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Introducción a los objetivos y procedimiento de trabajo para realizar una práctica de laboratorio con el fin de determinar el calor específico de varias piezas de metal, empleando técnicas de calorimetría. La finalidad del recurso es proporcionar información descriptiva del procedimiento de trabajo en el laboratorio a alumnos de primer curso de grados en Ingeniería. El recurso explica cómo determinar el calor específico de varias piezas de metal, a partir de técnicas de calorimetría.

Introducción a los objetivos y procedimiento de trabajo para realizar una práctica de laboratorio con el fin de validar la Ley de Ohm en un circuito eléctrico La finalidad del recurso es proporcionar información descriptiva del procedimiento de trabajo en el laboratorio a alumnos de primer curso de grados en Ingeniería. El recurso explica cómo demostrar empíricamente la validez de la Ley de Ohm. Para ello, los alumnos deben aprender a usar equipos de medida de resistencia, tensión y corriente, además de construir un circuito eléctrico simple con resistencia y fuente de alimentación.

Introducción a los objetivos y procedimiento de trabajo para realizar una práctica de laboratorio con el fin de medir experimentalmente la capacidad de un condensador, a partir de una experiencia de carga. La finalidad del recurso es proporcionar información descriptiva del procedimiento de trabajo en el laboratorio a alumnos de primer curso de grados en Ingeniería. El recurso explica cómo caracterizar experimentalmente capacidad de un condensador. Para ello, los estudiantes deben construir un circuito con una resistencia, condensador y fuente de alimentación (circuito RC), y observar el proceso de carga del mismo. A partir de los datos obtenidos, los estudiantes deben ser capaces de determinar la capacidad del condensador.

Introducción a los objetivos y procedimiento de trabajo para realizar una práctica de laboratorio con el fin de comprobar el circuito equivalente obtenido a partir de una asociación de resistencias conectadas en (1) serie, y (2) paralelo. La finalidad del recurso es proporcionar información descriptiva del procedimiento de trabajo en el laboratorio a alumnos de primer curso de grados en Ingeniería. El recurso explica cómo construir un circuito empleando una asociación de resistencias en serie y posteriormente en paralelo, además de comprobar que las medidas de tensión, corriente y resistencia de cada diseño se corresponden con el modelo del circuito equivalente respectivo.

Introducción a los objetivos y procedimiento de trabajo para realizar una práctica de laboratorio con el fin de determinar experimentalmente el campo magnético de un imán, a partir del concepto de Fuerza de Lorentz y Balanza Magnética. La finalidad del recurso es proporcionar información descriptiva del procedimiento de trabajo en el laboratorio a alumnos de primer curso de grados en Ingeniería. El recurso explica cómo determinar experimentalmente el campo magnético de un imán a partir de la Fuerza Magnética de Lorentz. Para ello, los estudiantes disponen de diferentes montajes experimentales donde pueden observar la influencia de la longitud de un cable eléctrico, de la variación de intensidad aplicada, o del ángulo relativo entre el campo magnético y una espira. En todos los casos, a partir de la medida de la fuerza magnética y la variable seleccionada, el estudiante debe ser capaz de obtener el campo magnético del imán.

Radiometric dating was a revolutionary contribution to the study of sedimentary processes. Empirical data from varved sediments show that unsupported 210Pb (210Pbexc) fluxes vary over time while they statistically correlate with sediment accumulation rates (SAR). This contradicts the basic assumption of the Constant Rate of Supply (CRS) model, which is the most widely used technique for recent sediments. This work is aimed at assessing the CRS model-errors by quantifying the effects on chronologies of various patterns of temporal variability of fluxes. Results are discussed through applications with synthetic and real cores for which and independent varve chronology or a set of reference dates are available. Periodic harmonic and random fluctuations in fluxes tend to cancel out positive and negative deviations in CRS ages, but they produce spurious variability in SARs. Persistent changes in fluxes lead to cumulated and unacceptable deviations of the CRS ages, which cannot be satisfactorily compensated by the use of a piecewise CRS model. The raw and piecewise CRS models can still be powerful tools of widespread use when the conditions for their applicability are well understood. The paper shows how the analysis of clusters in the 210Pbexc vs mass depth profile, along with the estimation of equivalent constant fluxes pre and post-dating a known reference date, are powerful methods to prevent misapplications of the CRS model.

About six million years ago, the Mediterranean Sea underwent a period of isolation from the ocean and widespread salt deposition known as the Messinian Salinity Crisis (MSC), allegedly leading to a kilometer-scale level drawdown by evaporation. One of the competing scenarios proposed for the termination of this environmental crisis 5.3 million years ago consists of a megaflooding event refilling the Mediterranean Sea through the Strait of Gibraltar: the Zanclean flood. The main evidence supporting this hypothesis is a nearly 390 km long and several hundred meters deep erosion channel extending from the Gulf of Cádiz (Atlantic Ocean) to the Algerian Basin (Western Mediterranean), implying the excavation of ca. 1000 km3 of Miocene sediment and bedrock. Based on the understanding obtained from Pleistocene onshore megaflooding events and using ad-hoc hydrodynamic modeling, here we explore two predictions of the Zanclean outburst flood hypothesis: 1) The formation of similar erosion features at sills communicating sub-basins within the Mediterranean Sea, specifically at the Sicily Sill; and 2) the accumulation of the eroded materials as megaflood deposits in areas of low flow energy. Recent data show a 6-km-wide amphitheater-shaped canyon preserved at the Malta Escarpment that may represent the erosional expression of the Zanclean flood after filling the western Mediterranean and spilling into the Eastern Basin. Next to that canyon, a ~1600 km3 accumulation of chaotic, seismically transparent sediment has been found in the Ionian Sea, compatible in age and facies with megaflood deposits. Another candidate megaflood deposit has been identified in the Alborán Sea in the form of elongated sedimentary bodies that parallel the flooding channel and are seismically characterized by chaotic and discontinuous stratified reflections, that we interpret as equivalent to gravel and boulder megabars described in terrestrial megaflood settings. Numerical model predictions show that sand deposits found at the Miocene/Pliocene (M/P) boundary in ODP sites 974 and 975 (South Balearic and Tyrrhenian seas) are consistent with suspension transport from the Strait of Gibraltar during a flooding event at a peak water discharge of ~108 m3 s−1. © 2019 The Authors, Funding has been provided by the COST Action Medsalt CA15103 , by the ETN SaltGiant ( European Union funded , Horizon2020 , Marie Skłodowska-Curie grant agreement No 765256 and 674899 ) and by the Spanish public projects MITE ( CGL2014-59516 ) FAUCES ( CMT2015-65461-C2-R , MINECO / FEDER ) and DAMAGE (AEI/FEDER CGL2016-80687-R )., With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

European Geosciences Union (EGU) General Assembly, 4-8 May 2020., The Mediterranean Sea underwent restriction from the ocean and widespread salt deposition during the Messinian Salinity Crisis (MSC), allegedly leading to a kilometer-scale level drawdown by evaporation. One of the competing scenarios proposed for the termination of this environmental crisis 5.3 million years ago consists of a megaflooding event refilling the Mediterranean Sea through the Strait of Gibraltar: the Zanclean flood. The main evidence supporting this hypothesis is a nearly 390 km long and several hundred meters deep erosion channel extending from the Gulf of Cádiz (Atlantic Ocean) to the Algerian Basin (Western Mediterranean), implying the excavation of ca. 1000 km3 of Miocene sediment and bedrock.

This work reports results from numerical simulations of the tsunami triggered by 1995 Nuweiba earthquake, in the Gulf of Aqaba, which are consistent with the available observations. A series of 12 potential tsunamigenic sources are then considered in the Red Sea: related to major submarine earthquakes; volcanism (entry of pyroclastic flows and caldera collapse) and submarine landslides. Numerical simulations have been carried out to solve the spatial distribution of maximum amplitudes of water elevations and currents, and the flooded coastal areas. The peak energy in the simulated events range from 1 kt (1 kt=4.18×10 12 J) up to 1.5 Mt, and global flood volumes range from 0.005 km3 up to 4.4 km3. A linear correlation can be established between both magnitudes for the set of tsunamis triggered by earthquakes up to 300 kt. Tsunamis triggered by submarine landslides show high directionality, but they occur in deep waters and showed lower impacts on the shoreline, as those triggered by volcanism. A FFT analysis shows that in this basin, tsunamis excite low frequency constituents which can be interpreted as eigenmodes. High frequencies are excited only in the proximity of the source, and the Gulf of Suez excites only those eigenmodes close to the ones of the main basin.

The incision Zanclean Channel, which crosses the Strait of Gibraltar and the Alboran Sea, has been interpreted as the geological fingerprint of a cataclysmic stream of water which flowed from the Atlantic into a desiccated Mediterranean about 5.33MaBP. The mathematical support for this theory is provided by a simple conceptual model for hydrodynamics and erosion that, regardless of the initial conditions, leads to scenarios of catastrophic flooding (with water flows exceeding tens or hundreds of Sv which fill 90% of the Mediterranean in few months or few years). This paper revisits the incision model and carries out new numerical simulations of the Zanclean flood of the Mediterranean with a two-dimensional non-linear depth-averaged hydrodynamic model. The numerical output allows solving the equation for time. This way, it is possible to estimate the final incision and the involved time scales under different modelled scenarios. When lateral erosion is reformulated in terms of the causal processes instead of a questionable scaling law, initial conditions become relevant. Those involving narrow connecting channels can be discarded. A flooding scenario with an excavated channel of a few hundred meter depth can be achieved with the initial conditions of a wide sill covered by a water lamina. The threshold stress to initialize erosion must be surpassed in the very early stages of the flooding, which requires a catastrophic start up. Tectonics may have played a major role in it through strike–slip faulting.

18 pages, 13 figures, 2 tables, supplementary material https://doi.org/10.1007/s42452-019-0374-y, A nearly 400-km-long erosion channel through the Strait of Gibraltar has been interpreted as evidence for a catastrophic refill of the Mediterranean at the end of the Messinian salinity crisis, 5.33 million years ago. This channel extends from the Gulf of Cadiz to the Algerian Basin and implies the excavation of ca. 1000 km3 of Miocene sediment from the Alboran Basin and bedrock from the Strait of Gibraltar. The fate of these eroded materials remains unknown. In a first attempt to predict the distribution of those flood deposits, we develop a numerical model to simulate the transport of material eroded from the Strait of Gibraltar. It is a Lagrangian model based upon standard sediment transport equations which is able to simulate suspended and bed load sediment transport. Water circulation during the flood was obtained from a hydrodynamic model of the whole Mediterranean Sea previously developed by the authors and applied to the Zanclean flood. Five particle sizes were considered for suspended load and three for bed load transport. Areas of sediment deposition in the Mediterranean Sea were determined. In the case of suspended load, these are related to hydrodynamic conditions: areas sheltered from the jet of incoming water by local topography and areas where water currents abruptly decrease due to a sudden increase in water depth. In the case of bed load transport, sediments follow water streamlines and deposits are much more localized than in the case of suspended load. Single channel seismic records were also analysed to identify and characterize flood-related deposits in the eastern Alboran Sea, Work partially supported by the Spanish Project FAUCES CMT2015-65461-C2-R (MINECO/FEDER)

Theoretical and experimental studies have shown that activity concentrations of fallout radionuclides (such as 137Cs and excess 210Pb) decrease with particles size in aqueous suspensions. This paper is aimed at reviewing the theoretical fundamentals for granulometric speciation of radionuclides, and at exploring its practical use in the analytical context of gamma spectrometry for the radiometric dating of recent sediments, with view to: i) improving the detection of 137Cs (since its use as independent chronostratigraphic mark is challenging in the southern hemisphere because its low fallout rate), ii) supporting refined CIC models and normalization techniques in 210Pb-based radiogeochronologies. The work uses surface sediments sampled from the Tinto Estuary (SW Spain), affected by mining and phosphate-fertilizer industries, and from the Ankobra Estuary (Ghana), affected by intensive artisanal gold-mining. Granulometric classes have been separated by a sieving column with decreasing mesh sizes and the obtained cumulative percentage of mass mathematically described by a Rosin-Rammler particle-size distribution. The target radionuclides for gamma spectrometry were 210Pb, 226Ra and137Cs, complemented with 40K, 234Th and 228Ra. Results revealed that, far from ideal experiments, under actual environmental conditions the increase in activity concentrations with decreasing particle sizes is too moderate, and in general they are affected by larger counting uncertainties due to the small available amount of mass. Indeed, there was no correlation between grain-size and 137Cs concentrations (p = 0.25), and similarly for excess 210Pb (p = 0.53). No effect of the organic matter content was observed in 137Cs (p = 0.58) and excess 210Pb (p = 0.85) concentrations. Present results pose some concerns to the general use of granulometric speciation in the context of gamma spectrometry for supporting the radiometric dating of recent sediments. A detailed discussion on the use of normalization methods is also presented., The authors would like to extend gratitude to the International Atomic Energy Agency (IAEA) for supporting the Regional Project RAF7009 and the fellowship GHA -16025.

Ercilla, Gemma ... et al.-- 16 pages, 11 figures, 1 table, supplementary material https://doi.org/10.1016/j.dsr.2018.12.002, This is an interdisciplinary study that combines morphoseismics, sedimentology and numerical modelling to elucidate at different scales of resolution the influence of alongslope processes on the turbidite systems (TSs) and canyons in the Alboran Sea (southwestern Mediterranean). Nine TSs are mapped in the Spanish margin (La Linea, Guadiaro, Baños, Torrenueva, Fuengirola, Salobreña, Sacratif, Calahonda and Almeria) and two in the Alboran Ridge (Piedra Escuela and Al-Borani). In the Moroccan margin, there are only two canyons (Ceuta and Nekor). Distinctive morphoseismic and sedimentological signatures from TSs and canyons have enabled three regional models of alongslope influence to be distinguished: a) Alongslope processes are dominant. This scenario characterizes the canyons of the Moroccan margin. The diagnostic signature is the lack of leveed channels and lobes at the Ceuta and Nekor Canyon mouths. b) Different degrees of interplay exist between alongslope and downslope processes. This scenario occurs in the TSs of the western Spanish margin. Here, the alongslope influence on TSs (La Linea, Guadiaro, Baños, Torrenueva and Fuengirola) is evidenced by the lack of overbank deposits in the La Linea and Guadiaro Canyons and an alongslope trend in the morpho-architecture of the channelized lobes and in the textural distribution of canyon/channel deposits (mass-flow deposits and turbidites). Both signatures indicate sandier TSs as well as Bouma turbidite sequences lacking the finest levels towards the Strait of Gibraltar. Local intercalations of contourites are also present in the Guadiaro lobe deposits. c) Downslope processes are dominant. This scenario characterizes the TSs of the eastern and central Spanish margin and Alboran Ridge. There, TSs seem to be controlled solely by the characteristics of the downslope gravity flows that transport sediment. The hydrodynamic and sediment dispersion models confirm that the main oceanographic factors governing the variable alongslope influence in TSs and canyons are the following: a vigorous WMDW flow along the Moroccan margin and the energetic Atlantic Jet, western Atlantic anticyclonic gyre and general acceleration of the Mediterranean waters towards the Strait of Gibraltar, along the western Spanish margin. This study demonstrates the pivotal role that alongslope processes can play in the onset and formation of TSs and canyons at continental margins, This research is part of the Spanish projects FAUCES CMT2015-65461-C2-R (Ministerio de Economía y Competitividad-MINEICO/Fondo Europeo de Desarrollo Regional-FEDER), DAMAGE (Ministerio de Economía y Competitividad/ AEI/FEDER CGL2016-80687-R) and MARSIBAL (Ministerio de Ciencia y Tecnología, REN2001-3868-C03). This work also benefited from the French program Actions Marges, the EUROFLEETS (Towards an Alliance of European Research Fleets) program (FP7/2007-2013; n°228344), project FICTS-2011-03-01. Part of this work was completed with support from the IHS Kingdom Suite® educational license

Unsupported (210)Pb ((210)Pbexc) vs. mass depth profiles do not contain enough information as to extract a unique chronology when both, (210)Pbexc fluxes and mass sediment accumulation rates (SAR) independently vary with time. Restrictive assumptions are needed to develop a suitable dating tool. A statistical correlation between fluxes and SAR seems to be a quite general rule. This paper builds up a new (210)Pb-based dating tool by using such a statistical correlation. It operates with SAR and initial activities that closely follow normal distributions, what leads to the expected correlation between fluxes and SAR. An intelligent algorithm solves their best arrangement downcore to fit the experimental (210)Pbexc vs. mass depth profile, generating then solutions for the chronological line, and for the histories of SAR and fluxes. Parametric maps of a χ-function serve to find out the solution and to support error estimates. Optionally, the model's answers can be better constrained through the use of time markers. The performance of the model is illustrated with a synthetic core, and with real cases using published data for varved sediment cores.

Lead-210 from natural atmospheric fallout is widely used in multidisciplinary studies for dating recent sediments. In anthropogenically-impacted and/or high energy systems the 210Pb flux onto the sediments may show non-random temporal variability, leading to the failure of classical dating models. The problem of how identifying and dating such cases remained unsolved, and it is the goal of the present work. Empirical evidences from varved sediments prove that initial activity concentrations of excess 210Pb (210Pbexc) and sediment accumulation rates (SARs) show large and independent temporal variability. M-TERESA model describes such variability by using multimodal frequency distributions and decodes the chronology from the 210Pbexc versus mass depth profile. The new model can solve scenarios with largely varying rates of supply, which fall beyond the limits of the piecewise versions of the classical models. Its use is demonstrated with some complex 210Pbexc profiles from varved sediments and synthetic cores for which an alternative and complete reconstruction of palaeofluxes and SARs is possible. The paper is supported by a wide set of supplementary material, including numerical codes for applying TERESA. The proposed methods are also useful for improving the reliability of routinely applications of the 210Pb-based radiometric dating of recent sediments.

After half a century, the use of unsupported 210 Pb ( 210 Pb exc ) is still far off from being a well established dating tool for recent sediments with widespread applicability. Recent results from the statistical analysis of time series of fluxes, mass sediment accumulation rates (SAR), and initial activities, derived from varved sediments, place serious constraints to the assumption of constant fluxes, which is widely used in dating models. The Sediment Isotope Tomography (SIT) model, under the assumption of non post-depositional redistribution, is used for dating recent sediments in scenarios in that fluxes and SAR are uncorrelated and both vary with time. By using a simple graphical analysis, this paper shows that under the above assumptions, any given 210 Pb exc profile, even with the restriction of a discrete set of reference points, is compatible with an infinite number of chronological lines, and thus generating an infinite number of mathematically exact solutions for histories of initial activity concentrations, SAR and fluxes onto the SWI, with these two last ranging from zero up to infinity. Particularly, SIT results, without additional assumptions, cannot contain any statistically significant difference with respect to the exact solutions consisting in intervals of constant SAR or constant fluxes (both being consistent with the reference points). Therefore, there is not any benefit in its use as a dating tool without the explicit introduction of additional restrictive assumptions about fluxes, SAR and/or their interrelationship.

Numerical simulations of the Mediterranean Sea filling after the Messinian salinity crisis have been carried out with a two-dimensional non-linear depth-averaged hydrodynamic model. It overcomes simplifications and gross estimates of previous 0-D models. Erosion of the seabed has been implemented in the model domain. The highest erosion rates were found in the Alboran Island passage and in the eastern side of the Strait of Gibraltar. Regressive erosion, at a final stage, can account for the incision channel found in Camarinal Sill. This last limits the inflow to some 90 Sv when the cross-section in the eastern side becomes higher. Water level in the Mediterranean increases at a rate of a few meters per day. Detailed views of the induced circulation in the Mediterranean Sea have also been obtained.

A numerical model which simulates the propagation of tsunamis in the Eastern Mediterranean has been developed. Several tsunami sources have been considered: earthquakes associated to geological faults, submarine landslides, entry of pyroclastic flows into the sea and the collapse of a volcano caldera. The model has been applied to different past events for which historic data or previous simulations exist, to test its performance. Then it has been applied to simulate tsunamis triggered by the explosion of Santorini volcano (17th century BC) in the Aegean Sea. While the model accounts for run-ups in the Aegean coasts, it fails to explain the isochronous tsunamigenic deposits reported in eastern Sicily and the levantine coasts. A scenario of a sequence of intense tectonics strain release triggering a series of tsunamis could better fit the whole dataset. Thus, a submarine landslide at the Gulf of Sirte may explain the Augias megaturbidite and the sedimentary deposits reported in Augusta Bay (Sicily). Similarly, a sequential tsunami in the eastern Nile Delta may explain the tsunamigenic deposits found in Israel and Gaza. Considering the former coastline at 3500 years BP, it could also provide a plausible scenario for the biblical sea crossing related in the Exodus.

At least five catastrophic tsunami events have affected the Iberian Atlantic coasts during the last 7000 years. During this time, the former Gulf of Tartessos evolved towards the present marshland area, in the lower Guadalquivir valley (SW Spain). Ancient cultures flourished and vanished around this waterbody which, with its tidal dynamics, was an essential part of their living environment. A numerical modeling study on oceanographic conditions (tide and tsunami propagation) in the former Gulf of Tartessos has been carried out, in order to improve our insight on how they could have influenced the human activities in this area. The model solves the 2D depth-averaged hydrodynamic equations with appropriate initial and boundary conditions for tides and tsunamis. The model has been tested through simulation of tides under present bathymetry and of past tsunamis for which historical records exist. Then the bathymetry of the Gulf of Tartessos has been reconstructed for 2200 and 4000 years BP. The two main tidal semidiurnal and diurnal constituents have been simulated. Results indicate that they suffer a strong attenuation in the Gulf for both bathymetries, with significant currents only in its entrance. The known main active faults in the Gulf of Cadiz and the 1755 Lisbon source have been selected as case studies of tsunami propagation in the former Gulf of Tartessos. The 1755 Lisbon tsunami represented the worst case situation, and its numerical simulation has been subjected to several sensitivity tests. Results reveal negligible impacts for the inner shoreline of the Gulf of Tartessos, but severe damage could have been produced along the Atlantic coasts of SW Spain, from Cadiz to Huelva.

Most 210Pb dating models assume that atmospheric flux of excess 210Pb (210Pbexc) to the sediment–water interface remains constant over time. We revisited this assumption using statistical analysis of a database of laminated sediments and evaluated the implications for radiometric dating of recent deposits. A bibliographic survey enabled us to create a database with 10 annually laminated sediment cores from a variety of aquatic systems. The database has records of 210Pbexc flux, initial 210Pbexc activity, and sediment accumulation rate (SAR). 210Pbexc flux to sediments varied with time, and 1/3 of the data had relative deviations from the mean value >25 %. There was no statistically significant correlation between activities at the core top and SAR, whereas a statistically significant (p

The use of normalized procedures designed for soil and sediment samples (like US-EPA 3051) to chemically prepare some kind of organic samples is a common practice in some laboratories. However, the performance of this method for other matrices has to be demonstrated. Three microwave-assisted digestion procedures with 0.5 g of sample and simplified reagents (10 mL HNO3 alone and mixtures of HNO3/HCl- and HNO3/H2O2 procedures A, B, and C, resp.) were compared for quantitative determination of 25 elements (Be, B, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Ag, Cd, Sb, Cs, Ba, Tl, Pb, Th and U) in three biological reference materials provided by NIST (mussel tissue (MT), tomato leaves (TL), and milk powder (MP)) by ICP-MS. From scaling masses (from 0.1 up to 0.9 g at 0.1 g interval) in procedure A, a linear relationship among instrumental signal and mass of digested sample could be constructed at 99% CL for most of the target analytes. The slope of this linear fit provided the estimation of sample concentration, while the ordinate in origin allowed the identification of matrix interferences which were absent in the reagent blank.

A numerical model to simulate tsunami propagation in south of Iberia waters has been developed. It is based on the 2D non-linear hydrodynamic equations and allows calculating tsunami run-ups. The model has been validated through the simulation of historical tsunamis. Then it is applied to a risk assessment study to evaluate tsunami flooding along the Spanish and Moroccan coasts. A spectral analysis of tsunami waves has also been carried out. Finally, the model has been applied to simulate tsunami propagation in the former Gulf of Tartessos, where the city of the same name could have been located. The objective consists of evaluating if a large tsunami could have destroyed it, as some historians suggest.

Most mathematical models for radiometric dating of recent sediments are particular solutions of a unique physical problem: the advective–diffusive transport of a particle-bound radiotracer within a sediment profile that undergoes accretion. Regardless of the particular assumptions about fluxes, sedimentation rates and the diffusion term, all models assume ideal deposition as a boundary condition at the sediment water interface, i.e. new radioactive input will be deposited above the previously existing material. In sediments with very high porosities, this assumption may be unrealistic, because a fraction of the incoming flux may penetrate rapidly through the connected pore spaces. This process will be referred to as non-ideal deposition. This paper reviews evidence from literature data, discusses the basic processes involved, and establishes the mathematical basis to incorporate non-ideal deposition into one-phase radiometric dating models, as depth-distributed local sources. Through analytical and numerical solutions, this work demonstrates that such penetration patterns can explain excess 210Pb subsurface maxima, often observed in sediment cores, as well as penetration of 137Cs to depths greater than expected from sedimentation rates and diffusion. These ideas are illustrated using examples from the literature in which sediment porosities were >90 %. Implications for radiometric dating include: (1) spurious accelerations in sedimentation rate inferred when applying the constant rate of supply model, and (2) erroneous chronologies, developed when using the maximum depth at which 137Cs can be measured as a chronostratigraphic marker.

Tile drainage and soil amendments have been found to affect losses of nitrate N from agricultural soils. This work was aimed at measuring nitrate N losses in a tile-drained marsh soil from SW Spain under traditional fertilization and irrigation practices, and how these losses were influenced by the application of soil amendments. To this end, a randomised block experiment with three replications was performed during two consecutive growing seasons—2003 to 2004 with cotton and sugar beet, respectively—involving four different amendment treatments: (1) control without amendment, (2) phosphogypsum (PG), (3) manure, and (4) sugar factory refuse lime (SFRL). Flow-weighted (FW) nitrate–N concentrations in drainage water, estimated as the slope of the regression of the instantaneous nitrate–N flow as a function of drain flow rate, was decreased by PG in some drainage events in the 2003 season and in the four last events of the 2004 season when compared with control without amendment. The increased FW nitrate–N concentrations in drainage from SFRL in comparison to control in a drainage event of 2003 season, and in the four last events of 2004, can be explained by the contribution of N present in the amendment. These effects did not account for significant differences in nitrate–N loss among treatments over the whole season in 2003, when they ranged from 19.3 to 24.9 kg N ha−1, accounting for 6–8% of applied N, nor in 2004, when they ranged from 4 to 6 kg N ha−1, accounting for 3–4% of applied N. The decrease in mean FW nitrate–N concentration after the third drainage event in 2003 was not the consequence of the depletion of total soil nitrate–N because soil mineral N was increased on average by 205 kg N ha−1 during the season. The high N extractions by sugar beet and the subsequent decrease in total soil nitrate–N can contribute to explain the decrease of mean FW nitrate–N concentrations along the 2004 season. Greater absolute nitrate–N loss in 2003 than in 2004 was explained by the lower efficiency of the furrow irrigation when compared with sprinkler irrigation. Results also revealed that traditional management of N fertilizer was inadequate: rates applied to cotton were excessive, increasing the risk of N losses not only during the cotton season, but also at the beginning of the following season.

Independent validation has to be an integral part of the 210Pb-based radiometric dating of recent sediments. The combined use of artificial fallout radionuclides leads to serious problems because only the identification of peaks and their use as time-marks is not sufficiently rigorous to ensure the accuracy of dates. Quantitative modelling of depth profiles requires reliable input functions, which can be substantially different from the atmospheric deposition records. The appropriate treatment of compaction is another source of complexity. Continuum mechanics provide a suitable framework to understand compaction in sedimentary basins with length scales of several km. Nevertheless, early compaction (with length scales of few cm at the sediment surface) takes place under hydrostatic equilibrium conditions, and it can be better understood as a transport phenomenon: a mass flow governed by spatial gradients of a compaction-potential energy, involving a conductivity function. This paper explores some analytical and numerical solutions for these equations to provide insight about the early compaction phenomenon. Given a conductivity function and a constant sedimentation rate, the system will evolve towards a steady-state profile for bulk density. The fingerprint of variable sedimentation rates, among other changes in environmental conditions, will be studied with numerical solutions. Finally, the paper explores the use of bulk density profiles for deriving information on recent sedimentation rates, which could provide independent support for the radiometric dating models.

Phosphogypsum (PG), a by-product of the P industries, has been widely applied as an amendment to reduce Na saturation in soils. However, some concern arises due to its content of some metals and radionuclides. Thus, it is necessary to optimize the PG rates to avoid excessive accumulation of such pollutants in soil. To evaluate the effects of PG on drain flow and on the displacement of Na by Ca in soils, a three-year field experiment was conducted in a commercial farm located in a reclaimed marsh area from SW Spain. It involved two treatments (control — without PG — and 25 Mg ha −1 of PG, applied in April 2003 and again in September 2004), done in triplicate in 250 × 20 m plots, following a randomized block design. Drainage flows were monitored, and drain-water samples were analyzed for Na and Ca concentrations. The recorded hydrographs revealed unexpected high lateral flows of water within these soils. No statistically significant differences were found in drained volumes, nor in Na and Ca losses through drainage, between both treatments in each of the three growing seasons ( Gossypium hirsutum L. in 2003 and 2005; Beta vulgaris L. in 2003–2004). Losses of Na and Ca in each irrigation event were linearly related to the drainage to irrigation volume ratio ( p ); Ca, however, showed significantly different slopes for both treatments. Cation concentration, Na adsorption ratio (SAR), and electrical conductivity (EC) in the saturation extract of soil at different depths were significantly affected by PG and by the oscillation of saline water table during the experiment. The efficiency of PG in displacing Na by Ca was estimated to be about 30%, with the PG-attributable changes in Ca and SAR also appearing in deeper soil layers and in adjacent control plots.

Phosphogypsum (PG) has been traditionally applied as Ca-amendment in saline marsh soils in SW Spain, where available PG has 710 ± 40 Bq kg −1 of 226 Ra. This work assesses the potential radiological risk for farmers through 222 Rn exhalation from PG-amended soils and by inhalation of PG-dust during its application. A three-year field experiment was conducted in a commercial farm involving two treatments: control and 25 t PG ha −1 with three replicates (each 0.5 ha plots). The 222 Rn exhalation rate was positively correlated with potential evapotranspiration, which explained 67% of the variability. Statistically significant differences between the control and PG treatments were not found for 222 Rn exhalation rates, and mean values were within the lowest quartile of the typical range for 222 Rn exhalation from soils. Airborne dust samples were collected during the application of PG and sugar-beet sludge amendments. The highest PG-attributable 226 Ra concentration in the dust samples was 3.3 × 10 2 μBq m −3 , implying negligible dose increment for exposed workers.

The accurate measurement and recording of water flow rates is necessary in the performance of field experiments in irrigation, overland flow or drainage studies. There is a lack of reliable, low-cost commercial flow meters that are able to operate under “non-pressure” conditions. This work describes a simply designed recording meter based on the ultrasonic measurement of water levels in a slotted U-pipe. A three-width slot design allows accurate flow measurements in the range 0–3 L s−1 and the ultrasonic probe allows for high resolution measurements. Six replications of the instrument have been performed and calibrated (water levels against water flows) in laboratory experiments. After that, they have been successfully tested under field conditions, monitoring water flows which were recorded by using a data logger in the drainage system of an experimental farm in southwest Spain during several irrigation episodes in summer 2005.

The measurement of trace element concentration in aerosols is of interest for environmental studies and for human health assessment. The temporal variability of total suspended particles (TSP) and its elemental composition in Seville, in SW Spain, is of particular complexity since Atlantic air masses and Saharan Dust Intrusions (SDI) overlap to local natural and anthropogenic sources. This paper is aimed to study the temporal evolution (in a monthly basis) of the concentrations of 25 trace elements, determined by ICP-MS, in high-volume air filter samples from Seville, covering a two-year period: 2001-2002. The mean TSP value for this period was 79.7μgm-3 and showed peak values in August 2001 and June 2002, likely related to SDI. Enrichment factors (EF) for Se, Sb and Zn and Pb were above 100, which revealed their anthropogenic sources. The comparison among EF from Seville and Huelva, a highly industrialized city nearby Seville, showed higher levels of anthropogenic elements there than in Seville. Simulations of the transport/dispersion of pollutants starting in Huelva confirm that air pollutants can reach Seville in the course of around 6hours although they do not contribute significantly to the levels found in this city. A significant temporal correlation was found between elements which have a common source, being crustal (Al, Ti, Be, Co, Cs, Fe, Cr, Mn, U, Sr and Th) or anthropogenic sources (Zn, Pb, Cd). The temporal variations of those crustal elements are similar and related with the TSP levels for both years, with the clearly visible peaks probably related with the Saharan dust intrusion., The authors would like to thank the Spanish Ministry of Science and Technology (FIS2012-31853) for the financial support.

An original decay correction procedure is proposed for the activity determination of short-lived radionuclides in airborne dust samples. To this end, the hypothesis of air flow rate attenuation during sampling is considered and tested. The other decay corrections: to the delay time, from the end of the sampling until the start of the counting; and to the counting time, were executed as standard. Differences from classic corrections, which consider a constant air flux rate in the sampling with a weekly sampling duration, are of the order of 1% for 7 Be and approximately 10% for 131 I. Moreover, the procedure can be applied to estimate the air volume sampled in the last 24 h before the end of the sampling. This volume can be used to calculate the activity concentration of a radionuclide (short-or long-lived radionuclide) if a major nuclear accident causes an instantaneous contamination immediately before the end of sampling.

The uptake of radionuclides and heavy metals by suspended particulate matter (SPM) features characteristic times, which actually affect the transport, bioavailability and the final fate of such substances in aquatic ecosystems. Box models represent a useful approach to study this process. Based upon constant reaction rates, they are developed and calibrated from batch experiments. Considerable discrepancy is found in the structure of the proposed multi-reaction models, while traditional experiments cannot account for the intimate detail of the uptake mechanisms. This paper demonstrates that apparently different models are, nevertheless, mathematically equivalent, thereby questioning the physical meaning of transfer coefficients. The mathematical demonstration is a straightforward consequence of the methodology in general use. The equivalence is preserved, for closed and open systems, even if modifications are made to parameters which affect the bioavailability of those pollutants in aquatic environments: SPM concentrations, specific surface area and concentration of competitive ions. Furthermore, the possibilities for further research are discussed since this equivalence can be broken by changes in temperature.

Radiotracer experiments are presented on 241Am uptake in natural aqueous suspensions from a reservoir and a river in SW Spain. The uptake was followed by measuring the 241Am activity in water using a liquid scintillation technique. Experimental results revealed a three-step kinetics in the uptake, which could be satisfactorily described by a model of two parallel and reversible reactions followed by a consecutive weakly-reversible reaction. This paper also studies the effects of the concentration of suspended matter and the specific surface area on the kinetic transfer coefficients.

Modern nuclear metrological tools allow the remote surveillance of the radiological status of the aquatic systems, providing an important advance in the protection of the environment. Nevertheless, the significance of the radiological data could be highly improved through simultaneous recording of physical and chemical variables that govern the behaviour and bioavailability of radionuclides in these aquatic systems. This work reviews some of these variables from the point of view of the environmental modelling. The amount, nature and dynamics of the suspended loads and bottom sediments strongly influence the behaviour of particle-reactive radionuclides. The kinetics of this process has a very fast component, as it is shown from our recent studies with 241Am, 239Pu and 133Ba in several aquatic systems from southern Spain. Changes in pH, temperature and in the electrical conductivity are influencing the uptake kinetics and the final partitioning of the radioactivity. Water currents govern the radionuclide transport and dispersion. These points are illustrated with modelling exercises in the scenarios of the Suez Canal (Egypt) and the Härsvatten Lake (Sweden).

Classical treatment of mass conservation of solids in growing sediments states an advection-diffusion equation for the bulk sediment density. Thus, the diffusion coefficient has to account for elemental processes of exchange of solid particles by pore water or reciprocally. Nevertheless, in a gravity field, these exchanges are forced and cannot be treated as diffusion but as mass flow. A compaction potential energy is defined so that its spatial gradients force a mass flow involving a conductivity function. This leads to a more consistent definition of mass sedimentation rates and to a writing of the continuity equation for density involving only an advection term. Typical bulk density profiles show an asymptotic increase with depth. With the present formulation, this can be obtained as a steady-state solution under constant sedimentation rate and constant conductivity, while the classical formulation fails to do it. Alternatively, it can be found that under these conditions, the compaction potential is a linear function of the bulk density. The mass flow due to compaction and the compaction potential are found for several sediment cores from literature data. From this basis, the advection-diffusion equation for a particle-associated tracer is rewritten. In particular, when the mass flow term due to compaction is considered, the resulting sub-grid scale processes lead to a different formulation of the diffusive fluxes: they are proportional to the gradients of specific concentration in solids instead of the concentration per unit bulk volume. This new formulation is most suitable to find out analytical solutions for radiometric dating models involving mixing and compaction. Numerical solutions are found for the new and the classical treatment for some particular cases to illustrate differences.

210Pb geochronologies should be validated with independent tracers such as 137Cs. In the cases with constant 210Pb activity in the topmost sediments, the presence of a distinct 137Cs peak within the 210Pb plateau has been used as a definitive demonstration of acceleration (increase in the sedimentation rate in recent years) versus fast mixing. Nevertheless, some limitations can be identified in the use of semiquantitative arguments, and a global understanding of the whole 137Cs activity profile is then required. Particularly, the incomplete mixing within the top sediment zone (described through the Incomplete Mixing Zone model) can explain quantitatively and simultaneously the 137Cs peak and the flattening in the 210Pb activity profile. This is demonstrated using selected examples from literature data. Thus, measured constant 210Pb activities in the top 6 cm of a sediment core from Lake Zurich. Nevertheless, they found 7Be only in the uppermost layer, the distinct 137Cs maximum at 6 cm depth, and undisturbed varves. The fast mixing seemed then opposed to common sense. The constant rate of supply model shows acceleration and it adequately matches the position of the 1963 137Cs peak. Nevertheless it fails to explain the whole 137Cs profile when handling time series of 137Cs atmospheric deposition. Finally, it is shown how the incomplete mixing of the activity (through the pore water) over a certain mass depth at the top sediment, with a finite value of the mixing coefficient, can quantitatively explain the whole activity versus mass depth profiles of 137Cs and 210Pb, and the presence of 7Be only in the uppermost sediment layer. A further validation of these ideas is presented from other literature data.

Increasing anthropogenic pressures coupled with climate change impacts on natural resources have promoted a quest for innovative tracing techniques for understanding soil redistribution processes and assessing the environmental status of soil resources. Among the different existing tracers, the fallout component of the radioisotope lead-210, also termed unsupported or excess lead-210 (210Pbex) when referring to its presence in soil or sediment, arguably offers the broadest potential for environmental applications, due to its origin and relatively long half-life. For more than five decades, 210Pbex has been widely used for dating sediments, to investigate sedimentation processes and, since the 1990s, to provide information on the magnitude of soil and sediment redistribution. The aim of this review is to provide a comprehensive evaluation and discussion of the various applications of 210Pbex as a tracer in terrestrial and aquatic environments, with particular emphasis on catchment sediment budget investigations. This paper summarizes the state-of-the-art related to the use of this tracer, the main assumptions, the requirements (including the need for accurate analytical measurements and for parallel validation), and the limitations which must be recognised when using this fallout radionuclide as a soil and sediment tracer. Lessons learned and current and future research needs in the environmental and radiochronological application of 210Pbex are also presented and discussed. International Atomic Energy Agency Research Project CRP D1.20.11

This paper describes work carried out under the IAEA Project EGY/07/002 to study the dispersion of radioactive material in the Suez Canal and the Bitter Lakes. This effort is linked with increased public concern about radiation safety through this important trade route. We apply a sequence of related modelling approaches, covering: (1) hydrodynamics, (2) transport of dissolved pollutants, (3) suspended loads and sediment dynamics, and (4) electrolytic reactions in aqueous suspension and in-sediment water pores. The final stage is a kinetic-reactive transport model for these tidal waters. The hydrodynamics have been studied using both 1D and 2D modelling approaches, and a reasonable calibration has been possible from the data set prepared with the collaboration of the Suez Canal Authority. Diffusion coefficients are calibrated from field tracing experiments included in the IAEA Project. They have been implemented in 1D and 2D models. Suspended matter dynamics and electrolytic reactions are documented from the available literature. Finally, different scenarios of discharges for both conservative and non-conservative radionuclides have been investigated.

This paper describes work carried out under the IAEA Project EGY/07/002 to study the dispersion of radioactive material in the Suez Canal. This effort is linked with the increased public concern about radiation safety through this important trade route. To follow the fate of radioactive wastes along this waterway, we had to solve the hydrodynamics of the water, governed mainly by tides, atmospheric forcing and the drift currents produced by horizontal salinity gradients and by differences in mean sea level (MSL) at the two entrances of the Canal. The hydrodynamics has been studied using both 1-D and 2-D modelling approaches, and a reasonable calibration has been possible from the data set prepared with the collaboration of the Suez Canal Authority. Dispersion of conservative pollutants has been preliminarily studied by using a 1-D-Gaussian approach. Thus, we are computing the path of the plumes and the time evolution of concentrations for different scenarios of discharges and under different seasonal conditions. The transit times can vary enormously during the year, ranging from a few days to several months, depending on the differences in MSL at the two entrances of the Canal.

In this paper we take advantage of the two field tracing experiments carried out under the IAEA project EGY/07/002, to develop a modelling study on the dispersion of radioactive pollution in the Suez Canal. The experiments were accomplished by using rhodamine B as a tracer, and water samples were measured by luminescence spectrometry. The presence of natural luminescent particles in the canal waters limited the use of some field data. During experiments, water levels, velocities, wind and other physical parameters were recorded to supply appropriate information for the modelling work. From this data set, the hydrodynamics of the studied area has been reasonably described. We apply a 1-D-Gaussian and 2-D modelling approaches to predict the position and the spatial shape of the plume. The use of different formulations for dispersion coefficients is studied. These dispersion coefficients are then applied in a 2-D-hydrodynamic and dispersion model for the Bitter Lake to investigate different scenarios of accidental discharges.

A considerable amount of international trade is transported in Egypt through the Suez Canal increasing public concern about hazardous safety. Through the canal, a relatively important flow of salt water enters the Mediterranean Sea, affecting its hydrologic deficit, and carrying algae and other non-swimmer species from the Red Sea. We are studying the hydrodynamics of the Suez Canal using both 1D and 2D modelling approaches. A reasonable calibration has been possible from the data set prepared with the collaboration of the Suez Canal Authority. Seasonal variations in Mean Sea Level in the northern Red Sea produce important drift currents. This is studied by means of our 1D model, being possible to estimate the net transport of salt and water towards the Mediterranean Sea. Diffusion coefficients are calibrated from two field-tracing experiments carried out in the southern Suez Canal. They are set up in a kinetic–reactive–transport model involving the dynamics of suspended loads and the electrolytic reactions between the dissolved species and the particulate matter in the water column and bottom sediments. We present an application to the short-term dispersion of Pu and Cs in the southern Suez Canal. Finally, we discuss the use of these modelling approaches into more global dynamic-ecological models.

Distribution coefficients, kd, are widely used as a first approach to the understanding and determination of the eventual fates of metals and radionuclides released into aquatic environments. The theoretical description of their dependence on particle size allows us to identify and separate in environmental samples of superficial bottom sediments the contributions of both naturally occurring particles and contaminated ones coming from radioactive emulsion wastes released into aquatic ecosystems. In this paper, we present the theoretical basis of this technique as well as its application to environmental samples from the Odiel river, an area affected by the phosphate industry, in Southwest Spain. The application of this technique provides both direct information about the extent of the radiological impact and a suitable data set for environmental modelling purposes.

From recent experimental findings on dissolved radionuclide adsorption by suspended particulate matter, some further theoretical effort is needed to explain both the wide k d variability range and the factors affecting uptake kinetics. In the previous paper we have studied the uptake of dissolved radionuclides by suspended particles from a microscopic viewpoint. We developed a mathematical description of the kinetic transfer and the k d distribution coefficients. The most relevant contribution is the assumption that exchange of radionuclides occurs across a specific surface layer of non-zero thickness on particles. A wide range of experimental findings can be explained by this theory as will be demonstrated here using literature data. Also, the derived governing equations can be solved using a finite differences method to illustrate the effects of particle size spectra, temperature, suspended load concentrations, pH and salinity, amongst other factors, on radionuclide partitioning.

The Odiel river is an estuary system located in the south-west of Spain and affected by tidal dynamics. A phosphate fertilizer processing plant releases part of its wastes directly into the Odiel river. The model described in a previous paper ( J. Environ. Radioactivity , 31 (2), 127–141 ) has been applied to study 226 Ra (discharged from the fertilizer plant) dispersion in the Odiel river. The model adequately reproduces the observed behaviour of 226 Ra in suspended matter and the dissolved phase along the Odiel river, as well as the general behaviour of the measured distribution coefficients. Some predictive studies as well as the corresponding sensitivity studies are also included in this paper.

kd distribution coefficients are widely used as a first approach to the understanding and determination of the eventual fate of metals and radionuclides released into the aquatic environment. For some radionuclides, kd varies within a range of more than two orders of magnitude. Based on some physical and chemical aspects of the interactions between the dissolved and the particulate phases, some mathematical equations have been developed to explain some features of the observed kd variability quantitatively. Thus, we have studied the decrease in particle size of kd in the case of man-made radionuclides interacting with natural particles, and its increase in the case of naturally occurring radionuclides. For the latter, the dependence of kd on the instantaneous water state has also been investigated. The study also shows the competition effects, particularly the dependence of kd on pH and salinity. Finally, the effects produced by the size distribution of a given population of particles or the mixture of different populations, are also included. The present work provides for each situation, experimental support from literature data and/or modelling exercises.

A 2D four-phase model to study the dispersion of non-conservative radionuclides in tidal waters, in conditions of disequilibrium for ionic exchanges, has been developed. At disequilibrium conditions, ionic exchanges cannot be formulated using distribution coefficients k d . Thus, kinetic transfer coefficients have been used. The model includes ionic exchanges among water and the solid phases (suspended matter and two grain size fractions of sediments), the deposition and resuspension of suspended matter and advective plus diffusive transport. In the second part of this work, which is presented in a separate paper, the model is applied to simulate 226 Ra dispersion, discharged from a fertilizer processing plant, in an estuarine system in the south-west of Spain.

The presence of226Ra and224Ra in suspended matter from an estuarine system which surrounds a phosphate fertilizer complex has been investigated. The results have confirmed an important radioactive impact from the industrial complex, since up to 2.5 Bq226Ra/g suspended matter (dry) has been measured. The influence of tides and seasonal conditions, through changes in salinity, has been found to be relevant. The distribution coefficients for226Ra between the suspended matter and the river water have been calculated. The values are in agreement by order of magnitude with those found in the literature, but they clearly depend on tidal state and seasonal conditions.

A numerical model to study 226 Ra dispersion in the Odiel River, in which two fertilizer plants release their wastes, has been developed. The hydrodynamic equations have been solved to obtain the instantaneous water state which allows us to describe the advective and diffusive transport of the radionuclides. The hydrodynamic model has been calibrated in order to reproduce field data. Diffusion coefficients have been formulated taking into account the shear effect. Good agreement between calculated and experimentally measured 226 Ra concentrations has been achieved. The source term, which was unknown, has been investigated and found to be comparable to that of other fertilizer plants.

This paper presents a numerical model for the transport of the nuclear contamination and other passive particles in the ocean. As a consequence of the Chernobyl accident (April, 26th, 1986), the radioactive plume drift over many countries in Europe, and after some days, the Baltic Sea became the most contaminated ecosystem beyond the Soviet Union. Our Dispersion Model has been validated in this system in order to be useful in other oceanic scenarios affected by radioactive fallout in the future. These investigations could be an interesting tool to predict and minimize the ecological and economical impacts of future accidents and can also be extended to non-nuclear contamination problems such as: oil accidents, chemical contamination, nutrients dynamics and other ecological problems. A new application devoted to the Guadalquivir River has been implemented with the methods used and validated for the Baltic Sea. This transport model is a first step for future applications to passive particles problems such as nutrients, chemical contamination, metals, suspended sediments, etc., or other active parts like salt and fresh water. A deeper knowledge on the Guadalquivir river estuary is being demanding for many socioeconomic and ecological applications in the future.