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Management of marine dredged sediments polluted with trace elements is prime issue in the French Mediterranean coast. The polluted sediments possess ecological threats to surrounding environment on land disposal. Therefore, stabilization of contaminants in multi-contaminated marine dredged sediment is a promising technique. Present study aimed to assess the effect of gypsum neutralized bauxaline(®) (bauxite residue) to decrease the availability of pollutants and inherent toxicity of marine dredged sediment. Bauxaline(®), (alumia industry waste) contains high content of iron oxide but its high alkalinity makes it not suitable for the stabilization of all trace elements from multi-contaminated dredged sediments. In this study, neutralized bauxaline(®) was prepared by mixing bauxaline(®) with 5% of plaster. Experiments were carried out for 3 months to study the effect of 5% and 20% amendment rate on the availability of Cu, Cd, Zn, As, Mo, and Cr. Trace elements concentration, pH, EC and dissolved organic carbon were measured in all leachates. Toxicity of leachates was assessed against marine rotifers Brachionus plicatilis. The Results showed that both treatments have immobilization capacity against different pollutants. Significant stabilization of contaminants (Cu, Cd, Zn) was achieved with 20% application rate whereas As, Mo, and Cr were slightly stabilized. Toxicity results revealed that leachates collected from treated sediment were less toxic than the control sediment. These results suggest that application of neutralized bauxaline(®) to dredged sediment is an effective approach to manage large quantities of dredged sediments as well as bauxite residue itself., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

This work investigates arsenic mobility, bioavailability and toxicity in marine port sediments using chemical sequential extraction and laboratory toxicity tests. Sediment samples were collected from two different Mediterranean ports, one highly polluted with arsenic and other inorganic and organic pollutants (Estaque port (EST)), and the other one, less polluted, with a low arsenic content (Saint Mandrier port (SM)). Arsenic distribution in the solid phase was studied using a sequential extraction procedure specifically developed for appraising arsenic mobility in sediments. Toxicity assessment was performed on sediment elutriates, solid phases and aqueous arsenic species as single substance using the embryo-toxicity test on oyster larvae (Crassostrea gigas) and the Microtox test with Vibrio fischeri. Toxicity results showed that all sediment samples presented acute and sub-chronic toxic effects on oyster larvae and bacteria, respectively. The Microtox solid phase test allow to discriminate As-contaminated samples from the less contaminated ones, suggesting that toxicity of whole sediment samples is related to arsenic content. Toxicity of dissolved arsenic species as single substance showed that Vibrio fischeri and oyster larvae are most sensitive to As(V) than As(III). The distribution coefficient (Kd) of arsenic in sediment samples was estimated using results obtained in chemical sequential extractions. The Kd value is greater in SM (450 Lkg(-1)) than in EST (55 Lkg(-1)), indicating that arsenic availability is higher for the most toxic sediment sample (Estaque port). This study demonstrates that arsenic speciation play an important role on arsenic mobility and its bioavailability in marine port sediments., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Competition between selenium (IV) and silicic acid for the hematite (alpha-Fe(2)O(3)) surface has been studied during this work. Single batch experiments have been performed to study separately the sorption of selenium (IV) and silicic acid as a function of the pH. With the help of the 2-pK surface complexation model, experimental data have been fitted using the FITEQL 4.0 program. Two monodentate inner-sphere surface complexes have been used to fit selenite ions retention, triple bond FeSeO(3)(-) and triple bond FeHSeO(3). In order to fit sorption of silicic acid, the two following surface complexes, namely triple bond FeH(3)SiO(4), and triple bond FeH(2)SiO(4)(-), have been used. Using the surface complexation constants coming from these two binary systems, prediction curves of the effect of silicic acid on the retention of selenium (IV) onto hematite have been obtained. Finally, performed experiments showed a competition between selenium (IV) and silicic acid for the surface sites of hematite. Experimental data matched DDLM predictions, confirming the ability of the surface complexation model to predict quantitatively and qualitatively the ternary system selenium (IV)/H(4)SiO(4)/hematite.