Shifts in N and δ15N in wheat and barley exposed to cerium oxide nanoparticles

From lab to ecosystem: Understanding the ecological footprints of engineered nanoparticles

Nanotechnology has attained significant attention from researchers in past decades due to its numerous advantages, such as biocompatibility, biodegradability, and improved stability over conventional drug delivery systems. The fabrication of engineered nanoparticles (ENPs), including carbon nanotubes (CNTs), fullerenes, metallic and metal oxide-based NPs, has been steadily increasing day due to their wide range of applications from household to industrial applications. Fabricated ENPs can release different materials into the environment during their fabrication process. The effect of such materials on the environment is the primary concern with due diligence on the safety and efficacy of prepared NPs. In addition, an understanding of chemistry, reactivity, fabrication process, and viable mechanism of NPs involved in the interaction with the environment is very important. To date, only a limited number of techniques are available to assess ENPs in the natural environment which makes it difficult to ascertain the impact of ENPs in natural settings. This review extensively examines the environmental effects of ENPs and briefly discusses useful tools for determining NP size, surface charge, surface area, and external appearance. In conclusion, the review highlights the potential risks associated with ENPs and suggests possible solutions.

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.

Wheat exposure to cerium oxide nanoparticles over three generations reveals transmissible changes in nutrition, biochemical pools, and response to soil N

This study investigated the effects of third generation exposure to cerium oxide nanoparticles (CeO₂-NPs) on biomass, elemental and ¹⁵N uptake, and fatty acid contents of wheat (Triticum aestivum). At low or high nitrogen treatment (48 or 112 mg N), seeds exposed for two generations to 0 or 500 mg CeO₂-NPs per kg soil treatment were cultivated for third year in soil amended with 0 or 500 mg CeO₂-NPs per kg soil. The results showed that parental and current exposures to CeO₂-NPs increased the root biomass in daughter plants with greater magnitude of increase at low N than high N. When wheat received CeO₂-NPs in year 3, root elemental contents increased primarily at low N, suggesting an important role of soil N availability in altering root nutrient acquisition. The δ¹⁵N ratios, previously shown to be altered by CeO₂-NPs, were only affected by current and not parental exposure, indicating effects on N uptake and/or metabolism are not transferred from one generation to the next. Seed fatty acid composition was also influenced both by prior and current exposure to CeO₂-NPs. The results suggest that risk assessments of NP exposure may need to include longer-term, transgenerational effects on growth and grain quality of agronomic crops.

Metal oxide nanomaterials used to remediate heavy metal contaminated soils have strong effects on nutrient and trace element phytoavailability

Engineered nanomaterials (ENMs) are increasingly utilised for the remediation of contaminated soils. In this study, contaminant (As, Pb), nutrient (N, P) and trace element (Cu, Fe, Mn, Zn) phytoavailability in three Australian soils contaminated (<10 years) with As (≈100 mg As kg^-1 soil) or Pb (≈300 mg Pb kg^-1 soil) was determined periodically. These soils were exposed to two ENMs (cerium dioxide - nCeO₂ or titanium dioxide - nTiO₂) (applied to soil at a concentration of 500 mg ENM kg^-1 soil) with contaminant, nutrient and trace element phytoavailability assessed over a 260-day period. While As phytoavailability was not influenced by either ENM, the presence of nCeO₂ in some soils increased Pb phytoavailability approximately two fold at the conclusion of the experiment (day 260), which was attributed to nCeO₂ decreasing soil pH and/or outcompeting Pb²⁺ ions for sorption sites. More significantly, both ENMs significantly altered the phytoavailability of N, P and Zn across soils. In some instances >90% of the soil N was lost in the presence of both ENMs, while in some instances the phytoavailability of P and Zn was tripled and doubled respectively in the presence of ENMs. For N it was hypothesised that both ENMs altered the mineralisation of organic N and/or soil nitrification rates due to the catalytic and/or anti-microbial properties of the ENMs. For P, it was hypothesised that anti-microbial effects of both ENMs altered the activity of P-solubilising microbes. For Zn competition between the positively charged ENMs and Zn²⁺ ions was the most likely mechanism for altered Zn phytoavailability. This study suggested that while ENMs can potentially be effective as metal remediation agents when applied to soils, there are however a range of potentially deleterious 'non-target' effects on soil ecosystems that have not as yet been widely considered.