Recent pollution records in Sidi Moussa coastal lagoon (western Morocco) inferred from sediment radiometric dating

• Published in: Journal of environmental radioactivity 2021-02, Vol.227, p.106464, Article 106464
• Main Authors: Benmhammed, A., Laissaoui, A., Mejjad, N., Ziad, N., Chakir, E., Benkdad, A., Bouh, H. Ait, El Yahyaoui, A.
• Format: Article
• Language: English
• Subjects: Environmental Monitoring; Geologic Sediments; Metals, Heavy - analysis; Morocco; Radiation Monitoring; Radiometric Dating; Sediment contamination; Sediment quality guidelines; Sidi Moussa lagoon; Water Pollutants, Radioactive - analysis
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2020.106464

The Sidi Moussa lagoon, located in western coastal Morocco and ranked as a wetland of biological and ecological importance (Ramsar site), is contaminated due to its proximity to the industrial phosphate plants and other anthropogenic activities around it. This study was carried out to assess the current environmental state of the lagoon as well as historical inputs of pollutants over several decades. Three sediment cores were collected and analyzed for the determination radionuclide activities (210Pb, 226Ra, 238U and 137Cs) by gamma spectrometry and element concentrations by Inductively Coupled Plasma – Mass Spectrometry. Age-depth relationships were established in two cores using 210Pb and 137Cs as chronometer and time-marker, respectively, and Constant Rate of Supply as radiometric dating model. 210Pb and 238U were present in sediment in activities much higher than those reported for non-contaminated coastal systems. Sediment accumulation rates showed a slight increase over time with a depth-averaged value of 0.16 g cm−2 y−1. Enrichment Factors and practically derived sediment quality guidelines were used to assess sediment contamination/pollution and toxicological effects linked with the measured concentrations of sediment-bound elements. The profiles of Cr, Co, Cu, As and Ni displayed maximums at depths matching the start of the phosphate industrial plants, and decreasing concentrations in the sections above the maximums, revealing the positive effects of the environmental management system adopted by the phosphate company since early 2000s. •The Sidi Moussa lagoon, located near the biggest phosphate processing plants in the world, is contaminated by some metals and radionuclides.•The agricultural activities and North-West African upwelling contribute to sediment contamination.•Results have revealed the positive effects of the environmental management system adopted by The Moroccan Phosphate Company.