Synchrotron XRF Analysis Identifies Cerium Accumulation Colocalized with Pharyngeal Deformities in CeO2 NP-Exposed Caenorhabditis elegans.

A combination of synchrotron radiation-based elemental imaging, in vivo redox status analysis, histology, and toxic responses was used to investigate the uptake, biodistribution, and adverse effects of Ce nanoparticles (CeO2 NP; 10 nm; 0.5-34.96 mg Ce L-1) or Ce(NO3)3 (2.3-26 mg Ce L-1) in Caenorhabditis elegans. Elemental mapping of the exposed nematodes revealed Ce uptake in the alimentary canal prior to depuration. Retention of CeO2 NPs was low compared to that of Ce(NO3)3 in depurated individuals. X-ray fluorescence (XRF) mapping showed that Ce translocation was confined to the pharyngeal valve and foregut. Ce(NO3)3 exposure significantly decreased growth, fertility, and reproduction, caused slightly reduced fecundity. XRF mapping and histological analysis revealed severe tissue deformities colocalized with retained Ce surrounding the pharyngeal valve. Both forms of Ce activated the sod-1 antioxidant defense, particularly in the pharynx, whereas no significant effects on the cellular redox balance were identified. The CeO2 NP-induced deformities did not appear to impair the pharyngeal function or feeding ability as growth effects were restricted to Ce(NO3)3 exposure. The results demonstrate the utility of integrated submicron-resolution SR-based XRF elemental mapping of tissue-specific distribution and adverse effect analysis to obtain robust toxicological evaluations of metal-containing contaminants.

Combined Computed Nanotomography and Nanoscopic X-ray Fluorescence Imaging of Cobalt Nanoparticles in Caenorhabditis elegans.

Synchrotron radiation phase-contrast computed nanotomography (nano-CT) and two- and three-dimensional (2D and 3D) nanoscopic X-ray fluorescence (nano-XRF) were used to investigate the internal distribution of engineered cobalt nanoparticles (Co NPs) in exposed individuals of the nematode Caenorhabditis elegans. Whole nematodes and selected tissues and organs were 3D-rendered: anatomical 3D renderings with 50 nm voxel size enabled the visualization of spherical nanoparticle aggregates with size up to 200 nm within intact C. elegans. A 20 × 37 nm2 high-brilliance beam was employed to obtain XRF elemental distribution maps of entire nematodes or anatomical details such as embryos, which could be compared with the CT data. These maps showed Co NPs to be predominantly present within the intestine and the epithelium, and they were not colocalized with Zn granules found in the lysosome-containing vesicles or Fe agglomerates in the intestine. Iterated XRF scanning of a specimen at 0° and 90° angles suggested that NP aggregates were translocated into tissues outside of the intestinal lumen. Virtual slicing by means of 2D XRF tomography, combined with holotomography, indicated presumable presence of individual NP aggregates inside the uterus and within embryos.

Micro-analytical characterization of thorium-rich aggregates from Norwegian NORM sites (Fen Complex, Telemark).

In this study we performed microscopic characterization of mineral particles that were collected in the thorium-rich Fen Complex in Norway and identified and isolated based on autoradiography in function of their radioactivity. For this we combined information obtained with X-ray absorption µ-CT, µ-XRF and µ-XRD, both in bi- and in three-dimensional (tomographic) mode. We demonstrate that radionuclides and metals are heterogeneously distributed both within soil samples and within individual Th-enriched aggregates, which are characterised as low-density mineral bulk particles with high density material inclusions, where Th as well as several metals are highly concentrated. For these sites, it is important to take into account how these inhomogeneous distributions could affect the overall environmental behaviour of Th and progeny upon weathering due to human or environmental factors. Moreover, the estimated size of the Th-containing inclusions as determined in this work represents information of importance for the characterization of radionuclides and toxic metals exposure, as well as for assessing the viability of mining for Th and rare-earth metals in the Fen Complex and the associated environmental impact.

Zinc and Iron Concentration as Affected by Nitrogen Fertilization and Their Localization in Wheat Grain.

Nearly half of the world cereal production comes from soils low or marginal in plant available zinc, leading to unsustainable and poor quality grain production. Therefore, the effects of nitrogen (N) rate and application time on zinc (Zn) and iron (Fe) concentration in wheat grain were investigated. Wheat (Triticum aestivum var. Krabat) was grown in a growth chamber with 8 and 16 h of day and night periods, respectively. The N rates were 29, 43, and 57 mg N kg-1 soil, equivalent to 80, 120, and 160 kg N ha-1. Zinc and Fe were applied at 10 mg kg-1 growth media. In one of the N treatments, additional Zn and Fe through foliar spray (6 mg of Zn or Fe in 10 ml water/pot) was applied. Micro-analytical localization of Zn and Fe within grain was performed using scanning macro-X-ray fluorescence (MA-XRF) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The following data were obtained: grain and straw yield pot-1, 1000 grains weight, number of grains pot-1, whole grain protein content, concentration of Zn and Fe in the grains. Grain yield increased from 80 to 120 kg N ha-1 rates only and decreased at 160 kg N ha-1 g. Relatively higher protein content and Zn and Fe concentration in the grain were recorded with the split N application of 160 kg N ha-1. Soil and foliar supply of Zn and Fe (Zn + Fes+f), with a single application of 120 kg N ha-1N at sowing, increased the concentration of Zn by 46% and of Fe by 35%, as compared to their growth media application only. Line scans of freshly cut areas of sliced grains showed co-localization of Zn and Fe within germ, crease and aleurone. We thus conclude that split application of N at 160 kg ha-1 at sowing and stem elongation, in combination with soil and foliar application of Zn and Fe, can be a good agricultural practice to enhance protein content and the Zn and Fe concentration in grain.

Thorium-229 quantified in historical Thorium-228 capsules.

Thorium-229 is a valuable, but scarce, radionuclide for nuclear clock applications or targeted alpha therapy. While it is mostly produced by the decay of 233U, 229Th can also be produced by neutron irradiation of 226Ra. At SCK•CEN, capsules containing mainly 228Th (by-product of 226Ra irradiation) were characterized to quantify the present amounts of 229Th, 228Th, 227Ac, 226Ra with high resolution gamma spectroscopy, after a decay period of 40 years in which 228Th has decayed. High purity 229Th was quantified, and after recovery using radiochemical separation processes, it can be used to support ongoing research.