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Article Title: Water and Sediment Quality of the Ekerekana and Okochiri Creeks – Hydrocarbon and Heavy Metal Perspectives.

Abstract:

Surface water and sediment were collected from the Ekerekana/Okochiri Creeks and the adjoining rivers for environmental quality assessment. Forty six samples were collected from twenty three stations divided into six zones (A – F) in two seasons. Samples were treated, analyzed and computed using standard methods. Mean THC (0.18 + 0.01 mg/l), TPH (4.2 + 3.93 mg/l) and oil & grease (0.13 + 0.03 mg/l) in surface water were observed at zone B on the Ekerekana Creek. Site characteristics of surface water using principal component analysis (PCA) distinguished four groups in a clear pattern which showed contamination along a gradient with activity related trend. Mean maximum PAH in sediment was 0.2 + 0.02 mg/kg (zone A) while TPH values varied from 7.6 + 0.14 mg/kg at zone E to 262.1 + 90.52 mg/kg at zone A. PAH in sediment differed significantly (p<0.01) between zone A and other zones while THC, TPH and oil & grease also differed significantly between zone A and others zones implicating zone A with higher concentration of these pollutants. Most of the heavy metals varied across zones with significant differences between zones and also between seasons. Mean concentration of Fe ranged from 4846.50 + 833.68 mg/kg to 22832.6 + 728.94 mg/kg with significant difference (p<0.001) between zone A and other zones. Zn levels in sediment showed significant difference between zone A and others while Co values gave significant difference between zones A, E, F and zones D, C and B. Cr, Pb and Mn differed significantly (p<0.001) between zones while Cd and Ni showed significant variation (p<0.05) between seasons. The study concluded that zones A and D on the Ekerekana and Okochiri creeks were hotspots of contamination with regards to industrial effluent discharges in the study area. Limit of detection of instrument used for heavy metals and hydrocarbon analysis were 0.001 ppm and 0.01 ppm respectively.