Particle-size dependent accumulation and trophic transfer of cerium oxide through a terrestrial food chain

Emerging concern of nano-pollution in agro-ecosystem: Flip side of nanotechnology

Nanomaterials (NMs) have proven to be a game-changer in agriculture, showcasing their potential to boost plant growth and safeguarding crops. The agricultural sector has widely adopted NMs, benefiting from their small size, high surface area, and optical properties to augment crop productivity and provide protection against various stressors. This is attributed to their unique characteristics, contributing to their widespread use in agriculture. Human exposure from various components of agro-environmental sectors (soil, crops) NMs residues are likely to upsurge with exposure paths may stimulates bioaccumulation in food chain. With the aim to achieve sustainability, nanotechnology (NTs) do exhibit its potentials in various domains of agriculture also have its flip side too. In this review article we have opted a fusion approach using bibliometric based analysis of global research trend followed by a holistic assessment of pros and cons i.e. toxicological aspect too. Moreover, we have also tried to analyse the current scenario of policy associated with the application of NMs in agro-environment.

Evaluation of the effect of nanoparticles on the cultivation of edible plants by ICP-MS: a review

Nanoparticle (NP) applications aiming to boost plant biomass production and enhance the nutritional quality of crops hae proven to be a valuable ally in enhancing agricultural output. They contribute to greater food accessibility for a growing and vulnerable population. These nanoscale particles are commonly used in agriculture as fertilizers, pesticides, plant growth promoters, seed treatments, opportune plant disease detection, monitoring soil and water quality, identification and detection of toxic agrochemicals, and soil and water remediation. In addition to the countless NP applications in food and agriculture, it is possible to highlight many others, such as medicine and electronics. However, it is crucial to emphasize the imperative need for thorough NP characterization beyond these applications. Therefore, analytical methods are proposed to determine NPs' physicochemical properties, such as composition, crystal structure, size, shape, surface charge, morphology, and specific surface area, detaching the inductively coupled plasma mass spectrometry (ICP-MS) that allows the reliable elemental composition quantification mainly in metallic NPs. As a result, this review highlights studies involving NPs in agriculture and their consequential effects on plants, with a specific focus on analyses conducted through ICP-MS. Given the numerous applications of NPs in this field, it is essential to address their presence and increase in the environment and humans since biomagnification and biotransformation effects are studies that should be further developed. In light of this, the demand for rapid, innovative, and sensitive analytical methods for the characterization of NPs remains paramount.

Mixed effects and co-transfer of CeO2 NPs and arsenic in the pakchoi-snail food chain

Nanomaterial application in agriculture offers novel solutions for soil arsenic (As) pollution control, yet safety along the food chain is of concern. We comprehensively assessed CeO2 nanoparticles (NPs) foliar application effects on As uptake by pakchoi and their presence in the pakchoi-snail food chain. CeO2 NPs reduced As transfer from pakchoi roots to shoots by 37.9%, lowered As in snail foot by 39%, and halved human As exposure risk. The NPs alleviated pakchoi shoot As toxicity by regulating antioxidants, enhancing water use efficiency, and photosynthesis. CeO2 +As treatment raised GSH/GSSG ratios by 38.92%- 167.54%, leading to an increased AsIII/AsV ratio and inorganic As detoxification compared to As alone. Metabolomics revealed CeO2's rapid As response via phosphatidylinositol signaling. The enzyme-like activity of CeO2 NPs may drive these effects. While CeO2 foliar application accumulated Ce on pakchoi leaves, > 99% of Ce was excreted following snail consumption. Ce transfer from pakchoi leaves to snail foot was minimal (trophic transfer factor ∼0.00007) due to limited bioavailability. The target hazard quotient of Ce in pakchoi shoot (1.21 ± 0.18) and snails (0.0016 ± 0.0004) indicated low exposure risk, suggesting a 'risk filter' effect for CeO2. Our results contribute to the safe and sustainable application of CeO2 NPs in the future implication.

Trophic transfer of nanomaterials and their effects on high-trophic-level predators

Nanotechnology offers great opportunities for numerous sectors in society. One important challenge in sustainable nanotechnology is the potential of trophic transfer of nanomaterials (NMs), which may lead to unintentional impacts on environmental and human health. Here, we highlight the key advances that have been made in recent 15 years with respect to trophic transfer of heterogeneous NMs, including metal-based NMs, carbon-based NMs and nanoplastics, across various aquatic and terrestrial food chains. Particle number-based trophic transfer factors (TTFs), rather than the variable mass-based TTFs, capture the particle-specific transfer, for which NMs exhibit dynamic and complex biotransformation (e.g., dissolution, sulfidation, reduction, and corona formation). Trophic transfer of NMs has toxicological significance to predators at molecular (e.g., increased oxidative stress and modified metabolites), physiological (e.g., feeding inhibition) and population (e.g., reproduction inhibition) levels. However, linking NM exposure and toxicity remains a challenge, partly due to the dynamic biotransformation along the food chain. Although NMs have been used to increase crop yield in agriculture, they can exert detrimental impacts on crop yield and modify crop quality, depending on NMs type, exposure dose, and crop species, with unknown consequences to human health via crop consumption. Given this information, we describe the challenges and opportunities in understanding the significance of NMs trophic transfer to develop more sustainable, effective and safer nanotechnology.

Ecotoxicity of non- and PEG-modified lanthanide-doped nanoparticles in aquatic organisms

Various types of nanoparticles (NPs) have been widely investigated recently and applied in areas such as industry, the energy sector, and medicine, presenting the risk of their release into the environment. The ecotoxicity of NPs depends on several factors such as their shape and surface chemistry. Polyethylene glycol (PEG) is one of the most often used compounds for functionalisation of NP surfaces, and its presence on the surfaces of NPs may affect their ecotoxicity. Therefore, the present study aimed to assess the influence of PEG modification on the toxicity of NPs. As biological model, we chose freshwater microalgae, a macrophyte and invertebrates, which to a considerable extent enable the assessment of the harmfulness of NPs to freshwater biota. SrF₂:Yb³⁺,Er³⁺ NPs were used to represent the broad group of up-converting NPs, which have been intensively investigated for medical applications. We quantified the effects of the NPs on five freshwater species representing three trophic levels: the green microalgae Raphidocelis subcapitata and Chlorella vulgaris, the macrophyte Lemna minor, the cladoceran Daphnia magna and the cnidarian Hydra viridissima. Overall, H. viridissima was the most sensitive species to NPs, which affected its survival and feeding rate. In this case, PEG-modified NPs were slightly more toxic than bare ones (non-significant results). No effects were observed on the other species exposed to the two NPs at the tested concentrations. The tested NPs were successfully imaged in the body of D. magna using confocal microscopy; both NPs were detected in the D. magna gut. The results obtained reveal that SrF₂:Yb³⁺,Er³⁺ NPs can be toxic to some aquatic species; however, the structures have low toxicity effects for most of the tested species.

Insights on the Dynamics and Toxicity of Nanoparticles in Environmental Matrices

The manufacturing rate of nanoparticles (10–100 nm) is steadily increasing due to their extensive applications in the fabrication of nanoproducts related to pharmaceuticals, cosmetics, medical devices, paints and pigments, energy storage etc. An increase in research related to nanotechnology is also a cause for the production and disposal of nanomaterials at the lab scale. As a result, contamination of environmental matrices with nanoparticles becomes inevitable, and the understanding of the risk of nanoecotoxicology is getting larger attention. In this context, focusing on the environmental hazards is essential. Hence, this manuscript aims to review the toxic effects of nanoparticles on soil, water, aquatic, and terrestrial organisms. The effects of toxicity on vertebrates, invertebrates, and plants and the source of exposure, environmental and biological dynamics, and the adverse effects of some nanoparticles are discussed.

Engineered Nanoparticle-Protein Interactions Influence Protein Structural Integrity and Biological Significance

Engineered nanoparticles (ENPs) are artificially synthesized particles with unique physicochemical properties. ENPs are being extensively used in several consumer items, elevating the probability of ENP exposure to biological systems. ENPs interact with various biomolecules like lipids, proteins, nucleic acids, where proteins are most susceptible. The ENP-protein interactions are mostly studied for corona formation and its effect on the bio-reactivity of ENPs, however, an in-depth understanding of subsequent interactive effects on proteins, such as alterations in their structure, conformation, free energy, and folding is still required. The present review focuses on ENP-protein interactions and the subsequent effects on protein structure and function followed by the therapeutic potential of ENPs for protein misfolding diseases.

An integrated ICP-MS-based analytical approach to fractionate and characterize ionic and nanoparticulate Ce species

Cerium dioxide nanoparticles (CeO₂ NPs) are widely used in various fields, leading to concern about their effect on human health. When conducting in vivo investigations of CeO₂ NPs, the challenge is to fractionate ionic Ce and CeO₂ NPs and to characterize CeO₂ NPs without changing their properties/state. To meet this challenge, we developed an integrated inductively coupled plasma-mass spectrometry (ICP-MS)-based analytical approach in which ultrafiltration is used to fractionate ionic and nanoparticulate Ce species while CeO₂ NPs are characterized by single particle-ICP-MS (sp-ICP-MS). We used this technique to compare the effects of two sample pretreatment methods, alkaline and enzymatic pretreatments, on ionic Ce and CeO₂ NPs. Results showed that enzymatic pretreatment was more efficient in extracting ionic Ce or CeO₂ NPs from animal tissues. Moreover, results further showed that the properties/states of all ionic and nanoparticulate Ce species were well preserved. The rates of recovery of both species were over 85%; the size distribution of CeO₂ NPs was comparable to that of original NPs. We then applied this analytical approach, including the enzymatic pretreatment and ICP-MS-based analytical techniques, to investigate the bioaccumulation and biotransformation of CeO₂ NPs in mice. It was found that the thymus acts as a "holding station" in CeO₂ NP translocation in vivo. CeO₂ NP biotransformation was reported to be organ-specific. This is the first study to evaluate the impact of enzymatic and alkaline pretreatment on Ce species, namely ionic Ce and CeO₂ NPs. This integrated ICP-MS-based analytical approach enables us to conduct in vivo biotransformation investigations of CeO₂ NPs.

Recent advances in responses of arbuscular mycorrhizal fungi - Plant symbiosis to engineered nanoparticles

The application of engineered nanomaterials (ENMs) is increasing in all walks of life, inevitably resulting in a high risk of ENMs entering the natural environment. Recent studies have demonstrated that phytoaccumulation of ENMs in the environment may be detrimental to plants to varying degrees. However, plants primarily assimilate ENMs through the roots, which are inevitably affected by rhizomicroorganisms. In this review, we focus on a group of common rhizomicroorganisms-arbuscular mycorrhizal fungi (AMF). These fungi contribute to ENMs immobilization and inhibition of phytoaccumulation, improvement of host plant growth and activation of systematic protection in response to excess ENMs stress. In present review, we summarize the biological responses of plants to ENMs and the modulatory mechanisms of AMF on the immobilization of ENMs in substrate-plant interfaces, and indirectly regulatory mechanisms of AMF on the deleterious effects of ENMs on host plants. In addition, the information of feedback of ENMs on mycorrhizal symbiosis and the prospects of future research on the fate and mechanism of phyto-toxicity of ENMs mediated by AMF in the environment are also addressed. In view of above, synergistic reaction of plants and AMF may prove to be a cost-effective and eco-friendly technology to bio-control potential ENMs contamination on a sustainable basis.

Trophic Transfer and Toxicity of (Mixtures of) Ag and TiO2 Nanoparticles in the Lettuce-Terrestrial Snail Food Chain

The increasing application of biosolids and agrochemicals containing silver nanoparticles (AgNPs) and titanium dioxide nanoparticles (TiO2NPs) results in their inevitable accumulation in soil, with unknown implications along terrestrial food chains. Here, the trophic transfer of single NPs and a mixture of AgNPs and TiO2NPs from lettuce to snails and their associated impacts on snails were investigated. Both AgNPs and TiO2NPs were transferred from lettuce to snails with trophic transfer factors (defined as the ratio of the Ag/Ti concentration in snail tissues to the Ag/Ti concentration in lettuce leaves) of 0.2-1.1 for Ag and 3.8-47 for Ti. Moreover, the majority of Ag captured by snails in the AgNP-containing treatments was excreted via feces, whereas more than 70% of Ti was distributed in the digestive gland of snails in the TiO2NP-containing treatments. Additionally, AgNP-containing treatments significantly inhibited the activity of snails, while TiO2NP-containing treatments significantly reduced feces excretion of snails. Furthermore, the concurrent application of AgNPs and TiO2NPs did not affect the biomagnification and distribution patterns of Ag and Ti in snails, whereas their co-existence exhibited more severe inhibition of the growth and activity of snails than in the case of applying AgNPs or TiO2NPs alone. This highlights the possibility of nanoparticle transfer to organisms of higher trophic levels via food chains and the associated risks to ecosystem health.

Effects of surface modification on toxicity of CeO2 nanoparticles to lettuce

Phytotoxicity of nanoceria (nCeO2) has been reported, but there are few studies on how to reduce its phytotoxicity. In the present study, we modified nCeO2 with two organophosphates (nCeO2@ATMP and nCeO2@EDTMP) and compared their toxicity to lettuce with that of uncoated nCeO2. The results showed that bare nCeO2 significantly inhibited the root growth of lettuce, leading to oxidative damages and root cell death. In contrast, after surface modification, the toxicity of nCeO2@ATMP to lettuce was weakened, while nCeO2@EDTMP was nontoxic to lettuce. It was found that the surface properties of the modified materials have been changed, resulting in sharp decreases in their bioavailability. Although nCeO2 with and without surface coatings were all transformed when interacting with plants, the absolute contents of Ce(III) in roots treated with modified nCeO2 decreased significantly, which may be the main reason for the reduction of toxicity. This study indicates that it is feasible to reduce the phytotoxicity of nanomaterials through surface coating.

Recent insights into the impact, fate and transport of cerium oxide nanoparticles in the plant-soil continuum

The advent of the nanotechnology era offers a unique opportunity for sustainable agriculture provided that the exposure and toxicity are adequately assessed and properly controlled. The global production and application of cerium oxide nanoparticles (CeO₂-NPs) in various industrial sectors have tremendously increased. Most of the nanoparticles end up in water and soil where they interact with soil microorganisms and plants. Investigating the uptake, translocation and accumulation of CeO₂-NPs is critical for its safe application in agriculture. Plant uptake of CeO₂-NPs may lead to their accumulation in different plant tissues and interference with key metabolic processes of plants. Soil microbes can also be affected by increasing CeO₂-NPs in soil, leading to changes in the physiology and enzymatic activity of soil microorganisms. The interactions between CeO₂-NPs, microbes and plants in the agricultural system need systemic research in ecologically relevant conditions. In the present review, The uptake pathways and in-planta translocation of CeO₂-NPs,and their impact on plant morphology, nutritional values, antioxidant enzymes and molecular determinants are presented. The role of CeO₂-NPs in modifying soil microbial community in plant rhizosphere is also discussed. Overall, the review aims to provide a comprehensive account on the behaviour of CeO₂-NPs in soil-plant systems and their potential impacts on the soil microbial community and plant health.

Copper Oxide Nanomaterial Fate in Plant Tissue: Nanoscale Impacts on Reproductive Tissues

A thorough understanding of the implications of chronic low-dose exposure to engineered nanomaterials through the food chain is lacking. The present study aimed to characterize such a response in Cucurbita pepo L. (zucchini) upon exposure to a potential nanoscale fertilizer: copper oxide (CuO) nanoparticles. Zucchini was grown in soil amended with nano-CuO, bulk CuO (100 mg Kg^-1), and CuSO₄ (320 mg Kg^-1) from germination to flowering (60 days). Nano-CuO treatment had no impact on plant morphology or growth nor pollen formation and viability. The uptake of Cu was comparable in the plant tissues under all treatments. RNA-seq analyses on vegetative and reproductive tissues highlighted common and nanoscale-specific components of the response. Mitochondrial and chloroplast functions were uniquely modulated in response to nanomaterial exposure as compared with conventional bulk and salt forms. X-ray absorption spectroscopy showed that the Cu local structure changed upon nano-CuO internalization, suggesting potential nanoparticle biotransformation within the plant tissues. These findings demonstrate the potential positive physiological, cellular, and molecular response related to nano-CuO application as a plant fertilizer, highlighting the differential mechanisms involved in the exposure to Cu in nanoscale, bulk, or salt forms. Nano-CuO uniquely stimulates plant response in a way that can minimize agrochemical inputs to the environment and therefore could be an important strategy in nanoenabled agriculture.

Comparative toxicity of rod-shaped nano-CeO2 and nano-CePO4 to lettuce

The influence of morphology on the biological effects of nanomaterials (NMs) has not been well understood. In the present study, we compared the phytotoxicity of rod-shaped nano-cerium dioxide (R-CeO2) and nano-cerium phosphate (R-CePO4) to lettuce plants. The results showed that R-CeO2 significantly inhibited the root elongation of lettuce, induced oxidative damages, and caused cell death, while R-CePO4 was nontoxic to lettuce. The different distribution and speciation of Ce in plant tissues were determined by transmission electron microscopy (TEM) and X-ray absorption near edge spectroscopy (XANES) combined with linear combination fitting (LCF). The results showed that in the R-CeO2 group, part of Ce was transformed from Ce(IV) to Ce(III), while only Ce(III) was present in the R-CePO4 group. When interacting with plants, R-CeO2 is easier to be dissolved and transformed than R-CePO4, which might be the reason for their different phytotoxicity. Although both are Ce-based NMs and have the same morphology, the toxicity of R-CeO2 seems to come from the released Ce3+ ions rather than its shape. This research emphasizes the importance of chemical composition and reactivity of NMs to their toxicological effects.

Ingestion and effects of cerium oxide nanoparticles on Spodoptera frugiperda (Lepidoptera: Noctuidae)

The objective of this study was to evaluate the biological and nutritional characteristics of Spodoptera frugiperda (Lepidoptera: Noctuidae), an arthropod pest widely distributed in agricultural regions, after exposure to nano-CeO₂ via an artificial diet and to investigate the presence of cerium in the body of this insect through X-ray fluorescence mapping. Nano-CeO₂, micro-CeO₂, and Ce(NO₃)₃ were incorporated into the diet (0.1, 1, 10, and 100 mg of Ce L^-1). Cerium was detected in caterpillars fed with diets containing nano-CeO₂ (1, 10 and 100 mg of Ce L^-1), micro-CeO₂ and Ce(NO₃)₃, and in feces of caterpillars from the first generation fed diets with nano-CeO₂ at 100 mg of Ce L^-1 as well. The results indicate that nano-CeO₂ caused negative effects on S. frugiperda. After it was consumed by the caterpillars, the nano-CeO₂ reduced up to 4.8% of the pupal weight and 60% of egg viability. Unlike what occurred with micro-CeO₂ and Ce(NO₃)₃, nano-CeO₂ negatively affected nutritional parameters of this insect, as consumption rate two times higher, increase of up to 80.8% of relative metabolic rate, reduction of up to 42.3% efficiency of conversion of ingested and 47.2% of digested food, and increase of up to 1.7% of metabolic cost and 8.7% of apparent digestibility. Cerium caused 6.8-16.9% pupal weight reduction in second generation specimens, even without the caterpillars having contact with the cerium via artificial diet. The results show the importance of new ecotoxicological studies with nano-CeO₂ for S. frugiperda in semi-field and field conditions to confirm the toxicity.

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.

Examining the uptake and bioaccumulation of molybdenum nanoparticles and their effect on antioxidant activities in growing rice seedlings

The synthesized α-MoO₃ and MoS₂ NPs had nanosheet and nanoflower-like structures with crystallite size of 21.34 nm and 4.32 nm, respectively. The uptake, bioaccumulation, and impact of these two Mo-NPs were studied in rice (Oryza sativa L) cv. HUR 3022 seedlings exposed to 100, 500, and 1000 ppm concentrations in hydroponics for 10 days in the growth medium. The uptake of α-MoO₃ and MoS₂ NPs by rice exposed to 100 ppm concentrations of NPs led to the accumulation of 7.32 ppm/4.55 ppm and 1.84 ppm/1.19 ppm in roots/shoots, respectively, as compared to controls. Unlike MoO₃, more accumulation of MoS₂ in roots reflect less translocation of this NP from roots to shoots. Results suggest tissue-specific distribution of NPs in rice seedlings. The increased growth and elevated protein levels in rice seedlings at 100 ppm concentrations of nanoparticles imply a stimulation in the repair mechanism at low doses indicating hormesis. MoS₂ NPs treatments led to increased chlorophyll a levels suggesting it to be non-compromising with photosynthetic process in rice. The high malondialdehyde levels and altered activities of antioxidant enzymes GPX, APX, and CAT in rice seedlings exposed to α-MoO₃ or MoS₂ NPs indicate oxidative imbalance. Between α-MoO₃ and MoS₂ NPs, the former shows toxic effects as reflected from the decreased levels of photosynthetic pigments at all concentrations; however, an activation of chloroplast ROS detoxification is evident in the presence of MoS₂ NPs. The BCF > 1 for both α-MoO₃ and MoS₂ NPs and TF of 0.6-2.0 and 0.42-0.65 suggest the latter to be more environmentally safe. In conclusion, a100 ppm MoS₂ NPs concentration has low translocation and less accumulation with no significant impact on growth of rice cv. HUR 3022 seedlings and appears to be environmentally safe for future applications.

DNA damage and ovarian ultrastructural lesions induced by nickel oxide nano-particles in Blaps polycresta (Coleoptera: Tenebrionidae)

Nickel oxide nanoparticles (NiO-NPs) have extensively used in industrial and consumer products. The present study conducted to gain more knowledge about the safe use of NiO-NPs and also to understand their impact on the environment and biological systems. Herein, we examined the genotoxic and ultra-structural effects of a sublethal dose of NiO-NPs (0.03 mg/g) on the ovarian tissues of the ground beetle, Blaps polycresta. The mean diameter of NiO-NPs was 24.49 ± 3.88 nm, as obtained through transmission electron microscopy (TEM). In terms of DNA damage levels, the frequency of micronucleus (MN) formation was highly significant in the NiO-NPs treated group versus the controls. Besides, NiO-NPs treatment resulted in a significant increase in the tail length of comets. Further, electron microscopy revealed a progressive increase in chromatin condensation of the ovarian nurse and follicular cells, in addition to the accumulation of lysosomes and endo-lysosomes in their cytoplasm. In conclusion, NiO-NPs are capable of gaining access to the ovary of B. polycresta and causing DNA damage and a high degree of cellular toxicity in the ovarian cells. The present study highlights, for the first time, the adverse effects of these NPs to female gonads of insects and raised the concern of its genotoxic potential. It would be of interest to investigate NiO-NPs mediated intracellular ROS generation in future studies.

Surface Properties and Environmental Transformations Controlling the Bioaccumulation and Toxicity of Cerium Oxide Nanoparticles: A Critical Review

Increasing production and utilization of cerium oxide nanoparticles (CNPs) in recent years have raised wide concerns about their toxicity. Numerous studies have been conducted to reveal the toxicity of CNPs, but the results are sometimes contradictory. In this review, the most important factors in mediating CNPs toxicity are discussed, including (1) the roles of physicochemical properties (size, morphology, agglomeration condition, surface charge, coating and surface valence state) on CNPs toxicity; (2) the phase transfer and transformation process of CNPs in various aqueous, terrestrial, and airborne environments; and (3) reductive dissolution of CNPs core and their chemical reactions with phosphate, sulfate/S^2-, and ferrous ions. The physicochemical properties play key roles in the interactions of CNPs with organisms and consequently their environmental transformations, reactivity and toxicity assessment. Also, the speciation transformations of CNPs caused by reactions with (in)organic ligands in both environmental and biological systems would further alter their fate, transport, and toxicity potential. Thus, the toxicity mechanisms are proposed based on the physical damage of direct adsorption of CNPs onto the cell membrane and chemical inhibition (including oxidative stress and interaction of CNPs with biomacromolecules). Finally, the current knowledge gaps and further research needs in identifying the toxicological risk factors of CNPs under realistic environmental conditions are highlighted, which might improve predictions about their potential environmental influences. This review aims to provide new insights into cost-effectiveness of control options and management practices to prevent environmental risks from CNPs exposure.

Ecological Drawbacks of Nanomaterials Produced on an Industrial Scale: Collateral Effect on Human and Environmental Health

Currently, hundreds of different nanomaterials with a broad application in products that make daily lives a little bit easier, in every aspect, are being produced on an industrial scale at thousands of tons per year. However, several scientists, researchers, politics, and ordinary citizens have stated their concern regarding the life cycle, collateral effects, and final disposal of these cutting-edge materials. This review summarizes, describes, and discusses all manuscripts published in the Journal Citation Reports during the last 10 years, which studied the toxicity or the effects of nanomaterials on human and environmental health. It was observed that 23.62% of the manuscripts analyzed found no ecological or human risks; 54.39% showed that several nanomaterials have toxicological effects on the ecosystems, human, or environmental health. In comparison, only 21.97% stated the nanomaterials had a beneficial impact on those. Although only 54.39% of the manuscripts reported unfavorable effects of nanomaterials on ecosystems, human, or environmental health, it is relevant because the potential damage is invaluable. Therefore, it is imperative to make toxicological studies of nanomaterials with holistic focus under strictly controlled real conditions before their commercialization, to deliver to the market only innocuous and environmentally friendly products.

Germination and Early Development of Three Spontaneous Plant Species Exposed to Nanoceria (nCeO2) with Different Concentrations and Particle Sizes

This study aimed to provide insight regarding the influence of Ce oxide nanoparticles (nCeO₂) with different concentrations and two different particle sizes on the germination and root elongation in seedlings of spontaneous terrestrial species. In a bench-scale experiment, seeds of the monocot, Holcus lanatus and dicots Lychnis-flos-cuculi and Diplotaxis tenuifolia were treated with solutions containing nCeO₂ 25 nm and 50 nm in the range 0-2000 mg Ce L^-1. The results show that nCeO₂ enters within the plant tissues. Even at high concentration, nCeO₂ have positive effects on seed germination and the development of the seedling roots. This study further demonstrated that the particle size had no influence on the germination of L. flos-cuculi, while in H. lanatus and D. tenuifolia, the germination percentage was slightly higher (+10%) for seeds treated with nCeO₂ 25 nm with respect to 50 nm. In summary, the results indicated that nCeO₂ was taken up by germinating seeds, but even at the highest concentrations, they did not have negative effects on plant seedlings. The influence of the different sizes of nCeO₂ on germination and root development was not very strong. It is likely that particle agglomeration and ion dissolution influenced the observed effects.

Abiotic mediation of common ions on the co-exposure of CeO2 NPs with Sb (III) or Sb (V) to Glycine max (Linn.) Merrill. (Soybean): Impacts on uptake, accumulation and physiochemical characters

With the most active Sb mines, the "dominance" on Sb production of China lead to increasingly release and omnipresence of Sb in environment through mining activities as well as the life cycle of Sb-containing productions. The introduction of engineered nanoparticles (ENPs) accidentally or intentionally (such as NP-containing sludge as fertilizer) might increase the probability of co-exposed with Sb to plants. In this study, CeO2 NPs, one of the most widely used nanomaterials in industries with potential oxidizing or reducing properties, was selected and co-exposed with Sb (III) or Sb (V) to investigate their mutual effects on uptake, accumulation and physiological effects in soybeans. The results showed that CeO2 NPs increased the Sb (III) and Sb (V) concentrations in roots by 36.7% and 14.0% respectively, while Sb (III) and Sb (V) inhibited the concentration of Ce in roots by 97.1% and 86.9% respectively. In addition, the impacts of extra common ions (Mn2+, Cu2+, Fe3+ and Zn2+) on the fate of Ce and Sb in soybeans in co-exposure of CeO2 NPs with Sb were investigated as well. Mn2+ and Fe3+ increased the accumulations of Ce and Sb (III) in the co-exposure of CeO2 NPs with Sb (III), but reduced that in the co-exposure of CeO2 NPs with Sb (V). Notably, the addition of Cu2+ and Zn2+ consistently increased the uptake and accumulation of Ce and Sb in the co-exposure treatments. Moreover, the effects of Sb on the dissolved portion of CeO2 NPs in soybean roots were also investigated. This study provided a perspective that extra ingredient (mineral elements, organic element or other nutrients) might regulated the interactions in ENPs-heavy metals-plants system which need further explorations.

Growth and Photosynthetic Inhibition of Cerium Oxide Nanoparticles on Soybean (Glycine max)

Cerium oxide nanoparticles (CeO2 NPs) are widely used in industries and have caused environmental problems. However, the phytotoxicity induced by CeO2 NPs lacks detailed information on phytotoxicity. In this research, the effect of CeO2 NPs on soybean plants (Glycine max) was studied. Scanning electron microscopy with the energy dispersion spectroscopy was used to characterize the NPs form in soybean. The growth of the root was increased, whereas the growth of shoot was inhibited. Besides, Chlorophyll Fluorescence Imager (CF Imager) showed that chlorophyll synthesis was inhibited: the maximum quantum yield of Photosystem II complex (PSII) (Fv/Fm) and photochemical quenching (qP) decreased. Moreover, transmission electron microscopy revealed that the chloroplast thylakoid structure was changed, and thus reduced the energy conversion in the Calvin cycle from C5 to C3. Our work suggests that CeO2 NPs will cause growth changes as well as irreversible damage to soybean plants. Our findings will provide evidence for estimation of plant toxicity induced by CeO2 NPs.

Effects of Ceria Nanoparticles and CeCl3 on Plant Growth, Biological and Physiological Parameters, and Nutritional Value of Soil Grown Common Bean (Phaseolus vulgaris)

The release of metal ions may play an important role in toxicity of metal-based nanoparticles. In this report, a life cycle study is carried out in a greenhouse, to compare the effects of ceria nanoparticles (NPs) and Ce³⁺ ions at 0, 50, 100, and 200 mg Ce kg^-1 on plant growth, biological and physiological parameters, and nutritional value of soil-grown common bean plants. Ceria NPs have a tendency to negatively affect photosynthesis, but the effect is not statistically significant. Ce³⁺ ionic treatments at 50, 100, and 200 mg Ce kg^-1 result in increases of 1.25-, 0.66-, and 1.20-fold in stomatal conductance, respectively, relative to control plants. Both ceria NPs and Ce³⁺ ions disturb the homeostasis of antioxidant defense system in the plants, but only 200 mg Ce kg^-1 ceria NPs significantly induce lipid peroxidation in the roots. Ceria NP treatments tend to reduced fresh weight and to increase mineral contents of the green pods, but have no effect on the organic nutrient contents. On the contrary, Ce³⁺ ion treatments modify the organic compositions and thus alter the nutritional quality and flavor of the green pods. These results suggest that the two Ce forms may have different mechanisms on common bean plants.

Risk assessment and biophysiochemical responses of spinach to foliar application of lead oxide nanoparticles: A multivariate analysis

Despite extensive research progress in the recent past, the data regarding foliar uptake of heavy metals, associated biophysiochemical changes inside plants and possible health hazards are limited. This study determined the effect of foliar application of lead oxide nanoparticles (PbO-NPs) on lead (Pb) accumulation, physiological and biochemical changes inside spinach plants and associated health risks. A green method was used to prepare PbO-NPs using coconut water. Scanning electron microscopy (SEM) showed the preparation of smooth, unwrinkled, granular and spherical PbO-NPs. Spinach leaves were exposed via foliar application to three concentrations of PbO-NPs (0, 10 and 50 mg/plant). Foliar PbO-NPs application resulted in a significant accumulation of Pb in leaves (42.25 μg g^-1), with limited translocation towards root tissues (4.46 μg g^-1). This revealed that spinach can accumulate considerable amount of Pb via foliar uptake. Lead accumulation inside spinach caused a significant decrease in pigment contents (38%) and dry weight (67%). After foliar uptake, Pb caused several-fold increase in the activities of catalase and peroxidase. However, foliar PbO-NPs did not induce significant changes in H₂O₂ production, lipid peroxidation and superoxide dismutase activity. Application of PbO-NPs (50 mg/plant) showed possible health risks (non-carcinogenic) due to ingesting Pb-contaminated leaves of spinach. It is proposed that atmospheric contamination and foliar deposition of metal-PM can seriously affect vegetable growth and can provoke health issues due to ingestion of metal-enriched vegetables. Therefore, atmospheric levels of heavy metals need to be monitored on a regular basis to avoid their food chain contamination and possible human exposure.

Interactions of CeO2 nanoparticles with natural colloids and electrolytes impact their aggregation kinetics and colloidal stability

The aggregation kinetics and colloidal stability of CeO₂-NPs in the presence of monovalent or divalent electrolytes, as well as inorganic (kaolin and goethite) and organic (humic acid, HA) colloids were evaluated using time-resolved dynamic light scattering, advanced spectroscopic tools, and theoretical calculations. Critical coagulation concentrations for CeO₂-NPs were generally lower in CaCl₂ than that in NaCl electrolyte. The negatively charged kaolin accelerated CeO₂-NPs aggregation due to electrostatic attraction, whilst opposite phenomenon was observed for the positively charged goethite in NaCl solution. In CaCl₂ solution, goethite destabilized CeO₂-NPs because of its well-crystal structure and specific adsorption of Ca²⁺. The presence of 0.1 mg C/L HA decreased the surface charge of CeO₂-NPs, resulting in lower critical coagulation concentrations. Increasing the HA concentration from 0.1 to 1 mg C/L improved CeO₂-NPs stability, mainly via electrostatic and steric repulsion. The Ca²⁺-bridging and complexation contributed significantly to CeO₂-NPs aggregation. Additional aggregation experiments in seven natural waters revealed that CeO₂-NPs remained stable in water types with high contents of organic colloids and low levels of salts, thus having higher transport potential. These findings provided new insights into the interactive influence of naturally occurring colloids and ions on the heteroaggregation behavior and fate of CeO₂-NPs.

Property-Activity Relationship of Black Phosphorus at the Nano-Bio Interface: From Molecules to Organisms

As a novel member of the two-dimensional nanomaterial family, mono- or few-layer black phosphorus (BP) with direct bandgap and high charge carrier mobility is promising in many applications such as microelectronic devices, photoelectronic devices, energy technologies, and catalysis agents. Due to its benign elemental composition (phosphorus), large surface area, electronic/photonic performances, and chemical/biological activities, BP has also demonstrated a great potential in biomedical applications including biosensing, photothermal/photodynamic therapies, controlled drug releases, and antibacterial uses. The nature of the BP-bio interface is comprised of dynamic contacts between nanomaterials (NMs) and biological systems, where BP and the biological system interact. The physicochemical interactions at the nano-bio interface play a critical role in the biological effects of NMs. In this review, we discuss the interface in the context of BP as a nanomaterial and its unique physicochemical properties that may affect its biological effects. Herein, we comprehensively reviewed the recent studies on the interactions between BP and biomolecules, cells, and animals and summarized various cellular responses, inflammatory/immunological effects, as well as other biological outcomes of BP depending on its own physical properties, exposure routes, and biodistribution. In addition, we also discussed the environmental behaviors and potential risks on environmental organisms of BP. Based on accumulating knowledge on the BP-bio interfaces, this review also summarizes various safer-by-design strategies to change the physicochemical properties including chemical stability and nano-bio interactions, which are critical in tuning the biological behaviors of BP. The better understanding of the biological activity of BP at BP-bio interfaces and corresponding methods to overcome the challenges would promote its future exploration in terms of bringing this new nanomaterial to practical applications.

Soybean Interaction with Engineered Nanomaterials: A Literature Review of Recent Data

With a continuous increase in the production and use in everyday life applications of engineered nanomaterials, concerns have appeared in the past decades related to their possible environmental toxicity and impact on edible plants (and therefore, upon human health). Soybean is one of the most commercially-important crop plants, and a perfect model for nanomaterials accumulation studies, due to its high biomass production and ease of cultivation. In this review, we aim to summarize the most recent research data concerning the impact of engineered nanomaterials on the soya bean, covering both inorganic (metal and metal-oxide nanoparticles) and organic (carbon-based) nanomaterials. The interactions between soybean plants and engineered nanomaterials are discussed in terms of positive and negative impacts on growth and production, metabolism and influences on the root-associated microbiota. Current data clearly suggests that under specific conditions, nanomaterials can negatively influence the development and metabolism of soybean plants. Moreover, in some cases, a possible risk of trophic transfer and transgenerational impact of engineered nanomaterials are suggested. Therefore, comprehensive risk-assessment studies should be carried out prior to any mass productions of potentially hazardous materials.

Airborne foliar transfer of particular metals in Lactuca sativa L.: translocation, phytotoxicity, and bioaccessibility

The uptake, translocation, and human bioaccessibility of metals originating from atmospheric fine particulate matters (PM) after foliar exposure is not well understood. Lettuce (Lactuca sativa L.) plants were exposed to micronic PbO, CuO, and CdO particulate matters (PMs) by the foliar pathway and mature plants (6 weeks old) were analyzed in terms of: (1) metal accumulation and localization on plant leaf surface, and metal translocation factor (TF) and global enrichment factor (GEF) in the plants; (2) shoot growth, plant dry weight (DW), net photosynthesis (Pn), stomatal conductance (Gs), and fatty acid ratio; (3) metal bioaccessibility in the plants and soil; and (4) the hazard quotient (HQ) associated with consumption of contaminated plants. Substantial levels of metals were observed in the directly exposed edible leaves and newly formed leaves of lettuce, highlighting both the possible metal transfers throughout the plant and the potential for human exposure after plant ingestion. No significant changes were observed in plant biomass after exposure to PbO, CuO, and CdO-PMs. The Gs and fatty acid ratio were increased in leaves after metal exposure. A dilution effect after foliar uptake was suggested which could alleviate metal phytotoxicity to some degree. However, plant shoot growth and Pn were inhibited when the plants are exposed to PbO, and necrosis enriched with Cd was observed on the leaf surface. Gastric bioaccessibility of plant leaves is ranked: Cd > Cu > Pb. Our results highlight a serious health risk of PbO, CuO, and CdO-PMs associated with consumption of vegetables exposed to these metals, even in newly formed leaves in the case of PbO and CdO exposure. Finally, the study highlights the fate and toxicity of metal rich-PMs, especially in the highly populated urban areas which are increasingly cultivated to promote local food.

Aggregation, Sedimentation, and Dissolution of Copper Oxide Nanoparticles: Influence of Low-Molecular-Weight Organic Acids from Root Exudates

The rhizosphere is an essential pathway for the uptake of metal-based nanoparticles (MNPs) by plant roots. However, the interaction between root exudates and MNPs is still unclear. In this study, we initially identified the major low-molecular-weight organic acids (LMWOAs) in the rice root exudates using hydroponics. Then, the individual LMWOAs were added to CuO nanoparticle suspensions to investigate their effects on the environmental behavior of the MNPs. The results showed that both the variety and the concentration of LMWOAs impacted the aggregation, sedimentation, and dissolution of CuO nanoparticles (NPs). Almost all LMWOAs except succinic acid inhibited the aggregation of CuO NPs by enhancing the electrostatic repulsive force between NPs. The presence of citric and oxalic acids rather than lactic acid greatly improved the stability of CuO NP suspensions, but other acids showed a low promoting and high inhibiting effect on NP sedimentation. Moreover, all the LMWOAs from root exudates facilitated the dissolution of CuO NPs with a positive dose-dependent correlation, especially formic acid. Notably, citric acid, as the most abundant LMWOAs in rice root exudates, largely determined the aggregation, sedimentation, and dissolution of CuO NPs. This study provides a better understanding on NP-plant interactions in the rhizosphere.

Influence of Surface Charge on the Phytotoxicity, Transformation, and Translocation of CeO2 Nanoparticles in Cucumber Plants

The physiochemical properties of nanoparticles (NPs), including surface charge, will affect their uptake, transformation, translocation, and final fate in the environment. In this study, we compared the phytoxoxicity and transport behaviors of nano CeO₂ (nCeO₂) functionalized with positively charged (Cs-nCeO₂) and negatively charged (PAA-nCeO₂) coatings. Cucumber seedlings were hydroponically exposed to 0-1000 mg/L of Cs-nCeO₂ and PAA-nCeO₂ for 14 days and the contents, distribution, translocation, and transformation of Ce in plants were analyzed using inductively coupled plasma mass spectrometry, micro X-ray fluorescence (μ-XRF), and X-ray absorption near-edge spectroscopy (XANES), respectively. Results showed that the seedling growth and Ce contents in plant tissues were functions of exposure concentrations and surface charge. Cs-nCeO₂ was adsorbed strongly on a negatively charged root surface, which led to significantly higher Ce contents in the roots and lower translocation factors of Ce from the roots to shoots in Cs-nCeO₂ group than in PAA-nCeO₂ group. The results of μ-XRF showed that Ce elements were mainly accumulated at the root tips and lateral roots, as well as in the veins and at the edge of leaves. XANES results revealed that the proportion of Ce(III) was comparable in the plant tissues of the two groups. We speculated that Cs-nCeO₂ and PAA-nCeO₂ were partially dissolved under the effect of root exudates, releasing Ce³⁺ ions as a result. Then, the Ce³⁺ ions were transported upward in the form of Ce(III) complexes along the vascular bundles and eventually accumulated in the veins. The other portion of Cs-nCeO₂ and PAA-nCeO₂ entered the roots through the gap of a Casparian strip at root tips/lateral roots and was transported upward as intact NPs and finally accumulated at the edge of the blade. This study will greatly advance our information on how the properties of NPs influence their phytotoxicity, uptake, and subsequent trophic transfer in terrestrial food webs.

Dissolved Organic Matter Modulates Algal Oxidative Stress and Membrane System Responses to Binary Mixtures of Nano-Metal-Oxides (nCeO2, nMgO and nFe3O4) and Sulfadiazine

Joint biomarker responses, oxidative stress and membrane systems, were determined for nano-metal-oxides (nMeO, i.e., nCeO₂, nMgO, and nFe₃O₄) and sulfadiazine (SDZ) exposed at relevant low concentrations to two freshwater microalgae Scenedesmus obliquus and Chlorella pyrenoidosa. The impacts of dissolved organic matter (DOM) on the joint biomarker responses were also investigated. Results indicated that the presence of SDZ significantly decreased the level of intercellular reactive oxygen species (ROS) in the algal cells exposed to each nMeO. Reduction of cell membrane permeability (CMP) and mitochondrial membrane potential (MMP) in the algal cells was observed when the algae were exposed to the mixture of SDZ and the nMeO. The degree of reduction of the ROS level, CMP, and MMP significantly went down with the addition of DOM to a certain extent. Changes in cellular oxidative stress and membrane function depended on the types of both nMeO and algal species. This contribution provides an insight into the hazard assessment of a mixture consisting of emerging contaminants and DOM, as they can coexist in the aquatic environment.

Impacts of Silver Nanoparticles on Plants: A Focus on the Phytotoxicity and Underlying Mechanism

Nanotechnology was well developed during past decades and implemented in a broad range of industrial applications, which led to an inevitable release of nanomaterials into the environment and ecosystem. Silver nanoparticles (AgNPs) are one of the most commonly used nanomaterials in various fields, especially in the agricultural sector. Plants are the basic component of the ecosystem and the most important source of food for mankind; therefore, understanding the impacts of AgNPs on plant growth and development is crucial for the evaluation of potential environmental risks on food safety and human health imposed by AgNPs. The present review summarizes uptake, translocation, and accumulation of AgNPs in plants, and exemplifies the phytotoxicity of AgNPs on plants at morphological, physiological, cellular, and molecular levels. It also focuses on the current understanding of phytotoxicity mechanisms via which AgNPs exert their toxicity on plants. In addition, the tolerance mechanisms underlying survival strategy that plants adopt to cope with adverse effects of AgNPs are discussed.

Iron Plaque: A Barrier Layer to the Uptake and Translocation of Copper Oxide Nanoparticles by Rice Plants

The waterlogging environment generally results in the deposition of iron plaque on plant roots, which may impact the fate of metal-based nanoparticles. Here, we investigated the influence of iron plaque on the uptake, translocation, and transformation of copper oxide nanoparticles (CuO NPs) in rice plants. The results show that the presence of iron plaque dramatically reduced the Cu contents in roots and shoots by 89% and 78% of those without iron plaque under 100 mg/L CuO NP treatment. Meanwhile, the Cu accumulation in plants was negatively related to the amount of iron plaque. X-ray absorption near edge structure (XANES) analysis demonstrated lower percentage of CuO but higher proportion of Cu(I) in shoots exposed to CuO NPs with the formation of iron plaque. Furthermore, micro X-ray fluorescence (μ-XRF) combined with μ-XANES revealed that the iron plaque in the root epidermis and exodermis consisted of goethite and ferrihydrite, which hindered the uptake of CuO NPs by roots. However, a few CuO NPs were still absorbed by roots via root hairs or lateral roots, and further translocated to shoots. But eventually, more than 90% of total Cu(II) was reduced to Cu(I)-cysteine and Cu₂O in leaf veins of rice plants with iron plaque.

Nanomaterials in the environment: Behavior, fate, bioavailability, and effects-An updated review

The present review covers developments in studies of nanomaterials (NMs) in the environment since our much cited review in 2008. We discuss novel insights into fate and behavior, metrology, transformations, bioavailability, toxicity mechanisms, and environmental impacts, with a focus on terrestrial and aquatic systems. Overall, the findings were that: 1) despite substantial developments, critical gaps remain, in large part due to the lack of analytical, modeling, and field capabilities, and also due to the breadth and complexity of the area; 2) a key knowledge gap is the lack of data on environmental concentrations and dosimetry generally; 3) substantial evidence shows that there are nanospecific effects (different from the effects of both ions and larger particles) on the environment in terms of fate, bioavailability, and toxicity, but this is not consistent for all NMs, species, and relevant processes; 4) a paradigm is emerging that NMs are less toxic than equivalent dissolved materials but more toxic than the corresponding bulk materials; and 5) translation of incompletely understood science into regulation and policy continues to be challenging. There is a developing consensus that NMs may pose a relatively low environmental risk, but because of uncertainty and lack of data in many areas, definitive conclusions cannot be drawn. In addition, this emerging consensus will likely change rapidly with qualitative changes in the technology and increased future discharges. Environ Toxicol Chem 2018;37:2029-2063. © 2018 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Trophic Transfer and Transformation of CeO2 Nanoparticles along a Terrestrial Food Chain: Influence of Exposure Routes

The trophic transfer and transformation of CeO₂ nanoparticles (NPs) through a simulated terrestrial food chain were investigated using a radiotracer technique and X-ray absorption near edge structure (XANES). Radioactive ¹⁴¹CeO₂ NPs were applied to head lettuce ( Lactuca sativa), treated via root exposure in its potting soil (5.5 or 11 mg/plant) for 30 days or foliar exposure (7.2 mg/plant, with half of the leaves treated and the other half not) for 7 days. Subsequently, two groups of land snails ( Achatina fulica) were exposed to ¹⁴¹Ce via either a direct (i.e., feeding on the lettuce leaves with ¹⁴¹Ce-contaminated surfaces) or an indirect/trophic (i.e., feeding on the lettuce leaves with systemically distributed ¹⁴¹Ce) route. To evaluate the influence of exposure routes, the Ce contents of the lettuce, snail tissues, and feces were determined by radioactivity measurements. The results show that both assimilation efficiencies (AEs) and food ingestion rates of Ce are greater for the trophic (indirect) exposure. The low AEs indicate that the CeO₂ NPs ingested by snails were mostly excreted subsequently, and those that remained in the body were mainly concentrated in the digestive gland. XANES analysis shows that >85% of Ce was reduced to Ce(III) in the digestive gland under direct exposure, whereas Ce in the rest of the food chain (including feces) was largely in its original oxidized (IV) state. This study suggests that CeO₂ NPs present in the environment may be taken up by producers and transferred to consumers along food chains and trophic transfer may affect food safety.

Effects of Cr2O3 nanoparticles on the chlorophyll fluorescence and chloroplast ultrastructure of soybean (Glycine max)

Chromic oxide nanoparticles (Cr2O3 NPs) are widely used in commercial factories and can cause serious environmental problems. However, the mechanism behind Cr2O3 NP-induced phytotoxicity remains unknown. In this study, the effects of Cr2O3 NPs on the growth, chlorophyll fluorescence, SEM-EDS analysis, and chloroplast ultrastructure of soybean (Glycine max) were investigated to evaluate its phytotoxicity. The growth of soybean treated with various Cr2O3 NP suspensions (0.01, 0.05, 0.1, and 0.5 g L-1) was significantly inhibited. Specially, shoot and root biomass decreased by 9.9 and 46.3%, respectively. Besides, the maximum quantum yield of PSII (Fv/Fm) as well as the photochemical quenching (qP) decreased by 8-22 and 30-37%, respectively, indicating that the photosynthetic system was damaged when treated with Cr2O3 NPs. Moreover, the inhibition was confirmed by the reduction of Rubisco and MDH enzyme activity (by 54.5-86.4 and 26.7-96.5%, respectively). Overall, results indicated that the damage was caused by the destruction of chloroplast thylakoid structure, which subsequently reduced the photosynthetic rate. Our research suggests that Cr2O3 NPs can be transported and cause irreversible damage to soybean plants by inhibiting the activity of electron acceptors (NADP+) and destroying ultrastructure of chloroplasts, providing insights into plant toxicity issues. Graphical abstract ᅟ.

Effects of soot by-product from the synthesis of engineered metallofullerene nanomaterials on terrestrial invertebrates

The synthesis of carbon-based nanomaterials is often inefficient, generating large amounts of soot with metals as waste by-product. Currently, there are no specific regulations for disposal of engineered nanomaterials or the waste by-products resulting from their synthesis, so it is presumed that by-products are disposed of in the same way as the parent (bulk) materials. We studied the terrestrial toxicity of soot from gadolinium metallofullerene nanomanufacturing on earthworms (Eisenia fetida) and isopods (Porcellio scaber). The metallofullerene soot consisted of carbon particle agglomerates in the nanometer and submicrometer ranges (1-100 and 101-999 nm, respectively), with metals used during nanomanufacturing detectable on the particles. Despite high metal concentrations (>100 000 mg/kg) in the soot, only a relatively small amount of metals leached out of a spiked field soil, suggesting only moderate mobility. Seven- and 14-d exposures in field soil demonstrated that the soot was only toxic to earthworms at high concentrations (>10 000 mg/kg); however, earthworms avoided spiked soils at lower concentrations (as low as 500 mg/kg) and at lower soil pH. The presence of soot in food and soil did not cause isopod avoidance. These data demonstrate that metallofullerene soot from nanomanufacturing may only be toxic to earthworms at high concentrations representative of improper disposal or accidental spills. However, our results indicate that terrestrial invertebrates may avoid soils contaminated with soot at sublethal concentrations. Environ Toxicol Chem 2018;9999:1-12. Published 2018 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US government work, and as such, is in the public domain in the United States of America.

Uptake of Engineered Nanoparticles by Food Crops: Characterization, Mechanisms, and Implications

With the rapidly increasing demand for and use of engineered nanoparticles (NPs) in agriculture and related sectors, concerns over the risks to agricultural systems and to crop safety have been the focus of a number of investigations. Significant evidence exists for NP accumulation in soils, including potential particle transformation in the rhizosphere and within terrestrial plants, resulting in subsequent uptake by plants that can yield physiological deficits and molecular alterations that directly undermine crop quality and food safety. In this review, we document in vitro and in vivo characterization of NPs in both growth media and biological matrices; discuss NP uptake patterns, biotransformation, and the underlying mechanisms of nanotoxicity; and summarize the environmental implications of the presence of NPs in agricultural ecosystems. A clear understanding of nano-impacts, including the advantages and disadvantages, on crop plants will help to optimize the safe and sustainable application of nanotechnology in agriculture for the purposes of enhanced yield production, disease suppression, and food quality.

Transformation and bioavailability of metal oxide nanoparticles in aquatic and terrestrial environments. A review

Metal oxide nanoparticles (MeO-NPs) are among the most consumed NPs and also have wide applications in various areas which increased their release into the environmental system. Aquatic (water and sediments) and terrestrial compartments are predicted to be the destination of the released MeO-NPs. In these compartments, the particles are subjected to various dynamic processes such as physical, chemical and biological processes, and undergo transformations which drive them away from their pristine state. These transformation pathways can have strong implications for the fate, transport, persistence, bioavailability and toxic-effects of the NPs. In this critical review, we provide the state-of-the-knowledge on the transformation processes and bioavailability of MeO-NPs in the environment, which is the topic of interest to researchers. We also recommend future research directions in the area which will support future risk assessments by enhancing our knowledge of the transformation and bioavailability of MeO-NPs.

Impact of Metal and Metal Oxide Nanoparticles on Plant: A Critical Review

An increasing need of nanotechnology in various industries may cause a huge environment dispersion of nanoparticles in coming years. A concern about nanoparticles interaction with flora and fauna is raised due to a growing load of it in the environment. In recent years, several investigators have shown impact of nanoparticles on plant growth and their accumulation in food source. This review examines the research performed in the last decade to show how metal and metal oxide nanoparticles are influencing the plant metabolism. We addressed here, the impact of nanoparticle on plant in relation to its size, concentration, and exposure methodology. Based on the available reports, we proposed oxidative burst as a general mechanism through which the toxic effects of nanoparticles are spread in plants. This review summarizes the current understanding and the future possibilities of plant-nanoparticle research.

Nano-cerium oxide functionalized biochar for phosphate retention: preparation, optimization and rice paddy application

In this study, nano-cerium oxide functionalized maize straw biochar (Ce-MSB) was prepared and utilized to remove P from agricultural wastewater. Response Surface Model was applied to optimize the operating conditions. Moreover, Ce-MSB was applied to actual rice paddy column for the first time. Response Surface Model (RSM) showed higher materials ratio had positive effect on PO₄^3- adsorption capacity, while higher pyrolysis temperature had negative effect. The maximum adsorption capacity of Ce-MSB for PO₄^3- was 78 mg g^-1, implying that Ce-MSB was an effective functionalized adsorbent for P removal. Paddy soil column experiment showed that application of Ce-MSB decreased total phosphorus concentration of surface water by 27.33% and increased total phosphors (TP) content of top soil by 7.22%. Further, Ce-MSB tends to increase rice plant height and leaf area. Therefore, Ce-MSB can be used as a promising functionalized biochar to reduce the risk of phosphorus loss from paddy field surface running water.

Biogenic copper nanoparticles promote the growth of pigeon pea (Cajanus cajan L.)

Environmental pollution and toxicity have been increasing due to the overuse of chemical fertilisers, which has encouraged nanotechnologists to develop eco‐friendly nano‐biofertilisers. The authors demonstrated the effect of biogenic copper nanoparticles (CuNPs) on the growth of pigeon pea (Cajanus cajan L.). The UV–visible analysis showed absorbance at 615 nm. Nanoparticle tracking and analysis revealed particle concentration of 2.18 × 10⁸ particles/ml, with an average size of 33 nm. Zeta potential was found to be −16.7 mV, which showed stability. X‐ray diffraction pattern depicted the face centred cubic structure of CuNPs; Fourier transform infrared spectroscopy demonstrated the capping due to acidic groups, and transmission electron micrograph showed nanoparticles with size 20–30 nm. The effect of CuNPs (20 ppm) on plant growth was studied, for the absorption of CuNPs by plants on photosynthesis, which was evaluated by measuring chlorophyll a fluorescence using Handy‐Plant Efficiency Analyser. CuNPs treatment showed a remarkable increase in height, root length, fresh and dry weights and performance index of seedlings. The overall growth of plants treated with CuNPs after 4 weeks was recorded. The results revealed that inoculation of CuNPs contribute growth and development of pigeon pea due to growth promoting activity of CuNPs.

Xylem and Phloem Based Transport of CeO2 Nanoparticles in Hydroponic Cucumber Plants

Uptake and translocation of manufactured nanoparticles (NPs) in plants have drawn much attention due to their potential toxicity to the environment, including food webs. In this paper, the xylem and phloem based transport of CeO₂ NPs in hydroponic cucumber plants was investigated using a split-root system. One half of the root system was treated with 200 or 2000 mg/L of CeO₂ NPs for 3 days, whereas the other half remained untreated, with both halves sharing the same aerial part. The quantitative distribution and speciation of Ce in different plant tissues and xylem sap were analyzed by inductively coupled plasma-mass spectrometry, transmission electron microscope, X-ray absorption near edge structure, and X-ray fluorescence. Results show that about 15% of Ce was reduced from Ce(IV) to Ce(III) in the roots of the treated-side (TS), while almost all of Ce remained Ce(IV) in the blank-side (BS). The detection of CeO₂ or its transformation products in the xylem sap, shoots, and BS roots indicates that Ce was transported as a mixture of Ce(IV) and Ce(III) from roots to shoots through xylem, while it was transported almost only in the form of CeO₂ from shoots back to roots through phloem. To our knowledge, this is the first report of root-to-shoot-to-root redistribution after transformation of CeO₂ NPs in plants, which has significant implications for food safety and human health.

Prospecting nanomaterials in aqueous environments by cloud-point extraction coupled with transmission electron microscopy

Increasing application of engineered nanomaterials (ENMs) in industry and consumer products inevitably lead to their release into and impact on aquatic environments. To characterize the NMs efficiently in surface water, a fast and simple method is needed to separate and concentrate nanomaterials from the aqueous matrix without altering their shape and size. Applying cloud-point extraction (CPE) using the surfactant Triton 114 to an array of NMs (titanium dioxide, gold, silver, and silicon dioxide) with different sizes or capping agents in nanopure water resulted in extraction efficiency of 83%-107%. Additional CPE experiments were conducted to extract NMs from surface, potable, and sewage waters, and NMs enriched in the surfactant phase were characterized using transmission electron microscopy coupled with energy dispersive x-ray spectroscopy. The most abundant nanoparticles identified in surface water were silica, titanium dioxide, and iron oxide with 4-99nm diameter. The extraction efficiencies of CPE for silicon, titanium, and iron elements from environmental water samples were 51%, 15%, and 99%, respectively. This study applied CPE with TEM to enrich and analyze popular nanoparticles such as SiO₂ and TiO₂ from natural waters, which has not been well addressed by previous researches. Overall, CPE coupled with transmission electron microscopy (TEM) can be an effective method to characterize NMs in aqueous water samples, and further optimization will increase the extraction efficiency of NMs in complicated surface water matrix.

Differential bioaccumulation patterns of nanosized and dissolved silver in a land snail Achatina fulica

With the increasing application in antimicrobial products, silver nanoparticles (AgNP) are inevitably released into the terrestrial environment, and pose potential risks to invertebrates such as land snails Achatina fulica, which take up AgNP from food and water. Here we differentiate Ag uptake biodynamic between Ag forms (i.e., PVP-AgNP vs. AgNO3) and between exposure pathways. Snails assimilated Ag efficiently from lettuce leaves pre-exposed to AgNP, with assimilation efficiencies (AEs) averaging 62-85% and food ingestion rates of 0.11 ± 0.03 g g-1 d-1. Dietary Ag bioavailability was independent on Ag forms, as revealed by comparable AEs between AgNP and AgNO3. However, the uptake rate constant from water was much lower for AgNP relative to AgNO3 (2 × 10-4 vs. 0.12 L g-1 d-1). The elimination rate constants were 0.0093 ± 0.0037 d-1 for AgNP and 0.019 ± 0.0077 d-1 for AgNO3. Biodynamic modeling further showed that dietary exposure was the dominant uptake pathway for AgNP in most circumstances, while for AgNO3 the relative importance of waterborne and dietary exposure depended on Ag concentrations in food and water. Our findings highlight the importance of dietary uptake of AgNP during bioaccumulation, which should be considered in the risk assessment of these nanoparticles.

Increasing evidence indicates low bioaccumulation of carbon nanotubes

As the production of carbon nanotubes (CNTs) expands, so might the potential for release into the environment. The possibility of bioaccumulation and toxicological effects has prompted research on their fate and potential ecological effects. For many organic chemicals, bioaccumulation properties are associated with lipid-water partitioning properties. However, predictions based on phase partitioning provide a poor fit for nanomaterials. In the absence of data on the bioaccumulation and other properties of CNTs, the Office of Pollution Prevention and Toxics (OPPT) within the US Environmental Protection Agency (EPA) subjects new pre-manufacture submissions for all nanomaterials to a higher-level review. We review the literature on CNT bioaccumulation by plants, invertebrates and non-mammalian vertebrates, summarizing 40 studies to improve the assessment of the potential for bioaccumulation. Because the properties and environmental fate of CNTs may be affected by type (single versus multiwall), functionalization, and dosing technique, the bioaccumulation studies were reviewed with respect to these factors. Absorption into tissues and elimination behaviors across species were also investigated. All of the invertebrate and non-mammalian vertebrate studies showed little to no absorption of the material from the gut tract to other tissues. These findings combined with the lack of biomagnification in the CNT trophic transfer studies conducted to date suggest that the overall risk of trophic transfer is low. Based on the available data, in particular the low levels of absorption of CNTs across epithelial surfaces, CNTs generally appear to form a class that should be designated as a low concern for bioaccumulation.

Weathering in soil increases nanoparticle CuO bioaccumulation within a terrestrial food chain

This study evaluates the bioaccumulation of unweathered (U) and weathered (W) CuO in NP, bulk and ionic form (0-400 mg/kg) by lettuce exposed for 70 d in soil co-contaminated with field incurred chlordane. To evaluate CuO trophic transfer, leaves were fed to crickets (Acheta domestica) for 15 d, followed by insect feeding to lizards (Anolis carolinensis). Upon weathering, the root Cu content of the NP treatment increased 214% (327 ± 59.1 mg/kg) over unaged treatment. Cu root content decreased in bulk and ionic treatments from 70-130 mg/kg to 13-26 mg/kg upon aging in soil. Micro X-ray fluorescence (μ-XRF) analysis of W-NP-exposed roots showed a homogenous distribution of Cu (and Ca) in the tissues. Additionally, micro X-ray absorption near-edge (μ-XANES) analysis of W-NP-exposed roots showed near complete transformation of CuO to Cu (I)-sulfur and oxide complexes in the tissues, whereas in unweathered treatment, most root Cu remained as CuO. The expression level of nine genes involved in Cu transport shows that the mechanisms of CuO NPs (and bulk) response/accumulation are different than ionic Cu. The chlordane accumulation by lettuce upon co-exposure to CuO NPs significantly increased upon weathering. Conversely, bulk and ionic exposures decreased pesticide accumulation by plant upon weathering. The Cu cricket fecal content from U-NP-exposed insects was significantly greater than the bulk or ion treatments, suggesting a higher initial NP accumulation followed by significantly greater elimination during depuration. In the lizard, Cu content in the intestine, body and head did not differ as a function of weathering. This study demonstrates that CuO NPs may undergo transformation processes in soil upon weathering that subsequently impact NPs availability in terrestrial food chains.