Caractérisation physico-chimique de tourbe utilisée en épuration d'eau usée urbaine

International audiencePeat beds are currently used for urban water treatment procedures, although reactions occuring within such beds are still unknown : filtration, ion exchange, adsorption or biodégradation by immobilized biomass. This work intends to characterize by physico-chemical parameters the evolution of peat used in water treatment. It is based upon comparison of 5 physical and 4 physico-chemical parameters on peat sampled either on 2 french treatment plants located in Queveauvillers (Somme department) and in Levis Saint Nom (Yvelynes department) or from 2 commercially available eutrophic and oligotrophic sources. Heurteauville and Floratorf, respectively.Among physical parameter tested, namely humidity and (M.O.T.) organic matter content, (R.A.) air and (R.F..) water retention values and (M.V.A.) apparent density, most significant changes were observed with organic matter content, i.e. its weight loss between 105 and 500 "C.Several physico-chemical parameter determinations have been tested, including equilibrium pH in peat suspensions, (C.E.P.) proton, (C.F.C.) alcaline and (C.E.M.) metallic cation exchange capacities. The first and most easily measured parameters, i.e. equilibrium pH within 40 g/1 peat suspensions, showed most significant variations when peat was used in treatment plants. Thus we recomend to compare organic matter content and/or equilibrium pH of peat sampled either on water treatment beds or on a reference source, i.e. « unused » peat, before deciding the renewal of such beds. Both parameters evolution may be related to inorganic deposition on beds, biodégradation of peat organic matter and/or partial dissolution of humic and fulvie acids in neutral or slightly basic pH waste waters, which all may play a prominent role in this treatment procedure.Des lits de tourbe sont couramment utilisés en assainissement urbain bien que la nature des phénomènes d'épuration soient encore inconnus : filtration, échange d'ions, adsorption ou biodégradation par biomasse immobilisée. Ce travail tente de caractériser l'évolution de la tourbe au cours de son utilisation en station à l'aide de paramètres physico-chimiques. Il repose sur la comparaison des valeurs de 5 paramètres physiques et 4 paramètres physico-chimiques d'échantillons de tourbe provenant soit de 2 stations françaises situées à Queveauvillers (Somme) et Levis Saint-Nom (Yvelynes), soit de 2 sources disponibles commercialement, à savoir une tourbe brune eutrophe d'Heurteauville et une tourbe blonde oligotrophe Floratorf. Parmi les paramètres physiques que nous avons testés, le taux d'humidité ou de matière organique (M.O.T.), de rétention d'air (R.A.) ou d'eau (R.E.) et la masse volumique apparente (M.V.A.), les variations les plus significatives ont été observées avec les taux de matière organique des échantillons de tourbe, c'est-à-dire leur perte de poids entre 105 et 500 "C. Nous avons mesuré plusieurs paramètres physico-chimiques, en particulier le pH d'équilibre, les capacités d'échange protonique (C.E.P.), canonique (C.E.C.) et métallique (C.E.M.) : la détermination du pH d'équilibre de suspensions de tourbe à 40 g/1 semble la méthode la plus simple à mettre en oeuvre et celle qui a permis de mettre en évidence les variations les plus significatives lors de l'utilisation de la tourbe en station. Nous suggérons par conséquent de comparer le taux de matière organique et/ou le pH d'équilibre d'échantillons de tourbe prélevés dans les lits et dans des lots de référence, c'est-à-dire non utilisés en station, avant de décider de renouveler ces lits. Les variations de ces deux paramètres lors de l'utilisation de la tourbe sont la conséquence de dépôts de matière minérale sur les lits, de biodégradation de la matière organique de la tourbe et/ou de la dissolution partielle des acides humiques et fulviques dans des eaux usées de pH neutre ou légèrement alcalin, phénomènes qui peuvent tous avoir un effet important sur ce procédé de traitement

BATCH METAL REMOVAL BY PEAT : KINETICS AND THERMODYNAMICS

International audiencePeat moss, a natural inexpensive material, is able to play an important rrle in treatment processes of metal-bearing industrial effluents since it adsorbs, complexes or exchanges various metal cations. This paper presents kinetics and thermodynamics of batch metal removal reactions by 50 g/l (dry wt) eutrophic or oligotrophic peat particles using Cu 2+, Cd 2÷, Zn 2÷ and Ni 2÷ concentrations ranging from 0.01 to 100 mM. Metal cation removal reactions are moderately rapid in l0 mM metal unbuffered solutions: the forward kinetic constant ranges between 0.005 and 0.17 M-1 s-1, and equilibrium is reached within about 1 h. Under these conditions of pH (2.2-4.2) and concentrations, apparent binding equilibrium constants were found to range between 2 and 3150 M-1 depending upon the peat origin and the metal cation. In 0-6.5 pH-buffered metal cation solutions, the four cations binding reactions behaved differently demonstrating that metal binding equilibrium constant decrease in the order Ni 2+ > Cu 2+ > Cd 2+ = Zn 2÷. When pH is higher than 6.7, more than 90% of a 10 mM metal cation solution is removed by 50 g/l peat particles and metal binding capacities equal 200 mmol kg-1 dry wt, whatever the metal nature and the peat origin. Except for nickel cation which is very strongly bound to peat, all metal cations are completely released when pH is fixed below 1.5

Spectroscopic binaries as observed by the future Gaia space mission

peer reviewedThe future Gaia satellite will observe a large number of stars through its three main channels: astrometric, photometric and, for the brightest stars, spectroscopic. The satellite is equipped with the RVS spectrograph, which will provide medium-resolution spectra over a small wavelength range. These spectra should allow us to identify stars exhibiting a composite spectrum, either because of a chance alignment or a true binarity. We discuss the various aspects related to the data treatment of the binary candidates and describe the algorithms that are intended to be included in the processing pipeline

Face processing limitation to own species in primates: a comparative study in brown capuchins, Tonkean macaques and humans

Most primates live in social groups which survival and stability depend on individuals' abilities to create strong social relationships with other group members. The existence of those groups requires to identify individuals and to assign to each of them a social status. Individual recognition can be achieved through vocalizations but also through faces. In humans, an efficient system for the processing of own species faces exists. This specialization is achieved through experience with faces of conspecifics during development and leads to the loss of ability to process faces from other primate species. We hypothesize that a similar mechanism exists in social primates. We investigated face processing in one Old World species (genus Macaca) and in one New World species (genus Cebus). Our results show the same advantage for own species face recognition for all tested subjects. This work suggests in all species tested the existence of a common trait inherited from the primate ancestor: an efficient system to identify individual faces of own species only

A 2.3-Day Periodic Variability in the Apparently Single Wolf-Rayet Star WR 134: Collapsed Companion or Rotational Modulation?

We present the results of an intensive campaign of spectroscopic and photometric monitoring of the peculiar Wolf-Rayet star WR 134 from 1989 to 1997. This unprecedentedly large data set allows us to confirm unambiguously the existence of a coherent 2.25 +/- 0.05 day periodicity in the line-profile changes of He II 4686, although the global pattern of variability is different from one epoch to another. This period is only marginally detected in the photometric data set. Assuming the 2.25 day periodic variability to be induced by orbital motion of a collapsed companion, we develop a simple model aiming at investigating (i) the effect of this strongly ionizing, accreting companion on the Wolf-Rayet wind structure, and (ii) the expected emergent X-ray luminosity. We argue that the predicted and observed X-ray fluxes can only be matched if the accretion on the collapsed star is significantly inhibited. Additionally, we performed simulations of line-profile variations caused by the orbital revolution of a localized, strongly ionized wind cavity surrounding the X-ray source. A reasonable fit is achieved between the observed and modeled phase-dependent line profiles of He II 4686. However, the derived size of the photoionized zone substantially exceeds our expectations, given the observed low-level X-ray flux. Alternatively, we explore rotational modulation of a persistent, largely anisotropic outflow as the origin of the observed cyclical variability. Although qualitative, this hypothesis leads to greater consistency with the observations.Comment: 34 pages, 16 figures. Accepted by the Astrophysical Journa

Evolution of Surface Hydrology in the Sahelo-Sudanian Strip: An Updated Review

In the West African Sahel, two paradoxical hydrological behaviors have occurred during the last five decades. The first paradox was observed during the 1968–1990s ‘Great Drought’ period, during which runoff significantly increased. The second paradox appeared during the subsequent period of rainfall recovery (i.e., since the 1990s), during which the runoff coefficient continued to increase despite the general re-greening of the Sahel. This paper reviews and synthesizes the literature on the drivers of these paradoxical behaviors, focusing on recent works in the West African Sahelo/Sudanian strip, and upscaling the hydrological processes through an analysis of recent data from two representative areas of this region. This paper helps better determine the respective roles played by Land Use/Land Cover Changes (LULCC), the evolution of rainfall intensity and the occurrence of extreme rainfall events in these hydrological paradoxes. Both the literature review and recent data converge in indicating that the first Sahelian hydrological paradox was mostly driven by LULCC, while the second paradox has been caused by both LULCC and climate evolution, mainly the recent increase in rainfall intensity

Temporal trends of population viral suppression in the context of Universal Test and Treat: the ANRS 12249 TasP trial in rural South Africa

Introduction: The universal test-and-treat (UTT) strategy aims to maximize population viral suppression (PVS), that is, the proportion of all people living with HIV (PLHIV) on antiretroviral treatment (ART) and virally suppressed, with the goal of reducing HIV transmission at the population level. This article explores the extent to which temporal changes in PVS explain the observed lack of association between universal treatment and cumulative HIV incidence seen in the ANRS 12249 TasP trial conducted in rural South Africa. Methods: The TasP cluster-randomized trial (2012 to 2016) implemented six-monthly repeat home-based HIV counselling and testing (RHBCT) and referral of PLHIV to local HIV clinics in 2 9 11 clusters opened sequentially. ART was initiated according to national guidelines in control clusters and regardless of CD4 count in intervention clusters. We measured residency status, HIV status, and HIV care status for each participant on a daily basis. PVS was computed per cluster among all resident PLHIV (≥16, including those not in care) at cluster opening and daily thereafter. We used a mixed linear model to explore time patterns in PVS, adjusting for sociodemographic changes at the cluster level. Results: 8563 PLHIV were followed. During the course of the trial, PVS increased significantly in both arms (23.5% to 46.2% in intervention, +22.8, p < 0.001; 26.0% to 44.6% in control, +18.6, p < 0.001). That increase was similar in both arms (p = 0.514). In the final adjusted model, PVS increase was most associated with increased RHBCT and the implementation of local trial clinics (measured by time since cluster opening). Contextual changes (measured by calendar time) also contributed slightly. The effect of universal ART (trial arm) was positive but limited. Conclusions: PVS was improved significantly but similarly in both trial arms, explaining partly the null effect observed in terms of cumulative HIV incidence between arms. The PVS gains due to changes in ART-initiation guidelines alone are relatively small compared to gains obtained by strategies to maximize testing and linkage to care. The achievement of the 90-90-90 targets will not be met if the operational and implementational challenges limiting access to care and treatment, often context-specific, are not properly addressed. Clinical trial number: NCT01509508 (clinicalTrials.gov)/DOH-27-0512-3974 (South African National Clinical Trials Register)

EuReCa ONE—27 Nations, ONE Europe, ONE Registry A prospective one month analysis of out-of-hospital cardiac arrest outcomes in 27 countries in Europe

AbstractIntroductionThe aim of the EuReCa ONE study was to determine the incidence, process, and outcome for out of hospital cardiac arrest (OHCA) throughout Europe.MethodsThis was an international, prospective, multi-centre one-month study. Patients who suffered an OHCA during October 2014 who were attended and/or treated by an Emergency Medical Service (EMS) were eligible for inclusion in the study. Data were extracted from national, regional or local registries.ResultsData on 10,682 confirmed OHCAs from 248 regions in 27 countries, covering an estimated population of 174 million. In 7146 (66%) cases, CPR was started by a bystander or by the EMS. The incidence of CPR attempts ranged from 19.0 to 104.0 per 100,000 population per year. 1735 had ROSC on arrival at hospital (25.2%), Overall, 662/6414 (10.3%) in all cases with CPR attempted survived for at least 30 days or to hospital discharge.ConclusionThe results of EuReCa ONE highlight that OHCA is still a major public health problem accounting for a substantial number of deaths in Europe.EuReCa ONE very clearly demonstrates marked differences in the processes for data collection and reported outcomes following OHCA all over Europe. Using these data and analyses, different countries, regions, systems, and concepts can benchmark themselves and may learn from each other to further improve survival following one of our major health care events