Mass balance of zinc redistribution during the pedogenesis of a soil developed on a natural geochemical anomaly

Pedogenetic processes that redistribute soil elements over time have been considerably investigated and clearly identified. Nevertheless, the quantification of their respective influences on element redistribution is still poorly known, while soil protection requires extensive knowledge of their long-time depending evolution. The quantitative redistribution of elements is of prime importance in polluted soils, since the long-term environmental hazards depend on their potential mobility and biodisponibility, thus speciation. Among the elements frequently encountered in polluted soils and exhibiting a well-established phytotoxic nature, zinc is of great concern. Nevertheless, pollutions are too recent to observe or even predict the long-term behavior of zinc in polluted soils. An alternative approach is to study paleosoil developed on natural geochemical anomalies. Indeed, such paleosoils display zinc concentrations equivalent to those of polluted soils with the advantage to involve long pedological time of contact between the elements and the different soil phases. Our study aims at quantifying the long-term redistribution of zinc during the pedogenesis of a soil developed upon a natural geochemical anomaly. We first determined zinc speciation both in the parental material and in the solum, then quantified redistribution by mass balance calculations. This approach permits to estimate Zn outputs or inputs in the solum and to quantify its redistribution along the profile and among the different mineral phases

Zinc Redistribution in a Soil Developed from Limestone During Pedogenesis

International audienceThe long-term redistribution of Zn in a naturally Zn-enriched soil during pedogenesis was quantified based on mass balance calculations. According to their fate, parent limestones comprised three Zn pools: bound to calcite and pyritesphalerite grains, bound to phyllosilicates and bound to goethite in the inherited phosphate nodules. Four pedological processes, i.e., carbonate dissolution, two stages of redox processes and eluviation, redistributed Zn during pedogenesis. The carbonate dissolution of limestones released Zn bound to calcite into soil solution. Due to residual enrichment, Zn concentrations in the soil are higher than those in parent limestones. Birnessite, ferrihydrite and goethite dispersed in soil horizon trapped high quantities of Zn during their formation. Afterwards, primary redox conditions induced the release of Zn and Fe into soil solution, and the subsequent individualization of Fe and Mn into Zn-rich concretions. Both processes and subsequent aging of the concretions formed induced significant exportation of Zn through the bottom water table. Secondary redox conditions promoted the weathering of Fe and Mn oxides in cements and concretions. This process caused other losses of Zn through lateral exportation in an upper water table. Concomitantly, eluviation occurred at the top of the solum. The lateral exportation of eluviated minerals through the upper water table limited illuviation. Eluviation was also responsible for Zn loss, but this Zn bound to phyllosilicates was not bioavailabl

LES NANOPARTICULES: QUELS RISQUES EN SEINE ?

32 pInternational audienceL'obtention de nanoparticules (NPs) manufacturées et les propriétés physico-chimiques spécifiques qu'elles présentent autorisent aujourd'hui des applications de plus en plus nombreuses et innovantes. La quantité de nanoparticules manufacturées mises sur le marché est en constante augmentation et elles sont aujourd'hui présentes dans de nombreux produits de consommation courante. Cela alimente un débat croissant sur les coûts environnementaux et sociétaux qui pourraient dépasser les bénéfices escomptés par l'utilisation des nanotechnologies en général et des nanomatériaux ou nanoparticules (i.e. taille < 100 nm) en particulier. Elles sont devenues un enjeu majeur de santé publique du point de vue de la toxicité potentielle qu'elles pourraient engendrer dans les écosystèmes. Les nanoparticules peuvent en effet présenter un risque écotoxicologique (dispersion et dégradation dans l'environnement) et un risque en termes de santé humaine (exposition au poste de travail par exemple). Il est donc nécessaire d'évaluer la persistance, le devenir et l'impact de ces nouveaux polluants sur les écosystèmes et sur la qualité des ressources naturelles (eaux, cultures, etc...). Dans ce contexte, l'objectif de cette étude était de mieux cerner l'état physique et chimique des NPs dans des concentrations représentatives des niveaux de toxicité observés et dans des conditions proches de celles des milieux naturels. Elle s'est focalisée sur l'eau de Seine, représentative des eaux naturelles de surface qui sont un des vecteurs principaux de la dispersion de ces NPs manufacturées. Les NPs étudiées ici sont produites en grande quantité et largement utilisées dans différents domaines industriels : il s'agit de NPs d'oxydes de zinc (ZnO) et de dioxyde de titane (TiO2). L'analyse des NPs de ZnO par XPS a mis en évidence l'existence d'un cœur de ZnO et d'un coquille de Zn(OH)2 en surface. Parallèlement, des NPs enrobées ont été étudiées et caractérisées, afin de mettre en évidence le rôle de l'enrobage organique sur la solubilité des NPs. Les expériences de mesures de solubilité des nanoparticules manufacturées en milieu naturel ont été réalisées par utilisation combinée des techniques de DMT et d'UF, associée à des calculs thermodynamiques. Il s'avère que la forme nanoparticulaire du TiO2 n'est pas davantage soluble que ses homologues microparticulaire ou macroparticulaire. A l'inverse, une fraction non négligeable des nanoparticules d'oxydes de zinc est rapidement dissoute dans l'eau de Seine. Puis les NPs sont "piégées" dans des phases secondaires carbonatées, ce qui peut signifier leur isolement par rapport au milieu et donc l'arrêt des réactions impliquant les NPs, soit une forme de passivation des nanoparticules. Le comportement des NPs dans le milieu est donc en grande partie contrôlé par la couche directement à leur surface (Gélabert et al., 2014; Sivry et al., 2014) : la couche d'hydroxydes de zinc contrôle le Ks apparent, l'enrobage organique augmente la vitesse et le taux de dissolution des NPs et, enfin, la formation d'une gangue carbonatée emprisonne les NPs et provoque potentiellement leur passivation

On the electromagnetic energy resolution of Cherenkov-fiber calorimeters

Electromagnetic calorimeters which sample the Cherenkov radiation of shower particles in optical fibers operate in a markedly different manner from calorimeters which rely on the dE/dx of shower particles. The well-understood physics of electromagnetic shower development is applied to the case of Cherenkov-fiber calorimetry (also known as quartz fiber calorimetry) and the results of systematically performed studies are considered in detail to derive an understanding of the critical parameters involved in energy measurement using such calorimeters. A quantitative parameterization of Cherenkov-fiber calorimetry electromagnetic energy resolution is proposed and compared with existing experimental results

Quartz fiber calorimetry

The fundamentals of a new electromagnetic and hadronic sampling calorimetry based on the detection of Cherenkov light generated in quartz optical fibers are presented. Optical fibers transport light only in a selected angular range which results in a non-obvious and absolutely unique characteristic for this new technique: showers of very narrow visible energy. In addition, the technique is characterized by radiation resistance measured in Gigarads and nanosecond signal duration. Combined, these properties make quartz fiber calorimetry a very promising technique for high intensity heavy ion experiments and for the high pseudorapidity regions of high intensity collider experiments. The results of beam tests and simulations are used to illustrate the basic properties and peculiar characteristics of this recent development

Search for charginos in e+e- interactions at sqrt(s) = 189 GeV

An update of the searches for charginos and gravitinos is presented, based on a data sample corresponding to the 158 pb^{-1} recorded by the DELPHI detector in 1998, at a centre-of-mass energy of 189 GeV. No evidence for a signal was found. The lower mass limits are 4-5 GeV/c^2 higher than those obtained at a centre-of-mass energy of 183 GeV. The (\mu,M_2) MSSM domain excluded by combining the chargino searches with neutralino searches at the Z resonance implies a limit on the mass of the lightest neutralino which, for a heavy sneutrino, is constrained to be above 31.0 GeV/c^2 for tan(beta) \geq 1.Comment: 22 pages, 8 figure

Search for composite and exotic fermions at LEP 2

A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172 GeV and 161 GeV. The search for pair-produced new leptons establishes 95% confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermio

Hadronization properties of b quarks compared to light quarks in e+e- -> q qbar from 183 to 200 GeV

The DELPHI detector at LEP has collected 54 pb^{-1} of data at a centre-of-mass energy around 183 GeV during 1997, 158 pb^{-1} around 189 GeV during 1998, and 187 pb^{-1} between 192 and 200 GeV during 1999. These data were used to measure the average charged particle multiplicity in e+e- -> b bbar events, _{bb}, and the difference delta_{bl} between _{bb} and the multiplicity, _{ll}, in generic light quark (u,d,s) events: delta_{bl}(183 GeV) = 4.55 +/- 1.31 (stat) +/- 0.73 (syst) delta_{bl}(189 GeV) = 4.43 +/- 0.85 (stat) +/- 0.61 (syst) delta_{bl}(200 GeV) = 3.39 +/- 0.89 (stat) +/- 1.01 (syst). This result is consistent with QCD predictions, while it is inconsistent with calculations assuming that the multiplicity accompanying the decay of a heavy quark is independent of the mass of the quark itself.Comment: 13 pages, 2 figure

Search for supersymmetric particles in scenarios with a gravitino LSP and stau NLSP

Sleptons, neutralinos and charginos were searched for in the context of scenarios where the lightest supersymmetric particle is the gravitino. It was assumed that the stau is the next-to-lightest supersymmetric particle. Data collected with the DELPHI detector at a centre-of-mass energy near 189 GeV were analysed combining the methods developed in previous searches at lower energies. No evidence for the production of these supersymmetric particles was found. Hence, limits were derived at 95% confidence level.Comment: 31 pages, 14 figure

Search for lightest neutralino and stau pair production in light gravitino scenarios with stau NLSP

Promptly decaying lightest neutralinos and long-lived staus are searched for in the context of light gravitino scenarios. It is assumed that the stau is the next to lightest supersymmetric particle (NLSP) and that the lightest neutralino is the next to NLSP (NNLSP). Data collected with the Delphi detector at centre-of-mass energies from 161 to 183 \GeV are analysed. No evidence of the production of these particles is found. Hence, lower mass limits for both kinds of particles are set at 95% C.L.. The mass of gaugino-like neutralinos is found to be greater than 71.5 GeV/c^2. In the search for long-lived stau, masses less than 70.0 to 77.5 \GeVcc are excluded for gravitino masses from 10 to 150 \eVcc . Combining this search with the searches for stable heavy leptons and Minimal Supersymmetric Standard Model staus a lower limit of 68.5 \GeVcc may be set for the stau mas