Experimental study on the use of granulometric speciation for the radiometric dating of recent sediments
| Autor: | Emmanuel Klubi, Rafael García-Tenorio, José María Abril Hernández, Juan Mantero, Elvis Nyarko |
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| Přispěvatelé: | Universidad de Sevilla. Departamento de Física Aplicada I, Universidad de Sevilla. Departamento de Física Aplicada II, Universidad de Sevilla. RNM-138: Física Nuclear Aplicada, International Atomic Energy Agency (IAEA), International Atomic Energy Agency, García-Tenorio, R. [0000-0002-3976-4695], García-Tenorio, R. |
| Rok vydání: | 2019 |
| Předmět: |
Normalization (statistics)
Geologic Sediments Water Pollutants Radioactive 010504 meteorology & atmospheric sciences Health Toxicology and Mutagenesis media_common.quotation_subject Granulometric speciation Context (language use) 010501 environmental sciences Mass spectrometry 01 natural sciences Ghana Mining Detection limit Radiation Monitoring Environmental Chemistry Organic matter Waste Management and Disposal 0105 earth and related environmental sciences media_common chemistry.chemical_classification geography Radionuclide geography.geographical_feature_category Radiometric dating Normalized activities Radiometric Dating Estuary General Medicine Pollution Spectrometry Gamma Speciation chemistry Spain Environmental chemistry Environmental science Gamma spectrometry |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| ISSN: | 1879-1700 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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