Radionuclide activities and metal concentrations in sediments of the Sebou Estuary, NW Morocco, following a flooding event

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.