Global fallout is the main source of anthropogenic radionuclides in the Mediterranean Sea. This work presents 137 Cs, 239+240 Pu and 241 Am concentrations in the water column in the southwest Alboran Sea, which was sampled in December 1999. A sediment core was taken at 800 m depth in the area (35°47 0 N, 04°48 0 W). 210 Pb, 226 Ra, 137 Cs and 239+240 Pu specific activities were measured at multiple depths in the core for dating purposes. 137 Cs and 239+240 Pu profiles did not show defined peaks that could be used as time markers, and they extended up to depths for which the 210 Pbbased constant rate of supply (CRS) dating model provided inconsistent dates. These profiles can be useful to test dating models, understood as particular solutions of a general advection-diffusion problem, if the time series of radionuclide inputs into the sediment is provided. Thus, historical records of depth-averaged 137 Cs and 239+240 Pu concentrations in water, and their corresponding fluxes into the sediment, were reconstructed. A simple water-column model was used for this purpose, involving atmospheric fallout, measured distribution coefficient (k d ) values, and a firstestimate of sedimentation rates. A dating model of constant mixing with constant sedimentation rate was applied successfully to three independent records (unsupported 210 Pb, 137 Cs and 239+240 Pu), and provided the objective determination of mixing parameters and mass sedimentation rate. These results provide some insight into the fate of atmospheric inputs to this marine environment and, particularly, into the contribution from the Chernobyl accident.
This study presents metal concentrations (Fe, Mg, Mn, Co, Cu, Zn, Pb, As, Sr and V) and radionuclide activities ((40)K, (137)Cs, (210)Pb, (226)Ra, (228)Ac, (234)Th and (212)Pb) in surface deposits and a sediment core from the Sebou Estuary, Northwest Morocco. Samples were collected in April 2009, about 2 months after a flooding event, and analysed using a well-type coaxial gamma-ray detector and inductively coupled plasma-quadrupole mass spectrometry. Activities of radionuclides and concentrations of almost all elements in surface samples displayed only moderate spatial variation, suggesting homogenous deposition of eroded local soil in response to intense precipitation. Excess (210)Pb displayed relatively constant activity throughout the sediment core, preventing dating and precluding determination of the historical accumulation rates of pollutants at the core site. Some elements showed non-systematic trends with depth and displayed local maxima and minima. Other elements presented relatively systematic concentration trends or relatively constant levels with discrete maxima and/or minima. Except for Mn, Sr and Cr, all metal concentrations in sediment were below levels typical of polluted systems, suggesting little human impact or losses of metals from sediment particles.
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