Synthesis and properties of nano-cadmium oxide and its size-dependent responses by barley plant

Present study included technological methods that made it possible to synthesize CdO nanoparticles and carry out their qualitative and quantitative diagnostics, confirming the as-prepared CdO nanoparticles (NPs) were spherical and had a size of 25 nm. Then, under the conditions of the model experiment the effect of CdO in macro and nanosized particles on absorption, transformation, and structural and functional changes occurring in cells and tissues of Hordeum vulgare L. (spring barley) during its ontogenesis was analyzed. Different analytical techniques were used to detect the transformation of CdO forms: Fourier-transform infrared spectroscopy (FTIR), Dynamic light scattering (DLS), X-ray fluorescence analysis (XRF), Scanning electron microscopy (SEM-EDXMA and TEM), X-ray diffraction (XRD), and X-ray absorption fine structure, consists of XANES - X-ray absorption near edge structure, and EXAFS - Extended X-ray absorption fine structure. Quantitative differences in the elemental chemical composition of barley root and leaf samples were observed. The predominant root uptake of Cd was revealed. CdO-NPs were found to penetrate deeply into barley plant tissues, where they accumulated and formed new mineral phases such as Cd5(PO4)3Cl and CdSO4 according to XRD analysis. The molecular-structural state of the local Cd environment in plant samples corresponding to Cd-O and Cd-Cd. The toxicity of CdO-NPs was found to significantly affect the morphology of intracellular structures are the main organelles of photosynthesis therefore, destructive changes in them obviously reduce the level of metabolic processes ensuring the growth of plants. This study is an attempt to show results how it is possible to combine some instrumental techniques to characterize and behavior of NPs in complex matrices of living organisms.

Application of X-ray based modern instrumental techniques to determine the heavy metals in soils, minerals and organic media

To evaluate the environmental concerns associated with heavy metals (HMs) during their translocations in food chains, it is crucial to gather data on the types of HMs present in soils in order to ascertain their toxicity and potential to migrate. An overview of the findings from several physical techniques used to determine and identify the HMs, sediments, individual minerals, and organic components in contaminated agricultural and industrial soils, is provided in this review article. These studies cover a variety of X-ray-based analytical techniques, including most widely used ones like X-ray absorption near edge structure, extended X-ray absorption fine structure, X-ray diffraction, and less popular ones X-ray fluorescence, etc. When compared to techniques that rely on laboratory radiation sources, synchrotron radiation offers more precision and efficiency. These methods could pinpoint the primary mechanisms influencing the soil's ability to transport contaminants and track their subsequent migration up the food chain.

Genotoxic and morpho-physiological responses of ZnO macro- and nano-forms in plants

In the current study, two plants, viz., Pisum sativum L. and Hordeum vulgare L., were exposed to nano- and macro-dispersed ZnO at 1, 10, and 30 times of maximal permissible concentration (MPC). The main objective of the study is to depict and compare the genotoxicity in terms of chromosomal anomalies, cytotoxicity (i.e., mitotic index), and phytotoxicity (viz., germination, morphometry, maximal quantum yield, and chlorophyll fluorescence imaging) of macro- and nano-forms of ZnO along with their accumulation and translocation. In the case of genotoxic and cytotoxic responses, the maximal effect was observed at 30 MPC, regardless of the macro- or nano-forms of ZnO. The phytotoxic observations revealed that the treatment with macro- and nano-forms of ZnO significantly affected the germination rate, germination energy, and length of roots and shoots of H. vulgare in a dose-dependent manner. The factor toxicity index of treated soil demonstrated that toxicity soared as concentrations increased and that at 30 MPC, toxicity was average and high in macro- and nano-dispersed ZnO, respectively. Furthermore, the photosynthetic parameters were observed to be negatively affected in both treatments, but the maximal effect was observed in the case of nano-dispersed form. It was noted that the mobility of nano-dispersed ZnO in the soil was higher than macro-dispersed. The increased mobility of nano-dispersed ZnO might have boosted their accumulation and translocation that subsequently led to the oxidative stress due to the accelerated production of reactive oxygen species, thus strengthen toxicity implications in plants.

Speciation of macro- and nanoparticles of Cr2O3 in Hordeum vulgare L. and subsequent toxicity: A comparative study

Chromium (Cr) is reported to be hazardous to environmental components and surrounding biota when levels exceed allowable thresholds. As Cr is extensively utilized in different industries, thereby comprehensively studied for its toxicity. Along with Cr, the applications of nano-Cr or chromium oxide nanoparticles (Cr₂O₃-NPs) are also expanding; however, the literature is scarce or limited on their phytotoxicity. Thereby, the current work investigated the morpho-physiological insights of macro- and nanoparticles of Cr in Hordeum vulgare L. plants. The increased accumulation and translocation of Cr under the exposure of both forms disturbed the cellular metabolism that might have inhibited germination and growth as well as interfered with the photosynthesis of plants. The overall extent of toxicity was noticeably higher under nanoparticles' exposure than macroparticles of Cr. The potential cue for such phytotoxic consequences mediated by Cr nanoparticles could be an increased bioavailability of Cr ions which was also supported by their total content, mobility, and factor toxicity index. Besides, to support further these findings, synchrotron X-ray technique was used to reliably identify Cr-containing compounds in the plant tissues. The X-ray spectra of the near spectral region and the far region of the spectrum of K-edge of Cr were obtained, and it was established that the dominant crystalline phase corresponds to Cr₂O₃ (eskolaite) from the recorded observations. Thus, the obtained results would allow revealing the mechanism of macro- and nanoparticles of Cr induced impacts on plant at the tissue, cellular- and sub-cellular levels.

Application of XAFS and XRD methods for describing the copper and zinc adsorption characteristics in hydromorphic soils

Modeling metal sorption in soils is of great importance to predict the fate of heavy metals and to assess the actual risk driven from pollution. The present study focuses on adsorption of HM ions on two types of hydromorphic soils, including calcaric fluvisols loamic and calcaric fluvic arenosols. The individual and competitive adsorption behaviors of Cu and Zn on soils and soil constituents are evaluated comprehensively. It is established that the sorption processes were best described with the Langmuir model. The results suggest that the calcaric fluvic arenosols are more vulnerable to heavy metal input compared to fluvisols loamic. In all cases, Cu had a higher range of values of the adsorption process parameters relative to Zn. The Zn is likely to be the most critical environmental factor in such soils since it exhibited a decreased sorption under competitive conditions. The retention mechanisms of HM in hydromorphic soils are considered. Based on theoretical calculations of ion activity in soil solutions using solubility diagrams of Cu and Zn compounds, the possibility of precipitation of Cu hydroxide and Zn carbonate in the studied soils is shown. Direct physical methods of nondestructive testing (XAFS and XRD) are applied to experimentally prove the formation of these HM compounds on the surface of montmorillonite, the dominant mineral in hydromorphic soils, and calcite. Thus, the combination of both physicochemical methods and direct physical methods can provide a large amount of real information about the mechanisms of HM retain with solid phases.

Speciation of Zn and Cu in Technosol and evaluation of a sequential extraction procedure using XAS, XRD and SEM-EDX analyses

Metal speciation, linked directly to bioaccessibility and lability, is a key to be considered when assessing associated human and environmental health risks originated from anthropogenic activities. To identify the Zn and Cu speciation in the highly contaminated, technogenically transformed soils (Technosol) from the impact zone near the industrial sludge reservoirs of chemical plant (Siverskyi Donets River floodplain, southern Russia), the validity of the BCR sequential extraction procedure using the X-ray absorption fine-structure and X-ray powder diffraction (XRD) analyses was examined after each of the three stages. After the removal of exchange and carbonate-bonded Zn and Cu compounds from Technosol (first stage of extraction), the resulting residual soil showed enrichment in a great diversity of metal compounds, primarily with Me-S and Me-O bonds. The number of compounds with a higher solubility decreased at the subsequent stages of extraction. In the residual soil left over after extracting the first and second fractions, the dominant Zn-S bond appeared as würtzite (hexagonal ZnS) that made up more than 50%, while the Cu-S bond was almost completely represented only by chalcocite (Cu₂S). The XRD analysis revealed the authigenic minerals of metals with S: sphalerite (cubic ZnS), würtzite (hexagonal ZnS), covellite (CuS) and bornite (Cu₅FeS₄). The scanning electron microscopy data confirmed that würtzite was the dominant form of Me with sulfur-containing and carbonate-containing minerals. The Zn-S bond was the main component (57%), whereas the Cu-O bond was dominant in the residual fraction (the fraction after the third-stage extraction). The results revealed that the composition of the residual fractions might include some of the most stable and hard-to-recover metal compounds of technogenic origin. Thus, the application of the novel instrumental methods, coupled with the chemical fractionation, revealed the incomplete selectivity of the extractants in the extraction of Zn and Cu in long-term highly contaminated soils.

The macroscopic symmetry of Pb(Mg1/3Nb2/3)1-xTixO3 in the morphotropic phase boundary region (x = 0.25-0.5)

The macroscopic symmetry of Pb(Mg_1/3Nb_2/3)_1-xTi_xO₃ (PMN-PT) crystals with x = 0.25-0.5 has been studied by optical microscopy. Precise data on the temperature dependence of the birefringence and optical extinction directions have been obtained. Two different low-symmetry phases separating rhombohedral and tetragonal phases have been observed in the compositional range x = 0.3-0.47. The optical extinction in the range x = 0.3-0.37 is consistent with Cm space group symmetry, while for x = 0.37-0.47 Pm symmetry is appropriate. Gradual rotation of the optical indicatrix has been found at temperatures just below T_c in crystals with x = 0.27-0.3. A refined phase diagram is presented.

The temperature dependence for the third shell's Fourier-peak of Nb-EXAFS in KNbO3 as additional source of information on the local atomic structure

The information on the structure of tetragonal KNbO3 is extracted from the temperature dependence of the third shell's Fourier-peak of Nb-EXAFS. It is shown that this dependence can be explained by two effects: 1) rigid rotations of the O6-octahedron and 2) increase of the third shell's DW-parameter. However, diffraction data on the temperature dependence of the DW-parameter permit us to conclude that the last effect only is sufficient and the O6-octahedron rotation doesn't occur in the high-temperature phases of KNbO3. Using EXAFS it is revealed that in the neighboring cells Nb-atoms are parallel shifted closely to [211] direction in tetragonal phase.

Deglitching procedure for XAFS

A computer program for eliminating artifacts such as glitches and Bragg peaks of the polarized XAFS spectra is presented. It permits to easily locate and to eliminate from the EXAFS spectra the additional signals originated from the Bragg scattering by crystalline samples. The test of the procedure on the spectra with specially introduced artifacts and on the experimental polarized XAFS spectra showed its high effectiveness.

Polarized XAFS study of high-temperature phases of NaNbO3

Temperature dependence of the Nb displacement relative to the center of oxygen octahedron in NaNbO3 has been studied by polarized Nb K XAFS. Spectra were measured at two orientations of a single crystalline sample. Room temperature EXAFS data are in a good agreement with earlier X-ray diffraction data: Nb antiferroelectric displacements were found to be orthogonal to the b axis. Analysis of the temperature dependent EXAFS data didn't reveal any abrupt changes of Nb-O distances in the phase transition points. In all high-temperature paraelectric phases Nb appeared to be displaced to the off-center positions. Displacements, orthogonal to b axis, remained almost constant, while displacement along b axis gradually increased with temperature, so that in the cubic phase the displacements along all axes became equal. This shows, that disorder plays an important role in the high temperature phases. The above results are supported also by the analysis of the pre-edge structure, - the integral intensity of the pre-edge peak was temperature-independent when the polarization vector of the X-rays was orthogonal to b axis and gradually increased with temperature when the polarization was parallel to b.