The Venetian Plain is known for the occurrence of areas with high concentrations of arsenic in groundwater (greater than 400μg/L). The study area represents the typical residential, industrial and ...agricultural features of most Western countries and is devoid of hydrothermal, volcanic or anthropogenic sources of arsenic. The aim of the study is to model the arsenic mobilization and the water–rock interaction by a complete hydrogeochemical investigation (analyses of filtered and unfiltered groundwater sediment mineralogy and geochemistry). The groundwater arsenic contamination and redox conditions are highly variable. Groundwaters with oxidizing and strongly reducing potentials have much lower arsenic concentrations than do mildly reducing waters. The grain size of the aquifer sediments includes gravels, sands and silty-clays. A continuous range of organic material concentrations is observed (from zero to 40%). The amount of sedimentary organic matter is highly correlated with the arsenic content of the sediments (up to 300mg/kg), whereas no relationships are detectable between arsenic and other chemical parameters.
The occurrence of arsenic minerals was observed as a peculiar feature under the scanning electron microscope. Arsenic and sulfur are the sole constituents of small tufts or thin crystals concentrated in small masses. These arsenic minerals were clearly observed in the peat sediments, in agreement with the geochemical modeling that requires very reducing conditions for their precipitation from the groundwater. The modeling suggests that, under oxidizing conditions, arsenic is adsorbed; moreover, a continuous decrease in the redox potential causes increasing desorption of arsenic. If the reducing conditions become more intense, the formation of As-S minerals would explain the lower concentration of arsenic measured in the strongly reducing groundwater. Even if As-sulfides are rare under low-temperature conditions, the anomalous abundance of reductants (organic matter) can locally stabilize As-S minerals, which can scavenge large quantities of groundwater arsenic.
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•Mildly reducing groundwater on the Venetian Plain is contaminated by arsenic.•Arsenic contamination decreases in strongly reducing groundwater.•Peat sediments have very high arsenic concentrations.•Arsenic sulfide minerals are detectable at the micron- to nano-scale.•Arsenic mobility is modeled as hydroxide desorption and As-sulfide precipitation.
Predicting the hydrological response of watersheds to climate disturbances requires a detailed understanding of the processes connecting hillslopes and streams. Using a network of soil moisture and ...temperature sensors, electrical resistivity tomography monitoring, and a weather station we assess the above and below‐ground processes driving the hydrological response of a hillslope during snowmelt and summer monsoon. The transect covers bedrock and vegetation gradients, with a steep upper part characterized by shallow bedrock, and gentle lower part underlain by colluvium. The main vegetation cover is conifers on the upper, and grass and veratrum on the lower part. Combined with a simplified hydrological model, we show that the thin soil layer of the steep slope acts as a preferential flow path, leading to mostly shallow lateral flow, interrupted by vertical flow, mostly at tree locations, and likely facilitated by flow along fractures and roots. Vertical flow and upstream‐driven groundwater dynamics are prevailing at the colluvium, presenting a very different hydrological behavior compared to the upper part. These results show that subsurface structure and features have a strong control on the hydrological response of a hillslope and that those can create considerably varying hydrological dynamics across small spatial scales.
Key Points
Vegetation, bedrock, and topographic characteristics define hydrological dynamics
Shallow lateral flow characterizes steep, shallow bedrock
Vertical up and downward flow prevails at gentle slope underlain by colluvium
Garnet is the archetypal cubic mineral, occurring in a wide variety of rock types in Earth's crust and upper mantle. Owing to its prevalence, durability and compositional diversity, garnet is used to ...investigate a broad range of geological processes. Although birefringence is a characteristic feature of rare Ca–Fe3+ garnet and Ca-rich hydrous garnet, the optical anisotropy that has occasionally been documented in common (that is, anhydrous Ca–Fe2+–Mg–Mn) garnet is generally attributed to internal strain of the cubic structure. Here we show that common garnet with a non-cubic (tetragonal) crystal structure is much more widespread than previously thought, occurring in low-temperature, high pressure metamorphosed basalts (blueschists) from subduction zones and in low-grade metamorphosed mudstones (phyllites and schists) from orogenic belts. Indeed, a non-cubic symmetry appears to be typical of common garnet that forms at low temperatures (<450°C), where it has a characteristic Fe–Ca-rich composition with very low Mg contents. We propose that, in most cases garnet does not initially grow cubic. Our discovery indicates that the crystal chemistry and thermodynamic properties of garnet at low-temperature need to be re-assessed, with potential consequences for the application of garnet as an investigative tool in a broad range of geological environments.
A pilot area within the Venetian Plain was selected to assess the arsenic (As) contamination of groundwater. The area represents a typical residential, industrial and agricultural organization ...representative of most western countries, and is also devoid of lithologies with high or anomalous As content. Hydrogeological and chemical data have been collected, the latter spatialized by a geostatistical approach. The unconfined aquifer reservoir varies from a predominantly gravel composition in the north to a sandy and silt–clay composition further south, including peat layers. The hydrochemical features of the waters are rather homogeneous, featuring low mineral content and a Ca-bicarbonate signature. In contrast, the redox state is highly variable; oxidizing conditions are predominant in the northern and coarse parts of the aquifer, whereas reducing potentials prevail in the southern and silt–clay parts. Several well waters contain arsenic in excess of drinkable limits (=10 ppb), and most of these wells are located in the southern area. A large portion of the studied area has a high probability of containing non-potable water (up to 150 ppb As). Remarkably, As “hot spots” (As > 300 ppb, up to 431 ppb) were identified at the transition from gravel to silt–clay sediments. No industrial or agricultural source of As has been found.
Primary cutaneous T-cell lymphomas NOS (CTCL not otherwise specified) involve a heterogeneous group of neoplasms that affect the skin, with no evidence of extracutaneous involvement at the time of ...diagnosis. The association with hemophagocytic lymphohistiocytosis (HLH) syndrome has been documented. They are rare in children, and usually are characterized by a dismal prognosis. We report an unusual case of a pediatric patient diagnosed as acute pityriasis lichenoide et varioliformis (PLEVA), with a torpid clinical course, association with HLH and a subsequent diagnosis of double negative (CD4/CD8) primary CTCL, with expression of cytotoxic molecules.
Coloured samples of glass and ceramic were selected for EBSD investigation to verify the potential (advantages and limitations) of this technique in the characterization of the raw materials used and ...the neoformation phases originating from the manufacturing processes. In the case of copper‐bearing red glasses, it was verified that micrometric droplets, residuals of the original copper source, can be ascribed to metallic copper or to a low‐Sn bronze, due to strongly similar lattice parameters. From the same samples, micrometric flakes were identified by EBSD as magnetite and interpreted as residues of the reducing agent used in the production of such red glasses. Further, the technique allowed the pigment responsible for the yellow colouring of some incised slipware to be recognized as bindheimite. In a third case, the black pigment, contained in some Nestorian decorated pottery, was identified as an amorphous phase of Mn oxide. The accurate identification of the colouring particles and other products or materials offered a more precise comprehension of the production technique, period and site of the examined artefacts, together with scientific parameters for the identification of the raw materials, their transformation during the production cycle and an evaluation of the most reliable recipes used for their preparation.
In this work the effects of prolonged heat treatments on the microstructural and crystallographic evolution of Al–Ni intermetallic compounds were studied in Al/Ni multilayer samples, produced by ...accumulative roll bonding (ARB) process. Starting from aluminium and nickel sheets, the stacks were composed alternating three aluminium with two nickel sheets. After six rolling passes, the roll-bonded material was heat treated in a tubular furnace at 500, 550 and 600 °C for different times (1–20 h). The ARB process followed by the diffusion heat treatments allowed the formation of four Al–Ni intermetallic phases (Al3Ni, Al3Ni2, AlNi and AlNi3). Microstructural analyses of the obtained samples were carried out by scanning electron microscopy (SEM). The electron backscattered diffraction (EBSD) technique was used for the crystallographic analysis of the samples. After the prolonged annealing, three different sequences of phases, starting from Al, were observed: Al3Ni2–AlNi–AlNi3, Al3Ni and AlNi–Al3Ni. The EBSD analysis showed that the intermetallic phases grew with a mean grain size between 0.5 μm and 3 μm and without a preferential crystallographic orientation.
•Study of the prolonged annealing on Al/Ni system.•The presence of AlNi3 phase, not detected in similar researches, has been observed.•Three different sequences of phases were detected.•From EBSD analysis the intermetallic compounds have no preferred orientation.
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