Evidence of non-Darcy flow and non-Fickian transport in fractured media at laboratory scale

Abstract. During a risk assessment procedure as well as when dealing with cleanup and monitoring strategies, accurate predictions of solute propagation in fractured rocks are of particular importance when assessing exposure pathways through which contaminants reach receptors. Experimental data obtained under controlled conditions such as in a laboratory allow to increase the understanding of the fundamental physics of fluid flow and solute transport in fractures. In this study, laboratory hydraulic and tracer tests have been carried out on an artificially created fractured rock sample. The tests regard the analysis of the hydraulic loss and the measurement of breakthrough curves for saline tracer pulse inside a rock sample of parallelepiped shape (0.60 × 0.40 × 0.08 m). The convolution theory has been applied in order to remove the effect of the acquisition apparatus on tracer experiments. The experimental results have shown evidence of a non-Darcy relationship between flow rate and hydraulic loss that is best described by Forchheimer's law. Furthermore, in the flow experiments both inertial and viscous flow terms are not negligible. The observed experimental breakthrough curves of solute transport have been modeled by the classical one-dimensional analytical solution for the advection–dispersion equation (ADE) and the single rate mobile–immobile model (MIM). The former model does not properly fit the first arrival and the tail while the latter, which recognizes the existence of mobile and immobile domains for transport, provides a very decent fit. The carried out experiments show that there exists a pronounced mobile–immobile zone interaction that cannot be neglected and that leads to a non-equilibrium behavior of solute transport. The existence of a non-Darcian flow regime has showed to influence the velocity field in that it gives rise to a delay in solute migration with respect to the predicted value assuming linear flow. Furthermore, the presence of inertial effects enhance non-equilibrium behavior. Instead, the presence of a transitional flow regime seems not to exert influence on the behavior of dispersion. The linear-type relationship found between velocity and dispersion demonstrates that for the range of imposed flow rates and for the selected path the geometrical dispersion dominates the mixing processes along the fracture network

On the reliability of analytical models to predict solute transport in a fracture network

Abstract. In hydrogeology, the application of reliable tracer transport model approaches is a key issue to derive the hydrodynamic properties of aquifers. Laboratory- and field-scale tracer dispersion breakthrough curves (BTC) in fractured media are notorious for exhibiting early time arrivals and late time tailing that are not captured by the classical advection–dispersion equation (ADE). These "non-Fickian" features are proven to be better explained by a mobile–immobile (MIM) approach. In this conceptualization the fractured rock system is schematized as a continuous medium in which the liquid phase is separated into flowing and stagnant regions. The present study compares the performances and reliabilities of the classical MIM and the explicit network model (ENM), taking expressly into account the network geometry for describing tracer transport behavior in a fractured sample at bench scale. Though ENM shows better fitting results than MIM, the latter remains still valid as it proves to describe the observed curves quite well. The results show that the presence of nonlinear flow plays an important role in the behavior of solute transport. First, the distribution of solute according to different pathways is not constant, but it is related to the flow rate. Second, nonlinear flow influences advection in that it leads to a delay in solute transport respect to the linear flow assumption. However, nonlinear flow is not shown to be related with dispersion. The experimental results show that in the study case the geometrical dispersion dominates the Taylor dispersion. However, the interpretation with the ENM shows a weak transitional regime from geometrical dispersion to Taylor dispersion for high flow rates. Incorporating the description of the flow paths in the analytical modeling has proven to better fit the curves and to give a more robust interpretation of the solute transport

Las isoetáceas argentinas

Los Isoetes son plantas de aspecto graminoide, Pteridófitas heterosporadas, de régimen acuático o palustre, aunque no falten algunos de hábitatterrestre; de tallo muy corto o rizoma, perenne surcado de arriba a abajo pordos o más hendiduras de donde salen las raíces, dicotómicas; con hojas reducidas al raquis, dispuestas en rosetas. Están desprovistos de órganos especiales para la protección de los esporangios, los que son grandes y se alojan debajo de la lígula en la base de algunas hojas (esporófilos) en una cavidad llamada fovea, muchas veces cubiertos o semicubiertos por una tenue membrana, el velo que deriva del tejido foliar. Este tejido origina también, entre la lígula y el esporangio, un corpúsculo laminar, llamado labio, y la lígula se continúa hacia el interior del esporófilo, terminando en un apéndice globoso: el glosopodio. Macrosporos y microsporos numerosos, los primeros notablemente más grandes. Los prótalos masculinos no abandonan los microsporos, consisten en una o dos células, formando un solo anteridio con cuatro anterozoides policiliados. El pequeño prótalo femenino se origina dentro mismo del macrosporo, rompiendo el episporio; desarrolla generalmente un solo arquegonio, concrescente con el prótalo. Fecundado el arquegonio se desarrolla el embrión el que quedará libre, más tarde, por putrefacción de la pared del esporangio.Facultad de Ciencias Naturales y Muse

Molecular characterization of officially registered Sangiovese clones and of other Sangiovese-like biotypes in Tuscany, Corsica and Emilia-Romagna

The present study was designed (1) to identify and determine the origin of the genetic variability via SSR and AFLP within a group of 39 Sangiovese clones officially listed in the National Grapevine Registry, (2) to pinpoint varietal differences and potential family relations among 34 Sangiovese-like biotypes, via the SSR markers. Most biotypes are regarded as Sangiovese but sometimes are known under different names. In both studies the reference standard was the registered Sangiovese clone SG 12T.No polymorphism was found among the officially listed 39 clones analysed at 6 microsatellite loci. This enabled us to confirm their origin from a single mother plant, thereby supporting the view that any morphological or qualitative differences may be the result of propagation-related mutagenic events. A subsequent AFLP analysis of 26 of the 39 clones showed polymorphic bands in three of them (two identical) that may correspond to a mutagenic event. Assays with SSR markers on 34 Sangiovese-like biotypes collected in Tuscany, Corsica and Emilia-Romagna showed that 28 are identical with the reference Sangiovese clone SG 12T, while the remaining 6 (Sangiovese 1, Sangiovese 6, Morellino, Poverina, Sangiovese forte and Brunellone) are genetically different from SG 12T and among one another so that no direct family relations could be established

Impacts of desalinated and recycled water in the Abu Dhabi surficial aquifer

In Abu Dhabi, one of the most arid regions in the world, in recent decades, desalinated water has been identified as a prime solution in solving the water demand issues. In this study, a three-dimensional coupled density-dependent flow and solute transport model was set up in order to study the effect of the artificial recharge using desalinated water and the influence of nonconventional water with a salt concentration in the range 0.1–2 g/L The results confirm that this region demands the adoption of a more rational use of irrigation water or additional usage of desalinated water and recycled water together with optimizing groundwater pumping at locations that are vulnerable to further quality degradation and depletion. The long-term storage of desalinated freshwater with a maximum radial distance of 653 m in the dune surface is ensured with the formation of the transition zone, and change in the groundwater head up to 5 km. The maximum recovery obtained by immediate recovery is 70%. The study expresses the long-term feasibility of desalinated freshwater storage and the need for further management practices in quantifying the contribution of desalinated and recycled water for agriculture activities which might have improved groundwater quality and increased hydraulic head at some locations

Experimental study of forced convection heat transport in porous media

Abstract. The present study is aimed at extending this thematic issue through heat transport experiments and their interpretation at laboratory scale. An experimental study to evaluate the dynamics of forced convection heat transfer in a thermally isolated column filled with porous medium has been carried out. The behavior of two porous media with different grain sizes and specific surfaces has been observed. The experimental data have been compared with an analytical solution for one-dimensional heat transport for local nonthermal equilibrium condition. The interpretation of the experimental data shows that the heterogeneity of the porous medium affects heat transport dynamics, causing a channeling effect which has consequences on thermal dispersion phenomena and heat transfer between fluid and solid phases, limiting the capacity to store or dissipate heat in the porous medium

Effect of pre-bloom anti-transpirant treatments and leaf removal on 'Sangiovese' (Vitis vinifera L.) winegrapes

Recent trials have shown that basal shoot leaf removal at pre-bloom is effective in reducing fruit-set and yield, leading to better grape quality composition. The present trial was designed to determine whether similar results can be achieved with 'Sangiovese' vines by testing a pre-bloom spray of film-forming anti-transpirant (P) against pre-bloom hand defoliation of basal shoots (HD) and no defoliation (C). The results of our threeyear experiment show that, compared to C, P reduced net assimilation of treated leaves for 20-40 days and photosynthetic compensation was not found after treatments in the upper untreated leaves of P and in the remaining upper HD leaves; berry-set, cluster weight and yield were significantly reduced in P and HD; bunch compactness decreased in HD, with P clusters registering an intermediate value; must soluble solids content (°Brix) and pH of P and HD were higher; no differences were found among treatments for titratable acidity. Berry and skin weight and anthocyanin content of P and C berries were similar, whereas HD berries, which were fully exposed to ambient light and temperature throughout each season, showed higher skin weight and skin weight-to-berry weight ratio, but a decreasing of total skin anthocyanins content compared to C and P.

Application of kaolin and italian natural chabasite-rich zeolitite to mitigate the effect of global warming in vitis vinifera l. Cv. sangiovese

High temperatures and the anomalous distribution of rainfall during the growing season may have a negative impact on grapevine yield and berry composition. In recent years, many studies have focused on the application of agronomical techniques to reduce the negative impact of heat waves on secondary metabolites such as phenols. In particular, treatments with kaolin have shown positive effects on reducing canopy temperatures, enhancing the accumulation of anthocyanins. In regard to the above, three treatments were evaluated: untreated control (C), kaolin (CAO), and chabasite-rich zeolitites (ZEO) applications on cv. Sangiovese in order to verify the cooling effects on leaves and bunches, and the impact on gas exchange, yield parameters, berry composition, and on both chemical and sensory notes of wine. Minerals were sprayed twice around the veraison on the entire canopy at a 3% concentration. The results showed that the application of the minerals was able to reduce the berry temperatures in both years of the trial as compared to the untreated control (C), without affecting vine gas exchange, yield, and soluble solid accumulation. Furthermore, the cooling effect determined an increase in anthocyanin on both the grapes and the wine. At testing, CAO and ZEO wines stood out regarding greater color intensity and were preferred by the judges

Validación y detección automática del transporte dispersivo del emisario submarino de Mar del Plata, Argentina

The submarine outfall of Mar del Plata city at Camet was projected considering the mean and maximum of forecasted sewage discharges, the inner-shelf depth, coliform concentration and its decay (T90) mainly induced by sunlight effect and costal salinity. In 2016 the outfall was operating with a length of 3,810 m and diffusers in the last 526 m. An economical method to monitor its performance in relation to the surroundings, is remote-sensing techniques, applying either visible or radar images. Tidal currents parallel to the coast are responsible for the transport of the sedimentary plume in the far field, after a primary dilution from a depth of 11 m. Visible images (1.5 to 6 m spatial resolution) are effective in monitoring the plume entrained in the upper portion of the water column. These analyses led to study the interaction between waves and coastal currents. Radar images (30 m resolution X and C bands) permit to survey the slick-alike plume that differs from the environment water by the surface roughness. Comparing both techniques visible images can distinguish the different colours of the plume; instead, the radar images are showing the surface roughness from the slick-alike plume. The main advantage of active sensors is that they can map the plume during a cloudy weather and even during night time.El emisario submarino de Mar del Plata en Camet fue proyectado considerando las descargas cloacales promedio y máximas previstas, la profundidad de la plataforma vecina, la concentración de coliformes y el decaimiento (T90) inducido por la luz solar y la salinidad. En 2016 el emisario operaba con una longitud de 3.810 m con difusores en los últimos 526 m. Un método poco oneroso para analizar su comportamiento en relación a su entorno es la aplicación de técnicas de teledetección tanto en el espectro visible como mediante imágenes de radar. Las corrientes de marea paralelas a la costa son responsables de una pluma sedimentaria en el campo lejano, luego de una dilución primaria desde una profundidad de 11 m. Las imágenes visibles (resolución espacial de 1,5 a 6 m) son efectivas para monitorear la pluma extendida en la capa superior del mar. Estos análisis permiten el estudio de la interacción entre olas y corrientes costeras. Las imágenes de radar (resolución de 30 m en las bandas X y C) permiten relevar plumas superficiales semejantes a derrames de aceites por su rugosidad. Comparando ambas técnicas las imágenes visibles pueden distinguir plumas de diferentes colores del agua; por el contrario, las imágenes de radar están mostrando diferencias en la tensión superficial. La principal ventaja de los sensores activos es que permiten monitorear la pluma durante tiempo nuboso incluso sin luz solar