Química, Física i Ciències Ambientals i del Sòl

Permanent URI for this community

https://repositori.udl.cat/handle/10459.1/239

Browse

Now showing 1 - 20 of 865

Open Access
100 key questions to guide hydropeaking research and policy
(Elsevier, 2023-09-16) Hayes, Daniel S.; Bruno, M.C.; Alp, Maria; Boavida, Isabel; Batalla, Ramon J.; Bejarano, Maria Dolores; Noack, Markus; Vanzo, Davide; Casas Mulet, Roser; Vericat Querol, Damià; Carolli, Mauro; Tonolla, Diego; Halleraker, Jo Halvard; Gosselin, M. P.; Chiogna, Gabriele; Zolezzi, Guido; Venus, Terese
As the share of renewable energy grows worldwide, flexible energy production from peak-operating hydropower and the phenomenon of hydropeaking have received increasing attention. In this study, we collected open research questions from 220 experts in river science, practice, and policy across the globe using an online survey available in six languages related to hydropeaking. We used a systematic method of determining expert consensus (Delphi method) to identify 100 high-priority questions related to the following thematic fields: (a) hydrology, (b) physico-chemical properties of water, (c) river morphology and sediment dynamics, (d) ecology and biology, (e) socio-economic topics, (f) energy markets, (g) policy and regulation, and (h) management and mitigation measures. The consensus list of high-priority questions shall inform and guide researchers in focusing their efforts to foster a better science-policy interface, thereby improving the sustainability of peak-operating hydropower in a variety of settings. We find that there is already a strong understanding of the ecological impact of hydropeaking and efficient mitigation techniques to support sustainable hydropower. Yet, a disconnect remains in its policy and management implementation.
Open Access
30 years in: Quo vadis generalized uncertainty principle?
(IOP Publishing, 2023) Bosso, Pasquale; Luciano, Giuseppe Gaetano; Petruzziello, L.; Wagner, Fabian
According to a number of arguments in quantum gravity, both model-dependent and model-independent, Heisenberg's uncertainty principle is modified when approaching the Planck scale. This deformation is attributed to the existence of a minimal length. The ensuing models have found entry into the literature under the term generalized uncertainty principle. In this work, we discuss several conceptual shortcomings of the underlying framework and critically review recent developments in the field. In particular, we touch upon the issues of relativistic and field theoretical generalizations, the classical limit and the application to composite systems. Furthermore, we comment on subtleties involving the use of heuristic arguments instead of explicit calculations. Finally, we present an extensive list of constraints on the model parameter β, classifying them on the basis of the degree of rigor in their derivation and reconsidering the ones subject to problems associated with composites.
Open Access
A carbon-sink in a sacred forest: Biologically-driven calcite formation in highly weathered soils in Northern Togo (West Africa)
(Elsevier, 2020-11-10) Ur-Rehman, Hafeez; Poch, Rosa M.; Scarciglia, Fabio; Francis, M. L.
Soil organic matter (OM) is a source of fertility for food provisioning and a means for climate mitigation. A high pedodiversity observed over very short distances due to both past and present land use, such as in Western Africa (Northern Togo), makes this a crucial issue. In particular, some small spots covered by sacred forests (forêts sacrées) of high cultural value in this area are extremely biodiverse, calcareous and high in OM in contrast with the non-calcareous, poor OM, overgrazed woody savannah and agricultural surroundings. The objectives of our work were to understand this pedodiversity and the process of CaCO3 formation in the soil under the highly biodiverse forest using morphological, micromorphological, chemical and mineralogical soil analyses. The results show a high degree of weathering of the gneiss parent material, presence of plinthite gravels, dominance of 1:1 clays, formation of swelling clays in the imperfectly drained soils, and low OM content. The presence of palygorskite, although in traces, suggests drier intervals and is consistent in this context with the extreme wet and dry climate conditions in the region. In the OM rich soils under forest, bio-calcification takes place in the form of CaCO3 needles, micrite hypocoatings around biopores and calcified cells. Oribatid excrements are associated with calcite and organic matter in the sacred forest soil, indicating that litter recycling has played an important role in the formation of calcite. We hypothesize that the high biological activity releasing CO2, formation of HCO3– and precipitation of CaCO3 due to the Ca2+ released by the recycled organic matter and weathering of plagioclases, lead to different forms of secondary calcium carbonate in the sacred forest soils. The high oxalate content of the vegetation in the sacred forest suggests that calcium carbonate formation, possibly via the oxalate-carbonate pathway, may also have played a role in calcite precipitation in these in organic matter rich soils. The parent material of these soils is not calcareous, meaning that these are not lithogenic carbonates, thus making them an important carbon sink. The soil characteristics indicate a high potential for development of the soils of the area in both agricultural yields and in potential carbon sequestration relevant to global change policies.
Open Access
A comparison between the determination of free Pb(II) by two techniques: Absence of gradients and Nernstian equilibrium stripping and resin titration
(Elsevier, 2007) Alberti, Giancarla; Biesuz, Raffaela; Huidobro Redondo, César; Companys Ferran, Encarnació; Puy Llorens, Jaume; Galceran i Nogués, Josep
Absence of gradients and Nernstian equilibrium stripping (AGNES) is an emerging electroanalytical technique designed to measure free metal ion concentration. The practical implementation of AGNES requires a critical selection of the deposition time, which can be drastically reduced if the contribution of the complexes is properly taken into account. The resin titration (RT) is a competition method based on the sorption of metal ions on a complexing resin. The competitor here considered is the resin Chelex 100 whose sorbing properties towards Pb(II) are well known. The RT is a consolidated technique especially suitable to perform an intercomparison with AGNES, due to its independent physicochemical nature. Two different ligands for Pb(II) complexation have been analyzed here: nitrilotriacetic acid (NTA) and pyridinedicarboxylic acid (PDCA). The complex PbNTA is practically inert in the diffusion layer, so, for ordinary deposition potentials, its contribution is almost negligible; however, at potentials more negative than −0.8 V vs. Ag/AgCl the complex dissociates on the electrodic surface giving rise to a second wave in techniques such as normal pulse polarography. The complex Pb
PDCA is partially labile, so that its contribution can be estimated from an expression of the lability degree of the complex. These new strategies allow us to reduce the deposition time. The free Pb(II) concentrations obtained by AGNES and by RT are in full agreement for both systems here considered. The main advantage of the use of AGNES in these systems lies in the reduction of the time of the experiment, while RT can be applied to non-amalgamating elements and offers the possibility of simultaneous determinations.
Open Access
A comparison of new and existing equations for estimating sensible heat flux using surface renewal and similarity concepts
(American Geophysical Union, 2006) Castellví Sentís, Francesc; Snyder, R. L.; Baldocchi, D. D.; Martínez-Cob, Antonio
This paper describes two approaches for estimating sensible heat flux, using surface renewal and similarity concepts. One approach depends on a temperature structure function parameter and is valid in the inertial sublayer. The other approach depends on the temperature standard deviation and operates when measurements are made above the canopy top, either in the roughness or inertial sublayer. The approaches were tested over grass, rangeland grass, wheat, grape vineyard, and nectarine and olive orchards. It is shown that the free convection limit expression for the standard deviation method holds for slightly unstable conditions. When surface homogeneity and fetch requirements are not fully met in the field, the results show that the equations based on surface renewal principles are more robust and accurate than equations exclusively based on similarity backgrounds. It is likely that the two methods are less sensitive to site‐specific adjustment of the similarity relationships unless the canopy is rather heterogeneous. Under unstable conditions, the free convection limit equation, which depends on the temperature standard deviation, can provide online sensible heat flux estimates using affordable battery‐powered data logger with temperature data as the only input. The approach performed well when measuring above the canopy in the roughness and inertial sublayers, thus suggesting that the method is useful for long‐term monitoring over growing vegetation.
Open Access
A data-driven method for unsupervised electricity consumption characterisation at the district level and beyond
(Elsevier, 2021) Mor Martínez, Gerard; Cipriano, Jordi; Martirano, Giacomo; Pignatelli, Francesco; Lodi, Chiara; Lazzari, Florencia; Grillone, Benedetto; Chemisana Villegas, Daniel
A bottom-up electricity characterisation methodology of the building stock at the local level is presented. It is based on the statistical learning analysis of aggregated energy consumption data, weather data, cadastre, and socioeconomic information. To demonstrate the validity of this methodology, the characterisation of the electricity consumption of the whole province of Lleida, located in northeast Spain, is implemented and tested. The geographical aggregation level considered is the postal code since it is the highest data resolution available through the open data sources used in the research work. The development and the experimental tests are supported by a web application environment formed by interactive user interfaces specifically developed for this purpose. The paper’s novelty relies on the application of statistical data methods able to infer the main energy performance characteristics of a large number of urban districts without prior knowledge of their building characteristics and with the use of solely measured data coming from smart meters, cadastre databases and weather forecasting services. A data-driven technique disaggregates electricity consumption in multiple uses (space heating, cooling, holidays and baseload). In addition, multiple Key Performance Indicators (KPIs) are derived from this disaggregated energy uses to obtain the energy characterisation of the buildings within a specific area. The potential reuse of this methodology allows for a better understanding of the drivers of electricity use, with multiple applications for the public and private sector.
Open Access
A data-driven methodology for enhanced measurement and verification of energy efficiency savings in commercial buildings
(Elsevier, 2021) Grillone, Benedetto; Mor, Gerard; Danov, Stoyan; Cipriano, Jordi; Sumper, Andreas
Methods to obtain accurate estimations of the savings generated by building energy efficiency interventions are a topic of great importance, and considered to be one of the keys to increase capital investments in energy conservation strategies worldwide. In this study, a novel data-driven methodology is proposed for the measurement and verification of energy efficiency savings, with special focus on commercial buildings and facilities. The presented approach involves building use characterization by means of a clustering technique that allows to extract typical consumption profile patterns. These are then used, in combination with an innovative technique to evaluate the building’s weather dependency, to design a model able to provide accurate dynamic estimations of the achieved energy savings. The method was tested on synthetic datasets generated using the building energy simulation software EnergyPlus, as well as on monitoring data from real-world buildings. The results obtained with the proposed methodology were compared with the ones provided by applying the time-of-week-and-temperature (TOWT) model, showing up to 10% CV(RMSE) improvement, depending on the case in analysis. Furthermore, a comparison with the deterministic results provided by EnergyPlus showed that the median estimated savings error was always lower than 3% of the total reporting period consumption, with similar accuracy retained even when reducing the total training data available.
Restricted
A dynamic model based on the piston flow concept for the thermal characterization of solar collectors
(Elsevier, 2012) Amrizal, N; Chemisana Villegas, Daniel; Rosell Urrutia, Joan Ignasi; Barrau, Jérôme
A simple, transient model for the characterization of the dynamic thermal performance of solar thermal collectors was developed and experimentally validated. The proposed model equation is linear with respect to the input parameters and does not require any treatment for ordinary differential equations (ODEs). The temperature distribution in the fluid flowing inside the collector is described by means of the piston flow and finite increment concepts. The dynamic effect, for a given flow rate, is expressed by the heat transport time and is based on the effective thermal capacity of the collector. The results reveal that the characteristic parameters involved in the model agree reasonably well with the experimental variables obtained from standard steady-state measurements. After a calibration process the model can well predict the thermal performance of a solar thermal collector, for a specific weather data set.
Open Access
A focus on the biosynthesis and composition of cuticle in fruits
(American Chemical Society, 2015-04-29) Lara Ayala, Isabel; Belge, Burcu; Goulao, Luis F.
Cuticles are plant structures, composed mostly by lipidic layers, synthesized by nonwoody aerial plant organs and deposited on the surface of outer epidermal cell walls. Although its significance has been often disregarded, cuticle deposition modifies organ chemistry, influences mechanical properties, and plays a central role in sensing and interacting with the surrounding environment. Even though some research has been undertaken addressing cuticle biosynthesis and composition in vegetative plant tissues, comparatively less information is available regarding cuticle composition in the epidermis of fruits. However, recent work points to a role for cuticles in the modulation of fruit quality and postharvest performance, indicating that current models for the investigation of fruit development, metabolism, and quality need to integrate a comprehensive knowledge of the cuticle layer. This paper provides an overview of recent findings and observations regarding cuticle biosynthesis and composition in fruits from species of agronomic and economic relevance. Important, but often neglected differences in cuticle composition and biosynthesis patterns among diverse fruit species are described herein to generate an atlas of what is currently known about fruit cuticles and to highlight what remains to be explored. Emphasis is placed on the need to investigate each genetic background considering its own specificities, to permit correlations with the particular physiology of each species considered. Both specific composition and changes during maturation and ripening are reviewed.
Open Access
A global meta-analysis of greenhouse gases emission and crop yield under no-tillage as compared to conventional tillage
(Elsevier, 2021-01-01) Shakoor, Awais; Shahbaz, Muhammad; Farooq, Taimoor Hassan; Sahar, Najam E.; Shahzad, Sher Muhammad; Mohsin Altaf, Muhammad; Ashraf, Muhammad
No-tillage (NT) practice is extensively adopted with aims to improve soil physical conditions, carbon (C) sequestration and to alleviate greenhouse gases (GHGs) emissions without compromising crop yield. However, the influences of NT on GHGs emissions and crop yields remains inconsistent. A global meta-analysis was performed by using fifty peer-reviewed publications to assess the effectiveness of soil physicochemical properties, nitrogen (N) fertilization, type and duration of crop, water management and climatic zones on GHGs emissions and crop yields under NT compared to conventional tillage (CT) practices. The outcome reveals that compared to CT, NT increased CO2, N2O, and CH4 emissions by 7.1, 12.0, and 20.8%, respectively. In contrast, NT caused up to 7.6% decline in global warming potential as compared to CT. However, absence of difference in crop yield was observed both under NT and CT practices. Increasing N fertilization rates under NT improved crop yield and GHGs emission up to 23 and 58%, respectively, compared to CT. Further, NT practices caused an increase of 16.1% CO2 and 14.7% N2O emission in the rainfed areas and up to 54.0% CH4 emission under irrigated areas as compared to CT practices. This meta-analysis study provides a scientific basis for evaluating the effects of NT on GHGs emissions and crop yields, and also provides basic information to mitigate the GHGs emissions that are associated with NT practice.
Open Access
A manera d'Introducció : nitrats, aigua i agricultura, un problema modern d'ús del sòl
(Institució Catalana d’Estudis Agraris, 1999) Boixadera Llobet, Jaume; Cortés Lucas, Amparo
Open Access
A method based on high‐frequency temperature measurements to estimate the sensible heat flux avoiding the height dependence
(American Geophysical Union, 2002) Castellví Sentís, Francesc; Pérez García, Pedro J.; Ibáñez, Manuel
A new method to estimate the sensible heat flux H using high‐frequency temperature data has been proposed. The new method proposes to scale the mean eddy vertical velocity responsible for the air parcels renewal using similarity formulae. It is shown that the empirical coefficient resulting from this scaling (apparently height dependant) is relatively constant with height when comparing estimated versus measured H over half hour periods. This work suggests that the coefficient is universal. This allows to us to propose a new method that provides useful advantages for field applications.
Restricted
A method for livestock waste management planning in NE Spain
(Elsevier, 2003) Teira Esmatges, Maria Rosa; Flotats i Ripoll, Xavier
A method of decision-making on livestock wastes management in areas with nutrient surplus due to high livestock density is applied in Catalonia (NE Spain). Nutrient balance is made considering soil nitrogen application as the limiting factor. Special attention is paid to the centralized treatment option. The method presented consists of: 1. minimizing livestock waste generation (at farm scale) as a step previous to any other, both in amount and limiting components, 2. applying the nitrogen balance method at regional and municipal scale and providing enough storage capacity in order to apply wastes in an agronomically correct way, 3. spatially refining the results of the nitrogen balance by a proposed method that allows precisely pinpointing the hotspots of livestock waste generation, where centralized treatment might be an interesting option, and 4. deciding on the waste treatment objectives, provided that treatments be necessary. Knowledge about the wastes, meeting the interests and merging the efforts of the various actors, as well as an adequate budget are necessary ingredients for the success of any waste management plan.
Open Access
A new Leafiness-LiDAR index to estimate light interception in intensive olive orchards
(2023-07) Sandonís Pozo, Leire; Martínez Casasnovas, José Antonio; Escolà i Agustí, Alexandre; Rosell Polo, Joan Ramon; Rufat i Lamarca, Josep; Pascual Roca, Miquel
Canopy light interception constitutes an important yield limiting factor in high density olive orchards. However, its characterisation still implies laborious measurements. A new index, the Leafiness-LiDAR index (LLI), is presented as a LAI estimator. LLI combines LiDAR-derived parameters: Cross-Section and Leafiness from 3D point clouds. To validate the results, photosynthetically active radiation (PAR) measurements, canopy volume, yield and quality parameters were collected and analysed. LLI showed significant correlations both with PAR and canopy volume (r = 0.8) and quality parameters (r = -0.6). LLI may be useful as an early decision canopy monitoring tool in the framework of Precision Fructiculture.
Restricted
A novel carotenoid, 4-keto-a-carotene, as an unexpected by-product during genetic engineering of carotenogenesis in rice callus
(Elsevier, 2014) Breitenbach, Jürgen; Bai, Chao; Rivera Vélez, Sol Maiam; Canela i Garayoa, Ramon; Capell Capell, Teresa; Christou, Paul; Zhu, Changfu; Sandmann, Gerhard
Rice endosperm is devoid of carotenoids because the initial biosynthetic steps are absent. The early carotenogenesis reactions were constituted through co-transformation of endosperm-derived rice callus with phytoene synthase and phytoene desaturase transgenes. Subsequent steps in the pathway such as cyclization and hydroxylation reactions were catalyzed by endogenous rice enzymes in the endosperm. The carotenoid pathway was extended further by including a bacterial ketolase gene able to form astaxanthin, a high value carotenoid which is not a typical plant carotenoid. In addition to astaxanthin and precursors, a carotenoid accumulated in the transgenic callus which did not fit into the pathway to astaxanthin. This was subsequently identified as 4-keto-a-carotene by HPLC co-chromatography, chemical modification, mass spectrometry and the reconstruction of its biosynthesis pathway in Escherichia coli. We postulate that this keto carotenoid is formed from a-carotene which accumulates by combined reactions of the heterologous gene products and endogenous rice endosperm cyclization reactions.
Open Access
A proposal of nitrogen balance in a very high density olive orchard
(El Oued University, 2016) Belguerri, Hemza; Villar Mir, Josep Ma.; Pascual Roca, Miquel; Fatmi, A.; Amadeu, A.; Rufat i Lamarca, Josep
The nitrogen (N) balance was estimated in a very high density olive orchard in north- east of Spain, in order to calculate the inputs and outputs of N related to tree response and soil nitrogen availability. The calculate N inputs and outputs showed that N exported by yield and pruning material were higher for fertilized plots than unfertilized ones, and no significant differences were recorded for nitrogen mineralization between both treatments. N balance, defined as the difference between inorganic N content in soil at the end and the beginning of each year, was positive for both treatments but when vegetative growth and olive yield were compared, fertilized plots showed higher values, So it is wrong noting that a positive N balance in both case means that olive tree will provide a peak yield and vegetative growth but it is an adaptation of the olive trees to different soil N availability conditions by equilibrating their vegetative growth and fruit yield.
Restricted
A rapid and reliable direct method for quantifying meat acylglycerides with monomode microwave irradiation
(Elsevier, 2009) Tomàs, Albert; Tor i Naudí, Marc; Villorbina Noguera, Gemma; Canela i Garayoa, Ramon; Balcells Fluvià, Mercè; Eras i Joli, Jordi
A rapid methodology for direct analysis of meat acylglycerides is proposed. A transesterification is carried out in a microwave reactor consisting of a monomode oven using chlorotrimethylsilane (CTMS) and methanol. High-temperature gas chromatography was used to check the absence of underivatized acylglycerides. Whereas transesterification is complete after 30 s at 90 °C in the microwave method, the reference method needs 2 h to complete this process. Moreover, the CTMS–microwave method shows higher recoveries of individual saturated, monounsaturated and polyunsaturated fatty acids. No influence of microwave irradiation on the composition of the fatty acids was observed.
Restricted
A rapid gas chromatographic injection-port derivatization method for the tandem mass spectrometric determination of patulin and 5-hydroxymethylfurfural in fruit juices
(Elsevier, 2016) Marsol i Vall, Alexis; Balcells Fluvià, Mercè; Eras i Joli, Jordi; Canela i Garayoa, Ramon
A novel method consisting of injection-port derivatization coupled to gas chromatography–tandem mass spectrometry is described. The method allows the rapid assessment of 5-hydroxymethylfurfural (HMF) and patulin content in apple and pear derivatives. The chromatographic separation of the compounds was achieved in a short chromatographic run (12.2 min) suitable for routine controls of these compounds in the fruit juice industry. The optimal conditions for the injection-port derivatization were at 270 °C, 0.5 min purge-off, and a 1:2 sample:derivatization reagent ratio (v/v). These conditions represent an important saving in terms of derivatization reagent consumption and sample preparation time. Quality parameters were assessed for the target compounds, giving LOD of 0.7 and 1.6 μg/kg and LOQ of 2 and 5 μg/kg for patulin and HMF, respectively. These values are below the maximum patulin concentration in food products intended for infants and young children. Repeatability (%RSD n = 5) was below 12% for both compounds. In addition, the method linearity ranged between 25 and 1000 μg/kg and between 5 and 192 μg/kg for HMF and patulin, respectively. Finally, the method was applied to study HMF and patulin content in various fruit juice samples.
Open Access
A review on electrochemical methods for trace metal speciation in environmental media
(Elsevier, 2017) Companys Ferran, Encarnació; Galceran i Nogués, Josep; Pinheiro, Jose Paulo; Puy Llorens, Jaume; Salaün, Pascal
Trace metal speciation is key to understand/predict bioavailability and potential toxicity of metals to biota and will, undoubtedly, be incorporated in future regulations. Electroanalytical methods have a role to play in such development: they offer a wide range of advantages such as speed, portability, economy, solid interpretation backgrounds and low limits of quantification. This review focusses on three selected stripping techniques: Competitive-Ligand Exchange - Cathodic Stripping Voltammetry (CLE-CSV), Scanned Stripping Chrono-Potentiometry (SSCP) and AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) reporting their working principles, characteristics (strong and weak points) and recent applications to systems of environmental relevance (such as seawaters, freshwaters or soil extracts).
Open Access
A semi-grand canonical Monte Carlo simulation model for ion binding to ionizable surfaces: Proton binding of carboxylated latex particles as a case study
(American Institute of Physics, 2011) Madurga, Sergio; Rey Castro, Carlos; Pastor, Isabel; Vilaseca i Font, Eudald; David, Calin; Garcés, Josep Lluís; Puy Llorens, Jaume; Mas i Pujadas, Francesc
In this paper, we present a computer simulation study of the ion binding process at an ionizable surface using a semi-grand canonical Monte Carlo method that models the surface as a discrete distribution of charged and neutral functional groups in equilibrium with explicit ions modelled in the context of the primitive model. The parameters of the simulation model were tuned and checked by comparison with experimental titrations of carboxylated latex particles in the presence of different ionic strengths of monovalent ions. The titration of these particles was analysed by calculating the degree of dissociation of the latex functional groups vs. pH curves at different background salt concentrations. As the charge of the titrated surface changes during the simulation, a procedure to keep the electroneutrality of the system is required. Here, two approaches are used with the choice depending on the ion selected to maintain electroneutrality: counterion or coion procedures. We compare and discuss the difference between the procedures. The simulations also provided a microscopic description of the electrostatic double layer (EDL) structure as a function of pH and ionic strength. The results allow us to quantify the effect of the size of the background salt ions and of the surface functional groups on the degree of dissociation. The non-homogeneous structure of the EDL was revealed by plotting the counterion density profiles around charged and neutral surface functional groups. © 2011 American Institute of Physics.