Performance des lieux d'enfouissement sanitaire de Laterrière et de Ste-Sophie, Québec, Canada

Ce travail décrit les caractéristiques hydrogéologiques et chimiques de deux lieux d'enfouissement de déchets municipaux localisés au Québec. Le site de Laterrière est en opération depuis 1971 dans une ancienne sablière. Sous les dépôts meubles, la topographie du sotte rocheux est marquée par une vallée qui forme une limite imperméable à l'aquifère de sable et impose un écoulement convergent de l'eau souterraine vers la rivière Chicoutimi. Le site de Ste-Sophie, en opération depuis 1976, repose sur une couche de 3,5 mètres de sables fins saturés recouvrant un lit d'argile marine. La surélévation de la nappe dans les déchets favorise un écoulement divergent vers le périmètre de la zone d'enfouissement.Un réseau de piézomètres installé en bordure des deux sites a permis pendant trente mois de prélever des échantillons d'eau et de les analyser. Dans chaque panache de contamination, l'alcalinité, les ions majeurs Na+, K+, Ca2+, Mg2+, Cl¯, le fer, le manganèse, l'azote total et ammoniacal, les DCO et DBO5 montrent des concentrations généralement supérieures à celles de L'eau naturelle ambiante. A proximité des deux Lieux d'enfouissement, les teneurs en cadmium, chrome, nickel et plomb excèdent les normes québécoises de potabiLité de l'eau. Dans chaque cas, ta distribution des contaminants est surtout régie par le réseau d'écoulement. La dispersion hydrodynamique et les réactions géochimiques dans le sous-sol sont des processus importants d'atténuation des contaminants.This paper describes the hydrogeological and geochemical features of two sanitary landfill sites located in the Province of Quebec : Laterriere and Ste-Sophie. The main objective is to evaluate the leachate attenuation performance of each site. For this project, the Quebec Ministry of the Environment chose two sites with contrasting hydrogeological settings.The Laterriere landfill, in operation since 1971, covers an area of about 32 ha. The refuse is deposited in an old sandpit and the landfill boundary is located 400 meters away from the Chicoutimi River, 25 meters above the stream water level. The bedrock topography shows a valley under the landfill which acts an an impervious base for the sand aquifer and induces a convergent groundwater flow towards the river.The Ste-Sophie landfill covers an area of 48 ha and began operating in 1976. The refuse zone is located on flat ground 350 meters away from the Ruisseau-aux-Castors. The refuse is deposited on a 3.5 meter layer of fine sands nearly saturated overlying a marine clay bed. A water table mound is observed beneath the landfill, resulting in diverging low lines outward from the center of the Landfill.For each site, the occurence and migration of contaminants was investigated using networks of piezometers. Sampling was performed monthly over a period of thirty months and thirty parameters were analyzed on each sample. The analytical results were entered in a database and treated by statistical methods.The shape of each contamination plume is controlled mainly by the groundwater flow system. At Laterriere, the plume is restricted to a narrow path between the landfill and the river and inside a bedrock valley. This flow net has been simulated by a two-dimensional finite elements model. At Ste-Sophie, the divergence of flow lines due to groundwater mounding beneath the site causes dispersion of contaminants around the landfill. The use of an analytical solution shows that longitudinal dispersivity is a major process of contaminant migration.For the two landfills, the highest concentrations of contaminants occur directly beneath or close to the boundaries of the landfills. Total alkalinity, Na+, K+, Ca2+, Mg2+, Cl¯, iron, manganèse, total and ammoniacal nitrogen, chemical and biological oxygen demand (COD and BOD) are much above background levels throughout the plume. Sulfate is also a major contaminant at Ste-Sophie with concentration of 1100/mg/l. The concentrations of cadmium, chrome, nickel and lead exceed the drinking water standards near the two landfill sites but they decline rapidly in the direction of flow. At Laterriere, the decline in chloride concentration measured at the discharge point S-23 is about 85 % while the decline of reactive contaminants, such as iron and COD, is respectively 98 and 99.7 %.Finally, we discuss hydrogeological criteria for landfill site selection in Quebec

Developing a Framework for Evaluating the Patient Engagement, Quality, and Safety of Mobile Applications

Rising ownership of smartphones and tablets across social and demographic groups has made mobile applications, or apps, a potentially promising tool for engaging patients in their health care, particularly those with high health care needs. Through a systematic search of iOS (Apple) and Android app stores and an analysis of apps targeting individuals with chronic illnesses, we assessed the degree to which apps are likely to be useful in patient engagement efforts. Usefulness was determined based on the following criteria: description of engagement, relevance to the targeted patient population, consumer ratings and reviews, and most recent app update. Among the 1,046 health care–related, patient-facing applications identified by our search, 43 percent of iOS apps and 27 percent of Android apps appeared likely to be useful. We also developed criteria for evaluating the patient engagement, quality, and safety of mobile apps

Emergent Potts Order in a Coupled Hexatic-Nematic XY model

Addressing the nature of an unexpected smectic-A' phase in liquid crystal 54COOBC films, we perform large scale Monte Carlo simulations of a coupled hexatic-nematic XY model. The resulting finite-temperature phase diagram reveals a small region with composite Potts $\mathbb{Z}_3$ order above the vortex binding transition; this phase is characterized by relative hexatic-nematic ordering though both variables are disordered. The system develops algebraic hexatic and nematic order only at a lower temperature. This multi-step melting scenario agrees well with the experimental observations of a sharp specific heat anomaly that emerges above the onset of hexatic positional order. We therefore propose that the smectic-A' phase is characterized by composite Potts order and bound-states of fractional vortices.Comment: 22 pages, 10 figures, 1 tabl

Milieu

Le concept de Milieu présente la particularité d'être présent de façon implicite dans de nombreux textes scientifiques sans faire l'objet d'une définition précise. Lorsqu'il est employé, on constate une large variabilité de significations, que l'on peut souvent rattacher aux stades successifs de son élaboration historique. De même, en situation didactique, l'emploi du mot milieu est beaucoup plus fréquent que les séances de classe où sa construction comme concept est travaillée précisément. Les AA. essaient, après une analyse de contenu de cette notion, de caractériser les obstacles auxquels sa construction se heurte et les étapes possibles de son appropriation. Ils étudient en fonction de cette grille de lecture quelques exemples de séances de classe, et proposent de situer les étapes de construction mises en oeuvr

Influence of the substrate-induced strain and irradiation disorder on the Peierls transition in TTF-TCNQ microdomains

The influence of the combined effects of substrate-induced strain, finite size and electron irradiation-induced defects have been studied on individual micron-sized domains of the organic charge transfer compound tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) by temperature-dependent conductivity and current-voltage measurements. The individual domains have been isolated by focused ion beam etching and electrically contacted by focused ion and electron beam induced deposition of metallic contacts. The temperature-dependent conductivity follows a variable range hopping behavior which shows a crossover of the exponent as the Peierls transition is approached. The low temperature behavior is analyzed within the segmented rod model of Fogler, Teber and Shklowskii, as originally developed for a charge-ordered quasi one-dimensional electron crystal. The results are compared with data obtained on as-grown and electron irradiated epitaxial TTF-TCNQ thin films of the two-domain type

Validation of the Aura Microwave Limb Sounder HNOmeasurements

We assess the quality of the version 2.2 (v2.2) HNO3 measurements from the Microwave Limb Sounder (MLS) on the Earth Observing System Aura satellite. The MLS HNO3 product has been greatly improved over that in the previous version (v1.5), with smoother profiles, much more realistic behavior at the lowest retrieval levels, and correction of a high bias caused by an error in one of the spectroscopy files used in v1.5 processing. The v2.2 HNO3 data are scientifically useful over the range 215 to 3.2 hPa, with single-profile precision of ∼0.7 ppbv throughout. Vertical resolution is 3–4 km in the upper troposphere and lower stratosphere, degrading to ∼5 km in the middle and upper stratosphere. The impact of various sources of systematic uncertainty has been quantified through a comprehensive set of retrieval simulations. In aggregate, systematic uncertainties are estimated to induce in the v2.2 HNO3 measurements biases that vary with altitude between ±0.5 and ±2 ppbv and multiplicative errors of ±5–15% throughout the stratosphere, rising to ∼±30% at 215 hPa. Consistent with this uncertainty analysis, comparisons with correlative data sets show that relative to HNO3 measurements from ground-based, balloon-borne, and satellite instruments operating in both the infrared and microwave regions of the spectrum, MLS v2.2 HNO3 mixing ratios are uniformly low by 10–30% throughout most of the stratosphere. Comparisons with in situ measurements made from the DC-8 and WB-57 aircraft in the upper troposphere and lowermost stratosphere indicate that the MLS HNO3 values are low in this region as well, but are useful for scientific studies (with appropriate averaging)