abundance of Bacteroidota and Patescibacteria as well as the enrichment of Saccharimonadales, Thauera, and Rhodocyclaceae (genera), enhancing system stability. This study confirms that iron–carbon–zeolite CWs provide an efficient and sustainable technological pathway for heavy metal-contaminated water remediation through multidimensional mechanisms of “chemical immobilization–plant enrichment–microbial metabolism”. Full article

Nitrate (NO₃⁻) and cadmium (Cd²⁺) are common water pollutants with distinct chemical behaviors, often requiring different removal strategies. This study presents a low-cost synthesis of carbonated hydroxyapatite nanopowder (cHA), Ca₅(PO₄)_3-y(CO₃)_y(OH) (y = 0.13–0.17), using eggshell waste as a calcium precursor, aimed at removing both NO₃⁻ and Cd²⁺ from wastewater. SEM and TEM analyses revealed a porous nanostructure with an average particle size of 13.53 ± 6.43 nm and a specific surface area of 7.568 m²/g. Adsorption experiments were conducted under varying conditions, including contact time (0.3–3 h), dosage (0.3–2 g/L), initial concentrations (10–100 mg/L for NO₃⁻; 5–15 mg/L for Cd²⁺), and temperature (22 and 50 ± 2 °C). Cd²⁺ removal reached up to 99% at pH 2–4.5, while NO₃⁻ removal peaked at 38% in competitive systems, within 30 min. In single-ion systems, maximum nitrate uptake was 19.14 mg/g at 50 °C. Characterization using FT-IR, EDS, and XRD (with Rietveld refinement) confirmed carbonate B-type substitution and structural changes due to ion exchange and chemisorption. The results demonstrate that cHA derived from food waste is an efficient and sustainable sorbent, particularly for cadmium removal in contaminated water. Full article

The increasing demand for rapid, sensitive, and eco-friendly methods for the detection of trace heavy metals in environmental samples, attributed to their serious threats to health and the environment, has spurred considerable interest in the development of sustainable sensor materials. Toxic metal ions, namely, lead (Pb²⁺), cadmium (Cd²⁺), mercury (Hg²⁺), arsenic (As³⁺), and chromium, are potential hazards due to their non-biodegradable nature with high toxicity, even at trace levels. Acute health complications, including neurological, renal, and developmental disorders, arise upon exposure to such metal ions. To monitor and mitigate these toxic exposures, sensitive detection techniques are essential. Pre-existing conventional detection methods, such as atomic absorption spectroscopy (AAS) and inductively coupled plasma-mass spectrometry (ICP-MS), involve expensive instrumentation, skilled operators, and complex sample preparation. Electrochemical sensing, which is simple, portable, and eco-friendly, is foreseen as a potential alternative to the above conventional methods. Carbon-based nanomaterials play a crucial role in electrochemical sensors due to their high conductivity, stability, and the presence of surface functional groups. Biochar (BC), a carbon-rich product, has emerged as a promising electrode material for electrochemical sensing due to its high surface area, sustainability, tunable porosity, surface rich in functional groups, eco-friendliness, and negligible environmental footprint. Nevertheless, broad-spectrum studies on the use of biochar in electrochemical sensors remain narrow. This review focuses on the recent advancements in the development of biochar-based electrochemical sensors for the detection of toxic heavy metals such as Pb²⁺, Cd²⁺, and Hg²⁺ and the simultaneous detection of multiple ions, with special emphasis on BC synthesis routes, surface modification methodologies, electrode fabrication techniques, and electroanalytical performance. Finally, current challenges and future perspectives for integrating BC into next-generation sensor platforms are outlined. Full article

In this study, a highly cadmium (II)-resistant bacterium strain, C10-4, identified as Bacillus altitudinis, was isolated from a sediment sample collected from Baiyangdian Lake, China. The minimum inhibitory concentration (MIC) of Cd(II) for strain C10-4 was 1600 mg/L. Factors such as the contact time, pH, Cd(II) concentration, and biomass dosage affected the adsorption of Cd(II) by strain C10-4. The adsorption process fit well to the Langmuir adsorption isotherm model and the pseudo-second-order kinetics model, based on the Cd(II) adsorption data obtained from the cells of strain C10-4. This suggests that Cd(II) is adsorbed by strain C10-4 cells via a single-layer homogeneous chemical adsorption process. According to the Langmuir model, the maximum biosorption capacity was 3.31 mg/g for fresh-strain C10-4 biomass. Cd(II) was shown to adhere to the bacterial cell wall through SEM-EDS analysis. FTIR spectroscopy further indicated that the main functional sites for the binding of Cd(II) ions on the cell surface of strain C10-4 were functional groups such as N-H, -OH, -CH-, C=O, C-O, P=O, sulfate, and phosphate. After the inoculation of strain C10-4 into Cd(II)-contaminated soils, there was a significant reduction (p < 0.01) in the exchangeable fraction of Cd and an increase (p < 0.01) in the sum of the reducible, oxidizable, and residual fractions of Cd. The results show that Bacillus altitudinis C10-4 has good potential for use in the remediation of Cd(II)-contaminated soils. Full article

The heavy metal contamination of soils is a global environmental challenge threatening water quality, food safety, and human health. Using a systematic literature review approach, this study aimed to assess the potential of bacterial strains to immobilize cadmium (Cd²⁺), lead (Pb²⁺), and copper (Cu²⁺) in contaminated soils. A total of 45 articles were analyzed, focusing on studies that reported heavy metal concentrations before and after bacterial treatment. The analysis revealed that bacterial genera such as Bacillus, Pseudomonas, and Enterobacter were most commonly used for the immobilization of these metals. Immobilization efficiencies ranged from 25% to over 98%, with higher efficiencies generally observed when microbial consortia or amendments (e.g., phosphate compounds and biochar) were applied. The main immobilization mechanisms included biosorption, bioprecipitation (such as carbonate-induced precipitation), bioaccumulation, and biomineralization, which convert mobile metal ions into more stable, less bioavailable forms. These findings highlight the promising role of microbial-assisted immobilization in mitigating heavy metal pollution and reducing ecological risks. Further laboratory and field studies are needed to optimize the use of these microbial strains under site-specific conditions to ensure effective and sustainable soil remediation practices. Full article

Phosphorylated cellulose is proposed as a bio-resin for the removal of heavy metals, as a substitute for synthetic polymer-based materials. Phosphorylation is carried out using kraft pulp fibers as the cellulose source, with phosphate esters and urea as reactants to prevent significant fiber degradation. Herein, phosphorylated fibers, with three types of counterions (sodium, ammonium, or hydrogen), are used in adsorption trials involving four individual metals: nickel, copper, cadmium, and lead. The Langmuir isotherm model is applied to determine the maximum adsorption capacities at four different temperatures (10, 20, 30, and 50 °C), enabling the calculation of the Gibbs free energy (ΔG), entropy (ΔS), and enthalpy (ΔH) of adsorption. The results show that the adsorption capacity of phosphorylated fibers is equal or even higher than that of commercially available resins (1.7–2.9 vs. 2.4–2.6 mmol/g). However, the nature of the phosphate counterion plays an important role in the adsorption capacity, with the alkaline form showing a superior ion exchange capacity than the hybrid form and acid form (2.7–2.9 vs. 2.3–2.7 vs. 1.7–2.5 mmol/g). The thermodynamic analysis indicates the spontaneous (ΔG = (-)16–(-)30 kJ/mol) and endothermic nature of the adsorption process with positive changes in enthalpy (0.45–15.47 kJ/mol) and entropy (0.07–0.14 kJ/mol·K). These results confirm the high potential of phosphorylated lignocellulosic fibers for ion exchange applications, such as the removal of heavy metals from process or wastewaters. Full article