Search Results (582)

Cadmium (Cd) toxicity destroys plant cells and affects plant growth and development. Due to its unique metallic properties, selenium (Se) has been shown to be effective in antioxidants, cellular immunity, and heavy metal detoxification. When Se and Cd are present together in plants, they antagonize. However, the mechanism of action of the two in the rice cell wall remains to be clarified. In this study, we analyzed the mechanism of Cd detoxification by rice (Oryza sativa L.) cellular polysaccharides mediated by Se, using the cell wall as an entry point. Proteomic and transcriptomic analyses revealed that “Glycosyl hydrolases family 17”, “O-methyltransferase”, and “Polygalacturonase” protein pathways were significantly expressed in the cell wall. The most abundant enzymes involved in polysaccharide biosynthesis were found, including bglB, otsB, HK, PFP, ADH1, and ALDH, which resulted in the synthetic pathway of polysaccharide formation in the rice cell wall. Finally, the essential genes/proteins, such as protein Os03g0170500, were identified. The study showed that Se inhibits Cd uptake and transport when Se (1 mg/kg) is low relative to Cd (3 mg/kg), has little inhibitory effect, and even promotes Cd (3 mg/kg) uptake when Se (5 mg/kg) is relatively high. Full article

This study investigates growth responses, heavy metal (Cd, As) uptake, translocation, and mineral nutrient regulation in leafy vegetables with varying heavy metal tolerance, addressing the threat posed by combined Cd and As pollution. Three high-tolerance, four moderate-tolerance, and one sensitive leafy vegetable were grown in Cd+As-contaminated hydroponics. Post-harvest yields and concentrations of Cd, As, and trace elements were assessed. Results showed that (1) compared with single heavy metal treatments, the combination of Cd and As significantly increased the translocation factor of Cd in black bean sprouts and white radish sprouts by up to 83.83% and 503.2%; (2) changes in mineral nutrient concentrations in leafy vegetables were similar between single and combined heavy metal stresses, but the regulatory patterns varied among different leafy vegetable species; (3) under Cd/As exposure, high-tolerance leafy vegetables (e.g., pak choi) had strong heavy metal accumulation abilities, and heavy metal stress positively regulated mineral elements in their roots; In contrast, sensitive leafy vegetables (e.g., pea sprouts) often exhibited suppressed mineral element content in their roots, which was a result of their strategy to reduce heavy metal uptake. These results offer key insights into resistance mechanisms against combined heavy metal pollution in leafy vegetables, supporting phytoremediation efforts and safe production. Full article

Biochar has emerged as a promising soil amendment for mitigating heavy metal contamination in agricultural systems. This study investigates the effects of biochar on cadmium (Cd) and copper (Cu) uptake, plant growth, oxidative stress, and physiological responses in lettuce (Lactuca sativa L.) plants exposed to different metal concentrations. Results indicate that biochar significantly influenced Cd bioavailability, reducing its accumulation in plant tissues by up to 31.9% and alleviating oxidative stress, with malondialdehyde and proline levels decreasing by up to 51.0% and 60.2%, particularly at higher application rates (5%). Cd-exposed plants treated with biochar exhibited an improved fresh weight (+22.6%), lower malondialdehyde and proline levels, and enhanced the chlorophyll content (+14.9% to 24.1%) compared to untreated plants. The bioaccumulation factor for Cd decreased (up to 31.8%) while the immobilization index (II) increased, confirming the role of biochar in limiting Cd mobility in soil. In contrast, Cu uptake remained consistently low across all treatments, with a significant reduction observed only at higher contamination levels (up to −34.2%). Biochar contributed to Cu immobilization, reflected in increased II values, and enhanced the plant biomass and chlorophyll content under Cu exposure (+15.4% and up to +24.1%, respectively), suggesting a partial alleviation of Cu toxicity. These findings highlight biochar’s potential in heavy metal remediation, particularly for Cd, by reducing bioavailability and improving plant resilience. However, its role in Cu-contaminated soils is mainly through immobilization rather than uptake reduction. Full article

Heavy metal contamination in paddy fields poses serious risks to food safety and crop productivity. This study evaluated the potential of native soil fungi as bioinoculants to reduce metal uptake in rice cultivated under contaminated conditions. Eight fungal strains—four indigenous and four allochthonous—were selected based on their plant growth-promoting traits, including siderophore production and phosphate solubilization. Additional metabolic analysis confirmed the production of bioactive secondary metabolites. In a greenhouse experiment, three rice cultivars were grown under permanent flooding (PF) and alternate wetting and drying (AWD) in soil enriched with arsenic, cadmium, chromium, and copper. Inoculation with indigenous fungi under AWD significantly reduced the arsenic accumulation in rice shoots by up to 75%. While AWD increased cadmium uptake across all cultivars, fungal inoculation led to a moderate reduction in cadmium accumulation—ranging from 15% to 25%—in some varieties. These effects were not observed under PF conditions. The results demonstrate the potential of native fungi as a nature-based solution to mitigate heavy metal stress in rice cultivation, supporting both environmental remediation and sustainable agriculture. Full article

Soil aggregates play critical roles in regulating the behavior of heavy metal in soils. To understand the distribution of cadmium (Cd) in aggregates of different soil types, as well as their roles in regulating the Cd bioavailability of bulk soils, four major arable soils, including acidic, neutral, and calcareous purple soils and calcareous yellow soil (APS, NPS, CPS, and CYS), were sampled from Chongqing, China, for aggregate separation and determination of the total Cd(T-Cd) distribution, fractionation, and extractability in various-sized aggregates. A pot experiment with ryegrass (Lolium perenne L.) was conducted to evaluate the Cd bioavailability in bulk soils as influenced by aggregates. The results show that the composition of soil aggregates varies a lot among soils: lower soil pH tends to increase the proportion of macroaggregates while decreasing that of smaller aggregates. The Cd distribution, HCl-extractability, and active fraction (AF, T-Cd/HCl-Cd) in aggregates are all soil type-dependent, with pH and particle size being the main determining factors; the distribution pattern of Cd concentrated in smaller aggregates is only found for CPS and CYS (pH > 7.5) upon exogenous Cd addition, though the finest aggregates (silt–clay, <0.053 mm) consistently exhibited the highest Cd enrichment for all tested soils. The Cd extractability and AF values in all aggregates show a sequence of APS > NPS > CPS > CYS, indicating the fundamental influence of soil pH on Cd availability. Higher AF values over bulk soils, either in silt–clay aggregates or in microaggregates (0.053–0.25 mm), whereas lower AF in macroaggregates (1–2 mm) are found for APS and NPS, which correspond to the relative portions of Ex-Cd and Fe/Mn oxide-bound Cd (Fe/Mn-Cd) in these aggregates. In contrast, less variation of AF values among aggregates is observed for CPS and CYS and for APS/NPS upon Cd addition. Pot experiments demonstrated strong positive correlations between ryegrass Cd uptake and HCl-Cd in silt–clay aggregates and T-Cd in microaggregates, while a negative correlation was observed with T-Cd in macroaggregates. These findings supply new insight into the mechanisms of aggregates in controlling Cd bioavailability in bulk soils and shed light on the development of new strategies for remediating Cd-polluted soils. Full article

Microalgae-based bioremediation is increasingly recognized as a sustainable, efficient, and straightforward technology. Despite this growing interest, the potential of Parachlorella hussii for metal biosorption remains underexplored. This study is the first report evaluating the metal biosorption activity in Parachlorella hussii ACOI 1508 (N9), highlighting the impact of the culture age on the monosaccharide composition and its correlation to the metal binding capacity. The capsular strain (N9) was isolated from the hypersaline ecosystem—Lake Chott Aïn El-Beida—in southeastern Algeria. Cultivated in Bold’s Basal medium, the strain produced 0.807 ± 0.059 g L⁻¹ of RPSs and 1.975 ± 0.120 g L⁻¹ of CPSs. Biochemical analysis of the extracts revealed a high total sugar content (% w/w) that ranged from 62.98 ± 4.87% to 95.60 ± 87% and a low protein content (% w/w) that ranged from 0.49 ± 0.08% to 1.35 ± 0.69%, with RPS-D7 and RPS-D14 having high molecular weight (≥2 MDa). HPLC-based monosaccharide characterization demonstrated compositional differences between the exponential and stationary phases, with rhamnose dominating (~55%) in RPS-D14 and with the presence of uronic acids comprising 7–11.3%. Metal removal efficiency was evaluated using the whole biomass in two growth phases. Copper uptake exhibited the highest capacity, reaching 18.55 ± 0.61 mg Cu g⁻¹ DW at D14, followed by zinc removal with 6.52 ± 0.61 mg Zn g⁻¹ DW. Interestingly, removal efficiencies increased to about twofold during the stationary phase, reaching 51.15 ± 1.14% for Cu, 51.08 ± 3.35% for Zn, and 36.55 ± 3.09% for Ni. The positive results obtained for copper/zinc removal highlight the biosorption potential of P. hussii, and notably, we found that the metal removal capacity significantly improved with culture age—a parameter that has been poorly investigated in prior studies. Furthermore, we observed a growth phase-dependent modulation in monosaccharide composition, which correlated with enhanced functional properties of the excreted biomolecules involved in biosorption. This metabolic adjustment suggests an adaptive response that may contribute to the species’ effectiveness in heavy metal uptake, underscoring its novelty and biotechnological relevance. Full article

Understanding microbial adaptation and tolerance based on the cellular concentration and biosorption capacity provides critical insights for evaluating microbial performance under heavy metal stress, which is essential for selecting efficient strains or consortia for bioremediation applications. In this study, the adaptation and tolerance of Bacillus megaterium and Rhodotorula mucilaginosa to elevated concentrations of copper (Cu) and manganese (Mn) were investigated by introducing the maximum adaptation concentration (MAC) alongside the maximum tolerable concentration (MTC) and the minimum inhibitory concentration (MIC). A Gaussian model was fitted to the relative growth responses to estimate the MACs, MTCs, and MICs. B. megaterium exhibited MACs of 4.6 ppm Cu and 393.9 ppm Mn, while R. mucilaginosa showed MACs of 59.6 ppm Cu and 64.4 ppm Mn, corresponding to concentrations that stimulated their maximum cell density. A biosorption analysis revealed average capacities of 6.3 ± 5.3 mg Cu/g biomass and 28.6 ± 17.2 mg Mn/g biomass, positively correlated with the MTCs, indicating enhanced metal uptake under sublethal stress. The co-culture assays demonstrated dynamic microbial interactions shaped by the type and concentration of metal, including coexistence, competitive substitution, and dominance by tolerance. These findings support the use of MACs as indicators of growth stimulation and MTCs as thresholds for enhanced metal uptake, providing a dual-parameter framework for selecting metallotolerant microorganisms for metal recovery strategies. Full article

Climate change poses significant risks to food security and contributes to widespread soil degradation. Effective strategies are urgently needed to mitigate its impacts and ensure stable crop production and food quality. Biochar has shown strong potential to reduce greenhouse gas emissions, enhance carbon sequestration, and immobilize soil contaminants such as heavy metals and organic pollutants. These benefits can lead to increased crop yields, improved nutritional quality, and reduced uptake of harmful substances by plants. This review summarizes the possible mechanisms through which biochar influences the biochar–soil–plant interface, aiming to provide a comprehensive understanding of its multifaceted roles. Although positive effects of biochar on crop production are frequently reported, neutral or even negative outcomes have also been observed. Such adverse effects may be attributed to the presence of volatile organic compounds, free radicals, or heavy metals in certain biochars that inhibit plant growth. Additionally, biochar application has been found to reduce plant infections caused by pathogens, likely due to the presence of organic compounds that act as microbial inhibitors. A deeper understanding of the mechanisms by which biochar affects plant growth is essential for its effective use as a tool to combat climate change and enhance food security. Full article

This study examined the impact of watering with air and oxygen nanobubble-saturated water (NBSW) on soil moisture retention, electrical conductivity (EC), nutrient leaching, and CO₂ emissions in sandy loam (SL) and silty clay loam (SCL) soils amended with composted sludge (CS). The results revealed that air nanobubbles (air NBs) had greater stability, while oxygen nanobubbles (ONBs) showed lower stability but higher oxygen diffusion potential. Soil moisture under NBSW treatment was more sensitive to changes in ambient conditions and tended to decrease due to higher evaporation compared to conventional water. NBSW was more effective in enhancing moisture in SL soil than in SCL soil. Overall, the results revealed that the application of NBSW tended to increase soil compaction due to stimulation of microbial activity; however, air NBs may temporarily reduce compaction and enhance soil–water interactions. Additionally, NBSW increased soil EC due to increased dissolved ion concentration, with effects more apparent in SL soil than in SCL. This may indicate increased nutrient availability for plant uptake. Notably, NBSW, particularly ONB, showed quick but short-lived changes in soil physical and microbial properties, and soil texture played a significant role in treatment results. Furthermore, the leaching of nutrients and heavy metals remained negligible across all treatments. The study confirms that using NB in controlled environments is more practical for boosting short-term plant growth than improving long-term soil water retention to support more sustainable agriculture systems. Full article

This study explores the bioaccumulation behavior of heavy metals (cadmium (Cd), lead (Pb), and zinc (Zn)) in lavender (Lavandula spp.) cultivated under controlled greenhouse conditions to assess its potential in sustainable phytoremediation. The plants were grown in pots filled with either unpolluted soil or soil artificially enriched with cadmium, lead, or zinc at concentrations exceeding the normal (Cd 1 mg/kg d.w.; Pb 20 mg/kg d.w.; Zn 100 mg/kg d.w.), alert (Cd 3 mg/kg d.w.; Pb 50 mg/kg d.w.; Zn 300 mg/kg d.w.), and intervention (Cd 5 mg/kg d.w.; Pb 100 mg/kg d.w.; Zn 600 mg/kg d.w.) thresholds set for sensitive land use. A comparative analysis of two lavender varieties (lavender and lavandin) over a four-month period revealed an accumulation trend of Pb > Cd > Zn. Empirical modeling indicated that cadmium uptake followed a linear pattern, lead accumulation conformed closely to the Mitscherlich model, while zinc uptake did not align well with any of the tested models. Overall, the results emphasize the potential of lavender species in developing biomimetic approaches for heavy metal remediation and contribute valuable insights into sustainable soil decontamination practices. Full article

Salinity and heavy metal stress significantly reduce agricultural productivity in arable lands, particularly affecting crops like rice (Oryza sativa L.). This study aimed to evaluate the efficacy of heavy metal-tolerant plant growth-promoting rhizobacteria (HMT-PGPR) in mitigating the harmful effects of salt (NaCl), chromium (Cr), and combined NaCl + Cr stress on rice plants. Two pre-isolated and well-characterized heavy metal-tolerant epiphytic (Ochrobactrum pseudogrignonense strain P14) and endophytic (Arthrobacter woluwensis strain M1R2) PGPR were tested. The LSD test (p ≤ 0.05) was used to assess the statistical significance between treatment means. Stresses caused by NaCl, Cr, and their combination were found to impair plant growth and biomass accumulation through mechanisms, including osmotic stress, oxidative damage, ionic imbalance, reduced photosynthetic pigment, lowered relative water content, and compromised antioxidant defense systems. Conversely, inoculation with HMT-PGPR alleviated these adverse effects by reducing oxidative stress indicators, including malondialdehyde (MDA), hydrogen peroxide (H₂O₂) content and electrolyte leakage (EL) and enhancing plant growth, osmolyte synthesis, and enzymatic antioxidant activity under single- and dual-stress conditions. The application of HMT-PGPR notably restricted Na⁺ and Cr⁶⁺ uptake, with an endophytic A. woluwensis M1R2 demonstrating superior performance in reducing Cr⁶⁺ translocation (38%) and bioaccumulation (42%) in rice under dual stress. The findings suggest that A. woluwensis effectively mitigates combined salinity and chromium stress by maintaining ion homeostasis and improving the plant’s antioxidant defenses. Full article

Heavy metal (HM) contamination poses a major threat to environmental health, agriculture and human well-being, requiring effective and sustainable remediation strategies. Phytoremediation, an eco-friendly and cost-effective approach, is widely used for the remediation of HM-contaminated soils. Although phytoremediation holds considerable potential in the extraction, stabilisation and degradation of HMs, its effectiveness is often constrained by limited metal bioavailability, plant stress under toxic conditions and slow metal uptake rates. To address these limitations, this review examines the integration of various soil amendments—the application of biochar, compost, plant exudates, microbial agents and chelating agents—to enhance phytoremediation efficiency. This review critically evaluates empirical evidence on the effectiveness, scalability, economic feasibility and environmental impact of these amendments. By synthesising recent studies, this review advances the understanding of amendment-assisted phytoremediation as a viable solution for treating HM-contaminated soils. In addition, this review identifies practical applications, discusses limitations and explores the potential synergies of these amendments to optimise phytoremediation strategies, ultimately contributing to more effective and sustainable environmental cleanup efforts. Full article

This study investigates the hydrothermal synthesis of calcium silicate hydrate (C-S-H) from photovoltaic (PV) waste glass and carbide sludge as a strategy for resource recovery and sustainable chromium removal from wastewater. Waste-derived precursors were co-ground, blended at controlled Ca/Si molar ratios (0.8, 1.0, 1.2), and hydrothermally treated at 180 °C for 96 h to yield C-S-H with tunable morphology and crystallinity. Comprehensive characterization using XRD, FT-IR, SEM-EDX, and UV-Vis spectroscopy revealed that a Ca/Si ratio of 1.0 produced a well-ordered tobermorite/xonotlite structure with a high surface area and fibrous network, which is optimal for adsorption. Batch adsorption experiments showed that this material achieved rapid and efficient Cr(III) removal, exceeding 90% uptake within 9 h through a combination of surface complexation, ion exchange (Ca²⁺/Na⁺ ↔ Cr³⁺), and precipitation of CaCrO₄ phases. Morphological and structural evolution during adsorption was confirmed by SEM, FT-IR, and XRD, while EDX mapping established the progressive incorporation of Cr into the C-S-H matrix. These findings highlight the viability of upcycling industrial waste into advanced C-S-H sorbents for heavy metal remediation. Further work is recommended to address sorbent regeneration, long-term stability, and application to other contaminants, providing a foundation for circular approaches in advanced wastewater treatment. Full article

The bioavailability of heavy metals is profoundly influenced by their interactions with active soil components (microorganisms, organic matter, and iron minerals). However, the effects of urease-producing bacteria combined with organo-Fe hydroxide coprecipitates (OFCs) on Cd accumulation in wheat, as well as the mechanisms underlying these effects, remain unclear. In this study, pot experiments integrated with high-throughput sequencing were employed to investigate the impacts of the urease-producing bacterial strain TJ6, ferrihydrite (Fh), and OFCs on Cd enrichment in wheat grains, alongside the underlying soil–microbial mechanisms. The results demonstrate that the strain TJ6-Fh/OFC consortium significantly (p < 0.05) reduced (50.1–66.7%) the bioavailable Cd content in rhizosphere soil while increasing residual Cd fractions, thereby decreasing (77.4%) Cd accumulation in grains. The combined amendments elevated rhizosphere pH (7.35), iron oxide content, and electrical conductivity while reducing (14.5–21.1%) dissolved organic carbon levels. These changes enhanced soil-colloid-mediated Cd immobilization and reduced Cd mobility. Notably, the NH₄⁺ content and NH₄⁺/NO₃⁻ ratio were significantly (p < 0.05) increased, attributed to the ureolytic activity of TJ6, which concurrently alkalinized the soil and inhibited Cd uptake via competitive ion channel interactions. Furthermore, the relative abundance of functional bacterial taxa (Proteobacteria, Gemmatimonadota, Enterobacter, Rhodanobacter, Massilia, Nocardioides, and Arthrobacter) was markedly increased in the rhizosphere soil. These microbes exhibited enhanced abilities to produce extracellular polymeric substances, induce phosphate precipitation, facilitate biosorption, and promote nutrient (C/N) cycling, synergizing with the amendments to immobilize Cd. This study for the first time analyzed the effect and soil science mechanism of urease-producing bacteria combined with OFCs in blocking wheat’s absorption of Cd. Moreover, this study provides foundational insights and a practical framework for the remediation of Cd-contaminated wheat fields through microbial–organic–mineral collaborative strategies. Full article

Lead (Pb) contamination in Moso bamboo forests poses a challenge in terms of sustainable development and raises concerns about the safety of bamboo shoots for consumption. However, the physiological impacts of Pb stress on Moso bamboo growth and the molecular mechanisms governing its adaptive responses remain poorly understood. This study comprehensively investigated the physiological and transcriptomic responses of Moso bamboo to Pb stress. The results showed that low concentrations (1–10 µM) of Pb stress had minimal adverse effects on biomass accumulation and the photochemical quantum yield of PSII in Moso bamboo. However, at a high Pb concentration (50 µM), the growth of roots was significantly inhibited, while Pb accumulation in the roots and shoots reached 15,611 mg·kg⁻¹ and 759 mg·kg⁻¹, respectively. The uptake of Pb was increased as the external Pb concentration increased, but the xylem loading of Pb reached saturation at 57.79 µM after six-hour exposure. Pb was mainly localized in the epidermis and pericycle cells in the roots, where the thickening of cell walls in these cells was found after Pb treatment. Transcriptomic profiling identified 1485 differentially expressed genes (DEGs), with significant alterations in genes associated with metal cation transporters and cell wall synthesis. These findings collectively indicate that Moso bamboo is a Pb-tolerant plant, characterized by a high accumulation capacity and efficient xylem loading. The tolerance mechanism likely involves the transcriptional regulation of genes related to heavy metal transport and cell wall biosynthesis. Full article