Levels and sources of heavy metals and PAHs in sediment of Djibouti-city (Republic of Djibouti)

Selected heavy metals and polycyclic aromatic hydrocarbons (PAHs) were determined in marine sediment from 28 sites Djibouti city. The concentrations of trace elements varied from 0 to 288.1 mg/kg with relative abundance of trace metals in sediments was in the order of Zn > Cu > Ni > Cr > Co > Pb > Cd. Zn, Cu and Ni exceeded consensus based sediment quality guideline values 7, 14, 15 sites respectively. Enrichment factor and pollution load index showed relatively low to moderate contamination. The concentrations of total 16 PAHs varied widely depending on the sample location and ranged from 2.65 to 3760.11 ng·g− 1, with the mean concentration value of 387.87 ng·g− 1. Compositions and relative abundance of individual PAH using molecular diagnostic ratio using congener's m/z 178 and 202 indicated pyrolytic origin and reflecting a petroleum combustion, grass/wood and coal combustion and a petrogenic source. This study represents the first pollution baseline and a reference for future studies in Djibouti.