Phytotoxicity of ionic, micro- and nano-sized iron in three plant species

Soil properties determine the impact of nZVI on Lactuca sativa L and its rhizosphere

Nanoscale zero-valent iron (nZVI) is a promising material tool for the remediation of metal(loid)-contaminated soils since it reduces metal(loid) availability and plant uptake, thereby enhancing the development of the plants. However, the effects of nZVI as nanoparticles on soil properties, plants, and the microbial rhizosphere in unpolluted soils are poorly understood. Here we tested the impact of nZVI at different doses (0.5 and 5% of commercial suspension) on soil properties, lettuce plants, and their microbial rhizosphere in two non-contaminated soils with distinct physico-chemical properties (alkaline versus acidic soil). To this end, a pot experiment was performed with lettuce plants in a growth chamber for a month. Both soils showed an increase in of pH and available Fe after nZVI application. However, these effects were more marked in the acidic soil. In this regard, the plants in this soil showed increased biomass and Fe content. TEM analysis revealed that although the roots and leaves of plants grown in the alkaline soil showed better cell integrity than those in acidic soil-an observation that was consistent with the visual appearance of the plants-the former were more affected by the nZVI treatment. Regarding the microbial rhizosphere, in general, nZVI enhanced enzyme activity regardless of the soil type. Microbial functional diversity showed a significant decline in response to nZVI in alkaline soil. In contrast, the 0.5% nZVI treatment had a positive effect on this parameter in acidic soil. Bacterial genetic diversity was less affected by the presence of nZVI than fungal diversity, which was higher in nZVI-treated acidic soils. In addition, alterations of bacterial and fungal communities were associated with available Fe in acidic soil. In conclusion, soil properties play a key role in determining the effects of nZVI on lettuce plants and their rhizosphere.

Antioxidant response to ZnO nanoparticles in juvenile Takifugu obscurus: protective effects of salinity

The extensive utilization of Zinc Oxide nanoparticles (ZnO NPs) has garnered significant attention due to their detrimental impacts on ecosystem. Unfortunately, ecotoxicity of ZnO NPs in coastal waters with fluctuating salinity has been disregarded. This study mainly discussed the toxic effects of ZnO NPs on species inhabiting the transition zones between freshwater and brackish water, who are of great ecological and economic importance among fish. To serve as the model organism, Takifugu obscurus, a juvenile euryhaline fish, was exposed to different ZnO NPs concentrations (0-200 mg/L) and salinity levels (0 and 15 ppt). The results showed that a moderate increase in salinity (15 ppt) could alleviate the toxic effect of ZnO NPs, as evidenced by improved survival rates. The integrated biomarker response index on oxidative stress also revealed that the toxicity of ZnO NPs was higher in freshwater compared to brackish water. These outcomes can be attributed to higher salinity (15 ppt) reducing the bioavailability of ZnO NPs by facilitating their aggregation and inhibiting the release of metal ions. It is noteworthy that elevated salinity was found to alleviate ZnO NPs toxicity by means of osmotic adjustment via the activation of Na+/K+-ATPase activity. This study demonstrates the salinity-dependent effect of ZnO NPs on T. obscurus, suggesting the possibility for euryhaline fish like T. obscurus to adapt their habitat towards more saline environments, under constant exposure to ZnO NPs.

Alteration of Hordeum vulgare and Sinapis alba germination and early growth in response to airborne low-metallic automotive brake wear debris

Road transportation significantly contributes to environmental pollution, both in terms of exhaust and non-exhaust (brake wear) emissions. As was proven, brake wear debris is released in a wide variety of sizes, shapes, and compositions. Although studies confirming the possible adverse health and environmental impact of brake wear debris were published, there is no standardized methodology for their toxicity testing, and most studies focus only on one type of brake pad and/or one test. The lack of methodology is also related to the very small amount of material released during the laboratory testing. For these reasons, this study deals with the mixture of airborne brake wear debris from several commonly used low-metallic brake pads collected following the dynamometer testing. The mixture was chosen for better simulation of the actual state in the environment and to collect a sufficient amount of particles for thorough characterization (SEM, XRPD, XRF, chromatography, and particle size distribution) and phytotoxicity testing. The particle size distribution measurement revealed a wide range of particle sizes from nanometers to hundreds of nanometers, elemental and phase analysis determined the standard elements and compounds used in the brake pad formulation. The Hordeum vulgare and Sinapis alba were chosen as representatives of monocotyledonous and dicotyledonous plants. The germination was not significantly affected by the suspension of brake wear debris; however, the root elongation was negatively influenced in both cases. Sinapis alba (IC50 = 23.13 g L-1) was more affected than Hordeum vulgare (IC50 was not found in the studied concentration range) the growth of which was even slightly stimulated in the lowest concentrations of brake wear debris. The plant biomass was also negatively affected in the case of Sinapis alba, where the IC50 values of wet and dry roots were determined to be 44.83 g L-1 and 86.86 g L-1, respectively.

Study of the Stability, Uptake and Transformations of Zero Valent Iron Nanoparticles in a Model Plant by Means of an Optimised Single Particle ICP-MS/MS Method

In the context of the widespread distribution of zero valent iron nanoparticles (nZVI) in the environment and its possible exposure to many aquatic and terrestrial organisms, this study investigates the effects, uptake, bioaccumulation, localisation and possible transformations of nZVI in two different forms (aqueous dispersion-Nanofer 25S and air-stable powder-Nanofer STAR) in a model plant-Arabidopsis thaliana. Seedlings exposed to Nanofer STAR displayed symptoms of toxicity, including chlorosis and reduced growth. At the tissue and cellular level, the exposure to Nanofer STAR induced a strong accumulation of Fe in the root intercellular spaces and in Fe-rich granules in pollen grains. Nanofer STAR did not undergo any transformations during 7 days of incubation, while in Nanofer 25S, three different behaviours were observed: (i) stability, (ii) partial dissolution and (iii) the agglomeration process. The size distributions obtained by SP-ICP-MS/MS demonstrated that regardless of the type of nZVI used, iron was taken up and accumulated in the plant, mainly in the form of intact nanoparticles. The agglomerates created in the growth medium in the case of Nanofer 25S were not taken up by the plant. Taken together, the results indicate that Arabidopsis plants do take up, transport and accumulate nZVI in all parts of the plants, including the seeds, which will provide a better understanding of the behaviour and transformations of nZVI once released into the environment, a critical issue from the point of view of food safety.

Toxicity of Binary Metal Mixtures to the Tropical Ostracod Strandesia Trispinosa

The ecotoxicity of metals is generally assessed individually, in part because current knowledge does not allow for the accurate prediction of the toxicity of metal mixtures to aquatic organisms. The objective of this study was to investigate the toxic effects of binary combinations of metal salts (copper sulphate-CuSO₄, cadmium chloride-CdCl₂, mercury chloride-HgCl₂ and manganese sulphate-MnSO₄) on the tropical ostracod Strandesia trispinosa through acute toxicity tests. To this end, ostracods were exposed to each individual metal salt as well as to their combinations by applying a full factorial design. The model that best explained the effects of the mixtures CuSO₄ x CdCl₂, CuSO₄ x HgCl₂ and CuSO₄ x MnSO₄ on the survival of S. trispinosa was Concentration Addition, whereas this was Independent Action for the CdCl₂ x HgCl₂ mixture. The observed synergistic interactions are likely to result in unacceptable risks to aquatic ecosystems under real field conditions. This is especially the case if CuSO₄ predominates the metal mixture, as observed for its combination with mercury and manganese.

Foliar-applied nanoscale zero-valent iron (nZVI) and iron oxide (Fe3O4) induce differential responses in growth, physiology, antioxidative defense and biochemical indices in Leonurus cardiaca L

The impacts of nZVI and iron oxides on growth, physiology and elicitation of bioactive antioxidant metabolites in medicinal aromatic plants must be critically assessed to ensure their safe utilization within the food chain and achieve nutritional gains. The present study investigated and compared the morpho-physiological and biochemical changes of Leonurus cardiaca L. plants as affected by various concentrations (0, 250, 500 and 1000 mg L^-1) of nZVI and Fe₃O₄. The foliar uptake of nZVI was verified through Scanning Electron Microscopy (SEM) images and Energy Dispersive X-ray (EDX) analytical spectra. Plants exposed to nZVI at low concentration showed comparatively monotonic deposition of NPs on the surface of leaves, however, the agglomerate size of nZVI was raised as their doses increased, leading to remarkable changes in anatomical and biochemical traits. 250 mg L^-1 nZVI and 500 mg L^-1 Fe₃O₄ significantly (P < 0.05) increased plant dry matter accumulation by 37.8 and 27% over the control, respectively. The treatments of nZVI and Fe₃O₄ at 250 mg L^-1 significantly (P < 0.01) improved chlorophyll a content by 22.4% and 15.3% as compared to the control, and then a rapid decrease (by 14.8% and 4.1%) followed at 1000 mg L^-1, respectively. Both nZVI and Fe₃O₄ at 250 mg L^-1 had no significant impact on malondialdehyde (MDA) formation, however, at an exposure of 500-1000 mg L^-1, the MDA levels and cellular electrolyte leakage were increased. Although nZVI particles could be utilized by plants and enhanced the synthesis of chlorophylls and secondary metabolites, they appeared to be more toxic than Fe₃O₄ at 1000 mg L^-1. Exposure to nZVI levels showed positive, negative and or neutral impacts on leaf water content compared to control, while no significant difference was observed with Fe₃O₄ treatments. Soluble sugar, total phenolics and hyperoside content were significantly increased upon optimum concentrations of employed treatments-with 250 mg L^-1 nZVI being most superior. Among the extracts, those obtained from plants treated with 250-500 mg L^-1 nZVI revealed the strong antioxidant activity in terms of scavenging free radical (DPPH) and chelating ferrous ions. These results suggest that nZVI (at lower concentration) has alternative and additional benefits both as nano-fertilizer and nano-elicitor for biosynthesis of antioxidant metabolites in plants, but at high concentrations is more toxic than Fe₃O₄.

Biochar from palm fiber wastes as an activator of different oxidants for the elimination of pharmaceuticals from diverse classes in aqueous samples

Biochar (BP) obtained from palm fiber wastes was combined with H₂O₂, peroxymonosulfate (PMS), or persulfate (PDS) to treat valsartan, acetaminophen, and cephalexin in water. BP activated PMS and PDS but no H₂O₂. Computational calculations indicated that interactions of PMS and PDS with BP are more favored than those with HP. The highest synergistic effect was obtained for the removal of valsartan by BP + PMS. This carbocatalytic process was optimized, evaluating the effects of pH, BP dose, and peroxymonosulfate concentration, and minimizing the oxidant quantity to decrease costs and environmental impacts of the process. SO₄•^-, HO•, ¹O₂, and O₂•^- were the agents involved in the degradation of the pharmaceuticals. The reusability of BP was tested, showing that the carbocatalytic process removed ∼80% of target pollutants after 120 min of treatment even at the fourth reuse cycle. Also, the process decreased the phytotoxicity of the treated sample. Simulated hospital wastewater was treated and its components induced competing effects, but the system achieved the target pharmaceuticals removal in this matrix. Additionally, the analysis of environmental impact using a life cycle assessment unraveled that the carbocatalytic process had a carbon footprint of 2.87 Kg CO₂-Eq, with the biochar preparation (which involves the use of ZnCl₂ and electric energy consumption) as the main hotspot in the process.

The role of iron nanoparticles on morpho-physiological traits and genes expression (IRT1 and CAT) in rue (Ruta graveolens)

The iron nanoparticles with different physic-chemical properties induce inconsistent effects on various studied plant species. Thus, the effect of ferric oxide (Fe₂O₃) nanoparticles was compared with Fe₂O₃ microparticles and FeSO₄complexes of EDTA for major physiological and gene expression in Rue (Ruta graveolens). Iron root content increased as Fe-MPs + EDTA ˂˂ Fe-NPs + EDTA˂ FeSO₄ + EDTA. The shoot's iron remained unchanged or slightly increased under most of FeSO₄ and Fe-MPs + EDTA treatments. Under Fe-NPs + EDTA treatment, 50 and 250 µM concentration decreased on shoot iron by 23.2% and 19.4% compared to control, respectively. But the shoot iron at 500 µM NPs was 28.2% higher than that of the control. A 46-58 fold lower Fe translocation was observed under Fe-NPs + EDTA than Fe-MPs + EDTA. The effect of Fe-NPs + EDTA was more significant on plant fresh and dry mass than the control. All treatments showed an increase in anthocyanin by 19-84% in leaves compared to the control. The Fe-NPs + EDTA and MPs + EDTA induced similar effects on enhanced growth parameters, total chlorophyll, catalase enzyme activity, gene, and reduced chlorophyll a/b and oxidants. Catalase enzyme activity in FeSO₄ and MPs + EDTA was similar, and in Fe-NPs + EDTA treatments were influenced by coarse and fine regulation mechanisms, respectively. Iron MPs + EDTA had a more negative effect on IRT₁ relative gene expression in roots as compared to other iron forms. The IRT₁ relative gene expression in shoots was positively affected by 31-81% under all treatment types (except control and 250 µM Fe-NPs + EDTA, and 250 µM MPs + EDTA). These results could reveal the potential mechanism of plant response to nanoparticles.

An Ecotoxicological Evaluation of Four Fungal Metabolites with Potential Application as Biocides for the Conservation of Cultural Heritage

Biocides based on chemical synthetic compounds have been commonly used to counteract damages caused by microorganisms on stone cultural heritage. However, in the last few years, the use of commercial and traditional biocides has been banned and/or limited due to their dangerous profile for the environment, as well as human and animal health. Natural products could be used as suitable alternatives for cultural heritage purposes, as they have low toxicity and stability compared with synthetic pesticides. Even if most of the investigated solutions have already shown promising results, their efficiency, ecotoxicological, and chemical features are poorly investigated. In this manuscript, we aimed to evaluate the ecotoxicological profile of four fungal metabolites-namely, cavoxin, epi-epoformin, seiridin, and sphaeropsidone-with potential antimicrobial properties for monumental artworks. A battery of ecotoxicological tests using Aliivibrio fischeri (bacterium), Raphidocelis subcapitata (alga), Raphanus sativus L. (macrophyte), Daphnia magna (crustacean), and Caenorhabditis elegans (nematode) revealed a relative lower toxicity of these compounds, especially when compared with Preventol^® and Rocima^®, commercial biocides mainly used for the conservation of cultural heritage.

Engineered Nanomaterial Exposure Affects Organelle Genetic Material Replication in Arabidopsis thaliana

Mitochondria and chloroplasts not only are cellular energy sources but also have important regulatory and developmental roles in cell function. CeO₂, FeOx ENMs, ZnS, CdS QDs, and relative metal salts were utilized in Murashige-Skoog (MS) synthetic growth medium at different concentrations (80-500 mg L^-1) and times of exposures (0-20 days). Analysis of physiological and molecular response of A. thaliana chloroplasts and mitochondrion demonstrates that ENMs increase or decrease functionality and organelle genome replication. Exposure to nanoscale CeO₂ and FeOx causes an 81-105% increase in biomass, whereas ZnS and CdS QDs yielded neutral or a 59% decrease in growth, respectively. Differential effects between ENMs and their corresponding metal salts highlight nanoscale-specific response pathways, which include energy production and oxidative stress response. Differences may be ascribed to ENM and the metal salt dissolution rate and the toxicity of the metal ion, which suggests eventual biotransformation processes occurring within the plant. With regard to specific effects on plastid (pt) and mitochondrial (mt) DNA, CdS QD exposure triggered potential variations at the substoichiometric level in the two organellar genomes, while nanoscale FeOx and ZnS QDs caused a 1- to 3-fold increase in ptDNA and mtDNA copy numbers. Nanoparticle CeO₂ exposure did not affect ptDNA and mtDNA stoichiometry. These findings suggest that modification in stoichiometry is a potential morpho-functional adaptive response to ENM exposure, triggered by modifications of bioenergetic redox balance, which leads to reducing the photosynthesis or cellular respiration rate.

Toxicity and physicochemical parameters of composts including distinct residues from agribusiness and slaughterhouse sludge

Composting is useful for treatment of residues from agribusiness, but the potential toxicity of the final compost should be evaluated before its agricultural destination. The objective of this study was to evaluate the physicochemical characteristics and the toxicity of agribusiness residues using onion seeds as bioindicators. All tested treatments were composed by sludge from a swine slaughterhouse and sawdust. Besides the control, which included no additional materials, the other treatments included aviary bedding, rice husk and residue from tobacco industries as structuring materials. After 120 days of composting, for all treatments, the temperature inside the composting piles approached the environmental temperature, the physicochemical parameters indicated that the composts were stabilized and, except for the treatment including tobacco residues, that could be used for agriculture without impairing plant germination. Although the treatments including tobacco residues and rice husk showed evidence of cytotoxicity and genotoxicity at the beginning of the composting period, that was not observed for the treatment including aviary bedding. Such potential toxicity was not observed at the end of composting for any of the tested treatments.

Genotoxic Evaluation of Fe3O4 Nanoparticles in Different Three Barley (Hordeum vulgare L.) Genotypes to Explore the Stress-Resistant Molecules

Sustainable agricultural practices are still essential due to soil degradation and crop losses. Recently, the relationship between plants and nanoparticles (NPs) attracted scientists’ attention, especially for applications in agricultural production as nanonutrition. Therefore, the present research was carried out to investigate the effect of Fe₃O₄ NPs at low concentrations (0, 1, 10, and 20 mg/L) on three genotypes of barley (Hordeum vulgare L.) seedlings grown in hydroponic conditions. Significant increases in seedling growth, enhanced chlorophyll quality and quantity, and two miRNA expression levels were observed. Additionally, increased genotoxicity was observed in seedlings grown with NPs. Generally, Fe₃O₄ NPs at low concentrations could be successfully used as nanonutrition for increasing barley photosynthetic efficiency with consequently enhanced yield. These results are important for a better understanding of the potential impact of Fe₃O₄ NPs at low concentrations in agricultural crops and the potential of these NPs as nanonutrition for barley growth and yield enhancement. Future studies are needed to investigate the effect of these NPs on the expression of resistance-related genes and chlorophyll synthesis-related gene expression in treated barley seedlings.

In situ nanoremediation of soils and groundwaters from the nanoparticle's standpoint: A review

Anthropogenic pollution coming from industrial processes, agricultural practices and consumer products, results in the release of toxic substances into rural and urban environments. Once released, these chemicals migrate through the atmosphere and water, and find their way into matrices such as sediments and groundwaters, thus making large areas potentially uninhabitable. Common pollutants, including heavy metal(loid)s, radionuclides, aliphatic hydrocarbons and halogenated organics, are known to adversely affect physiological systems in animal species. Pollution can be cleaned up using techniques such as coagulation, reverse osmosis, oxidation and biological methods, among others. The use of nanoparticles (NPs) extends the range of available technologies and offers particular benefits, not only by degrading, transforming and immobilizing contaminants, but also by reaching inaccessible areas and promoting biotic degradation. The development of NPs is understandably heralded as an environmentally beneficial technology; however, it is only now that the ecological risks associated with their use are being evaluated. This review presents recent developments in the use of engineered NPs for the in situ remediation of two paramount environmental matrices: soils and groundwaters. Emphasis will be placed on (i) the successful applications of nano-objects for environmental cleanup, (ii) the potential safety implications caused by the challenging requirements of [high reactivity toward pollutants] vs. [none reactivity toward biota], with a thorough view on their transport and evolution in the matrix, and (iii) the perspectives on scientific and regulatory challenges. To this end, the most promising nanomaterials will be considered, including nanoscale zerovalent iron, nano-oxides and carbonaceous materials. The purpose of the present review is to give an overview of the development of nanoremediators since they appeared in the 2000s, from their chemical modifications, mechanism of action and environmental behavior to an understanding of the problematics (technical limitations, economic constraints and institutional precautionary approaches) that will drive their future full-scale applications.

Cerium, gadolinium, lanthanum, and neodymium effects in simplified acid mine discharges to Raphidocelis subcapitata, Lepidium sativum, and Vicia faba

The alteration of rare earth elements (REEs) biogeochemical cycles has increased the potential effects related to their environmental exposure in a one-health perspective. Cerium (Ce), gadolinium (Gd), lanthanum (La), and neodymium (Nd) are frequently related to technological applications and their environmental concentrations are already in the μg/kg - mg/kg (i.e., or L) range depending on the considered matrices. The effect of Ce, Gd, La, and Nd was investigated in a simulated AMD (0.01-10.22 mg/L) at pH 4 and 6 considering a battery of photosynthetic organisms (Raphidocelis subcapitata, Lepidium sativum, and Vicia faba) according to a multiple-endpoint approach (growth inhibition, germination index, and mutagenicity). According to modelled chemical speciation, the considered elements were mostly in the trivalent free form (86-88%) at pH 4. Gd, La, and Nd exerted the most relevant toxic effect at pH 4. The pH 6 scenario evidenced a reduction in REEs toxicity level. Mutagenicity was detected only at pH 4 by Gd (up to 3-fold compared to negative controls), La and Nd, while Ce did not show any adverse effect. Toxic effects due to Ce, Gd, La, and Nd can be reduced by controlling the pH, but several gaps of knowledge still remain about their uptake and trophic transfer, and long-term effects on targeted species.

Influence of GdVO4:Eu3+ Nanocrystals on Growth, Germination, Root Cell Viability and Oxidative Stress of Wheat (Triticum aestivum L.) Seedlings

The increasing application of lanthanide-doped nanocrystals (LDNCs) entails the risk of a harmful impact on the natural environment. Therefore, in the presented study the influence of gadolinium orthovanadates doped with Eu³⁺ (GdVO₄:Eu³) nanocrystals on wheat (Triticum aestivum L.), chosen as a model plant species, was investigated. The seeds were grown in Petri dishes filled with colloids of LDNCs at the concentrations of 0, 10, 50 and 100 µg/mL. The plants’ growth endpoints (number of roots, roots length, roots mass, hypocotyl length and hypocotyl mass) and germination rate were not significantly changed after the exposure to GdVO₄:Eu³⁺ nanocrystals at all used concentrations. The presence of LDNCs also had no effect on oxidative stress intensity, which was determined on the basis of the amount of lipid peroxidation product (thiobarbituric acid reactive substances; TBARS) in the roots. Similarly, TTC (tetrazolium chloride) assay did not show any differences in cells’ viability. However, root cells of the treated seedlings contained less Evans Blue (EB) when compared to the control. The obtained results, on the one hand, suggest that GdVO₄:Eu³⁺ nanocrystals are safe for plants in the tested concentrations, while on the other hand they indicate that LDNCs may interfere with the functioning of the root cell membrane.

Nano Zero Valent Iron (nZVI) as an Amendment for Phytostabilization of Highly Multi-PTE Contaminated Soil

In recent years, a lot of attention has been given to searching for new additives which will effectively facilitate the process of immobilizing contaminants in the soil. This work considers the role of the enhanced nano zero valent iron (nZVI) strategy in the phytostabilization of soil contaminated with potentially toxic elements (PTEs). The experiment was carried out on soil that was highly contaminated with PTEs derived from areas in which metal waste had been stored for many years. The plants used comprised a mixture of grasses-Lolium perenne L. and Festuca rubra L. To determine the effect of the nZVI on the content of PTEs in soil and plants, the samples were analyzed using flame atomic absorption spectrometry (FAAS). The addition of nZVI significantly increased average plant biomass (38%), the contents of Cu (above 2-fold), Ni (44%), Cd (29%), Pb (68%), Zn (44%), and Cr (above 2-fold) in the roots as well as the soil pH. The addition of nZVI, on the other hand, was most effective in reducing the Zn content of soil when compared to the control series. Based on the investigations conducted, the application of nZVI to soil highly contaminated with PTEs is potentially beneficial for the restoration of polluted lands.

Petroleum sludge polluted soil remediation: Integrated approach involving novel bacterial consortium and nutrient application

Petroleum sludge has been reported as noteworthy hazardous solid waste generated from industrial activities of petroleum sector. Environment friendly and economically sound treatment of petroleum sludge has attracted global attention worldwide and has become a thrust area of research. Petroleum sludge bioremediation is gaining interest of researchers globally to clean pollutants from soil ecosystems. To date of submission of the work there is no literature available reporting comparing five approaches for remediation of agricultural soil polluted with petroleum sludge employing hydrocarbon utilizing bacterial consortium (HUBC). Further studies on toxicity were performed through pot experiments using Vigna radiata. The aim of this research work was to compare capability of five approaches for remediating petroleum sludge polluted agricultural soil by employing soil microcosms. Best results were obtained when simultaneous application of HUBC and nutrients was performed in microcosm. Highest decrease (93.14 ± 1.75%) of petroleum sludge with sufficient count of hydrocarbon utilizers and decreased nutrients in 42 days was reported. Quality improvement of petroleum sludge contaminated agricultural soil after its bioremediation was performed by pot experiments by checking germination of V. radiata seeds. 85.71% germination of seeds in 5 days was noted for treated soil. Thus, HUBC can be applied as a bioremediating consortium to reclaim petroleum sludge polluted soil.

Successful remediation of soils with mixed contamination of chromium and lindane: Integration of biological and physico-chemical strategies

Soils contaminated by organic and inorganic pollutants like Cr(VI) and lindane, is currently a main environmental challenge. Biological strategies, such as biostimulation, bioaugmentation, phytoremediation and vermiremediation, and nanoremediation with nanoscale zero-valent iron (nZVI) are promising approaches for polluted soil health recovery. The combination of different remediation strategies might be key to address this problem. For this reason, a greenhouse experiment was performed using soil without or with an organic amendment. Both soils were contaminated with lindane (15 mg kg^-1) and Cr(VI) (100 or 300 mg kg^-1). After one month of aging, the following treatments were applied: (i) combination of bioaugmentation (actinobacteria), phytoremediation (Brassica napus), and vermiremediation (Eisenia fetida), or (ii) nanoremediation with nZVI, or (iii) combination of biological treatments and nanoremediation. After 60 days, the wellness of plants and earthworms was assessed, also, soil health was evaluated through physico-chemical parameters and biological indicators. Cr(VI) was more toxic and decreased soil health, however, it was reduced to Cr(III) by the amendment and nZVI and, to a lesser extent, by the biological treatment. Lindane was more effectively degraded through bioremediation. In non-polluted soils, nZVI had strong deleterious effects on soil biota when combined with the organic matter, but this effect was reverted in soils with a high concentration of Cr(VI). Therefore, under our experimental conditions bioremediation might be the best for soils with a moderate concentration of Cr(VI) and organic matter. The application of nZVI in soils with a high content of organic matter should be avoided except for soils with very high concentrations of Cr(VI). According to our study, among the treatments tested, the combination of an organic amendment, biological treatment, and nZVI was shown to be the strategy of choice in soils with high concentrations of Cr(VI) and lindane, while for moderate levels of chromium, the organic amendment plus biological treatment is the most profitable treatment.

Toxicological effects of different-sized Co-Fe (CoFe2O4) nanoparticles on Lepidium sativum L.: towards better understanding of nanophytotoxicity

Due to their widespread therapeutic and agricultural applicability and usefulness in removing metals and metalloids from water, cobalt ferrite nanoparticles (NPs) are currently receiving increasing attention from researchers. However, their potential phytotoxicity is still poorly understood. Thus, the aim of the current study was to assess the effects of synthesized cobalt ferrite (CoFe₂O₄) NPs on biological (morphological, physiological, and biochemical) parameters of edible plant garden-cress (Lepidium sativum L.), depending on particle size and concentrations. In this study, physical characteristics of cobalt ferrite NPs were determined. Increased total content of Co and Fe in L. sativum tissues and their transfer from roots to above-ground parts of seedlings, which depended on the size of NP (15 < 5 < 1.65 nm), indicated that plants had been exposed to Co ferrite NPs. The relative growth of roots, biomass of roots and above-ground parts of seedlings, amounts of chlorophylls a and b, carotenoids, and malondialdehyde (MDA) were determined. The dependence of the tested garden-cress parameters on the size and concentrations of NPs was revealed. Our data showed that the content of MDA in test plants in some cases increased up to 2.5 folds in comparison to control. The increase of the content of chlorophyll b pigment and MDA in test plants is an appropriate indicator of the impact of cobalt ferrite NPs. The findings of our study into toxicological effects of Co-Fe (CoFe₂O₄) NPs on L. sativum are expected to deepen the knowledge of the nanophytotoxicity of ferromagnetic NPs and their potential application in biomedicine and agriculture.

Phytotoxic Evaluation of Phytosynthesized Silver Nanoparticles on Lettuce

The increasing metal release into the environment warrants investigating their impact on plants, which are cornerstones of ecosystems. Here, Lactuca sativa L. (lettuce) seedlings were exposed hydroponically to different concentrations of silver ions and nanoparticles (Ag NPs) for 25 days to evaluate their impact on plant growth. Seedlings taking Ag+ ions showed an increment of 18% in total phenolic content and 12% in total flavonoid content, whereas under Ag NPs, 7% free radical scavenging activity, 12% total phenolic contents (TPC), and 10% total reducing power are increased. An increase in 31% shoot length, 25% chlorophyll, 11% carbohydrate, and 16% protein content of the lettuce plant is observed in response to Ag NPs, while silver nitrate (AgNO3) has a reduced 40% growth. The lettuce plant was most susceptible to toxic effects of Ag+ ions at a lower concentration, i.e., 0.01 mg/L, while Ag NPs showed less toxicity, only when higher concentrations >100 mg/L were applied. Further, biomolecules other than antioxidant enzymes showed higher phytotoxicity for Ag+ ions, followed by Ag NPs with the concentration of 25, 50, and 100 mg/L compared to the control. Thus, moderate concentrations of Ag NPs have a stimulatory effect on seedling growth, while higher concentrations induced inhibitory effects due to the release of Ag+ ions. These results suggest that optimum metallic contents are desirable for the healthier growth of plants in a controlled way.

Uptake, translocation, and physiological effects of hematite (α-Fe2O3) nanoparticles in barley (Hordeum vulgare L.)

There has been a growing concern with the environmental influences of nanomaterials due to recent developments in nanotechnology. This study investigates the impact and fate of hematite nanoparticles (α-Fe₂O₃ NPs) (∼14 nm in size) on a crop species, barley (Hordeum vulgare L.). For this purpose, hematite NPs (50, 100, 200, and 400 mg/L) were hydroponically applied to barley at germination and seedling stages (three weeks). Inductively coupled plasma mass spectrophotometry (ICP-MS) along with vibrating sample magnetometer (VSM) techniques were used to track the NPs in plant tissues. The effects of NPs on the root cells were observed by scanning electron microscopy (SEM) and confocal microscopy. Results revealed that α-Fe₂O₃ NPs significantly reduced the germination rate (from 80% in control to 30% in 400 mg/L), as well as chlorophyll (36-39%) and carotenoid (37%) contents. Moreover, the treatment led to a significant decline in the quantum yield of photosystem II (Fv/Fm). Leaf VSM analysis indicated a change in magnetic signal for NPs-treated samples compared with untreated ones, which is mostly attributed to the iron (Fe) ions incorporated within the leaf tissue. Besides, Fe content in the roots and leaf had gradually increased by the increasing doses of NPs, which was confirming NPs' translocation to the aerial parts. Microscopic observations revealed that α-Fe₂O₃ NPs altered root cell morphology and led to the injury of cell membranes. This study, in the light of our findings, shows that α-Fe₂O₃ NPs (∼14 nm in size) are taken up by the roots of the barley plants, and migrate to the plant leaves. Besides, NPs are phytotoxic for barley as they inhibit germination and pigment biosynthesis. This inhibition is probably due to the injury of the cell membranes in the roots. Therefore, the use of hematite NPs in agriculture and thereby their environmental diffusion must be addressed carefully.

Bioremediation of oily sludge polluted soil employing a novel strain of Pseudomonas aeruginosa and phytotoxicity of petroleum hydrocarbons for seed germination

Agricultural land pollution is key a problem globally, which is linked with growth of industries. Petroleum industrial sector is one of the major industrial sectors and the activities of petroleum industry lead to the agricultural land pollution. Oily sludge is a type of solid and hazardous waste generated from petroleum industrial activities. Hence, there is an urgent need to find remediation methods of the oily sludge contaminated agricultural land. Thus, the aim of this work was to study bioremediation of oily sludge polluted soil employing a novel strain of Pseudomonas aeruginosa and evaluation of phytotoxicity on germination of Vigna radiata seed in pots. Five different approaches were adopted for the bioremediation studies, which included Bioaugmentation + Biostimulation, bioaugmentation, biostimulation, natural attenuation and abiotic factors. Simultaneous application of P. aeruginosa NCIM 5514 and nutrients in microcosm showed 92.97 ± 0.92% decrease in oily sludge with good hydrocarbon utilizing bacterial count and decreased nutrient level in 56 days. Pot experiments on seed germination of mung beans (Vigna radiata) seeds was performed by pot experiments. 80.95% germination in five days in treated soil. From the results it was concluded that simultaneous use of oily sludge degraders and nutrient supplement could revive seed germination ability of oily sludge polluted soil effectively. This is first report of comparing five techniques to bioremediate oily sludge polluted soil using Pseudomonas aeruginosa, followed by pot study using V. radiata seeds, showing that P. aeruginosa can be an efficient bioremediation agent and can be effectively used for remediation of oily sludge contaminated soil.

Engineered magnetic nanoparticles enhance chlorophyll content and growth of barley through the induction of photosystem genes

This study investigates the impact of an engineered magnetic nanoparticle (MNP) on a crop plant. For this purpose, a sonochemical synthetic approach was utilized in order to dope magnetic elements (Co and Nd) into technologically important iron oxide NPs. After being characterized by using TEM, SEM, and XRD instruments, the MNPs were hydroponically applied to barley plants with varying doses (from 125 to 1000 mg/L) both in germination (4 days) and early growing stages (3 weeks). Physiological responses, as well as expression of photosystem marker genes, were assessed. Compared to the untreated control, MNP treatment enhanced germination rate (~ 31%), tissue growth (8% in roots, 16% in shoots), biomass (~ 21%), and chlorophyll (a, b) (~ 20%), and carotenoids (~ 22%) pigments. In general, plants showed the highest growth enhancement at 125 or 250 mg/L treatment. However, higher doses diminished the growth indices. Compared to the control, the catalase activity was significantly reduced in the leaves (~ 33%, p < 0.005) but stimulated in the roots (~ 46%, p < 0.005). All tested photosystem marker genes (BCA, psbA, and psaA) were overexpressed in MNP-treated leaves than non-treated control. Moreover, the gene expressions were found to be proportionally increased with increasing MNP doses, indicating a positive correlation between MNPs and the photosynthetic machinery, which could contribute to the enhancement of plant growth.

Nanoscale Zero-Valent Iron Has Minimum Toxicological Risk on the Germination and Early Growth of Two Grass Species with Potential for Phytostabilization

Two Poaceae species, Agrostis capillaris and Festuca rubra, were selected for their potential as phytostabilizing plants in multicontaminated soils. These species are resistant to contamination and maintain high concentrations of contaminants at the root level. Nanoscale zero-valent iron (nZVI) is an engineered nanomaterial with the ability to stabilize metal(loid)s in soils; its potential toxicological effects in the selected species were studied in a germination test using: (i) control variant without soil; (ii) soil contaminated with Pb and Zn; and (iii) contaminated soil amended with 1% nZVI, as well as in an hydroponic experiment with the addition of nZVI 0, 25, 50 and 100 mg L⁻¹. nZVI had no negative effects on seed germination or seedling growth, but was associated with an increase in shoot growth and reduction of the elongation inhibition rate (root-dependent) of F. rubra seedlings. However, applications of nZVI in the hydroponic solution had no effects on F. rubra but A. capillaris developed longer roots and more biomass. Increasing nZVI concentrations in the growing solution increased Mg and Fe uptake and reduced the Fe translocation factor. Our results indicate that nZVI has few toxic effects on the studied species.

Phytotoxicity of iron-based materials in mung bean: Seed germination tests

Environmental applications and potential risks of iron-based materials have attracted increasing attention. However, most previous studies focused on a single material. Comparative research using different iron-based materials under the same experimental conditions is still lacking. Here, six iron-based materials, including micro-sized and nanoscale Fe₃O₄ (i.e., mFe₃O₄ and nFe₃O₄), bulk and bare nanoscale zero-valent iron (i.e., mZVI and B-nZVI), starch-supported nZVI (S-nZVI), and activated carbon-supported nZVI (A-nZVI), were studied to compare their phytotoxicity in mung bean grown in suspensions with doses of 0, 300, 600 and 1000 mg/L. Taking the four toxicology parameters (seed germination rate, germination index, seedling elongation and biomass) together, the iron-based materials except mFe₃O₄ generally produced no significant phytotoxicity to mung bean even at 1000 mg/L. nFe₃O₄ and B-nZVI showed no higher phytotoxicity than their micro-sized counterparts (mFe₃O₄ and mZVI). All the materials resulted in increased Fe concentrations in seedlings particularly in roots, and mZVI and B-nZVI produced more significant effects. However, the Fe in the roots was difficultly translocated to the shoots. Compared to B-nZVI, nFe₃O₄ had lower bioavailability and bioaccumulation potential. XRD results confirmed that most Fe₃O₄ and B-nZVI remained unchanged during seedling growth, while support materials accelerated the corrosion and transformation of S-nZVI and A-nZVI. In conclusion, the tested nanoscale iron-based materials generally possess no obvious phytotoxicity within the dose range, but cause excess Fe accumulation in seedlings. Introduction of support materials may reduce such risk, allowing safer applications of these iron-based materials.

Detail investigation of toxicity, bioaccumulation, and translocation of Cd-based quantum dots and Cd salt in white mustard

In this study, a model crop plant white mustard (Sinapis alba L.) was treated with an aqueous dispersion of silica-coated CdTe quantum dots (CdTe/SiO₂ QDs) in a 72-h short-term toxicity test. The toxicity was established via measurements of (i) the root length and (ii) the chlorophyll fluorescence. These results were compared to two other sources of cadmium, free Cd ions (CdCl₂) and prime un-shell nanoparticles CdTe QDs. Tested compounds were applied in concentrations representing 20 and 200 μM Cd. The uptake and translocation of Cd were investigated using inductively coupled plasma optical emission spectrometry (ICP-OES) and the spatial Cd distribution was investigated in detail applying laser induced breakdown spectroscopy (LIBS). The LIBS maps with a lateral resolution of 100 μm were constructed for the whole plants, and maps with a lateral resolution of 25 μm (micro-LIBS arrangement) were used to analyse only the most interesting parts of plants with Cd presence (e.g. root tips or a part crossing the root into the above-ground part). Our results show that the bioaccumulation patterns and spatial distribution of Cd in CdTe/SiO₂ QDs-treated plants differ from the plants of positive control and CdTe QDs. Fluorescence microscopy photographs revealed that CdTe/SiO₂ became adsorbed onto the plant surface in comparison to CdTe QDs. Further, a physico-chemical characterization of QDs before and after the test exposure showed only minor changes in the nanoparticle diameters and no tendencies of QDs for agglomeration or aggregation during the exposure.

Evaluation of Ecotoxicology Assessment Methods of Nanomaterials and Their Effects

This paper describes the ecotoxicological effects of nanomaterials (NMs) as well as their testing methods. Standard ecotoxicity testing methods are applicable to nanomaterials as well but require some adaptation. We have taken into account methods that meet several conditions. They must be properly researched by a minimum of ten scientific articles where adaptation of the method to the NMs is also presented; use organisms suitable for simple and rapid ecotoxicity testing (SSRET); have a test period shorter than 30 days; require no special equipment; have low costs and have the possibility of optimization for high-throughput screening. From the standard assays described in guidelines developed by organizations such as Organization for Economic Cooperation and Development and United States Environmental Protection Agency, which meet the required conditions, we selected as methods adaptable for NMs, some methods based on algae, duckweed, amphipods, daphnids, chironomids, terrestrial plants, nematodes and earthworms. By analyzing the effects of NMs on a wide range of organisms, it has been observed that these effects can be of several categories, such as behavioral, morphological, cellular, molecular or genetic effects. By comparing the EC₅₀ values of some NMs it has been observed that such values are available mainly for aquatic ecotoxicity, with the most sensitive test being the algae assay. The most toxic NMs overall were the silver NMs.

Phosphate-modified ferric-based material remediates lead and arsenic co-contaminated soil and enhances maize seedling growth

Soil heavy metal pollution, especially lead (Pb) and arsenic (As), is a global issue that requires urgent attention. In the present study, phosphate-modified ferric-based material (PFM) was used to remedy Pb and As co-contaminated soil. The remediation potential of PFM on Pb and As co-contaminated soil was studied by static culture experiments, and the effect on maize (Zea mays L.) seedling growth was studied using pot experiments. The results showed that the bioavailability of Pb and As in the soil and their accumulation in the seedlings were reduced when PFM was added to the soil. At 2-6 wt% PFM, the remediation rates of Pb and As reached 57%-82% and 62%-76%, respectively, and their accumulation in the seedlings decreased by 27.8%-68% and 55.6%-70%. The optimal amount of PFM was 4 wt% of the soil. There was a linear correlation between the amount of DTPA-extractable Pb or NaHCO₃-extractable As in the soil and the amount of Pb or As accumulated by the seedlings. The correlation coefficients of Pb and As reached 0.7690-0.8166 and 0.9982-0.9779. Seedling growth was also promoted. Compared with the controls, the seedling emergence rate increased by 1.4%-4%, plant height increased by 4.1%-12.4%, plant weight increased by 29.6%-37%, and the root length increased by 5%-52%. In summary, PFM offers an environmentally friendly approach with excellent potential for the remediation of Pb and As co-contaminated soil.

Evaluating phytotoxicity of bare and starch-stabilized zero-valent iron nanoparticles in mung bean

Zero-valent iron nanoparticles (nZVI) are among the most widely used nanoparticles in nanoremediation of various environmental pollutants. Environmental fate and impact of nZVI has attracted increasing concerns due to their potential risks. However, phytotoxicity of nZVI still remains poorly understood. Here, the phytotoxic effects of bare nZVI (B-nZVI) and starch-stabilized nZVI (S-nZVI) were evaluated on the germination of mung bean seeds exposed to suspensions with different doses of 0-1000 mg/L and the growth of hydroponically cultured seedling at 600 mg/L. In most cases, B-nZVI had no inhibition on seed germination, and even promotion on shoot and root elongation. However, S-nZVI displayed dose-dependent effects, with a decreased germination rate at 600-750 mg/L. B-nZVI at 600 mg/L showed no obvious phytotoxic but even stimulatory effects on seedling growth. Comparatively, S-nZVI at 600 mg/L produced significant phytotoxicity on mung bean plants, leading to decreased seedling growth, altered nutritional balance, and excess Fe accumulation in roots (>400 mg/kg). S-nZVI were observed to form a coating of insoluble Fe(III) compounds on root surface. Simultaneously, some nZVI penetrated and accumulated into root cells, but did not move to shoots. In conclusion, B-nZVI easily aggregate into larger particles in solution, leading to decreased adhesion to root surface and lower uptake by roots, whereas the higher dispersity and hydrophilicity of S-nZVI makes them more readily be adhered to root surface forming a coating, and penetrated into roots, resulting in excess Fe accumulation, consequently interfering with root functions such as the adsorption and transport of water and nutrients.

Bibliometric study of the toxicology of nanoescale zero valent iron used in soil remediation

The application of nanoscale zero-valent iron is one of the most widely used remediation technologies; however, the potential environmental risks of this technology are largely unknown. In order to broaden the knowledge on this subject, the present work consists of a bibliometric study of all of publications related to the toxicity of zero-valent iron nanoparticles used in soil remediation available from the Scopus (Elsevier) and Web of Science (Thompson Reuters) databases. This study presents a temporal distribution of the publications, the most cited articles, the authors who have made the greatest contribution to the theme, and the institutions, countries, and scientific journals that have published the most on this subject. The use of bibliometrics has allowed for the visualization of a panorama of the publications, providing an appropriate analysis to guide new research towards an effective contribution to science by filling the existing gaps. In particular, the lack of studies in several countries reveals a promising area for the development of further research on this topic.

Hydroponic grown tobacco plants respond to zinc oxide nanoparticles and bulk exposures by morphological, physiological and anatomical adjustments

Zinc oxide nanoparticles (NPs) are the third highest in terms of global production among the various inorganic nanoparticles, and there are concerns because of their worldwide availability and accumulation in the environment. In contrast, zinc is an essential element in plant growth and metabolism, and ZnO NPs (nano-ZnO) may have unknown interactions with plants due to their small sizes as well as their particular chemical and physical characteristics. The present study examined the effect of nano-ZnO (25nm) and bulk or natural form (<1000nm, bulk-ZnO), compared with zinc in the ionic form (ZnSO4) on Nicotiana tabacum seedlings in a nutrient solution supplemented with either nano-ZnO, bulk-ZnO (0.2, 1, 5 and 25µM) or ZnSO4 (control) for 21 days. Results showed that nano-ZnO at most of the levels and 1µM bulk-ZnO positively affected growth (root and shoot length/dry weight), leaf surface area and its metabolites (auxin, phenolic compounds, flavonoids), leaf enzymatic activities (CAT, APX, SOD, POX, GPX, PPO and PAL) and anatomical properties (root, stem, cortex and central cylinder diameters), while bulk-ZnO caused decreases at other levels. The activities of enzymes were induced to a greater extent by intermediate nano-ZnO levels than by extreme concentrations, and were higher in nano-ZnO treated than in bulk treated tobacco. As the ZnO level increased, the vascular expansion and cell wall thickening of the collenchyma/parenchyma cells occurred, which was more pronounced when treated by NPs than by its counterpart. The Zn content of root and leaf increased in most of ZnO treatments, whereas the Fe content of leaves decreased. Our findings indicate that tobacco responded positively to 1µM bulk-ZnO and to nearly all nano-ZnO levels (with the best levels being at 0.2µM and 1µM) by morphological, physiological and anatomical adjustments.

Crystal violet and toxicity removal by adsorption and simultaneous photocatalysis in a continuous flow micro-reactor

A continuous flow micro-reactor irradiated by UV-LEDs was employed to treat coloured wastewater by adsorption and simultaneous photocatalysis. Zinc oxide (ZnO) immobilized on commercial zeolites pellets in spherical shape (ZEO) was used as catalytic material in a micro-reactor maximizing the photocatalyst exposition to light sources, irradiating uniformly the entire solution volume and improving the mass transfer phenomena. Experimental tests were carried out on crystal violet dye (CV) as one of the main dying agent present in textile wastewater. The comparison between adsorption and adsorption/photocatalytic tests showed that UV irradiation can achieve a steady state CV concentration value corresponding to an equilibrium condition between adsorption and photocatalytic oxidation. The higher removal efficiency (i.e. 93%) was observed with a liquid flow rate of 1.1 mL/min (contact time = 4.7 min; CV = 10 mg/L) under UV light irradiation. In the steady state, CV removal remained constant for the overall testing time. Bioassays evidenced that toxicity was not completely removed (i.e. final effluent ranked as "slight acute toxic") from wastewater suggesting its suitability for sewage collection discharge. A Dubinin Radushkevich (D-R) isotherm model was applied for studying the adsorption behaviour of ZnO/ZEO sample. CV adsorption constants were evaluated from experimental data carried out in dark conditions in a batch system. Kinetic expression of CV removal and the D-R adsorption were incorporated in the CV mass balance estimating the kinetic parameter. The model was validated comparing the calculated CV conversion with the experimental tests collected at different CV inlet concentration.

Impact of surface modification on the toxicity of zerovalent iron nanoparticles in aquatic and terrestrial organisms

Nanoscale zerovalent iron (nZVI)-based materials are increasingly being applied in environmental remediation, thereby lead to their exposure to aquatic and terrestrial biota. However, little is known regarding the toxic effects of surface-modified nZVI on multiple species in the ecosystem. In this study, we systematically compared the toxicities of different forms of nZVIs, such as bare nZVI, carboxymethyl cellulose (CMC)-stabilized nZVI, tetrapolyphosphate (TPP)-coated nZVI and bismuth (Bi)-doped nZVI, on a range of aquatic and terrestrial organisms, including bacteria (Escherichia coli and Bacillus subtilis), plant (Arabidopsis thaliana), water flea (Daphnia magna) and earthworm (Eisenia fetida). The Bi- and CMC-nZVI induced adverse biological responses across all the test systems, except E. fetida, varying from cell death in E. coli and B. subtilis to inhibition of the physiological states in D. magna and A. thaliana. The particle characterization under exposure conditions indicated that the surface modification of nZVI played a significant role in their toxicities by changing their physicochemical properties. The underlying mechanisms by which nZVI induces toxicity might be a combination of oxidative stress and another mechanism such as cell membrane disruption, chlorosis and hypoxia. Overall, our findings could provide important implications for the development of environment-friendly nanomaterials and direct further ecotoxicological researches regarding interspecies exploration.

Nano Zero-Valent Iron Mediated Metal(loid) Uptake and Translocation by Arbuscular Mycorrhizal Symbioses

Nano zero-valent iron (nZVI) has great potential in the remediation of metal(loid)-contaminated soils, but its efficiency in metal(loid) stabilization in the plant-microbe continuum is unclear. This study investigated nZVI-mediated metal(loid) behavior in the arbuscular mycorrhizal (AM) fungal-maize ( Zea mays L.) plant association. Plants with AM fungal inoculation were grown in metal(loid)- (mainly Zn and Pb) contaminated soils (Litavka River, Czech Republic) amended with/without 0.5% (w/w) nZVI. The results showed that nZVI decreased plant metal(loid) uptake but inhibited AM development and its function in metal(loid) stabilization in the rhizosphere. AM fungal inoculation alleviated the physiological stresses caused by nZVI and restrained nZVI efficiency in reducing plant metal(loid) uptake. Micro proton-induced X-ray emission (μ-PIXE) analysis revealed the sequestration of Zn (possibly through binding to thiols) by fungal structures in the roots and the precipitation of Pb and Cu in the mycorrhizal root rhizodermis (possibly by Fe compounds originated from nZVI). XRD analyses further indicated that Pb/Fe mineral transformations in the rhizosphere were influenced by AM and nZVI treatments. The study revealed the counteractive effects of AM and nZVI on plant metal(loid) uptake and uncovered details of metal(loid) behavior in the AM fungal-root-nZVI system, calling into question about nZVI implementation in mycorrhizospheric systems.

Effects of ZnO nanoparticles in the Caspian roach (Rutilus rutilus caspicus)

Most studies investigating the toxicity of zinc oxide nanoparticles (ZnO NPs) focused on the effect of size, whereas exposure concentration and duration remained poorly understood. In this study, the effect of acute and sub-acute exposures of ZnO NPs on Zn compartmentalization and biomarkers' expression were investigated in Rutilus rutilus caspicus (Caspian roach) considering various exposure scenarios: i) the assessment of the concentration-response curves and median lethal concentration (LC₅₀); ii) the assessment of the effects of organisms exposed at LC₅₀ value and one tenth of LC₅₀ value of ZnO NPs suspensions for 4 d and 28 d, respectively; iii) the assessment of 14 d depuration period. The same concentrations of ZnSO₄ were investigated. The highest Zn accumulation was detected in gill after sub-acute exposure (4.8 mg/L; 28 d) followed by liver, kidney and muscle. In gill, liver and muscle, Zn from Zn NPs accumulated higher concentrations. Depuration (14 d) decreased Zn content in each organ, but no complete removal occurred except for muscle. Biomarkers' activity was significantly over expressed after treatments, but depuration brought back their values to background levels and most effects were related to acute concentrations (48 mg/L; 4 d) and in presence of ZnSO₄. Histopathological analyses showed that the exposure to ZnO NPs increased lesions in gill, liver and kidney, with a direct proportionality between alterations and Zn accumulated in the target organs. After depuration, lesions regressed for both ZnO NPs and ZnSO₄, but not in a complete way. These data could contribute to increase the knowledge about ZnO NPs risk assessment in aquatic vertebrates, suggesting that the size of ZnO NPs can influence biomarker and histopathological effects.

Remediation of contaminated soils by enhanced nanoscale zero valent iron

The use of nanoscale zero valent iron (nZVI) for in situ remediation of soil contamination caused by heavy metals and organic pollutants has drawn great concern, primarily owing to its potential for excellent activity, low cost and low toxicity. This reviews considers recent advances in our understanding of the role of nZVI and enhanced nZVI strategy in the remediation of heavy metals and persistent organic contaminants polluted soil. The performance, the migration and transformation of nZVI affected by the soil physical and chemical conditions are summarized. However, the addition of nZVI inevitably disturbs the soil ecosystem, thus the impacts of nZVI on soil organisms are discussed. In order to further investigate the remediation effect of nZVI, physical, chemical and biological method combination with nZVI was developed to enhance the performance of nZVI. From a high efficient and environmentally friendly perspective, biological method enhanced nZVI technology will be future research needs. Possible improvement of nZVI-based materials and potential areas for further applications in soil remediation are also proposed.

Toxicity assessment within the application of in situ contaminated sediment remediation technologies: A review

Polluted sediment represents a great problem for aquantic environments with potential direct acute and chronic effects for the biota and can be tackled with both in situ and ex situ treatments. Once dredging activities are not compulsory, sediment can be kept in place and managed with techniques involving the use of amendment and/or capping. Before their application, the assessment of their potential impact to the target environment cannot ignore the safe-by-design approach. The role of toxicity in in situ sediment remediation was reviewed discussing about how it can be used for the selection of amendments and the monitoring of treatment technologies. Results evidenced that capping technology coupled to activated carbon (AC) is the most frequently applied approach with effects varying according to the rate of contamination in treated sediment, the amount of AC used (% v/v), and target biological models considered. Little data are available for zerovalent iron as well as other minor amending agents such as hematite, natural zeolite, biopolymers and organoclays. Current (eco-)toxicological information for in situ sediment remediation technologies is fragmentary and incomplete or entirely missing, making also the interpretation of existing data quite challenging. In situ sediment remediation represents an interesting potentially effective approach for polluted sediment recovering. As its application in some lab-based and field studies reported to induce negative effects for target organisms, amendments and capping agents must be attentively evaluated for short- and long-term environmental effects, also in the perspective of the remediated site monitoring and maintenance.

Environmental Risks of Nano Zerovalent Iron for Arsenate Remediation: Impacts on Cytosolic Levels of Inorganic Phosphate and MgATP2- in Arabidopsis thaliana

The use of nano zerovalent iron (nZVI) for arsenate (As(V)) remediation has proven effective, but full-scale injection of nZVI into the subsurface has aroused serious concerns for associated environmental risks. This study evaluated the efficacy of nZVI treatment for arsenate remediation and its potential hazards to plants using Arabidopsis thaliana grown in a hydroponic system. Biosensors for inorganic phosphate (Pi) and MgATP^2- were used to monitor in vivo Pi and MgATP^2- levels in plant cells. The results showed that nZVI could remove As(V) from growth media, decrease As uptake by plants, and mitigate As(V) toxicity to plants. However, excess nZVI could cause Pi starvation in plants leading to detrimental effects on plant growth. Due to the competitive adsorption of As(V) and Pi on nZVI, removing As(V) via nZVI treatment at an upstream site could relieve downstream plants from As(V) toxicity and Pi deprivation, in which case 100 mg/L of nZVI was the optimal dosage for remediation of As(V) at a concentration around 16.13 mg/L.

New insights into the cellular responses to iron nanoparticles in Capsicum annuum

In this study, the anatomical and ultrastructural responses of Capsicum annuum to iron nanoparticles (Fe NPs) were determined. The results showed that the bio-effects of Fe NPs on plants could be positive or negative, depending on the additive concentrations. Low concentrations of Fe NPs were found to promote plant growth. Light and electron microscope analyses showed that the Fe NPs promoted plant growth by altering the leaf organization, and increasing the chloroplast number and grana stacking, as well as regulating the development of vascular bundles. Meanwhile, it was found that the Fe NPs could be absorbed in the roots, and then transported to the central cylinder in bio-available forms, where they were translocated and utilized by the leaves and stems. In contrast, high concentrations of Fe NPs appeared to be harmful to the plants, and the majority of Fe NPs were aggregated into cell walls and transported via the apoplastic pathway in the roots, which may potentially block the transfer of iron nutrients. Taken together, the aforementioned data showed that the rational use of Fe NPs could alleviate iron deficiency, and Fe NPs could be an ideal supply for Fe²⁺ ions fertilizers in agriculture.

Assessment of metal pollution in the Lambro Creek (Italy)

This study assessed the effect of metal pollution in the Lambro Creek (Southern Italy). Water, sediment and biota were collected at six sampling sites (June) for metal concentration assessment (Cr, Cu, Ni, Pb and Zn). Sequential extraction was performed to determine the distribution of metals in different geochemical sediment fractions. The influence of pH and leaching time on the release of metals from sediment to the water column was investigated via remobilization tests. A battery of toxicity tests (Vibrio fischeri, Raphidocelis subcapitata, Phaeodactylum tricornutum, and Daphnia magna) with multi-endpoints (bioluminescence, growth inhibition, and immobilization) was used to determine the overall toxicity in sediment water extracts. The results showed that metals did not exceed the probable effect concentration levels, with Cr concentration exceeding the threshold effect concentration level at all sampling points except for the one closer to the source of the creek, suggesting potential negative effect on the biota. Considering the cumulative criterion unit, sediment contamination was moderate at all sampling sites, except for L3 and L5 where biota was exposed to a very high risk. With respect to sequential analysis, the most readily available fraction of metal can be generalised as Ni > Cr > Cu > Zn > Pb. For better understanding the fate of metals in the water-sediment environment, their biogeochemical cycles should also be investigated in small creeks including both fresh (watercourse) and saltwater (river mouth) sediments.

Environmental transformations and ecological effects of iron-based nanoparticles

The increasing application of iron-based nanoparticles (NPs), especially high concentrations of zero-valent iron nanoparticles (nZVI), has raised concerns regarding their environmental behavior and potential ecological effects. In the environment, iron-based NPs undergo physical, chemical, and/or biological transformations as influenced by environmental factors such as pH, ions, dissolved oxygen, natural organic matter (NOM), and biotas. This review presents recent research advances on environmental transformations of iron-based NPs, and articulates their relationships with the observed toxicities. The type and extent of physical, chemical, and biological transformations, including aggregation, oxidation, and bio-reduction, depend on the properties of NPs and the receiving environment. Toxicities of iron-based NPs to bacteria, algae, fish, and plants are increasingly observed, which are evaluated with a particular focus on the underlying mechanisms. The toxicity of iron-based NPs is a function of their properties, tolerance of test organisms, and environmental conditions. Oxidative stress induced by reactive oxygen species is considered as the primary toxic mechanism of iron-based NPs. Factors influencing the toxicity of iron-based NPs are addressed and environmental transformations play a significant role, for example, surface oxidation or coating by NOM generally lowers the toxicity of nZVI. Research gaps and future directions are suggested with an aim to boost concerted research efforts on environmental transformations and toxicity of iron-based NPs, e.g., toxicity studies of transformed NPs in field, expansion of toxicity endpoints, and roles of laden contaminants and surface coating. This review will enhance our understanding of potential risks of iron-based NPs and proper uses of environmentally benign NPs.

Uptake and transformations of engineered nanomaterials: Critical responses observed in terrestrial plants and the model plant Arabidopsis thaliana

With the applications of engineered nanomaterials (ENMs) continually expanding and production quickly growing, residues of ENMs will end up in the environment at levels that may be harmful to non-target organisms. Many of the tunable properties that have made them desirable, such as type, size, charge, or coating, also contribute to the current difficulties in understanding the fate of ENMs in the environment. This review article focuses on studies that investigate plant-ENM interactions, including techniques used to study these interactions and documented plant responses due to the phytotoxic effects of ENMs. The many variables which can be altered for an experiment, such as type, size, and concentration of ENMs, make it difficult to formulate generalizations about the uptake mechanism involved, or to make an inference on the subcellular localization and distribution of the internalized ENMs in plant tissue. In order to avoid these challenges, studies can utilize a model organism such as Arabidopsis thaliana, and a combination of analytical techniques that can reveal complementary information in order to assess how the different experimental conditions influence the uptake and phytotoxicity of ENMs. This review presents recent studies regarding plant-ENM interactions employing Arabidopsis to demonstrate how the use of this model plant can advance our understanding of plant-ENM interactions and guide additional studies using other plant species. Overarching results suggest that more sensitive tests and consistency in experimental designs are needed to fully assess and understand the phytotoxic effects of ENMs in the environment.

Stabilized Nanoscale Zerovalent Iron Mediated Cadmium Accumulation and Oxidative Damage of Boehmeria nivea (L.) Gaudich Cultivated in Cadmium Contaminated Sediments

Nanoparticles can be absorbed by plants, but their impacts on phytoremediation are not yet well understood. This study was carried out to determine the impacts of starch stabilized nanoscale zerovalent iron (S-nZVI) on the cadmium (Cd) accumulation and the oxidative stress in Boehmeria nivea (L.) Gaudich (ramie). Plants were cultivated in Cd-contaminated sediments amended with S-nZVI at 100, 500, and 1000 mg/kg, respectively. Results showed that S-nZVI promoted Cd accumulation in ramie seedlings. The subcellular distribution result showed that Cd content in cell wall of plants reduced, and its concentration in cell organelle and soluble fractions increased at S-nZVI treatments, indicating the promotion of Cd entering plant cells by S-nZVI. In addition, the 100 mg/kg S-nZVI alleviated the oxidative damage to ramie under Cd-stress, while 500 and 1000 mg/kg S-nZVI inhibited plant growth and aggravated the oxidative damage to plants. These findings demonstrate that nanoparticles at low concentration can improve the efficiency of phytoremediation. This study herein develops a promising novel technique by the combined use of nanotechnology and phytoremediation in the remediation of heavy metal contaminated sites.

Toxicity Effects of Functionalized Quantum Dots, Gold and Polystyrene Nanoparticles on Target Aquatic Biological Models: A Review

Nano-based products are widespread in several sectors, including textiles, medical-products, cosmetics, paints and plastics. Nanosafety and safe-by-design are driving nanoparticle (NP) production and applications through NP functionalization (@NPs). Indeed, @NPs frequently present biological effects that differ from the parent material. This paper reviews the impact of quantum dots (QDs), gold nanoparticles (AuNPs), and polystyrene-cored NPs (PSNPs), evidencing the role of NP functionalization in toxicity definition. Key biological models were taken into consideration for NP evaluation: Saccharomyces cerevisiae, fresh- (F) and saltwater (S) microalgae (Raphidocelis subcapitata (F), Scenedesmus obliquus (F) and Chlorella spp. (F), and Phaeodactylum tricornutum (S)), Daphnia magna, and Xenopus laevis. QDs are quite widespread in technological devices, and they are known to induce genotoxicity and oxidative stress that can drastically change according to the coating employed. For example, AuNPs are frequently functionalized with antimicrobial peptides, which is shown to both increase their activity and decrease the relative environmental toxicity. P-NPs are frequently coated with NH₂⁻ for cationic and COOH⁻ for anionic surfaces, but when positively charged toxicity effects can be observed. Careful assessment of functionalized and non-functionalized NPs is compulsory to also understand their potential direct and indirect effects when the coating is removed or degraded.

Engineered nano particles: Nature, behavior, and effect on the environment

Increased application of engineered nano particles (ENPs) in production of various appliances and consumer items is increasing their presence in the natural environment. Although a wide variety of nano particles (NPs) are ubiquitously dispersed in ecosystems, risk assessment guidelines to describe their ageing, direct exposure, and long-term accumulation characteristics are poorly developed. In this review, we describe what is known about the life cycle of ENPs and their impact on natural systems and examine if there is a cohesive relationship between their transformation processes and bio-accessibility in various food chains. Different environmental stressors influence the fate of these particles in the environment. Composition of solid media, pore size, solution chemistry, mineral composition, presence of natural organic matter, and fluid velocity are some environmental stressors that influence the transformation, transport, and mobility of nano particles. Transformed nano particles can reduce cell viability, growth and morphology, enhance oxidative stress, and damage DNA in living organisms.

Effects of nanoparticles in species of aquaculture interest

Recently, it was observed that there is an increasing application of nanoparticles (NPs) in aquaculture. Manufacturers are trying to use nano-based tools to remove the barriers about waterborne food, growth, reproduction, and culturing of species, their health, and water treatment in order to increase aquaculture production rates, being the safe-by-design approach still unapplied. We reviewed the applications of NPs in aquaculture evidencing that the way NPs are applied can be very different: some are direclty added to feed, other to water media or in aquaculture facilities. Traditional toxicity data cannot be easily used to infer on aquaculture mainly considering short-term exposure scenarios, underestimating the potential exposure of aquacultured species. The main outputs are (i) biological models are not recurrent, and in the case, testing protocols are frequently different; (ii) most data derived from toxicity studies are not specifically designed on aquaculture needs, thus contact time, exposure concentrations, and other ancillary conditions do not meet the required standard for aquaculture; (iii) short-term exposure periods are investigated mainly on species of indirect aquaculture interest, while shrimp and fish as final consumers in aquaculture plants are underinvestigated (scarce or unknown data on trophic chain transfer of NPs): little information is available about the amount of NPs accumulated within marketed organisms; (iv) how NPs present in the packaging of aquacultured products can affect their quality remained substantially unexplored. NPs in aquaculture are a challenging topic that must be developed in the near future to assure human health and environmental safety. Graphical abstract ᅟ.

Toxicity-based toxicokinetic/toxicodynamic assessment of bioaccumulation and nanotoxicity of zerovalent iron nanoparticles in Caenorhabditis elegans

Elucidating the relationships between the toxicity-based-toxicokinetic (TBTK)/toxicodynamic (TD) properties of engineered nanomaterials and their nanotoxicity is crucial for human health-risk analysis. Zerovalent iron (Fe⁰) nanoparticles (NPs) are one of the most prominent NPs applied in remediating contaminated soils and groundwater. However, there are concerns that Fe⁰NP application contributes to long-term environmental and human health impacts. The nematode Caenorhabditis elegans is a surrogate in vivo model that has been successfully applied to assess the potential nanotoxicity of these nanomaterials. Here we present a TBTK/TD approach to appraise bioaccumulation and nanotoxicity of Fe⁰NPs in C. elegans. Built on a present C. elegans bioassay with estimated TBTK/TD parameters, we found that average bioconcentration factors in C. elegans exposed to waterborne and food-borne Fe⁰NPs were ~50 and ~5×10^-3, respectively, whereas 10% inhibition concentrations for fertility, locomotion, and development, were 1.26 (95% CI 0.19-5.2), 3.84 (0.38-42), and 6.78 (2.58-21) μg·g^-1, respectively, implicating that fertility is the most sensitive endpoint in C. elegans. Our results also showed that biomagnification effects were not observed in waterborne or food-borne Fe⁰NP-exposed worms. We suggest that the TBTK/TD assessment for predicting NP-induced toxicity at different concentrations and conditions in C. elegans could enable rapid selection of nanomaterials that are more likely to be nontoxic in larger animals. We conclude that the use of the TBTK/TD scheme manipulating C. elegans could be used for rapid evaluation of in vivo toxicity of NPs or for drug screening in the field of nanomedicine.

In situ remediation of contaminated marinesediment: an overview

Sediment tends to accumulate inorganic and persistent hydrophobic organic contaminants representing one of the main sinks and sources of pollution. Generally, contaminated sediment poses medium- and long-term risks to humans and ecosystem health; dredging activities or natural resuspension phenomena (i.e., strongly adverse weather conditions) can remobilize pollution releasing it into the water column. Thus, ex situ traditional remediation activities (i.e., dredging) can be hazardous compared to in situ techniques that try to keep to a minimum sediment mobilization, unless dredging is compulsory to reach a desired bathymetric level. We reviewed in situ physico-chemical (i.e., active mixing and thin capping, solidification/stabilization, chemical oxidation, dechlorination, electrokinetic separation, and sediment flushing) and bio-assisted treatments, including hybrid solutions (i.e., nanocomposite reactive capping, bioreactive capping, microbial electrochemical technologies). We found that significant gaps still remain into the knowledge about the application of in situ contaminated sediment remediation techniques from the technical and the practical viewpoint. Only activated carbon-based technologies are well developed and currently applied with several available case studies. The environmental implication of in situ remediation technologies was only shortly investigated on a long-term basis after its application, so it is not clear how they can really perform.