Caractérisation des sédiments des retenues pour la prévision des risques écotoxicologiques liés aux vidanges

L'acumulation de sédiments dans les retenues de barrages hydro-électriques nécessite de procéder à des opérations régulières de désenvasement indispensables à leur bon fonctionnement.Ces opérations de vidange ont le plus souvent un effet destructeur sur la faune et la flore aquatique.Cet effet destructeur est principalement lié à une diminution de la concentration en oxygène dissous et une augmentation de la teneur en matières en suspension.La méthodologie présentée a pour but d'estimer préalablement à toute vidange les risques écotoxicologlques correspondant à une telle opération. Elle implique d'une part la description et l'analyse physico-chimique des sédiments en place, d'autre part la mesure en laboratoire de la consommation en oxygène dissous des matériaux remis en suspension au cours du temps.La fiabilité d'une telle procédure a été montrée en particulier à l'occasion de vidanges de retenues situées sur le cours de l'Isère.Le protocole est décrit précisément de façon à pouvoir guider les exploitants de retenues à l'occasion des opérations de vidange qu'ils dirigent.Sediment silting up in hydroelectric dams Implies regular draining operations in order to prevent disfunction of the dams.These operations often lead to drastic lethal affects on aquatic fauna and flora.A toxicological study has clearly shown two main factors responsible for acute toxicological effects : dissolved oxygen deficit and suspended solids increase.These effects have been quantified by experimental tests on Brown trout fry (Salmo trutta fario) the results of which are summarized.The second step consisted in the prediction of water quality evolution downstream during dam draining operation, regarding both factors suspected, in order to assess ecotoxicological hazard.The proposed methodology based on a sedimentological study made in Grangent dam, located on river Loire and immediately downstream of St. Etienne urban area, and in St. Hilaire dam situated on the river Isère downstream partIt consists in sampling cored sediments and in measuring dissolved oxygen kinetic by mixing sediments with water In a reactor.The sample conservation as carried out in jar glasses kept at 4 °C.Results are reproducible as long as residual dissolved oxygen concentration is higher than 3 mg/l. If this condition is respected, oxygen consumption is strictly dependent on suspended sediment concentration.An increase in test water temperature makes the oxygen consumption rise.In accordance with these results, recommendations for dissolved oxygen measures are about 5 g/l suspended sediment concentration, with an experimental temperature reaching the temperature observed during dam draining.The variability of the results for different samples depends on the dam studied. Surface tore samples collected in St. Hilaire dam consume dissolved oxygen faster than the same bottom tore samples.However, in Grangent dam, only one surface core sample collected near the dam construction has clearly shown reducing properties. The difference between two dam sediments is very important : Grangent dam sediment have, on average, dissolved oxygen consumption three more times higher than St. Hilaire in the same duration.Taking into account dissolved oxygen kinetics by mixed sediments, and a simple aeration model using water and sediment deposits from downstream dam, may expert both suspended sediment and oxygen consumption evolution.Hazardous mortality of trout fario fry in downstream dam are quickly graphically visualized.Dam draining operator may so assess, for different suspended sediment land the harmful exposition to fish at any distance from it.This knowledge allows him to plan more strictly floodgate working : pointly dissolved oxygen continuous measurement on downstream dam is sufficient to give a mark related to model hazard assessment.The model reliability has been demonstrated by the examination of data collected during St. Hilaire dam draining operation

Towards a 3-D tomographic retrieval for the air-borne limb-imager GLORIA

GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) is a new remote sensing instrument essentially combining a Fourier transform infrared spectrometer with a two-dimensional (2-D) detector array in combination with a highly flexible gimbal mount. It will be housed in the belly pod of the German research aircraft HALO (High Altitude and Long Range Research Aircraft). It is unique in its combination of high spatial and state-of-the art spectral resolution. Furthermore, the horizontal view angle with respect to the aircraft flight direction can be varied from 45° to 135°. This allows for tomographic measurements of mesoscale events for a wide variety of atmospheric constituents. <br><br> In this paper, a tomographic retrieval scheme is presented, which is able to fully exploit the manifold radiance observations of the GLORIA limb sounder. The algorithm is optimized for massive 3-D retrievals of several hundred thousands of measurements and atmospheric constituents on common hardware. The new scheme is used to explore the capabilities of GLORIA to sound the atmosphere in full 3-D with respect to the choice of the flightpath and to different measurement modes of the instrument using ozone as a test species. It is demonstrated that the achievable resolution should approach 200 m vertically and 20 km–30 km horizontally. Finally, a comparison of the 3-D inversion with conventional 1-D inversions using the assumption of a horizontally homogeneous atmosphere is performed

Modeling SOA formation from the oxidation of intermediate volatility <i>n</i>-alkanes

The chemical mechanism leading to SOA formation and ageing is expected to be a multigenerational process, i.e. a successive formation of organic compounds with higher oxidation degree and lower vapor pressure. This process is here investigated with the explicit oxidation model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere). Gas phase oxidation schemes are generated for the C₈–C₂₄ series of <i>n</i>-alkanes. Simulations are conducted to explore the time evolution of organic compounds and the behavior of secondary organic aerosol (SOA) formation for various preexisting organic aerosol concentration (<i>C</i>_OA). As expected, simulation results show that (i) SOA yield increases with the carbon chain length of the parent hydrocarbon, (ii) SOA yield decreases with decreasing <i>C</i>_OA, (iii) SOA production rates increase with increasing <i>C</i>_OA and (iv) the number of oxidation steps (i.e. generations) needed to describe SOA formation and evolution grows when <i>C</i>_OA decreases. The simulated oxidative trajectories are examined in a two dimensional space defined by the mean carbon oxidation state and the volatility. Most SOA contributors are not oxidized enough to be categorized as highly oxygenated organic aerosols (OOA) but reduced enough to be categorized as hydrocarbon like organic aerosols (HOA), suggesting that OOA may underestimate SOA. Results show that the model is unable to produce highly oxygenated aerosols (OOA) with large yields. The limitations of the model are discussed

Explicit modelling of SOA formation from α-pinene photooxidation: sensitivity to vapour pressure estimation

The sensitivity of the formation of secondary organic aerosol (SOA) to the estimated vapour pressures of the condensable oxidation products is explored. A highly detailed reaction scheme was generated for α-pinene photooxidation using the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A). Vapour pressures (P^(vap)) were estimated with three commonly used structure activity relationships. The values of P^(vap) were compared for the set of secondary species generated by GECKO-A to describe α-pinene oxidation. Discrepancies in the predicted vapour pressures were found to increase with the number of functional groups borne by the species. For semi-volatile organic compounds (i.e. organic species of interest for SOA formation), differences in the predicted Pvap range between a factor of 5 to 200 on average. The simulated SOA concentrations were compared to SOA observations in the Caltech chamber during three experiments performed under a range of NO_x conditions. While the model captures the qualitative features of SOA formation for the chamber experiments, SOA concentrations are systematically overestimated. For the conditions simulated, the modelled SOA speciation appears to be rather insensitive to the P^vap estimation method

The Chlamydomonas genome project: A decade on

The green alga Chlamydomonas reinhardtii is a popular unicellular organism for studying photosynthesis, cilia biogenesis, and micronutrient homeostasis. Ten years since its genome project was initiated an iterative process of improvements to the genome and gene predictions has propelled this organism to the forefront of the omics era. Housed at Phytozome, the plant genomics portal of the Joint Genome Institute (JGI), the most up-to-date genomic data include a genome arranged on chromosomes and high-quality gene models with alternative splice forms supported by an abundance of whole transcriptome sequencing (RNA-Seq) data. We present here the past, present, and future of Chlamydomonas genomics. Specifically, we detail progress on genome assembly and gene model refinement, discuss resources for gene annotations, functional predictions, and locus ID mapping between versions and, importantly, outline a standardized framework for naming genes

Trends and Emerging Areas of Agile Research: the Report on XP2014 PhD Symposium

The PhD symposium of XP2014, the 15th International Conference on Agile Software Development, was organized as a half-day event prior to the main conference program. Seven PhD candidates came from different research institutes across the globe to present their own research proposals at the symposium. The symposium was run in a lively and interactive manner. The candidates received constructive feedback on their proposals from all the symposium participants. In this report we describe the presented proposals, focusing on the content and feedback. Through them we can take a peek at the trends and emerging areas of agile research in the coming years

Validation of first chemistry mode retrieval results from the new limb-imaging FTS GLORIA with correlative MIPAS-STR observations

We report first chemistry mode retrieval results from the new airborne limb-imaging infrared FTS (Fourier transform spectrometer) GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) and comparisons with observations by the conventional airborne limb-scanning infrared FTS MIPAS-STR (Michelson Interferometer for Passive Atmospheric Sounding – STRatospheric aircraft). For GLORIA, the flights aboard the high-altitude research aircraft M55 Geophysica during the ESSenCe campaign (ESa Sounder Campaign 2011) were the very first in field deployment after several years of development. The simultaneous observations of GLORIA and MIPAS-STR during the flight on 16 December 2011 inside the polar vortex and under conditions of optically partially transparent polar stratospheric clouds (PSCs) provided us the first opportunity to compare the observations by two different infrared FTS generations directly. We validate the GLORIA results with MIPAS-STR based on the lower vertical resolution of MIPAS-STR and compare the vertical resolutions of the instruments derived from their averaging kernels. The retrieval results of temperature, HNO3, O3, H2O, CFC-11 and CFC-12 show reasonable agreement of GLORIA with MIPAS-STR and collocated in situ observations. For the horizontally binned hyperspectral limb images, the GLORIA sampling outnumbered the horizontal cross-track sampling of MIPAS-STR by up to 1 order of magnitude. Depending on the target parameter, typical vertical resolutions of 0.5 to 2.0 km were obtained for GLORIA and are typically a factor of 2 to 4 better compared to MIPAS-STR. While the improvement of the performance, characterization and data processing of GLORIA are the subject of ongoing work, the presented first results already demonstrate the considerable gain in sampling and vertical resolution achieved with GLORIA

The \u3cem\u3eChlamydomonas\u3c/em\u3e Genome Reveals the Evolution of Key Animal and Plant Functions

Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella

Geological Field Trips

This field trip guide organized in the framework of the Goldschmidt Conference 2013, held in Florence from August 25 to 30, 2013, is here presented. The two-days field trip, shows some of the many geological, naturalistic and cultural features in the Fiorano area (Modena), in which history, geology and passion for Ferrari come together in a perfect marriage. The first excursion day is dedicated to visit the Natural Reserve of Salse di Nirano, where the mud volcanoes, produced by the cold mud, salt water and hydrocarbons - mainly methane- can be observed. The second day is devoted to visit the Ferrari Museum and goes on at the Spezzano Castle, hosting the Ceramics Museum. Clays are, in fact, abundant in the hilly margin, where they form badlands, characteristic narrow crests washed out by running waters. In the Castle there is also a Balsamic Vinegar producing Consortium, it’s a peculiar and typical product of Modena province. The itinerary ends with the tour to Enzo Ferrari’s Birthplace at Modena