Tracking natural and human impact on sediment dynamics using radiometric approach in Oualidia lagoon (Morocco)
Nezha Mejjad, Abdelmourhit Laissaoui, Ahmed Fekri, Nour El Houda Hassen, Ayoub Benmhammed, Ouafa El Hammoumi, Azzouz Benkdad, Hamid Amsil
Abstract
Chemical analysis, grain size distribution and short-lived radionuclides (210Pb and 137Cs) were combined to investigate the sedimentary processes in the Oualidia lagoon. Grain size and major elements profiles indicate an unexpected change in the layers characterising 1978 and 1986. Sediment accumulation rates (SAR) depth profiles exhibited the same behaviour and revealed two different sediment deposition conditions or regimes, involving modification of this ecosystem equilibrium. The profiles of major elements behave vertically almost the same as SAR, and grain size distribution. The observed changes reflect modifications in sediments supply and ecosystem drivers due to the variation of hydrodynamics conditions, confinement phenomena located in the upstream zone of the lagoon and to the various anthropogenic activities around the Oualidia lagoon.