Search

The release of engineered titanium dioxide nanoparticles in the environment is nowadays continuously increasing due to their wide range of industrial applications. Their potential toxicity effects became of major concern and several assessment studies in natural waters were already undertaken. However, no consensus arised about the environmental factors influencing their hazardous impact, but rather contrary conclusions were drawn. In this study, the acute toxicity of commercial TiO2 nanoparticles suspensions at different concentrations on microcrustacean (Daphnia magna), marine rotifers (Brachionus plicatilis) and marine microalgae (Phaeodactylum tricornutum) under environmental conditions, in synthetic fresh and marine water, was investigated. Factors driving TiO2 adverse effects on aquatic environment, such as allotropic form, primary particle size, surface area, particle concentration and agglomerate size were studied. A thorough characterization of both surface and bulk properties of nano-sized TiO2 particles was therefore performed. Our results showed that Daphnia magna test is the most sensitive test for assessing toxicity of TiO2 samples on aquatic organisms. For anatase samples, toxicity towards aquatic organisms depends (i) on the primary particle size and the extent of agglomeration (mass median diameter d50), and consequently on surface reactivity (total surface site concentration, specific surface area, pHIEP) (ii) on the presence of rutile impurities in the sample. Toxicity results of rutile and anatase samples of comparable primary particle size (sub micrometric range) are of same order of magnitude and remained less toxic than nanometric particles. Rutile agglomeration was found to be higher than anatase agglomeration, toxicity results obtained for rutile could be attribute to the shape of particles, or it could be due to the presence of BaTiO3 impurities. This work emphasized the importance of studying the effects of different bulk and surface parameters of engineered TiO2 nanoparticles to understand their reactivity towards micro-organisms under environmental conditions.

101 children, each of them with two teleradiographies, were selected. The first X-ray was taken at the time of the mixed dentition, the second one, when the permanent dentition was established. The purpose of the research is to show the oscillations of the palatine and mandibular planes, and their link to the movements of the first permanent molars. The palatine plane is found to swing between - 7° and +5°, with an average of -0.97°. The posterior part of that plane rocks downwards in 51% of the children. The limits are -7° and -1°, with an average of -3.2°. In 22%, the plane rocks upwards between +1° and +5° with an average of +3.1°. In 27% it moves parallel to itself. The posterior part of the mandibular plane varies between -6° and +5°, with an average of -1.1°. It rocks downwards in 48% of the cases, between -6° and -1° with an average of -3.9°. In 22% of the children, this plane rocks upwards between +1° and +5°with an average of +2.5°. In 30%, it moves parallel to itself. The overall result is that the more the posterior part of the palate, or of the mandibule moves downwards, the more the first permanent molars get straight or move forwards., Le but de ce travail est de déterminer les oscillations des plans palatin et mandibulaire ainsi que leur lien avec les mouvements des premières monophysaires. Les téléradiographies, prises à quelques années d’intervalle, de 101 enfants, sont superposés sur le compas ptérygo-clivien. Plus la partie postérieure des lames palatines ou de la mandibule s’abaisse, plus les premières molaires se redressent ou se déplacent vers l’avant.

Titanium oxides nanoparticles have been widely used in industrial applications such as cosmetics, food industries, environment, paints and surface coatings…Face to their growing use in various domains and the difficulties to separate them from the aqueous phase during wastewaters treatment due to their nanometric size, one can expect that the final host for these particles should be environmental compartments (soil, air and water). Nanometric-sized particles are known to cause pulmonary damages and to be toxic for mammals (mice, rats). Nevertheless, few studies dealt with the toxic impact of nanoparticles with ecosystems. Previous studies have shown that the toxic effect was dependent (i) on the size of the particles and (ii) on the allotropic form of TiO2 (anatase or rutile). But a lack of information remains concerning the relationship between the surface properties of TiO2 nanoparticles (surface site density, surface charge) and the observed toxicity. In this study we were interested in anatase (15 nm, 32 nm, 44 μm) and rutile (1 μm) commercial particles. Their toxic effect (acute or chronic) versus microcrustaceans, algae and plants was measured and compared to the particles size. Surface properties of each TiO2 particles were determined by acid-base titration, and electrokinetics measurements, in order to complete data concerning the relationship between nanoparticles toxicity, size and allotropic form.

Bauxite extraction by-products (red mud) were used to evaluate their potential ability to stabilize trace elements from dredged and aerated/humidified marine sediment. The investigated by-products were: bauxaline(®)(BX) that is a press-filtered red mud; bauxsol™(BS) that is a press-filtered red mud previously washed with excess of seawater, and gypsum neutralized bauxaline(®) (GBX). These materials were separately mixed to dredged composted sediment sample considering 5% and 20% sediment: stabilizer ratios. For pilot experiments, rainfall events were regularly simulated for 3 months. Concentrations of As, Mo, Cd, Cr, Zn, Cu, and Ni were analyzed in collected leachates as well as toxicity. Results showed that Cd, Mo, Zn, and Cu were efficiently stabilized in the solid matrix when 20% of BX, BS, and GBX was applied. Consequently, toxicity of leachates was lower than for the untreated sediment, meaning that contaminants mobility was reduced. A 5% GBX was also efficient for Mo, Zn and Cu stabilization. In all scenarios, As stabilization was not improved. Compared to all other monitored elements, Mo mobility seemed to depend upon temperature-humidity conditions during pilot experiments suggesting the need of further investigations.

The ecotoxicological effect of dredged sediments was estimated by embryo-larval toxicity of the oyster Crassosstrea gigas in sediment elutriates (filtered and unfiltered). The study covers the main ports from the French Mediterranean coast. Composted sediments from a navy harbour (A), a commercial port (B) and two composite specimens (C and D) obtained after mixing various sediments were taken into consideration. Effective concentrations affecting 50% of larvae (EC50) were obtained from different elutriate concentrations (from 0 to 100%). Toxicity results obtained from filtered elutriates decreased according to the following gradient: sample A (5.68%), B (20.50%), C (37.60%) and D (47.17%). Chemical concentrations in whole sediments were in agreement with those in elutriates. Among the measured contaminants in elutriates, Cu and Zn resulted as the main contributors to toxicity. Dissolved organic carbon played an important role by exerting a protective effect against the toxicity of dissolved Cu. Toxicity results were interpreted on the basis of toxicity scores to give indication about sediment quality which provided more severe judgement than risk score based on chemical concentrations in sediments.