Charlotte Hurel

Toxicity of TiO2 nanoparticles to cladocerans, algae, rotifers and plants – Effects of size and crystalline structure

With the rapid development of nanotechnology, there is an increasing risk of human and environmental exposure to nanotechnology-based materials. However, the data on the potential environmental effects of nanoparticles are scarce. The aim of this study is to assess the effect of particle size and crystal structure (anatase and rutile) of titanium dioxide on their toxicity. Thus, acute and chronic toxicity tests included a modified acute test (72 h) using daphnies and algae, rotifers and plants as model organisms. Gradient of toxicity varied with the tested biological organisms. Our results revealed that TiO(2) nanoparticles in anatase crystal structure are toxic in the entire set of tests conducted. However, at highconcentration, through their antimicrobial properties, they significantly promoted growth of roots. Because of its lipophilicity, the rutile crystalline structure of TiO(2) NPs form larger aggregates in aqueous medium; then they have less effect on biological organisms, and thus a lower toxicity than the anatase crystalline form of TiO(2). We also demonstrated that exposure duration, aggregation and concentrations are contributing factors in nanoparticles-mediated toxicity.

Sorption of Cr(VI) onto natural iron and aluminum (oxy)hydroxides: effects of pH, ionic strength and initial concentration.

The aim of this work is to study the performances of removal of hexavalent chromium from aqueous solution by three different oxy-hydroxides: hematite, goethite and alpha-alumina. Batch experiments were conducted to measure the effects on adsorption of Cr(VI) of different parameters such as pH of the medium, ionic strength, and initial concentration. Results showed that the adsorption of Cr(VI) depends strongly on the pH, but is independent of ionic strength for hematite and goethite. For alpha-alumina, adsorption is strongly dependent on pH values and ionic strength. Equilibrium studies showed that Cr(VI) had a high affinity in an acidic medium, but decreased as solution pH increased. Equilibrium isotherms were measured experimentally. Results were analyzed by the Langmuir and Freundlich equations using linearized correlation coefficient at room temperature. The characteristic parameters for each isotherm have been determined. Langmuir equation was found to fit the equilibrium data for Cr(VI) adsorption.

The toxicity of composted sediments from Mediterranean ports evaluated by several bioassays.

This work investigates the ecotoxicological evaluation of contaminated dredged sediments from French Mediterranean navy harbour (A), commercial port (B) and two composite specimens (C) and (D) coming from the mixture of A and B with other port sediments. The toxicity of elutriates from these sediments is estimated using embryo-toxicity test, Microtox® solid phase test, LuminoTox, phytotoxicity tests and genotoxicity test. Bioassay responses are not clearly correlated with chemical contamination in the whole sediment and vary as a function of tested organisms. The highest contaminated samples (A and C) are almost always more toxic than the less contaminated samples (B and D). Among composite sediments, the mixture effect with other sediments is not efficient to decrease toxicity in sample C, suggesting that other parameters influence toxicity level such as particle size or organic matter content. These parameters should be taken into consideration in order to improve the efficiency of the mixture process and produce composite sediments with low toxicity.

Ecotoxicological evaluation of Mediterranean dredged sediment ports based on elutriates with oyster embryotoxicity tests after composting process

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.

Toxicity assessment of silica nanoparticles, functionalised silica nanoparticles, and HASE-grafted silica nanoparticles

Numerous nanomaterials have recently been developed, and numerous practical applications have been found in water treatment, medicine, cosmetics, and engineering. Associative polymers, such as hydrophobically modified alkali-soluble emulsion (HASE) systems are involved in several applications and have been extensively studied due to their ability to form three-dimensional networked gels. However, the data on the potential environmental effects of this polymers are scarce. The aim of this study is to assess the effect of functionalisation of silica nanoparticles, and coupling of functionalised silica nanoparticles to the associative polymer HASE on their toxicity. Thus, acute and chronic toxicity tests included a modified acute test (72 h) using daphnies, algae, and plants as model organisms. Gradient of toxicity varied with the tested organisms. Our results revealed that the functionalised nanoparticules and NP grafted polymer cause a global decrease in toxicity compared to commercial nanoparticule and HASE polymer.

Comparison of mineral-based amendments for ex-situ stabilization of trace elements (As, Cd, Cu, Mo, Ni, Zn) in marine dredged sediments: a pilot-scale experiment.

Trace element pollution of marine dredged sediments is an emerging problem all over the world. Comparing to other wastes, trace elements stabilization is more difficult both due to the wide range of contaminants present in the marine sediments and their inherent physicochemical properties. In this study, a pilot-scale experiment was performed to stabilize As, Cd, Cu, Mo, Ni, and Zn in a multi-contaminated sediment sample using hematite, zero-valent iron and zeolite. Results showed that iron-based amendments were able to reduce the leaching and the bioavailability of trace elements in the sediment sample, while zeolite was unsuitable. Chemical stabilization through iron-based amendments seems to be a promising approach as a low-cost alternative to traditional stabilization methods involving chemical reagents.

Ex situ remediation of contaminated sediments using mineral additives: assessment of pollutant bioavailability with the Microtox solid phase test.

The aim of this work is to assess the potential ecotoxicological effects of contaminated sediments treated with mineral additives. The Microtox solid phase test was used to evaluate the effect of mineral additives on the toxicity of sediment suspensions. Four Mediterranean port sediments were studied after dredging and bioremediation: Sample A from navy harbor, sample B from commercial port and samples C and D from pleasure ports. Sediment samples were stabilized with three mineral additives: hematite, zero-valent iron and zeolite. Results show that all studied mineral additives can act as stabilizer agent in highly contaminated sediments (A and C) by decreasing dissolved metal concentrations and sediment toxicity level. On the contrary, for the less contaminated samples (B and D) hematite and zeolite can provoke toxic effect towards Vibrio fischeri since additive particles can favor bacteria retention and decrease bioluminescence emission.

Minerals as additives for decreasing the toxicity of Mediterranean contaminated dredged sediments

The management of dredged sediments is a priority issue in the Mediterranean sea where sediments are historically polluted. The aims of this study were to evaluate the toxicity of port sediment samples and the effect of three mineral additives (hematite, zerovalent iron (ZVI) and natural zeolite (NZ)) on sediment elutriate toxicity. Four sediments (A, B, C and D) were provided by port authorities after composting procedure; particle size, particulate organic carbon, metals and organic pollutants (TBT, PAHs, PCBs) were determined in whole sediments. Elutriates from these composted sediments were analyzed by determining toxicity level using oyster (Crassostrea gigas) larvae bioassay, metal and dissolved organic carbon concentrations. Toxicity, measured on undiluted elutriates (250 g/L), decreased as follows: A≥B>C∼D. The treatment of sediments with mineral additives (5%) revealed that hematite tends to decrease the elutriate toxicity in all samples, particularly in samples B and C. This effect may be related to metal concentration decrease in elutriates, in particular Cu and Zn, that have a significant toxic effect on oyster larvae. ZVI and NZ have a variable influence on elutriate toxicity. Results suggest that hematite may be a possible candidate for decreasing chemical concentration and improving the quality of elutriates. Hematite could be used for sediment stabilization prior to the deposit in a specific site or landfill.

Arsenic in Marina Sediments from the Mediterranean Coast: Speciation in the Solid Phase and Occurrence of Thioarsenates

Arsenic speciation was determined in marina sediments of the French Mediterranean coast. The sediment from L′Estaque marina was highly impacted by both metallurgical activities and by the commercial port of Marseille, in contrast to the sediment from St. Mandrier marina that was less polluted. In the solid phases, As(III) was the dominant species in the L′Estaque sediment, whereas As(V) was the main form in the St. Mandrier sediment, with total As concentrations in the range 160–350 mg/kg and 17–20 mg/kg, respectively. In both sites, arsenic was the major trace element detected in interstitial water, its concentration reaching values higher than 1 mg/L in the L′Estaque sediment. Sulfate-reduction seemed to be more active in the L′Estaque site, probably because of the availability of easily biodegradable organic matter. This condition favored the formation of thioarsenates that were quantified here for the first time in a polluted marine sediment. Thioarsenates represented 69 ± 24% of total dissolved As in the 15–60 cm depth sediment layer. Our results suggest that bacterial activity may significantly contribute to increased arsenic solubility and mobility in harbor sediments, where crude oil input stimulates sulfate-reducers.

Effects of mineral amendments on trace elements leaching from pre-treated marine sediment after simulated rainfall events☆

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.