Física Aplicada II

URI permanente para esta comunidadhttps://hdl.handle.net/11441/10853

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129I in sediment cores from the Celtic Sea by AMS through a microwave digestion process
(Elsevier, 2022) Lérida Toro, Victoria; Abascal Ruíz, Unai; Villa Alfageme, María; Klar, Jessica K.; Hicks, Natalie; López Gutiérrez, José María; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Física Aplicada I
Radiochemical methods before measurement are indispensable to determine Iodine-129 by Accelerator Mass Spectrometry (AMS) in environmental samples. In particular, in sediments, iodine is associated with both inorganic and organic matter, and it presents in several chemical forms. Therefore, the radiochemical procedure must be designed to extract all the different iodine species from the matrix, whilst being as robust and time effective as possible. In this work, different microwave digestion methods, together with the processing of the iodine species to be measured by AMS, were tested and their performances are presented here. Two sediment cores, one with muddy sediment (core A) and one with permeable sandy sediment (core I), collected in the Celtic Sea, were used and the results were evaluated to determine an optimized iodine extraction. The method consisted of a microwave digestion with concentrated nitric acid followed by a double liquid–liquid extraction and the final precipitation of silver iodide (AgI), required to measure iodine by AMS. Back extraction of iodine in a reducing solution during purification was carried out with hydrazine (NH2-NH2). Subsequent additional steps were added to optimize all iodine species extraction. First, hydrochloric hydroxylamine (NH2OH⋅HCl) and so dium bisulfite (Na2S2O5) were used to homogenize all iodine species before extraction through a redox process. Second, sodium hypochlorite (NaOCl) was added to remove any final organic matter after digestion. The final method incorporated sodium hydroxide (NaOH) combined with NaOCl to facilitate reduction of iodine in so lution and enhance the NaOCl effect. The different methods were validated against an internal standard and the last method was chosen, as it showed the most reproducible and accurate results. As practical application, Iodine129 concentration from both cores were compared, showing concentrations between 0.19 × 1012 at/kg and 7.16 × 1012 at/kg for core A and between 0.28 × 1012 at/kg and 2.40 × 1012 at/kg for core I. Despite the 129I diffusion detected in the deeper layers, depth profiles accurately reproduced Sellafield discharges, which is the nuclear fuel reprocessing plant closest to the cores.
129I, 236U, 239Pu and 240Pu profiles in a peatbog from the Southern Hemisphere
(2016) Chamizo, E.; López Gutiérrez, José María; Holm, Elis; García-Tenorio García-Balmaseda, Rafael; Universidad de Sevilla. Departamento de Física Aplicada II
129I, 236U, 239Pu and 240Pu isotopes have been analyzed in the different layers of a peatbog core collected in Madagascar Island (South Hemisphere) and representing at least the last 100 years of atmospheric deposition. The determination of ultra-low levels of these isotopes has been possible by applying the Accelerator Mass Spectrometric Technique (AMS) by using the 1 MV Tandetrom AMS facility located at CNA (Seville, Spain). The elements of interest were extracted and isolated previous to the measurements by applying validated radiochemical procedures. In this contribution, the behavior along the core of the different isotopes under analysis will be discussed, evaluating in particular the magnitude of their post-depositional retention/migration. In this sense, it will be highlighted the great mobility of the 129I with a near uniform profile along the core, in opposition for example with the preservation for the Pu isotopes of the fallout bomb peak. In the case of 236U, the 236U/239Pu atomic ratios determined in a total of eight layers of the core are ranging in the interval 0.02 – 0.29 with an average value of 0.15. As far as we know, these are the first 236U results seeing the light that were obtained in deposits as peatbogs collected in the southern hemisphere.
210Po levels and distribution in different environmental compartments from a coastal lagoon. The case of Briozzo lagoon, Uruguay
(Elsevier, 2020) Bañobre, Cristina; Díaz Francés, Inmaculada; Scarabino, Fabrizio; Fornaro, Laura; García-Tenorio García-Balmaseda, Rafael; Universidad de Sevilla. Departamento de Física Aplicada II
This paper presents the levels and distribution of 210Po in different compartments of a coastal lagoon on the east coast of Uruguay (South America). Activity concentrations of 210Po have been obtained in different matrices, such as water, superficial sediments, clams (Diplodon sp.), freshwaters snails (Pomacea sp.), zooplankton, and fishes (Jenynsia sp.), collected at different points of the lagoon and during several sampling campaigns. In addition, the organic matter content of the sediment was determined to study the variation of 210Po along the lagoon. The activity concentrations of 210Po in the water samples are in the range between 1.1 ± 0.2–3.5 ± 0.4 mBq/L while in the sediment samples vary between 17.1 ± 1.4 and 540 ± 12 Bq/kg, DW. In the case of biota, the ranges obtained were 182 ± 5–265 ± 6 Bq/kg, DW in clams and 134 ± 4–1245 ± 16 Bq/kg, DW in snail samples. A good correlation of 210Po with the organic fractions of the sediment was observed (r ¼ 0.8798, p-value < 0.001), being obtained high values for the distribution coefficient Kd (104 -105 ). In the biota samples, a clear difference was observed in the 210Po concentration values in both species, mainly due to the different feeding habits of both aquatic organisms, as it is reflected in the associated concentration ratios (CR). In this paper, a good set of results of 210Po, Kd, and CR have been obtained in different matrices, enhancing the limited archives available for modelers concerning these parameters for 210Po and freshwater systems.
226Ra, 210Po and lead isotopes in a pit lake water profile in Sweden
(Elsevier, 2020-11) Thomas, R.; Mantero Cabrera, Juan; Pérez Moreno, Silvia María; Ruiz Cánovas, Carlos; Vioque Romero, Ignacio; Isaksson, M.; Forssell-Aronsson, E.; Holm, E.; García-Tenorio García-Balmaseda, Rafael; Universidad de Sevilla. Departamento de Física Aplicada II; Swedish Radiation Safety Authority; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
A pit lake arises as a consequence of anthropogenic activities in opencast mining areas. These water bodies may be enriched in hazardous stable contaminants and/or in naturally occurring radionuclides depending on the local geological conditions. Mining legacy in Sweden produced hundreds of these pit lakes and most of them are used for recreational purposes in the southern part of the country. In this paper, one pit lake was selected for having enhanced levels of natural radionuclides. Physico-chemical parameters (temperature, pH, oxidation-reduction potential, dissolved oxygen and depth), elemental composition (via Inductive Coupled Plasma Mass Spectrometry) and radiometric characterization (via alpha spectrometry of 226Ra, 210Po and 210Pb) were carried along the depth of a 60 m depth pit lake, with the main aim to describe how natural radionuclides and elements behaves with depth in a non-uraniferous pit lake. Based on observed changes in physico-chemical parameters, a thermocline and a chemocline region were identified at around 10 and 30 m depth respectively. Concerning radionuclides, 226Ra ranged from 75 ± 3 up to 360 ± 12 mBq/kg while 210Po ranged from 11 ± 1 up to 71 ± 3 mBq/kg. 210Pb distribution with depth was also determined via secular equilibrium with 210Po after 2 years and also stable Pb was measured. Disequilibrium 226Ra-210Pb was found and the residence time of 210Pb in the water column was assessed. Additionally, different vertical distributions between 210Pb and Pb were found which points out different sources for different lead isotopes in the water body.
234Th-derived particle fluxes and seasonal variability: when is the ss assumption reliable? Insights from a novel Approach for carbon flux simulation
(AGU Publications, 2018-12) Ceballos Romero, Elena; Soto, Feliciano de; Le Moigne, Frederic; García-Tenorio García-Balmaseda, Rafael; Villa Alfageme, María; Universidad de Sevilla. Departamento de Física Aplicada II; Fundación la Caixa; Universidad de Sevilla; Spanish MICINN Spanish Government
Th measurements are widely used to estimate the downward carbon ﬂux of particles via the oceanic Biological Pump. Carbon export is evaluated from 234Th-238U disequilibrium assuming either steady state (SS) conditions, or including a non-SS (NSS) correction. We use a novel stochastic simulation to quantify the temporal variation of vertical carbon and 234Th (dissolved and particulate) concentration proﬁles with high temporal resolution. We calculate seasonal export as if in situ measured with sediment trap and SS- and NSS-234ThapproachesandquantifytheperiodsofvalidityforSS/NSSconditionsdeﬁnedinpreviousworks.The SS approach is valid throughout the entire season in oligotrophic regions. In temperate regions, the SS introduces a bias in the export if sampling takes place outside speciﬁc temporal windows. Windows of validity range from days in short blooms of ~15-day duration to weeks in blooms longer than ~30 days.
239Pu sorption by suspended matter from Hueznar reservoir (southern Spain): Experimental and modelling study
(E. D. P. Sciences, 2005) El Mrabet, Rachid; Barros Rojas, Haydn; Abril Hernández, José María; Manjón Collado, Guillermo; García-Tenorio García-Balmaseda, Rafael; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Física Aplicada II; ENRESA
Kinetic transfer coefficients are important parameters to understand and reliably model the behaviour of non-conservative radionuclides in aquatic environments. This report pertains to a series of radiotracer experiments on 239Pu uptake in natural unfiltered waters from the Hueznar reservoir (southern Spain). The experimental procedure ensures the preservation of environmental conditions and the dissolved Pu activity was measured by liquid scintillation technique. The data suggest that the main pathways for Pu uptake consist of two parallel and reversible reactions. We studied the effects of suspended matter concentrations and the specific surface area on the kinetic transfer coefficients.
239PU, 240PU, and 241AM Determination in Hot Particles by Low Level Gamma-Spectrometry
(American Chemical Society, 2010) Jiménez Ramos, María del Carmen; Hurtado Bermúdez, Santiago José; Chamizo, E.; García-Tenorio García-Balmaseda, Rafael; León Vintró, Luis; Mitchell, P. I.; Universidad de Sevilla. Departamento de Física Aplicada II
A nondestructive method based on low-energy, highresolution photon spectrometry is presented which allows accurate determination of 239Pu, 240Pu, and 241Am (as a daughter of 241Pu) activities in radioactive particles containing relatively high levels of plutonium isotopes. The proposed method requires only one measurement for the establishment of an absolute efficiency curve. Since the density and composition of the radioactive particles of interest may vary, a self-absorption correction is required for the accurate determination of isotopic activities and ratios. This correction is carried out for each individual particle using the convenient gamma-ray emissions of 241 Am.
3D information-theoretic analysis of the simplest hydrogen abstraction reaction
(American Chemical Society, 2023-07-21) Esquivel Olea, Rodolfo Octavio; Molina Espíritu, Moyocoyani; López Rosa, Sheila; Universidad de Sevilla. Departamento de Física Aplicada II; Ministerio de Economia, Industria y Competitividad (MINECO). España; Junta de Andalucía; Universidad de Granada; Universidad de Sevilla. FQM239: Fundamentos de Mecánica Cuántica
We investigate the course of an elementary chemical reaction from the perspective of information theory in 3D space through the hypersurface of several information-theoretic (IT) functionals such as disequilibrium (D), Shannon entropy (S), Fisher information (I), and the complexity measures of Fisher-Shannon (FS) and López-Mancini-Calbet (LMC). The probe for the study is the hydrogenic identity abstraction reaction. In order to perform the analysis, the reactivity pattern of the reaction is examined by use of the aforementioned functionals of the single-particle density, which is analyzed in position (r) and momentum (p) spaces. The 3D analyses revealed interesting reactivity patterns in the neighborhood of the intrinsic reaction coordinate (IRC) path, which allow to interpret the reaction mechanism for this reaction in a novel manner. In addition, the chemically interesting regions that have been characterized through the information functionals and their complexity measures are depicted and analyzed in the framework of the three-dimensional structure of the information-theoretical data of a chemical reaction, that is, the reactant/product (R/P) complexes, the transition state (TS), and the ones that are only revealed through IT measures such as the bond-cleavage energy region (BCER), the bond-breaking/forming (B-B/F) region, and the spin-coupling (SC) process. Furthermore, focus has been placed on the diagonal part of the hypersurface of the IT functionals, aside from the IRC path itself, with the purpose of analyzing the dissociation process of the triatomic transition-state complex that has revealed other interesting features of the bond-breaking (B-B) process. In other respects, it is shown throughout the combined analyses of the 3D structure of the IT functionals in conjugated spaces that the chemically significant regions occurring at the onset of the TS are completely characterized by information-theoretic aspects of localizability (S), uniformity (D), and disorder. Further, novel regions of low complexity seem to indicate new boundaries for chemically stable complex molecules. Finally, the study reveals that the chemical reaction occurs at low-complexity regions, where the concurrent phenomena take place: bond-breaking/forming (B-B/F), bond-cleavage energy reservoirs (BCER), spin-coupling (SC), and transition state (TS).
90Sr and 89sr in seawater off Japan as a consequence of the Fukushima Dai-ichi nuclear accident
(2013) Casacuberta, Nuria; Masqué, Pere; García Orellana, J.; García-Tenorio García-Balmaseda, Rafael; Buesseler, Ken O.; Universidad de Sevilla. Departamento de Física Aplicada II; Gordon and Betty Moore Foundation; Chemical Oceanography Program of the US National Science Foundation; Woods Hole Oceanographic Institution
The impact of the earthquake and tsunami on theeast coast of Japan on 11 March 2011 caused a loss of powerat the Fukushima Dai-ichi nuclear power plant (NPP) thatresulted in one of the most important releases of artificialradioactivity into the environment. Although several workswere devoted to evaluating the atmospheric dispersion of ra-dionuclides, the impact of the discharges to the ocean hasbeen less investigated. Here we evaluate the distribution ofFukushima-derived90Sr (n=57) and89Sr (n=19) through-out waters 30–600 km offshore in June 2011. Concentrationsof90Sr and89Sr in both surface waters and shallow profilesranged from 0.8±0.2 to 85±3 Bq m−3and from 19±6 to265±74 Bq m−3, respectively. Because of its short half-life,all measured89Sr was due to the accident, while the90Srconcentrations can be compared to the background levels inthe Pacific Ocean of about 1.2 Bq m−3. Fukushima-derivedradiostrontium was mainly detected north of Kuroshio Cur-rent, as this was acting as a southern boundary for transport.The highest activities were associated with near-shore ed-dies, and larger inventories were found in the closest stationsto Fukushima NPP. The data evidence a major influence ofdirect liquid discharges of radiostrontium compared to theatmospheric deposition. Existing137Cs data reported fromthe same samples allowed us to establish a90Sr /137Cs ratioof 0.0256±0.0006 in seawater off Fukushima, being signif-icantly different than that of the global atmospheric fallout(i.e., 0.63) and may be used in future studies to track waterscoming from the east coast of Japan. Liquid discharges of of90Sr to the ocean were estimated, resulting in an inventory of53±1 TBq of90Sr in the inshore study area in June 2011 andtotal releases of90Sr ranging from 90 to 900 TBq, dependingupon the reported estimates of137Cs releases that are consid-ered.
A benchmark for Monte Carlo simulation in gamma-ray spectrometry
(Elsevier, 2019-12) Lépy, M. C.; Thiam, C.; Anagnostakis, M.; Galea, R.; Gurau, D.; Hurtado Bermúdez, Santiago José; Karfopoulos, K.; Liang, J.; Liu, H.; Luca, A.; Mitsios, I.; Potiriadis, C.; Savva, M. I.; Thanh, T. T.; Thomas, V.; Townson, R. W.; Vasilopoulou, T.; Zhang, M.; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
Monte Carlo (MC) simulation is widely used in gamma-ray spectrometry, however, its implementation is not always easy and can provide erroneous results. The present action provides a benchmark for several MC software for selected cases. The examples are based on simple geometries, two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The action outputs (input files and efficiency calculation results, including practical recommendations for new users) are made available on a dedicated webpage.
A comparative evaluation of the CF:CS and CRS models in 210Pb chronological studies applied to hydrographic basins in Brazil
(Elsevier, 2014) Bonotto, Daniel Marcos; García-Tenorio García-Balmaseda, Rafael; Universidad de Sevilla. Departamento de Física Aplicada II
The Constant Flux: Constant Sedimentation (CF:CS) and Constant Rate of Supply (CRS) of unsupported⧸ excess 210Pb models have been applied to a 210Pb data set providing of eighteen sediments profiles sampled at four riverine systems occurring in Brazil, South America: Corumbataí River basin (S1¼Site 1, São Paulo State), Atibaia River basin (S2¼Site 2, São Paulo State), Ribeirão dos Bagres basin (S3¼Site 3, São Paulo State) and Amazon River mouth (S4¼Site 4, Amapá State). These sites were chosen for a comparative evaluation of the performance of the CF:CS and CRS models due to their pronounced differences on the geographical location, geological context, soil composition, biodiversity, climate, rainfall, and water flow regime, among other variable aspects. However, all sediments cores exhibited a common denominator consisting on a database built from the use of the same techniques for acquiring the sediments major chemical composition (SiO2, Al2O3, Na2O, K2O, CaO, MgO, Fe2O3, MnO, P2O5, TiO2 and LOI-Loss on Ignition) and unsupported⧸excess 210Pb activity data. In terms of sedimentation rates, the performance of the CRS model was better than that of the CF:CS model as it yielded values more compatible with those expected from field evidences. Under the chronological point of view, the CRS model always provided ages within the permitted range of the 210Pb-method in the studied sites, whereas the CF:CS model predicted some values above 150 years. The SiO2 content decreased in accordance with the LOI increase in all cores analyzed and such inverse relationship was also tracked in the SiO2–LOI curves of historical trends. The SiO2–LOI concentration fluctuations in sites S1 and S3 also coincided with some Cu and Cr inputs in the drainage systems.
A comparison of 210Pbxs, 137Cs, and Pu isotopes as proxies of soil redistribution in South Spain under severe erosion conditions
(Springer, 2023-06-01) Peñuela Fernández, Andrés; Hurtado Bermúdez, Santiago José; García Gamero, Vanesa; Más Balbuena, José Luis; Ketterer, M. E.; Vanwalleghem, Tom; Gómez Calero, José Alfonso; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Física Aplicada I; Ding, Shiming; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Universidad de Sevilla; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
Purpose The use of fallout radionuclides as proxies for the study of soil redistribution processes in semiarid environments of Southern Spain has been restricted to 137Cs. The potential and limitations of alternative proxies such as 239+240Pu and 210Pbxs should be explored given the expected constrains imposed by the features of the study area. Materials and methods Four soil and one sediment cores were collected in a highly eroded area to test the feasibility of these proxies under demanding conditions. The use of gamma spectrometry and ICP-MS did allow exploring the potential of 210Pbxs and Pu isotopes against the well-established tracer, 137Cs. The activity ratios 239+240Pu/137Cs were explored to evaluate the previous evolution of the sampling sites. Soil redistribution rates were estimated using the model MODERN. Results and discussion Despite all the profles showed intense perturbation, Pu isotopes showed the highest potential thanks to higher sensitivity and sample throughput. The deviations of 239+240Pu/137Cs inventory ratios (0.012–0.158) from the global fallout average (0.026±0.003) suggest that the sediment core was a deposition site involving alternate episodes of topsoil removal and incorporation from diferent sources. The calculated erosion rates ranged 34–43 t ha−1 year−1, being in good agreement for 137Cs and 239+240Pu. 210Pbxs was not used due to low-quality data. Conclusions The use of Pu as a tracer of soil redistribution processes in semiarid areas seems to be promising even under severe erosion conditions. The use of 210Pbxs is not recommended in this area due to its low concentration.
A comparison of two micro-beam X-ray emission techniques for actinide elemental distribution in microscopic particles originating from the hydrogen bombs involved in the Palomares (Spain) and Thule (Greenland) accidents
(Elsevier, 2010) Jiménez Ramos, María del Carmen; Eriksson, Mats; García López, Francisco Javier; Ranebo, Y.; García-Tenorio García-Balmaseda, Rafael; Betti, Marco; Holm, Elis; Universidad de Sevilla. Departamento de Física Aplicada II
In order to validate and to gain confidence in two micro-beam techniques: particle induced X-ray emission with nuclear microprobe technique (μ-PIXE) and synchrotron radiation induced X-ray fluorescence in a confocal alignment (confocal SR μ-XRF) for characterization of microscopic particles containing actinide elements (mixed plutonium and uranium) a comparative study has been performed. Inter-comparison of the two techniques is essential as the X-ray production cross-sections for U and Pu are different for protons and photons and not well defined in the open literature, especially for Pu. The particles studied consisted of nuclear weapons material, and originate either in the so called Palomares accident in Spain, 1966 or in the Thule accident in Greenland, 1968. In the determination of the average Pu/U mass ratios (not corrected by self-absorption) in the analysed microscopic particles the results from both techniques show a very good agreement. In addition, the suitability of both techniques for the analysis with good resolution (down to a few μm) of the Pu/U distribution within the particles has been proved. The set of results obtained through both techniques has allowed gaining important information concerning the characterization of the remaining fissile material in the areas affected by the aircraft accidents. This type of information is essential for long-term impact assessments of contaminated sites
A dosimetric model for determining the effectiveness of soil covers for phosphogypsum waste piles
(Lippincott, 2001) Más Balbuena, José Luis; Bolívar, Juan Pedro; García-Tenorio García-Balmaseda, Rafael; Aguado Casas, Juan Luis; Gutiérrez San Miguel, Enrique; González Labajo, Jesús; Universidad de Sevilla. Departamento de Física Aplicada II
Phosphogypsum (PG) is a by-product of the phosphoric acid production process that contains high concentrations of U-series radionuclides. PG piles formed during the last 30 years cover about 1,200 hectares and are located close to the town of Huelva (Spain) on a salt-marsh. The regional government of Andalusia restored the area beginning in 1990 by covering it with a 25-cm-thick layer of natural soil. With this restoration, the external gamma-dose rate in the zone has decreased drastically, approaching near environmental background values. This conclusion is based on results obtained through in-situ monitoring measurements and through a dosimetric model developed for that particular radiation source. As the model uses average parameters of the studied site, its output does not show a correlation point by point with the in-situ monitoring measurements. However, a good agreement is observed in average values over the covered piles. The model gives an average dose rate of 0.41 mGy y21 and the in situ monitoring 0.40 mGy y21 . Based on this model, it is possible to calculate the necessary thickness of soil to reduce the dosimetric contribution from a similar extension of PG until the desired level is reached. In our conditions, in a 25-cm-thick soil, about 0.19 mGy y21 is the increase produced by the PG layer in relation to an infinitum soil layer. Consequently, no radiological concern exists in the restored zones with respect to the external gamma radiation
A fitting algorithm based on simulated annealing techniques for efficiency calibration of HPGe detectors using different mathematical functions
(Elsevier, 2008) Hurtado Bermúdez, Santiago José; García León, Manuel; García-Tenorio García-Balmaseda, Rafael; Universidad de Sevilla. Departamento de Física Aplicada II
In this work several mathematical functions are compared in order to perform the full-energy peak efficiency calibration of HPGe detectors using a 126 cm3 HPGe coaxial detector and gamma-ray energies ranging from 36 to 1460 keV. Statistical tests and Monte Carlo simulations were used to study the performance of the fitting curve equations. Furthermore the fitting procedure of these complex functional forms to experimental data is a non-linear multi-parameter minimization problem. In gamma-ray spectrometry usually non-linear least-squares fitting algorithms (Levenberg–Marquardt method) provide a fast convergence while minimizing w2 R, however, sometimes reaching only local minima. In order to overcome that shortcoming a hybrid algorithm based on simulated annealing (HSA) techniques is proposed. Additionally a new function is suggested that models the efficiency curve of germanium detectors in gamma-ray spectrometry
A method for the determination of counting efficiencies in gamma-spectrometric measurements with HPGe detectors
(Elsevier, 1996) Bolívar, Juan Pedro; García-Tenorio García-Balmaseda, Rafael; García León, Manuel; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear
In this paper a general method for y-ray efficiency calibration is presented. The method takes into account the differences of densities and counting geometry between the real sample and the calibration sample. It is based on the y-transmission method and gives the correction factorf as a function of Ey, the density and counting geometry. Altough developed for soil samples, its underlying working philosophy is useful for any sample whose geometry can be adequately reproduced.
A new approach to process planktonic foraminifera for radiocarbon measurements
(2016) Guerra, Roberta; Santos Arévalo, Francisco Javier; García-Tenorio García-Balmaseda, Rafael; Universidad de Sevilla. Departamento de Física Aplicada II
Carbonate shells from foraminifera are often analyzed for radiocarbon to determine the age of deep-sea sediments or to assess radiocarbon reservoir ages. The Centro Nacional de Aceleradores (CNA) is equipped for the AMS radiocarbon analysis with a MICADAS (MIni CArbon DAting System), and a sample processing line including vial flushing, carbonate dissolution and transfer of the evolved CO2 from the septum sealed tubes to the automated graphitization equipment (AGE). In this work, we have tested a fullyautomated setup from sampling the released CO2 from small carbonate samples (i.e. foraminifera shells) for radiocarbon analysis, where the formed CO2 is later flushed by helium flow by means of a double-wall needle mounted from the tubes to the zeolite trap of the existing AGE-2. This carbonate dissociation line essentially replaces the elemental analyser normally used for the combustion of organic samples to further reduce the effort involved for sample preparation. The automated method yields in low sample blanks of about 50,000 years. Results of the processed reference materials (IAEA-C1 and IAEA-C2) are in agreement with their consensus values. Using this automated dissociation line we were able to date samples of monospecific foraminifera shells (~10 mg) of ~ 1000 radiocarbon years.
A new approach to process planktonic foraminifera for radiocarbon measurements [Poster]
(2016) Guerra, Roberta; Santos Arévalo, Francisco Javier; García-Tenorio García-Balmaseda, Rafael; Universidad de Sevilla. Departamento de Física Aplicada II
A new methodology for estimating rainfall aggressiveness risk based on daily rainfall records for multi-decennial periods
(Elsevier, 2018) García Barrón, Leoncio; Morales González, Julia; Sousa Martín, Arturo; Universidad de Sevilla. Departamento de Biología Vegetal y Ecología; Universidad de Sevilla. Departamento de Física Aplicada II
The temporal irregularity of rainfall, characteristic of a Mediterranean climate, corresponds to the irregularity of the environmental effects on soil. We used aggressiveness as an indicator to quantify the potential environmental impact of rainfall. However, quantifying rainfall aggressiveness is conditioned by the lack of sub-hourly frequency records on which intensity models are based. On the other hand, volume models are characterized by a lack of precision in the treatment of heavy rainfall events because they are based on monthly series. Therefore, in this study, we propose a new methodology for estimating rainfall aggressiveness risk. A new synthesis parameter based on reformulation using daily data of the Modified Fournier and Oliver's Precipitation Concentration indices is defined. The weighting of both indices for calculating the aggressiveness risk is established by multiple regression with respect to the local erosion R factor estimated in the last decades. We concluded that the proposed methodology overcomes the previously mentioned limitations of the traditional intensity and volume models and provides accurate information; therefore, it is appropriate for determining potential rainfall impact over long time periods. Specifically, we applied this methodology to the daily rainfall time series from the San Fernando Observatory (1870–2010) in southwest Europe. An interannual aggressiveness risk series was generated, which allowed analysis of its evolution and determination of the temporal variability. The results imply that environmental management can use data from long-term historical series as a reference for decision making.
A new numerical approach for efficient modeling of positive corona discharge and its associated electric wind
(IOP Publishing, 2023) Yanallah, Khelifa; Chelih, Amine; Bouazza, Mohamed Ridha; Pontiga Romero, Francisco de Paula; Bouadi, M.; Vázquez González, Pedro Ángel; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Física Aplicada III; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Universidad de Sevilla. FQM253: Electrohidronámica y Medios Granulares Cohesivos
Research on corona wind generation has been increasing in recent years because of its potential technological applications, particularly those related to improving heat transfer in small-scale devices. Since numerical simulations play a key role in the design of these applications, computationally efficient modeling of corona discharge is imperative. This work presents a new approach that allows rapid computation of the electrohydrodynamic (EHD) force density responsible for the generation of electric wind. Arbitrary electrode configurations can easily be dealt with in the model, since only the Laplacian electric field lines have to be determined numerically. Then, using approximated analytical approximations of the electric field intensity along the field lines, the spatial distribution of the current density and the space charge density can be easily determined. The model has been satisfactorily tested against experimental measurements of the current–voltage characteristic and the current density distribution on the cathode. Furthermore, the electric wind computed from the EHD force agrees quite satisfactorily with measurements carried out in different electrode configurations. Finally, the model has been applied to a new electrode configuration that has greater potential for heat transfer applications.

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