Artículos (Física Aplicada I)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10849

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Examinando Artículos (Física Aplicada I) por Materia "210Pb"

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    Environmental radioactivity in a sediment core from Algiers Bay: Radioecological assessment, radiometric dating and pollution records
    (Elsevier, 2020) Errahmani, Djabel Taieb; Noureddine, Abdelkader; Abril Hernández, José María; Boulahdid, Mostefa; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. RNM-138: Física Nuclear Aplicada
    The sedimentary system of the Algiers Bay has been impacted in the last decades by the exponential increases in population, urbanism and industrial activities of the city of Algiers, and by episodic floods, mudflows, earthquakes and tsunamis. Activity concentrations of environmental gamma-emitters, namely 210Pb, 226Ra, 40K, 228Ra, 228Th and 137Cs, were measured in a sediment core sampled in 2015 at the central zone of this bay, at 73 m depth from the surface water. The 210Pb-based radiometric dating was challenging due to the incomplete recovery of the inventory, the absence of 137Cs peaks, and the failure of classical models. The analysis of clusters in the logarithmic plot of the excess 210Pb versus mass depth profile allowed for establishing a reliable chronology. Fluxes of excess 210Pb and sediment accumulation rates (SAR) have both varied over the last five decades. Recent SAR values are of 0.73 ± 0.21 g cm−2y−1. Major and trace elements were determined by X-Ray Fluorescence in some selected sediment slices. Moderate enrichments have been observed for Mn, Zn, Br, Rb, Sr, Y and Pb in the 0–1 cm sediment layer (when using Al as normalization element), being governed by Fe-rich carriers. The major impact is observed in the carbon content, which increased by two orders of magnitude (from their basal values) for three decades since early 70's. The dataset also allowed for a radioecological assessment in the area, performed using the ERICA software.
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    Settling fluxes and sediment accumulation rates by the combined use of sediment traps and sediment cores in Tema Harbour (Ghana)
    (Elsevier, 2017) Botwe, Benjamin O.; Abril Hernández, José María; Schirone, Antonio; Barsanti, Mattia; Delbono, Ivana; Delfanti, Roberta; Nyarko, Elvis; Lens, Piet N.L.; Universidad de Sevilla. Departamento de Física Aplicada I; University of Ghana; Universidad de Sevilla. RNM-138: Física Nuclear Aplicada
    Settling fluxes and sediment accumulation rates in coastal Tema Harbour (Ghana) were investigated by the combined analyses of results in sediment traps and sediment cores. Sediment traps were deployed at 5 stations within the Tema Harbour at two sampling depths and were retrieved every two weeks till the end of 12 weeks to estimate the Settling Fluxes (SFs). Four sediment cores from the harbour were analysed for their radioactivity (7Be, 234Th, 210Pb, 212Pb, 226Ra, 40K and 137Cs) profiles to quantify Sediment Accumulation Rates (SARs). The sediment cores exhibited variable bulk density profiles, indicating highly dynamic and non-steady sedimentation conditions. 7Be-derived gross-estimates of very recent SARs using the constant flux-constant sedimentation (CF-CS) model were in the range of 2.5–9.0 g·cm− 2·y− 1. These values were much lower than the estimated average SFs (15.2–53.8 g·cm− 2·y− 1), indicating sediment resuspension plays an important role. On a decadal time scale, conventional 210Pb sediment dating models did not allow any estimation of SARs in the Tema Harbour. Thus, the 210Pb-based TERESA model was applied to depict a reliable scenario for sedimentation with time-averaged SARs in the range of 1.4–3.0 g·cm− 2·y− 1 and fluxes of matter contributed by the marine inflow and local sources. Sediment accretion rates of 1.7–3 cm·y− 1 were also inferred, which may pose a moderate problem of sustainability for the Tema Harbour. This study reveals how the geochemical behaviour of different radionuclides with Gamma spectrometry in the marine environment can be used to obtain reliable information on the complex dynamics of Suspended Particulate Matter (SPM), even in a very disturbed and anthropic environment as a coastal harbour area where (1) conventional 210Pb-based dating methods fail and (2) the use of sediment traps and 234Th and 7Be profiles in sediment cores show serious constraints.