Abstract

The level and the ecological risk assessment of heavy metals were evaluated in surface sediments of 72 samples from 12
stations located in the Toukouzou Hozalem-Assinie zone along the Ivorian coast using X-ray fluorescence spectroscopy.
The heavy metals contamination was assessed using pollution indices: Modified degree of contamination (mCd), potential
acute toxicity (TU), and potential ecological risk index (RI). The results revealed that they are ranked in descending order:
Fe>Cr>Mn>V>Zn>Ni>Pb>As>Cu>Cd and the mCd values are between 4.15 and 7.86 which reflect a high degree of
contaminations. The highest total toxic units (ΣTUs) were calculated in sediment samples with Cr and Cd presenting the higher
TUs compared to the rest of heavy metals and contributed the most (80%) to the overall TUs. It reveals a high potential toxicity
for the marine ecosystems in the Ivorian coast. Comparison with sediment quality guidelines (TEC, PEC, PEL, and mPECq)
showed that Cr, Cd, and As are 75% toxic to most species of aquatic organisms living in sediments. Potential ecological RI
values indicate moderate ecological risk for Cr, considerable for As, and very high for Cd for most sites.