Median, maximal and minimal values of 48-h L(E)C₅₀ of daphnids species tested with TiO₂ NPs calculated from differents studies [38], [58]–[72].

<p>Median, maximal and minimal values of 48-h L(E)C₅₀ of daphnids species tested with TiO₂ NPs calculated from differents studies <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071260#pone.0071260-Klaper1" target="_blank">[38]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071260#pone.0071260-Lovern2" target="_blank">[58]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071260#pone.0071260-Marcone1" target="_blank">[72]</a>.</p

Effect curve <i>vs</i> time of <i>D. similis</i> and <i>D. pulex</i> at 0.1 mg.L⁻¹, 1 mg.L⁻¹, 10 mg.L⁻¹, 50 mg.L⁻¹ and 100 mg.L⁻¹ of CeO₂ NPs.

<p>Values are Mean EC₅₀±SD.</p

Representative image of distal spine (ds) and ventral margin of the shield (vms) in <i>D. pulex</i> and <i>Daphnia similis</i> exposed to 10 mg^.L⁻¹ of CeO₂ NPs for 48 h.

<p>Note the accumulation of particles onto the cuticle of <i>D. similis</i>. The optical image (E) represents the <i>D. similis</i> after 48 h exposure to 10 mg.L⁻¹ of CeO₂ NPs.</p

Distribution of Ce (Lα line), P (Kα line) and Ca (Kα line) on the posterior region of <i>D. pulex</i> and <i>D. similis</i> exposed 48 h to CeO₂ NPs.

<p>Chemical map parameters: 128 pixel² image, 1 pixel: 8 µm, total counting time 20000: sec, scale (white bar): 500 µm. Mean XRF spectra corresponding to specific area of the individual were generated from the hyperspectral map.</p

Thallium Long-Term Fate from Rock-Deposit to Soil: The Jas Roux Sulfosalt Natural Analogue

Inorganic contaminant release resulting from mining activities can impact surrounding ecosystems. Ores formed by primary sulfide minerals produce sulfuric acid after mineral oxidation, which is the driving force of metal release. Yet secondary metal sulfates may form and play a crucial role in controlling the metal fate. In the case of thallium (Tl), it has been shown that in natural Tl-rich sulfide deposits and those found in mining areas, Tl can be trapped by Tl-jarosite (Tl-rich iron sulfate) and dorallcharite (TlFe3(SO4)2(OH)6). Our Tl speciation characterization results have generated novel insight into the long-term behavior of this metal derived from a unique natural hotspot: the Jas Roux site (France). The biogeochemical cycle of the soil ecosystems of Jas Roux dates back almost 15000 years ago and has now reached a steady state. A chemical gradient was found in soils across the toposequence underlying the Jas Roux outcrop. X-ray absorption spectroscopy revealed that Tl was mainly present in secondary minerals at the top of the studied zone. Oxidative dissolution of Tl-rich sulfide minerals and pyrite accounts for the presence of Tl-jarosite in soils, either by direct formation in soils or by gravity erosion from the outcrop. The Tl-jarosite quantity was found to decrease from the top to the bottom of the toposequence, probably due to sulfate leaching. Released Tl likely adsorbed on phyllosilicates such as Illite or muscovite, and a fraction of Tl was found to have oxidized into Tl(III) along the toposequence

Transformation of Pristine and Citrate-Functionalized CeO₂ Nanoparticles in a Laboratory-Scale Activated Sludge Reactor

Engineered nanomaterials (ENMs) are used to enhance the properties of many manufactured products and technologies. Increased use of ENMs will inevitably lead to their release into the environment. An important route of exposure is through the waste stream, where ENMs will enter wastewater treatment plants (WWTPs), undergo transformations, and be discharged with treated effluent or biosolids. To better understand the fate of a common ENM in WWTPs, experiments with laboratory-scale activated sludge reactors and pristine and citrate-functionalized CeO₂ nanoparticles (NPs) were conducted. Greater than 90% of the CeO₂ introduced was observed to associate with biosolids. This association was accompanied by reduction of the Ce­(IV) NPs to Ce­(III). After 5 weeks in the reactor, 44 ± 4% reduction was observed for the pristine NPs and 31 ± 3% for the citrate-functionalized NPs, illustrating surface functionality dependence. Thermodynamic arguments suggest that the likely Ce­(III) phase generated would be Ce₂S₃. This study indicates that the majority of CeO₂ NPs (>90% by mass) entering WWTPs will be associated with the solid phase, and a significant portion will be present as Ce­(III). At maximum, 10% of the CeO₂ will remain in the effluent and be discharged as a Ce­(IV) phase, governed by cerianite (CeO₂)

Molecular Insights of Oxidation Process of Iron Nanoparticles: Spectroscopic, Magnetic, and Microscopic Evidence

Oxidation behavior of nano-Fe⁰ particles in an anoxic environment was determined using different state-of-the-art analytical approaches, including high resolution transmission electron microscopy (HR-TEM) combined with energy filtered transmission electron microscopy (EFTEM), X-ray absorption spectroscopy (XAS), and magnetic measurements. Oxidation in controlled experiments was compared in standard double distilled (DD) water, DD water spiked with trichloroethene (TCE), and TCE contaminated site water. Using HR-TEM and EFTEM, we observed a surface oxide layer (∼3 nm) formed immediately after the particles were exposed to water. XAS analysis followed the dynamic change in total metallic iron concentration and iron oxide concentration for the experimental duration of 35 days. The metallic iron concentration in nano-Fe⁰ particles exposed to water, was ∼40% after 35 days; in contrast, the samples containing TCE were reduced to ∼15% and even to nil in the case of TCE contaminated site water, suggesting that the contaminants enhance the oxidation of nano-Fe⁰. Frequency dependence measurements confirmed the formation of superparamagnetic particles in the system. Overall, our results suggest that nano-Fe⁰ oxidized via the Fe⁰ – Fe­(OH)₂ – Fe₃O₄ – (γ-Fe₂O₃) route and the formation of superparamagnetic maghemite nanoparticles due to disruption of the surface oxide layer

Influence of the Length of Imogolite-Like Nanotubes on Their Cytotoxicity and Genotoxicity toward Human Dermal Cells

Physical–chemical parameters such as purity, structure, chemistry, length, and aspect ratio of nanoparticles (NPs) are linked to their toxicity. Here, synthetic imogolite-like nanotubes with a set chemical composition but various sizes and shapes were used as models to investigate the influence of these physical parameters on the cyto- and genotoxicity and cellular uptake of NPs. The NPs were characterized using X-ray diffraction (XRD), small angle X-ray scattering (SAXS), and atomic force microscopy (AFM). Imogolite precursors (PR, ca. 5 nm curved platelets), as well as short tubes (ST, ca. 6 nm) and long tubes (LT, ca. 50 nm), remained stable in the cell culture medium. Internalization into human fibroblasts was observed only for the small particles PR and ST. None of the tested particles induced a significant cytotoxicity up to a concentration of 10^–1 mg·mL^–1. However, small sized NPs (PR and ST) were found to be genotoxic at very low concentration 10^–6 mg·mL^–1, while LT particles exhibited a weak genotoxicity. Our results indicate that small size NPs (PR, ST) were able to induce primary lesions of DNA at very low concentrations and that this DNA damage was exclusively induced by oxidative stress. The higher aspect ratio LT particles exhibited a weaker genotoxicity, where oxidative stress is a minor factor, and the likely involvement of other mechanisms. Moreover, a relationship among cell uptake, particle aspect ratio, and DNA damage of NPs was observed