Chimie

A new method is proposed to characterize the complexation properties of colloids and metal-colloid interactions in natural waters. Based on the association of ultrafiltration with isotopic tracing, this method could quantify the pool of elements in an exchangeable position and also address the kinetic aspects of these exchanges. Basically, it consists of the comparison of isotopic compositions between the bulk sample and a succession of filtrates through time. Exchanges between colloidal humic acids (HA) and metals were first characterized, before applying such manipulations on natural waters. A few elements, representative of a wide range of complexation properties, were chosen: Cu, Zn, Cd, Pb, Sr, Nd, Ni, Th and U. In the case of humic acids, very small (less than 10% of isotopes), but significant isotopic shifts were observed compared to the isotopic equilibrium. It means that more than 90% of the isotopes were exchanged just after addition of isotopic tracers. Experiments on natural organic-rich waters (Mengong and Nyong streams) indicate isotopic composition variations close to those of humic acids. On the contrary, ultrafiltration performed on the total Sanaga River water (including suspended matter bSMQ) shows an important isotopic shift between the filtered and unfiltered solutions. It means that in the case of the Sanaga River, a significant part of the chemical elements did not exchange. D

Zn isotopes were used to trace the anthropogenic sources in the Lot watershed (Aveyron, SW France) where a small river, the Riou Mort drains an industrial exploitation of zinc ore. The zinc isotopes in industrial tailings are highly fractionated relatively to Zn ore (δ 66 Zn ∼ 0.16‰), due to metallurgical processes, reaching δ 66 Zn values up to + 1.49‰. Zn extraction yields for these samples were calculated using presumable conservative elements (Fe, Ca, Mg, K, Na and Mn) and vary from 95.4% to 99.4%. Extraction yields are related to the intensity of Zn isotopic fractionation. Different Rayleigh isotope fractionation scenarios for Zn refining yielded α ore-tailings ranging from 1.00012 to 1.00062. The δ 66 Zn of the Riou Mort sediments downstream from the former Zn-ore facility is presently +0.91 ± 0.04‰, i.e. significantly different from the signature of upstream sediments and of the regional geochemical background, +0.31 ± 0.06‰, (2SD, n = 3). Sediment core δ 66 Zn values in the 40 km downstream Cajarc hydroelectric reservoir are also consistently 'heavier' (+0.75 to +1.35‰) than the regional geochemical background. Both top-core Zn concentrations and isotopic signatures can be explained by the contribution of 9% of present-day Riou Mort sediments. δ 66 Zn variations in the 137 Csdated downcore sediments are suggested to reflect historical changes in metallurgical processes of the Viviez facility, such as improved Zn extraction efficiency and the related evolution of tailings. In sediments deposited during 1952-1972, the mean δ 66 Zn is + 0.95 ± 0.08‰, representative of the combined electrolysis and thermal process used at that time for the Zn extraction. In sediments deposited during the late seventies, δ 66 Zn increases, reaching a maximum of 1.35‰ during the eighties. These heavier δ 66 Zn are likely related to further increased Zn extraction after replacement of thermal waste processing by electrolysis in 1976/77. The nature of the extraction processes, especially electrolysis, may therefore play a major role in the Zn isotopic fractionation produced. The soils located on the Lot riverbanks have chemical and Zn isotopic compositions (+0.74‰ to +0.96‰) close to the Cajarc sediments, indicating that they were also impacted by tailings erosion and leaching. The soils located in the vicinity of the plant display lower δ 66 Zn (+ 0.40‰ to 0.48‰). That corresponds to mixtures of several atmospheric sources like coal fly ashes, ore and tailing dusts. The relation between Zn isotopic fractionation, extraction yields and/or extraction processes clearly demonstrates the efficiency of δ 66 Zn as tracer of environmental contamination.

Zinc and Cd distribution and mobility in a polluted soil were studied using a combination of micro5 characterization, physical, chemical and isotopic techniques. The study was conducted in a fluvisol, polluted by non5ferrous metallurgical activities. Results showed large amounts of metals in mineral phases resulting from the industrial activity. The main mineral phases detected due to metallurgic activity were coal, coke, iron and multimetallic oxides, pure metal alloys, sulphides and glass. Zinc was mainly extracted in the reducible pool (64%). This pool comprised reducible FeIII oxides and oxy5hydroxide including hematite, goethite, magnetite and multimetallic oxide phases (franklinite). Only 10% of Zn was extracted in the exchangeable pool, whereas 40% of Cd was extracted in this pool and 46% in the reducible pool. The isotopically exchangeable kinetic method showed that 60% of Cd and only 4% of Zn were exchanged after one week. Zn exchanges were quicker than Cd ones. Zn is prefe...

Manufactured nanoparticles (NPs) are highly susceptible to being released in the environment. However, studies on their fate and behavior presented in the literature are often carried out at concentrations far from those in real environmental media [1], because of the difficulty to detect NPs in complex and ”noisy” matrices. Nevertheless, changes in NPs concentration are known to affect its physicochemical behavior. In order to overcome analytical barriers while working at representative realistic concentration, innovative tools such as HR-ICP-MS and non-traditional stable isotopes (isotopically modified NPs [2] or ”spiked”) have been used. 7 nm sized isotopically labelled quantum dots (QDs), CdSe/ZnS core-shell structure were synthesized, enriched in 68Zn, 77Se and 111Cd. These multi-spiked QDs were disseminated at very low concentrations (from 0.1 ng/L to 5 μg/L) in aquatic media, and the isotopic compositions were determined by HR-ICP-MS. On this basis, the initial QDs concentrat...

The interaction between live organisms and nanosized particles has become a current focus in toxicology. The aims of the present work are: (i) to assess the zinc oxide (ZnO) toxicity and its mechanisms into the aquatic environment, using the green algae Chlorella vulgaris as biological indicator; (ii) to compare the ZnO behavior and toxic profile in synthetic (Bold's Basal) and natural (Seine River Water, SRW) culture media; and (iii) to address whether the obtaining route is an issue in ZnO particles toxicity or not. Responses such as growth inhibition, cell viability, superoxide dismutase (SOD) activity, adenosine-5-triphosphate (ATP) content and photosynthetic efficiency were evaluated. The main conclusions are: (i) nanoparticulate ZnO have an statistically significant toxic effect on C. vulgaris growth since the lower concentration tested (1ppm), that seems to be mediated by a induced oxidative stress (probably due to extensive release of Zn 2+ into the media); (ii) the ZnO behavior in synthetic and natural culture media were statistically similar, although the toxic effects were more pronounced in SRW; and (iii) the production process does not seem to be an issue in ZnO nanoparticles toxicity since all tested particles produced significant effects on microalgae growth

Engineered nanoparticles (ENPs) are highly susceptible to arrive to environmental compartments (e.g., surface waters). However, studies on their fate and behaviour are often carried out at concentrations far from those predicted in real environmental media,1 due to the difficulty to detect these NPs in complex matrices with high background noise (i.e., the occurrence of NPs constitutive elements in the natural media in varying concentrations). Nevertheless, changes in NPs concentration are known to affect its physicochemical behaviour. Therefore, we propose in this study to use non-traditional stable isotopes (isotopically labelled2 NPs) to overcome analytical barriers when working at relevant concentrations (ng/L). The behaviour of 7 nm-sized multi-isotopically labelled 111Cd77Se/68ZnS quantum dots (QDs) coated with thioglycolic acid (TGA) was evaluated after dispersion at the ng/L level in different synthetic river waters (in absence and presence of fulvic acids and goethite). Met...

Correct characterization of metal speciation and reactivity is a prerequisite for the risk assessment and remedial activity management of contaminated soil. To better understand the intrinsic lability of Pb and Zn, nine non-contaminated and contaminated soils were investigated using the combined approaches of chemical extractions, multi-element stable isotopic dilution (ID) method, and multisurface modelling. The ID results show that 0.1-38% of total Pb and 3-45% of total Zn are isotopically exchangeable after a 3-day equilibration. The intercomparison between experimental and modelling results evidences that single extraction with 0.43 M HNO3 solubilizes part of nonisotopically exchangeable fraction of Pb and Zn in the studied soils, and cannot be used as a surrogate for ID to assess labile Pb and Zn pools in soil. Both selective sequential extraction (SSE) and modelling reveal that Mn oxides are the predominant sorption surface for Pb in the studied soils; while Zn is predicted to...

Mineralogical Magazine | www.minersoc.org 2261 COMBINING μSXRF, EXAFS AND ISOTOPIC SIGNATURE TO UNDERSTAND THE NI CYCLE IN IMPACTED ULTRAMAFIC SOILS CÉCILE QUANTIN, DELPHINE JOUVIN, ALEXANDRE GÉLABERT, EMMANUELLE MONTARGES-PELLETIER, YANN SIVRY, , ISABELLA ZELANO , RÉMY PICHON, JÉRÉMIE GARNIER, AND MARC F. BENEDETTI UMR 8148 IDES, UPS-CNRS, Orsay, France ([email protected], [email protected], [email protected]) UMR 7154, Université Paris Diderot Sorbonne Paris Cité IPGP , Paris , France ([email protected], [email protected], [email protected], [email protected]) UMR 7569 LEM, CNRS-Nancy I, Nancy, France ([email protected]) Instituto de Geociências, Universidade de Brasilia, Brasilia DF, Brazil (*[email protected])

Les nanoparticules (NPs) manufacturees ont ete developpees et utilisees au cours de la derniere decennie dans de nombreux do-maines, allant de l'optique jusqu'a la remediation environnementale, en passant par l'electronique, les produits menagers, les cos-metiques ou encore les produits de sante (1). Sur la base de la definition des nanomateriaux proposee par l'Union europeenne (2), les NPs sont reconnues comme ayant au minimum une dimension dans la gamme 1-100 nm (3). La production de produits contenant des NPs augmente annee apres annee, et on estime que ce marche devrait atteindre les 3000 milliards de dollars US en 2020 (4). Il en decoule une inevitable dissemination des NPs dans le milieu naturel (5) et une potentielle exposition de l'homme. Le secteur agro-alimentaire est parmi les principaux vecteurs d'exposition identifies (6) : les aliments, ainsi que l'eau de boisson, peuvent con-tenir de facon volontaire ou non des NPs manufacturees et donc imp...

Les nanoparticules constituent aujourd’hui une nouvelle classe de micropolluants, dont le cycle de vie dans l’environnement doit etre defini avec precision afin d’evaluer leur impact potentiel. si de premieres etudes montrent des resultats contradictoires, elles soulignent neanmoins le caractere important des conditions environnementales. Des phenomenes varies peuvent intervenir. Par exemple, les nanoparticules d’oxyde de zinc (ZnO) sont peu stables dans les milieux aquatiques naturels comme l’eau de mer ; elles se dissolvent tres vite, et meme plus rapidement que les particules d’oxyde de zinc de taille micrometrique. Il est donc tres difficile de travailler avec des conditions representatives de l’environnement, qu’il s’agisse d’etudier la dynamique de ces nanoparticules ou leur ecotoxicite. Cela necessite de lever un verrou analytique. L’utilisation, pour la nanometrologie, d’outils innovants tels que la spectrometrie de masse Haute-Resolution (HR-ICPMS) combinee avec un marquage...

(10), Micka€ el Tharaud (11), Fr ed eric Candaudap (8), J erôme Chmeleff (8), Christophe Cloquet (1), Sophie Delpoux (10), Marie Labatut (7), R emi Losno (6), Catherine Pradoux (7), Yann Sivry (11) and Jeroen E. Sonke (8, 9) (1) Service d'Analyse des Roches et des Min eraux (SARM),

Soils and ore samples influenced by mining and metallurgical activity were collected in ultramafic soils (UM) complexes of Barro Alto and Niquelândia, in order to determine the contribution of each Ni bearing phases to the total exchangeable pool of Ni, and to point out if this pool was affected by anthropic activities. For this purpose, the IEK-model previously developed by the group (Zelano et al., submitted) was applied, on the basis of IEK experiments performed on pure typical Ni scavengers (serpentines, chlorite, smectite and iron oxydes) from ultramafic systems. For each typical scavenger, this model describes the percentage of Ni associated to exchangeable pool(s) as well as their corresponding kinetic constant(s) of exchange. The mineralogical composition of soil and ore samples and Ni solid speciation were first determined, and the IEK-model was applied on these bases. In almost all samples, an important contribution of serpentine to Ni exchangeable pool was highlighted, ranging between 10% and 45%. The important amount of organic matter (OM) in one of the studied soil samples, allowed to extrapolate generic OM E Ni and k parameters, which were introduced in the IEK-model to improve its predictive capability. Obtained results provided evidences of how even a small content (3 wt%) of organic carbon (OC), can represent an important contribution of OM to the total E Ni pool (60%). In the investigated ore samples, up to the 60% of E Ni was attribute to smectite, responsible for fast E Ni pool kinetic evolution. In addition, the model highlighted the role of the Fine Black Ash (FBA), by-products of the pyrometallurgical activity, detected into a soil sample, that is responsible for the 15% of E Ni. This approach allowed to determine, for the first time, the relative contribution of each Ni bearing phase to the total exchangeable pool, in terms of concentration and kinetics.

Depuis le debut des annees 2000, on assiste a un developpement considerable de la production et des usages industriels des nanomateriaux. Les questionnements quant aux risques pour la sante et l’environnement associes a cet essor technologique se sont developpes en parallele. A travers le programme national de recherche environnement-sante-travail (PNR EST), des projets sur la thematique « nanomateriaux et sante » sont regulierement finances, pour contribuer a faire progresser les connaissances et rapprocher la recherche des besoins en evaluation de risques. Les projets sont notamment selectionnes en fonction de leur impact potentiel, sur la clarte de la methode et en particulier les moyens mis en œuvre pour caracteriser les particules utilisees. Le present numero des Cahiers de la Recherche en presente quatorze - l’objectif est de donner un apercu des questions que se posent les chercheurs dans le domaine des nanomateriaux et des moyens mis en œuvre pour y repondre.