Nickel (Ni) is a trace element that is toxic to plants and consequently results in toxicity symptoms and hazardous fitness problems in human beings through food chains. Nanoparticles (NPs) are being used in new ways to directly help plants handle Ni stress and act as nano-fertilizers. The purpose of the current study was to establish the use of biogenically produced zinc oxide nanoparticles (ZnONPs) to reduce Ni-induced toxic effect on the growth and development of watermelon (Citrullus lanatus). Watermelon seeds were sown in pot filled with five kg of soil and placed in a greenhouse. The watermelon plants were treated with Ni stress (70 mg/kg soil) at 20 DAS (days after sowing), and the treatment was applied directly into the soil. The supply of ZnONPs (100 mg/L) as foliar spray was given at 30 DAS and 38 DAS, and the sampling was performed at 55-60 DAS for biochemical and physiological analysis. The results showed that watermelon plants that were exposed to Ni had oxidative damage, which was shown by more electrolyte leakage, hydrogen peroxide, lipid peroxidation, pigment and osmolyte loss, and a loss of ultrastructural integrity in the chloroplasts. However, watermelon plants supplemented with ZnONPs under the Ni toxicity revealed significantly increased plant fresh weight (53.18%), plant dry weight (51.25%), and root length (32.14%). Moreover, the ZnONPs supplement has beneficial impacts on photosynthesis attributes, SPAD value (21.93%), and chloroplast structure observed by transmission electron microscopy (TEM) under Ni stress. Application of ZnONPs also substantially reduced the oxidative stress by lowering the levels of superoxide radical (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\:{\text{O}}_{2}{-\cdot\:}$$\end{document}; 22.68%), hydrogen peroxide (H2O2; 21.18%), malondialdehyde (MDA; 21.34%), and electrolyte leakage (EL; 34.613%). The results showed that ZnONPs enhanced enzymatic activities of superoxide dismutase (SOD; 39.95%), peroxidase (POD; 19.95%), catalase (CAT; 32.85%), ascorbate peroxidase (APX; 25%) that metabolize reactive oxygen species (ROS); these increases correlated with the changes observed in the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\:{\text{O}}_{2}{-\cdot\:}$$\end{document}, H2O2 and MDA after ZnONPs application. Application of ZnONPs increased the transcriptional levels of antioxidant defense genes as compared to the Ni plants alone. In conclusion, spraying ZnONPs on foliage has high effectiveness in increasing biomass, photosynthesis, protein and antioxidant enzymes, mineral nutrient concentrations, and lowering Ni concentrations in watermelon. The results indicate biogenically produced ZnONPs can be a promising technique for the remediation of Ni-contaminated soils.

The prerequisite for breeding a plant to be used in phytoremediation is its high tolerance to grow normally in soil contaminated by certain heavy metals. As mechanisms of plant uptake and transport of nickel (Ni) are not fully understood, it is of significance to utilize exogenous genes for improving plant Ni tolerance. In this study, rcnA from Escherichia coli encoding an exporter of Ni and cobalt was overexpressed constitutively in Arabidopsis thaliana, and the performance of transgenic plants was assayed under Ni stress. The subcellular localization of rcnA in plant cells was found to be the plasma membrane. Constitutive overexpression of rcnA in Arabidopsis rendered better growth of either seedlings on agar medium containing 85, 100, and 120 mu M NiCl2 or adult plants in a nutrient solution with 5 mM NiCl2 added. Compared to the wildtype, rcnA-OE transgenic plants under Ni stress accumulated lower levels of reactive oxygen species (i.e., superoxide and hydrogen peroxide) in leaves and exhibited less oxidative damage in shoots, as demonstrated by less electrolyte leakage and the lower malondialdehyde content. Notably, rcnA-OE transgenic plants retained a higher content of Ni in roots and had a lower content of Ni in shoots. Therefore, our findings indicated that the bacterial rcnA gene may be utilized to improve plant Ni tolerance through genetic transformation.

Prior research has explored the relationship between occupational exposure to nickel and lung function. Nonetheless, there is limited research examining the correlation between blood nickel levels and lung function among young adults in the general population. The metabolomic changes associated with nickel exposure have not been well elucidated. On August 23, 2019, we enrolled 257 undergraduate participants from the Chinese Undergraduates Cohort to undergo measurements of blood nickel levels and lung function. The follow-up study was conducted in May 2021. A linear mixed-effects model was employed to assess the relationship between blood nickel levels and lung function. We also conducted stratified analyses by home address. In addition, in order to explore the biological mechanism of lung function damage caused by nickel exposure, we performed metabolomic analyses of baseline serum samples (N = 251). Both analysis of variance and mixed linear effect models were utilized to assess the impact of blood nickel exposure on metabolism. Our findings from cross-sectional and cohort analyses revealed a significant association between blood nickel levels and decreased forced expiratory volume in the first second (FEV1) and forced vital capacity (FVC) among young adults in the general population. Furthermore, we found stronger associations in urban areas. In metabolomics analysis, a total of nine metabolites were significantly changed under blood nickel exposure. The changed metabolites were mainly enriched in six pathways including carbohydrate, amino acid, and cofactor vitamin metabolism. These metabolic pathways involve inflammation and oxidative stress, indicating that high concentrations of nickel exposure can cause inflammation and oxidative stress by disrupting the above metabolism of the body.

The current research investigates individual and combined toxicity effects of nickel (Ni) and imidacloprid (IMI) on earthworm species Eisenia fetida fetida. Employing standardized toxicity parameters, we assessed the impact of environmentally relevant concentrations (ERC) of Ni, IMI, and their mixtures on key biomarkers and reproductive fitness of earthworms. Our findings reveal concentration-dependent responses with discernible adverse effects on physiological parameters. The ERC obtained for Ni was 0.095 ppm, and for imidacloprid was 0.01 ppm. Two concentrations (ERC and 1/5th) of both toxicants (individually and in combinations) were further given for 14 days, and parameters like avoidance behaviour, antioxidants, histology, and metabolomic profile were observed. The behaviour of earthworms was noted, where at 24-48 h, it was found to be in control soil, while later, at 72-96 h, they migrated to toxicants-treated soil. Levels of antioxidants (superoxide dismutase, catalase, reduced glutathione, ascorbic acid), lipid peroxidation, and lactate dehydrogenase were elevated in the testis, spermatheca, ovary, and prostate gland in a high concentration of Ni + IMI. Histological studies showed more vacuolization and disruption of epithelium that was increased in the prostate gland of the Ni + IMI high group, decreased number of spermatids, and damaged cell architecture was noted in testis and spermatheca of the Ni + IMI high group. The highest number of metabolites was found in Ni exposed group (181), followed by IMI (131) and Control (125). Thus, this study sheds light on the ecotoxicological effects of combinational exposure of these contaminants on an essential soil-dwelling organism, where IMI was more toxic than Ni, and both toxicants decreased earthworm reproductive fecundity.

Plant growth requires a complex network of arbuscular mycorrhizal (AM) fungi and bacteria to supply organic compounds and major (C, N, P, etc.) and trace nutrients to the roots. Hyperaccumulation by certain plant species is based on the threshold 'maxima' a plant can safely ingest/absorb an element from soils without tissue damage. The latter criteria for hyperaccumulation vary between elements. The amount of an element a plant can absorb depends both on the ability of the species to uptake the element and on the element concentrations and bioavailability in the substrate. A plant growing directly on a mineral-rich substrate or a short height above the soil should be able to access inorganic matter via the roots. In contrast, a plant capable of accumulating inorganic elements, but growing on a peat without direct root contact with the inorganic soil fraction, would suffer a dearth of mineral nutrients. Partitioning of elements occurs within hyperaccumulators. For example, the preferential binding of heavy rare earth elements (HREE) to organic ligands leads to the relative enrichment of HREE in aerial plant structures. The presence of hyperaccumulators in a wide range of present-day plant species suggests that this mechanism was present among peat-forming plants in the fossil record. Examples from peats through low-rank coals to high volatile A bituminous coals show that hyperaccumulation provides a viable hypothesis for the consequent enrichment of certain elements. Complications from the depositional history and diagenetic alteration of the peat; metamorphism and mineralization through the history of the coal; and, not the least, the problems implicit in sampling suitable intervals in working mines, cores, natural exposures, etc., present problems in the extrapolation of the modern plant mechanisms to coals. Coal represents natural settings and, apart from Miocene and younger coals produced from vegetation with known relatives in modern setting, we cannot experiment on the ancient plants. The analogies between the geochemical appearance of coals and the element uptake and partitioning behavior of modern plants, however, does offer hope that hyperaccumulation might have been a mechanism, potentially one of many mechanisms, for the organic associations of inorganic elements in coals.

Nickel-iron slag, a byproduct of industrial processes in China with an annual production exceeding 400,000 tons, is considered an industrial waste material. This study focuses on the rational utilization of nickel-iron slag by investigating its mechanical properties and road performance as a roadbed fill material. Initially, a detailed analysis of the grading curve of pure nickel-iron slag was conducted, leading to the proposal of various modification schemes for nickel-iron slag. Subsequently, static triaxial tests were performed on nickel-iron slag-clay mixtures to explore the impact of different factors on the stress-strain curve of nickel- iron slag-modified soil. Utilizing these discoveries, a formula for the molar Coulomb shear strength of nickel-iron slag-modified soil was derived. In addition, a numerical simulation study of a nickel-iron slagreinforced embankment was conducted, integrating field tests. This aimed to investigate the variations in the compression layer sedimentation-thickness ratio and settlement factor of nickel-iron slag-modified soil reinforced embankment under different filling heights and slope rates. The results informed the development of a prediction model for the settlement ratio of nickel-iron slag-modified soil-reinforced embankment. Key findings indicate that pure nickel-iron slag exhibits poorly graded gravel sand characteristics, and optimal gradation is achieved when clay doping ranges from 30% to 40%. As the clay content increases, the stress- strain curve of nickel-iron slag-clay transitions from strain-hardening to strain-softening. Furthermore, the stress-strain curve of nickel-iron slag-cement-clay exhibits strain-softening, and the shear strength fitting formula demonstrates high computational accuracy with a small error range. Numerical simulations reveal that the sink-thickness ratio and settlement factor are minimally affected by the slope rate. The sink-thickness ratio increases with the elevation of filling height, while the settlement factor fluctuates within a small range. The proposed sink-thickness ratio prediction model exhibits high accuracy and strong generalization capabilities. This comprehensive study provides valuable insights into the efficient utilization of nickel-iron slag in construction and road engineering.

Ferronickel slag is the solid waste slag produced by smelting nickel-iron alloy. After grinding ferronickel slag into powder, it has potential chemical activity. It can partially replace cement and reduce the amount of cement, and is conducive to environmental protection. The mechanical properties of soil cement were investigated through the compressive strength test and inter-split tensile test of ferronickel slag powder soil cement with different dosages. To further study the mechanism of ferronickel slag powder's action on soil cement microscopically, the microstructure of soil cement was analyzed by using a scanning electron microscope and nuclear magnetic resonance equipment. The results of the study show that the incorporation of ferronickel slag powder can enhance the compressive and tensile strength of soil cement. The best performance enhancement of ferronickel slag powder was achieved when it was doped with 45% of its mass. The hydration products of soil cement increased with the increase in the doping amount, but the excessive doping of ferronickel slag powder would lead to a weakening of the hydration reaction and a decrease in the strength of the soil cement. At the same time, ferronickel slag powder plays the role of filling the void of soil cement. With the increase in ferronickel slag powder, the large pores inside the soil cement are reduced and the structure is denser.

Chemical stabilization is considered a more effective and efficient method for improving soft soil in road foundation construction. Nickel slag, a byproduct of the nickel industry, has the potential to be developed as an environmentally friendly pozzolanic material for soft soil improvement. Our previous research has shown that nickel slag enhances the mechanical properties of high-plasticity organic soil but fails to meet road foundation standards. As such, additional materials are needed to achieve the required specifications. This study aims to analyze the effect of adding aluminum hydroxide [Al(OH)3] to soil stabilized with nickel slag. The addition of Al(OH)3 is based on weight ratios of nickel slag at 1.5, 2.5, and 3.5. The effectiveness of adding nickel slag was assessed based on the unconfined compressive strength (qu) of the mixture matrix. In addition, mineral characterization of the mixture matrix was tested using X-ray diffraction (XRD) to observe changes in mineral fractions. The results of this study indicate that the addition of Al(OH)3 can improve the mechanical performance of soft clay soil better than soil stabilized with nickel slag alone, with the 1.5% weight ratio providing the highest compressive strength value of 237.39 kPa. This improvement may be due to the formation of pozzolanic reactions, including C-S-H, C-A-H, and C-S-A-H, as shown by the XRD test results.