SURVEY OF HEAVY METALS CONCENTRATIONS IN WATER AND SEDIMENTS OF THE ESTUARY BIETRI BAY, EBRIE LAGOON, COTE D'IVOIRE
To provide information on heavy metals mercury (Hg) cadmium (Cd) lead (Pb) copper (Cu) and zinc (Zn) concentrations in water and sediments, monthly samples were collected in five sites in the Betri Bay from February 2008 to January 2009. The average values of water physicochemical parameters temperature, pH, dissolved oxygen, transparency, salinity and MES ranged between 28.12 30.49 degC; 7.46 8.17; 5.10 6.62 mgL 1 0.39 0.95 m; 7, 21 30.28 %0 and 13, 78 65, 53 mgL 1 respectively. The average mean water concentrations of heavy metals ranged between 0.01 0.03 ugL 1 (Hg) 0.02 0.26 mgL 1 (Cd) 2.40 4.80 mgL 1 (Pb) 9.05 9.68 mgL 1 (Cu) and 12.05 19.87 mgL 1 (Zn) The average mean sediments concentrations of heavy metals ranged between 0.35 1.33 ugkg 1 (Hg) 0.11 1.25 mgkg 1 (Cd) 26.53 120.05 mgkg 1 (Pb) 21.12 86.21 mgkg 1 (Cu) and 106.32 509.73 mgkg 1 (Zn) Results showed significant differences in levels of some water physicochemical parameters (salinity and MES) and heavy metals in water and sediments among dry, rainy and swelling seasons. The annual mean heavy metals were in the order of Zn Cu Pb Cd Hg and Zn Pb Cu Cd Hg respectively in water and sediments. The correlation analysis showed a strong positive relationship between heavy metals and physicochemical parameters in water. The concentrations of water metals were influenced by temperature, salinity and dissolved oxygen; while the concentrations of sediments metals were influenced by water metal levels. The exchange factor determined to assess the extent of metal accumulation in the sediments showed a higher value of exchange between water and sediments. Deleterious water quality levels of Pb, Cd, Cu and Zn, above recommended levels, in both water and sediments of Bietri Bay poses potential health hazards to the aquatic organisms and the inhabitants of the area that use this water resource directly for domestic or agricultural purpose without treatment.