Geochemical, radiometric, and environmental approaches for the assessment of the intensity and chronology of metal contamination in the sediment cores from Oualidia lagoon (Morocco)

The present study evaluates the distribution of metals over the last 100 years in the Oualidia lagoon by examining their concentrations in the sediment cores. The samples were analyzed by instrumental neutron activation analysis and inductively coupled plasma mass spectrometry. Activities of 210Pb, 226Ra, and 137Cs were determined by gamma-ray spectrometry for establishing the age-depth relationships throughout the sediment cores by applying conventional models. The results indicated that the study area is contaminated by As and Cd revealing a detectable anthropogenic input of occurring metals as a consequence of the continuous development of human activities around the lagoon since 1950. The enrichment factor calculated for each layer of the three cores revealed that the studied sediments present no enrichment by Pb, K, and Mn; minor enrichment by Zn, Cr, Co, Cu, V, and Ni; and a moderately to severe enrichment by As and Cd. The pollution load index values increase from the bottom to the top of cores, and ranged from 0.9 to 2.8, which indicates levels of pollutants ranging from background to relatively high concentrations in the investigated sediments.