The contamination of aquatic environments by organic pollutants such as PAHs constitutes a worrying threat to water quality, but also to the survival of aquatic biodiversity. The present study aims to assess the risk linked to the presence of such contaminants in the surface sediments of a lagoon subject to urban influence. The method used for this purpose first consisted of collecting eighteen (18) representative samples of sediment at the bottom of the water using a grab. Then, an analysis of their PAH content was carried out using the gas chromatography technique coupled with mass spectrometry (GC-MS) in the laboratory. The different concentrations obtained of each PAH were finally compared with corresponding LEL and SEL tolerance threshold values. These analyzes reveal the presence of 8 main PAHs in the sediments studied with a range of concentrations going from 0 to 32.08 μg/kg. Among these, light PAHs such as Fluoranthene and Pyrene with respective maximum contents of 6.25 and 32.08 μg/kg. Heavy PAHs such as: Benzo (b) fluoranthene, Benzo (k) fluoranthene, Benzo (a) pyrene, Indeno (1, 2,3-cd) pyrene, Benzo (a) anthracene and Benzo (g, h, i) perylene, with concentrations ranging between 0 and 31.46 μg/kg. All the PAH values obtained were well below the usage rights thresholds. From the analysis of the various results, it appears that all of these quantified organic compounds did not currently represent a danger for the lagoon environment due to their very low levels.

The coastal unit between the Vridi canal and the Port-Bouët lighthouse, south of Abidjan, is the subject of this study. It was followed over two periods (November 2015 and October 2016) following the eviction, downstream, on the waterfront of several precarious neighborhoods (Derrière Wharf, Adjouffou, Gonzagueville, ...). This study uses GPS data coupled with worksite level data to reconstruct the morphology of the study area as well as its description and evolution from different beach profiles. The acquired data is processed from the software "MapSource", "Excel" and "Surfer". For each profile, the different morphological units of the range were determined from classical terminology. In general, all the recorded profiles have a straight or concave shape. This is characteristic of an unbalanced beach profile with sand start and erosion. The length of the profiles varies between 16 m and 53 m. The elevation difference is between 4 m and 7 m with a variable slope (2.86 ° to 14.03 °). They are reflexive beaches with a strong erosional tendency.