HYDROCARBON PROFILE AND HEAVY METAL LEVELS OF EDE-ONYIMA LAKE IN OKARKI-ENGENNI, RIVERS STATE, NIGERIA

Abstract

Freshwater quality is deteriorating as a result of ongoing threats from both anthropogenic and natural sources, resulting in an overall loss of ecological integrity petroleum hydrocarbon profiles and heavy metals (Mg, Fe, Ni, Mn, Pb, Cd, Cu, Cr, and Zn) were determined in water samples collected at six sampling sites in Ede Onyima lake, Okarki-Engenni, Rivers State, Nigeria using gas chromatography, flame ionization detector, and Atomic Absorption Spectroscopy.  Results showed that total petroleum hydrocarbon (TPH) varied from (0.27 -252.20 mg/L) with mean : 77.30 mg/L; Total hydrocarbon content (0.43 - 347.70 mg/L) with mean : 97.97 mg/L; Benzene, Toluene, and Xylene (9.00E-04- 6.60 mg/L) with mean : 0.11mg/L; polycyclic aromatic hydrocarbons (0.16- 3.51mg/L) with mean : 1.93mg/L. The heavy metal results showed Mg (1.11- 8.67mg/L) with mean : 2.87 mg/L; Fe (0.13 - 20.73mg/L) with mean : 7.29mg/L; Mn (0.001- 5.92 mg/L) with mean : 1.69 mg/L; Pb (0.06 - 0.06 mg/L) with mean : 0.06 mg/kg;  Cu (6.33E-04- 0.31 mg/L) with mean : 0.07mg/L;  Zn (9.90E-04- 0.38 mg/L) with mean : 0.08 mg/L;  Ni (0.04 - 0.04 mg/L) with mean : 0.04 mg/L; Cd and Cr were less than  0.01 mg/L. The CWQI was used to capture the overall spatial and temporal trends in water quality in the Ede Onyima lake. The results showed that while PAHs and Fe exceeded guideline values and failed 100% of the time. The large magnitude of F3 is as a result of varying degrees of failure of Mn, Fe, THC, TPH, and PAHs, all of which exceeded regulatory thresholds by several magnitudes. Furthermore, the flood event had a significant effect on the quality of the water, remobilizing pollutants' availability while washing away legacy contaminated streambed deposits during baseflow.