EVALUATION DE LA CONCENTRATION DES ELEMENTS TRACES (Pb, Cu, Zn, Fe, Cd et Hg) DANS LES CREVETTES (macrobrachium vollenhovenii) DES LAGUNES AGHIEN ET POTOU (SUD-EST DE LA CÔTE D’IVOIRE)

Abstract

This study aims to determine the concentrations of heavy metals (Cu, Pb, Fe, Cd, Zn and Hg) in prawns (Macrobrachium vollenhovenii) of lagoons Aghien and Potou in order to protect population’s heath. Nitric acid was added to every sample of water. Sediments samples were mineralized with hydrofluoric acid (HF) and aqua regia (HNO₃: HCl; 1:3, v/v). Prawns samples were mineralized with nitric acid (HNO₃) and hydrogen peroxide (H₂O₂). Then, all samples were analyzed with atomic absorption spectrometer (AAS) SpectrAA 110. Using AAS allowed showing that in lagoons waters the average concentrations of Pb (19.17 ± 1.93 µg/L) and Fe (2640.09 ± 256.22 µg/L) are higher than WHO standards. The average concentration of Cu (61.57 ± 19.36 mg/kg), Fe (63223.57 ± 5244.81 mg/kg) and Hg (1.77 ± 0.08 mg/kg) in lagoons sediments are superior to the concentrations of not polluted sediments. The average concentration of heavy metals in prawns are 0.34 ± 0.05 mg/kg, 0.02 ± 0.01 mg/kg, 1.12 ± 0.29 mg/kg, 0.04 ± 0.003 mg/kg, 2.21 ± 0.33 mg/kg and 0.71 ± 7.62 mg/kg respectively for Pb, Cd, Cu, Zn, Fe and Hg. 27 ± 7.4% of prawns are contaminated by lead, 24 ± 7.15% by cadmium, 38 ± 8.08% by copper, 70 ± 7,62% by iron and 76 ± 7.15% by mercury. All the analyzed prawns are unfit for human consumption. Bioconcentration factors show that heavy metals found in prawns come from waters and sediments as well as food they consume. Heavy metals which affect prawns habitats have natural and anthropogenic springs. Heavy metal accumulation can cause several diseases and dysfunctions of human body.