Heavy metals are determinant factors in increasing environmental pollution, and chromium is considered to be of highest concern because of its genotoxicity in microorganisms, animals, and humans. Relatively few studies are focused on the injury induced in plant genetic material. Therefore, the main objective of this work was to evaluate the extent of the cytogenetic damage induced in root meristems of barley (Hordeum vulgare L.) after short-term seed exposure to 10, 100, 250, and 500 μM K₂Cr₂O₇(Cr(VI) concentration is 1.04, 10.39, 25.99, and 51.99 μg ml⁻¹) and 10, 100, 250, and 500 μM CrCl₃(Cr(III) concentration is 0.52, 5.19, 12.99, and 25.99 μg ml⁻¹). Chromium genotoxic potential was proved by significant increases in the rates of the ana-telophase chromosomal aberrations (1.3–2.3 times higher for K₂Cr₂O₇and 1.7–2.2 times higher for CrCl₃, as compared to the control; p < 0.05, p < 0.01) and of metaphase disturbances (5.0–7.5 times more numerous in chromium-treated groups than in control; p < 0.001). The pattern of the chromosomal aberrations is constituted by chromatid bridges, complex aberrations, lagging, and vagrant chromosomes, while the abnormal metaphases are c-like metaphases, sticky metaphases, and metaphases with chromosomes expulsed from equatorial plate. The mitotic indices and the growth of the barley plantlets in the early ontogeny were stimulated by chromium. The changes induced in the frequency of division stages mainly consisted in prophase and telophase accumulation and diminution of metaphase and anaphase proportion.

The disposal of cyanogenic residues from the processing of cassava, during the flour production in certain regions of the Brazilian northeastern, has been a cause of concern in recent years, since this practice may lead to environmental imbalances. The results obtained in this work show a possible impact caused by the release of this kind of waste into water bodies, as well as its potential use as biofertilizer, mainly due to its high nutrient content. Humic substances (HS) from water and soil showed high interaction with cyanide ions (CN⁻), being the main responsible for the bioavailability of these ions into the environment. Furthermore, studies in microcosms propose viable and low-cost alternatives to decrease the levels of CN⁻ions in the liquid waste (called “manipueira”), as well as its potential use as biofertilizer.

The carbon balance of secondary dry tropical forests of Mexico’s Yucatan Peninsula is sensitive to human and natural disturbances and climate change. The spatially explicit process model Forest-DeNitrification-DeComposition (DNDC) was used to estimate forest carbon dynamics in this region, including the effects of disturbance on carbon stocks. Model evaluation using observations from 276 sample plots in a tropical dry forest in the Yucatan Peninsula indicated that Forest-DNDC can be used to simulate carbon stocks for this forest with good model performance efficiency. The simulated spatial variability in carbon stocks was large, ranging from 5 to 115 Mg carbon (C) ha⁻¹, with a mean of 56.6 Mg C ha⁻¹. Carbon stocks in the forest were largely influenced by human disturbances between 1985 and 2010. Based on a comparison of the simulations with and without disturbances, carbon storage in the year 2012 with disturbance was 3.2 Mg C ha⁻¹, lower on average than without disturbance. The difference over the whole study area was 154.7 Gg C, or an 8.5 % decrease. There were substantial differences in carbon stocks simulated at individual sample plots, compared to spatially modeled outputs (200 m²plots vs. polygon simulation units) at some locations due to differences in vegetation class, stand age, and soil conditions at different resolutions. However, the difference in the regional mean of carbon stocks between plot-level simulation and spatial output was small. Soil CO₂and N₂O fluxes varied spatially; both fluxes increased with increasing precipitation, and soil CO₂also increased with an increase in biomass. The modeled spatial variability in CH₄uptake by soils was small, and the flux was not correlated with precipitation. The net ecosystem exchange (NEE) and net primary production (NPP) were nonlinearly correlated with stand age. Similar to the carbon stock simulations, different resolutions resulted in some differences in NEE and NPP, but the spatial means were similar.

Silver-doped TiO₂(Ag-TiO₂) immobilized onto polystyrene (PS) waste was prepared using a thermal attachment method. Its efficiencies as a photocatalyst under UVA light (λ = 365 nm) for the removal of Cr(VI), methylene blue, Escherichia coli, and Aspergillus niger from water were studied. The results showed that Ag-TiO₂-PS material removes pollutants at significantly high rates and especially posseses strong disinfection properties. The morphological study of Ag-TiO₂-PS material was carried out using X-ray diffraction, scanning electron microscope, and energy dispersive X-ray spectroscopy. The catalyst can be prepared using waste PS employing a simple immobilization method and it is highly effective for the removal of biological and chemical impurities from drinking and underground water supplies.

This study was performed to evaluate the ability of white-rot fungi to decolorize dye effluents. A total of 222 isolates of white-rot fungi were initially investigated to assess their ability to decolorize chemically different synthetic dyes in solid medium, resulting in selection of 25 isolates including four isolates of Berkandera adusta, five isolates of Ceriporia lacerata, three isolates of Irpex lacteus, one isolate of Perenniporia fraxinea, ten isolates of Phanerochaete spp., one isolate of Phlebia radiata, and one isolate of Porostereum spadiceum. Of the 25 isolates, B. adusta KUC9065, C. lacerata KUC8090, P. calotricha KUC8003, and P. spadiceum KUC8602 were finally selected on the basis of their ability to decolorize synthetic dyes in liquid medium, and were used to decolorize industrial effluents. B. adusta KUC9065 increased the transmittance of visible light by 71–92 %. Decolorization of wastewater by B. adusta KUC9065 was probably caused by the lignin-modifying enzymes produced by the fungus. In addition, the acute toxicity to Daphnia magna decreased from 2.5 to 2.1 and from 3.5 to 2.6 toxic units over 24 and 48 h, respectively.

A novel mesoporous, nanocomposite, magnetically separable adsorbent, namely activated alumina (γ-Al₂O₃)/ferrite (Ni₀.₅Zn₀.₅Fe₂O₄) microfibers have been successfully prepared by the sol–gel process. These nanocomposite γ-Al₂O₃/Ni₀.₅Zn₀.₅Fe₂O₄microfibers are formed after calcination of the precursor at 450 °C for 3 h, and characterized with high aspect ratios and uniform diameters of 1–10 μm. In the nanocomposite γ-Al₂O₃/Ni₀.₅Zn₀.₅Fe₂O₄microfibers, the spherical γ-Al₂O₃particles are homogeneously embedded on the microfiber. Their specific surface areas and magnetic properties are significantly influenced by the γ-Al₂O₃content and calcination conditions. With the designed γ-Al₂O₃mass fraction of 0.2 and the calcination temperature of 550 °C, the γ-Al₂O₃/Ni₀.₅Zn₀.₅Fe₂O₄microfibers possess a high specific surface area of 118.3 m²/g and saturation magnetization (Mₛ) of 20.4 Am² kg⁻¹, respectively. The adsorption behaviors of the nanocomposite γ-Al₂O₃/Ni₀.₅Zn₀.₅Fe₂O₄microfibers were examined using the Congo red and methyl blue dyes as the adsorbate. The adsorption kinetics, effects of the adsorbent dosage and solution pH, adsorption isotherms, and regeneration of the microfiber adsorbents were investigated. The pseudo-second-order model can be used to describe the adsorption kinetics. The resultant isotherm data are well fitted by the Temkin model, implying that the dyes adsorption on the γ-Al₂O₃/Ni₀.₅Zn₀.₅Fe₂O₄microfibers is a multilayer adsorption combined with some degrees of chemical interactions. Considering the simple synthesis process, high adsorption and unique magnetic property, these mesoporous, magnetic, nanocomposite γ-Al₂O₃/Ni₀.₅Zn₀.₅Fe₂O₄microfibers can be used as a highly efficient, fast, and convenient adsorbent for dyes removal.Highlights The magnetic mesoporous Al₂O₃/Ni₀.₅Zn₀.₅Fe₂O₄microfibers were synthesized. Adsorption kinetics and adsorption isotherms were investigated. The separation, regeneration, and adsorption efficiency were enhanced.

Fluoride is among the most phytotoxic atmospheric pollutants, commonly linked to the appearance of lesions in susceptible plants around emitting sources. In order to assess the effects of fluoride on leaves of Spondias dulcis Parkinson (Anacardiaceae), plants were examined 78 km (non-polluted area) and 0.78 km (polluted area) from an aluminium smelter. The level of fluoride increased with the exposure time of the plants in the polluted area. On the third day of exposure in the polluted area, necroses with typical colouration were observed. Micromorphological damage began at the abaxial epidermis, mainly associated with the stomata. Starch grain accumulation was more pronounced in the midrib. The cell membranes and chloroplasts were greatly affected by the pollutant. We observed accumulation of phenolic compounds and electron-dense material at the boundaries of the ending veinlets. The microscopic events described precede the appearance of symptoms and are therefore of prognostic value in predicting injury by fluoride and will be useful as biomarkers. The high sensitivity of S. dulcis to fluoride and the specificity of the symptoms confirm, for the first time, in an experiment of active biomonitoring, the potential of this species as a bioindicator.

Accumulation of heavy metals due to pollution of the environment, particularly in agricultural ecosystems, can cause serious deterioration of crop yield and quality. In this study, we assessed the effect of silicon on physiological, photosynthetic and stress-related aspects of cadmium toxicity in hydroponically grown maize plants (Zea mays L., hybrid Valentina). One concentration of silicon (5 mM) and two concentrations of cadmium (5 and 50 μM) added to the cultivation medium were tested. Cadmium alone led to a significant growth inhibition and negatively affected the content of total chlorophylls and the efficiency of photosystem II. Especially in roots, application of cadmium resulted in the accumulation of reactive oxygen species and consequent membrane lipid peroxidation. The supplementation of silicon successfully ameliorated the toxic effect of cadmium on maize plants and enhanced growth, some of the photosynthetic parameters and reduced the level of oxidative stress. In plants exposed to higher concentrations of cadmium silicon also reduced its accumulation, especially in roots. Changes in the accumulation of phenolic compounds may indicate the influence of silicon on this aspect of secondary plant metabolism and its importance in the detoxification of heavy metals.

The main objective of the present study is to measure the levels of heavy metals in important fruit species such as apple, apricot, and nectarine and their nine, five, and six cultivars, respectively. This work investigates the accumulation of Fe, Cu, Zn, Ni, Cd, Pb, and Cr in flowers of above species, to measure the levels of heavy metal contamination. The obtained results revealed that amounts of heavy metals significantly varied among cultivars at the same species and were within the permissible amounts in general. The Cd was not detected in apricot, nectarine, and the most of apple cultivars. Results for floral Fe, and also for Cu and Zn, which are the most important micronutrients for fruit production, suggest that levels of these elements might be used for assessing the storage of these elements during the previous season. We assume that the production of apple, apricot, and nectarine is safe, and there is no risk of contamination with heavy metals.

Activated natural siderite (ANS) was used to investigate its characteristics and mechanisms of As(V) adsorption from aqueous solution. Batch tests were carried out to determine effects of contact time, initial As(V) concentration, temperature, pH, background electrolyte, and coexisting anions on As(V) adsorption. Arsenic(V) adsorption on ANS well-fitted pseudo-second-order kinetics. ANS showed a high-adsorption capacity of 2.19 mg/g estimated from Langmuir isotherm at 25 °C. Thermodynamic studies indicated that As(V) adsorption on ANS was spontaneous, favorable, and endothermic. ANS adsorbed As(V) efficiently in a relatively wide pH range between 2.0 and 10.0, although the removal efficiency was slightly higher in acidic conditions than that in basic conditions. Effects of background electrolyte and coexisting anions were not significant within the concentration ranges observed in high As groundwater. Results of XRD and Fe K-edge XANES analysis suggested ANS acted as an Fe(II)/(III) hybrid system, which was quite effective in adsorbing As from aqueous solution. There was no As redox transformation during adsorption, although Fe(II) oxidation occurred in the system. Two infrared bands at 787 and 872 cm⁻¹after As(V) adsorption suggested that As(V) should be predominantly adsorbed on ANS via inner-sphere bidendate binuclear surface complexes.