Sedimentation Processes on Intertidal Areas of the Lagoon of Venice: Identification of Exceptional Flood Events (Acqua Alta) Using Radionuclides

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Plutonium measurements at NEA’s North East Atlantic dumpsites

Surface, intermediate and near-bottom water samples were collected at two of the North East Atlantic radioactive waste dumping sites (47∘ 14’N, 05∘ 33’W and 45∘ 27’N, 06∘ 16’W) in the course of a sampling campaign in June–July 1998. Analysis of 239,240Pu concentrations show no significant differences with respect to measured concentrations in waters taken from control (background) stations well removed from the dumping sites

Historical record of heavy metals in a highly contaminated Mediterranean deposit: The Besòs prodelta

9 pages, 6 figures, 1 tableThe Besos prodelta, located around a highly populated area, receives the discharge of the Bests River, one of the most contaminated rivers discharging into the Mediterranean sea. The record of heavy metals accumulated in this prodelta is studied to assess the sedimentary behaviour and the history of the anthropogenic heavy metals in the area. 210Pb dated sediments have allowed the identification of the sedimentation patterns and the elaboration of dated heavy metals and cenospheres profiles, which reflected the evolution of the anthropogenic impact in this marine environment. Sediments accumulated during the 18th and 19th centuries were already affected by a moderate heavy metal contamination. This contamination increased drastically in the sediments accumulated during the last decades. This dam is well correlated with the increase in industrialisation, population and energy consumption in the Besos drainage basin during the last centuryThis research was supported by the project AMB92-0251-CO2-01 and MAR96-1781-CO2 funded by the Comisión Interministerial de Ciencia y Tecnologı́a and the project MAS2-CT93-0053 funded by the C.E.E

Actinides studies on hot particles at the 1 MV CNA AMS facility

Resumen del póster presentado a la "Thirteenth International Conference on Accelerator Mass Spectrometry" celebrada en Aix-en-Provence (Francia) del 24 al 29 de agosto de 2014.Following nuclear events such as nuclear weapons tests and nuclear accidents, particles containing actinides are released into the environment. The actinides isotopic signatures of these particles can be used to label the source and gained additional information on their long-term environmental impact, for instance. To date, much information has been published on the physical and chemical speciation of the particles, environmental behaviour and composition for the most conventional actinides (241Am,239,240Pu,234,235,238U). However, due to the lack of abundance sensitivity of the conventional techniques, very scarce information has been published on 237Np and 236U. In this work, we present the first comprehensive information on 237Np, 236U and, also,239,240Pu, in four different escenarios: fragments of the so-called Trinitite, a mineral produced in the detonation of the nuclear weapon Trinity (1945, Alamogordo, New Mexico) ; μm-size particles from Palomares (1966, Spain) and Thule (1968, Greenland), where the nuclear fuel of two thermonuclear devices was accidentally spread due to accidents during their transportation ; and μm-size particles from the former Russian nuclear test site Semipalatinsk. Preliminary results point out to 237Np/239Pu atom ratios ranging from 1x10-4 to 8x10-4, and 236U/239Pu from 1x10-3 to 9x10-3. The actinides measurements were performed on the 1 MV AMS system at the Centro Nacional de Aceleradores (CAN, Seville, Spain), whose performance for the heaviest masses has been studied in different works. The procedure used to measure those samples by AMS and the environmental implications of the results will be discussed.Peer Reviewe

Uranium-thorium disequilibrium in north-east Atlantic waters

International audienceIn this paper we report and compare the concentrations of 234 Th and 238 U measured in surface and subsurface waters collected in the course of a sampling campaign in the north east Atlantic in June-July 1998. Dissolved 234 Th concentrations in surface waters ranged from 5 to 20 Bq m-3 , showing a large deficiency relative to 238 U concentrations (typically 42 Bq m-3). This disequilibrium is indicative of active 234 Th scavenging from surface waters. Observed 234 Th/ 238 U activity ratios, together with corresponding 234 Th particulate concentrations , were used to calculate mean residence times for 234 Th with respect to scavenging onto particles (s diss) and subsequent removal from surface waters (s part). Residence times in the range 5-30 days were determined for s diss and 4-18 days for s part (n ¼ 14). In addition, ultrafiltration experiments at six stations in the course of the same expedition revealed that in northeast Atlantic surface waters a significant fraction (46 AE 17%; n ¼ 6) of the thorium in the (operationally-defined) dissolved phase (0.45 lm) phase. Thus, the time (s c) for fully dissolved 234 Th to appear in the filter-retained fraction is dependent on the rate of colloidal aggregation. Here, we determined s c values in the range 3-17 days.

Concentrations of plutonium and americium in plankton from the western Mediterranean Sea

13 pages, 4 figures, 8 tablesUnderstanding the transfer of radionuclides through the food chain leading to man and in particular, the uptake of transuranic nuclides by plankton, is basic to assess the potential radiological risk of the consumption of marine products by man. The main sources of transuranic elements in the Mediterranean Sea in the past were global fallout and the Palomares accident, although at present smaller amounts are released from nuclear establishments in the northwestern region. Plankton from the western Mediterranean Sea was collected and analyzed for plutonium and americium in order to study their biological uptake. The microplankton fractions accounted for approximately 50% of the total plutonium contents in particulate form. At Garrucha (Palomares area), microplankton showed much higher 239,240Pu activity, indicating the contamination with plutonium from the bottom sediments. Concentration factors were within the range of the values recommended by the International Atomic Energy Agency. Continental shelf mesoplankton was observed to efficiently concentrate transuranics. In open seawaters, concentrations were much lower. We speculate that sediments might play a role in the transfer of transuranics to mesoplankton in coastal waters, although we cannot discard that the difference in species composition may also play a role. In Palomares, both 239,240Pu and 241Am showed activities five times higher than the mean values observed in continental shelf mesoplankton. As the plutonium isotopic ratios in the contaminated sample were similar to those found in material related to the accident, the contamination was attributed to bomb debris from the Palomares accident. Concentration factors in mesoplankton were also in relatively good agreement with the ranges recommended by IAEA. In the Palomares station the highest concentration factor was observed in the sample that showed predominance of the dynoflagellate Ceratium spp. Mean values of the enrichment factors showed, on average, discrimination rather than enrichment in the primary producer trophic chain. © 2003 Elsevier Science B.V. All rights reservedFinancial support was received from the European Union (FI3P-CT92-0046), DGICYT (CE94-0010) and ENRESA (Contrato 70.2.4.11.01) and is gratefully acknowledged. [...] Project AMB93-0814-C02-02 (CICYT, Spain) with the collaboration of the Department of Ecology of Universitat de BarcelonaPeer Reviewe

Diagenetic reactivity of the plutonium in marine anoxic sediments (Cumbrian mud patch - eastern Irish Sea)

An extensive diagenetic study carried out on a sediment core collected in the Cumbrian mud patch off the Sellafield nuclear reprocessing plant, is presented. Sequential leaching data, using a thoroughly validated protocol specifically designed to prevent any resorption of the released plutonium in the course of the extraction, demonstrate that a significant proportion of the plutonium is loosely bound to sites that readily exchange with seawater, oxidise upon oxygenated water contact (reactive sulphides) or easily dissolve upon changes in pH. Such a result contradicts many previous sequential extraction studies which have reported that little of the plutonium in Irish Sea sediments is in a readily available form. The profile of dissolved plutonium in pore waters indicates an active uptake process at depth, probably linked to sulphide (Acid Volatile Sulphide) precipitation. These reactive sulphides are liable to act as source of plutonium to the overlying water if they are brought close the interface by bioturbation or in contact with oxygenated seawater by burrowing activity