Articles publicats (Química, Física i Ciències Ambientals i del Sòl)

Permanent URI for this collection

Browse

Recent Submissions

Now showing 1 - 5 of 862
  • Item
    Open Access
    Constant-pH simulations of a coarse-grained model of polyfunctional weak charged biopolymers
    (MDPI, 2024) Naranjo, David; Blanco, Pablo M.; Garcés, Josep Lluís; Madurga, Sergio; Mas, Francesc
    A coarse-grained model of linear polyfunctional weak charged biopolymers was implemented, formed of different proportions of acid-base groups resembling the composition of humic substances. These substances are mainly present in dissolved organic matter in natural water. The influence of electrostatic interactions computing methods, factors concerning the structure of the chain, different functional groups, and the ionic strength on polyelectrolytes were studied. Langevin dynamics with constant pH simulations were performed using the ESPResSO package and the Python-based Molecule Builder for ESPResSo (pyMBE) library. The coverage was fitted to a polyfunctional Frumkin isotherm, with a mean-field interaction between charged beads. The composition of the chain affects the charge while ionic strength affects both the charge and the radius of gyration. Additionally, the parameters intrinsic to the polyelectrolyte model were well reproduced by fitting the polyfunctional Frumkin isotherm. In contrast, the non-intrinsic parameters depended on the ionic strength. The method developed and applied to a polyfunctional polypeptide model, that resembles a humic acid, will be very useful for characterizing biopolymers with several acid-base functional groups, where their structure, the composition of the different functional groups, and the determination of the main intrinsic proton binding constants and their proportion are not exactly known.
  • Item
    Open Access
    Biogenic carbonates (queras) in loess-palaeosol sequences of the Ebro Basin and their potential use as a palaeoenvironmental proxy
    (Elsevier, 2024) Álvarez, Daniela; Torres-Guerrero, Carlos Alberto; Travé, Anna; Preusser, Frank; Plata Moreno, José Manuel; Poch, Rosa M.
    Secondary carbonate accumulations are very common in arid and semi-arid soils but are often poorly described and classified. This is the case for queras that are observed in several loess-palaeosol sequences of the Ebro Basin. Micromorphologically, queras are complex pedogenic features basically consisting of infillings of calcified root cells in channels, surrounded by decarbonated hypocoatings. They apparently result from biologically mediated calcification/decalcification processes at a microscale. The aim of this study is to systematically characterize biocalcifications found in dated loess-palaeosol sequences, to determine the main factors of formation, and to discuss their possible use as a palaeoenvironmental proxy. Different queras show a similar number of biosparite layers (four to five) around a central channel, and a decarbonated hypocoating around the queras. This supports the hypothesis that queras originate from the calcification of root tips and are related to the acidification of surrounding soil for nutrient absorption. Under cathodoluminescence microscopy, biosparite has a different behaviour than non-biological calcite crystals: the latter appears reddish while biosparite remains black. The queras, with ages corresponding to Marine Isotope Stages 1–3, are younger than that of the loess where they are found in. The stable isotope values likely correspond to C3 plants, and the estimated temperatures of formation reflect a Mediterranean temperate climate. This suggests that the biocalcifications developed during short moist seasons amidst arid periods of the Quaternary.
  • Item
    Open Access
    Phase structure of charged AdS black holes surrounded by exotic fluid with modified Chaplygin equation of state
    (Springer, 2024) Sekhmani, Y.; Rayimbaev, J.; Luciano, Giuseppe Gaetano; Myrzakulov, R.; Gogoi, D. J.
    By considering the concept of the modified Chaplygin gas (MCG) as a single fluid model unifying dark energy and dark matter, we construct a static, spherically charged black hole (BH) solution in the framework of General Relativity. The P–V criticality of the charged anti-de Sitter (AdS) BH with a surrounding MCG is explored in the context of the extended phase space, where the negative cosmological constant operates as a thermodynamical pressure. This critical behavior shows that the small/large BH phase transition is analogous to the van der Waals liquid/gas phase transition. Accordingly, along the P–V phase spaces, we derive the BH equations of state and then numerically evaluate the corresponding critical quantities. Similarly, critical exponents are identified, along with outcomes demonstrating the scaling behavior of thermodynamic quantities near criticality to a universal class. The use of geometrothermodynamic (GT) tools finally offers a new perspective on the discovery of the critical phase transition point. At this stage, we apply a class of GT tools, such as Weinhold, Ruppeiner, HPEM, and Quevedo classes I and II. The findings are therefore non-trivial, as each GT class metric captures at least either the physical limitation point or the phase transition critical point. Overall, this paper provides a detailed study of the critical behavior of the charged AdS BH with surrounding MCG.
  • Item
    Open Access
    NIR-HSI as a tool to predict deoxynivalenoland fumonisins in maize kernels: a stepforward in preventing mycotoxincontamination
    (John Wiley & Sons Ltd, 2024) Borràs-Vallverdú, Bernat; Marín Sillué, Sònia; Sanchís Almenar, Vicente; Gatius Cortiella, Ferran; Ramos Girona, Antonio J.
    Maize is frequently contaminated with deoxynivalenol (DON) and fumonisins B1 (FB1) and B2 (FB2). In the European Union, these mycotoxins are regulated in maize and maize-derived products. To comply with these regulations, industries require a fast, economic, safe, non-destructive and environmentally friendly analysis method. RESULTS: In the present study, near-infrared hyperspectral imaging (NIR-HSI) was used to develop regression and classification models for DON, FB1 and FB2 in maize kernels. The best regression models presented the following root mean square error of cross validation and ratio of performance to deviation values: 0.848 mg kg−1 and 2.344 (DON), 3.714 mg kg−1 and 2.018 (FB1) and 2.104 mg kg−1 and 2.301 (FB2). Regarding classification, European Union legal limits for DON and FB1 + FB2 were selected as thresholds to classify maize kernels as acceptable or not. The sensitivity and specificity were 0.778 and 1 for the best DON classification model and 0.607 and 0.938 for the best FB1 + FB2 classification model. CONCLUSION: NIR-HSI can help reduce DON and fumonisins contamination in the maize food and feed chain. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
  • Item
    Open Access
    Evaluation of 2D hydrodynamic-based rainfall/runoff modelling for soil erosion assessment at a seasonal scale
    (Elsevier, 2024) Costabile, Pierfranco; Cea, Luis; Barbaro, Gabriele; Costanzo, Carmelina; Llena, Manel; Vericat Querol, Damià
    Badlands are often the source of a significant fraction of the sediment reaching the river network due to the exposure of the bare soil to the impact of rain drops and to the bed shear stress generated by the surface runoff. Hence, a correct understanding of the soil erosion and sediment transport processes inside badlands can help to a better characterisation of the suspended sediment production at the catchment scale. In this work we study the suitability of a two-dimensional (2D) physically-based event-scale erosion model as a tool to represent soil erosion and sediment transport in badlands at a seasonal scale. The model solves the 2D shallow water equations, including infiltration and rainfall, in order to compute the generation and routing of surface runoff within the badland. Coupled to the hydrodynamic equations, the model solves a 2D suspended sediment transport equation with source terms that account for rainfall- and runoff-driven erosion and sediment deposition. Based on this model, an overall procedure was developed and tested considering, as case study, a badland located in El Soto catchment (central Pyrenees, Iberian Peninsula). For the analysed badland, several high-resolution topography surveys were available, which allowed for the estimation of the soil loss and the spatial distribution of erosion patterns for periods of 3–4 months over two years. These data sets were used to calibrate and validate the proposed modelling approach, and to analyse its capabilities and limitations for the assessment of soil erosion at the seasonal scale.