Determination of the Levels of Heavy Metals in Surface Water, Tilapia Fish (Oreochromis Niloticus) and Soil Within the Vicinity of Oil Production Facilities During Wet and Dry Season in Omoku, Rivers State

Abstract

This study determined the levels of heavy metals in surface water, tilapia fish (Oreochromis niloticus) and soil within the vicinity of oil production facilities during wet and dry seasons in Omoku, Rivers State, Nigeria. Samples of surface water, Oreochromis niloticus and soil were collected from Obrikom River (Onosi Ognu), Onosi Okpasimini and a control location during the wet and dry seasons. The samples were properly preserved, prepared and digested using standard analytical procedures, while the concentrations of lead (Pb), copper (Cu), chromium (Cr), cadmium (Cd), nickel (Ni) and iron (Fe) were determined using atomic absorption spectrophotometry. The data obtained were subjected to appropriate descriptive and pollution assessment indices, including bioaccumulation factor (BAF), contamination factor (CF) and pollution load index (PLI). The results showed that heavy metals occurred in all the investigated matrices, with generally higher concentrations during the dry season. In surface water, Pb concentrations ranged from 1.10 ± 0.00–2.49 ± 0.01 mg/L during the wet season and 1.24 ± 0.01 2.86 ± 0.01 mg/L during the dry season, while Fe ranged from 45.19 ± 0.23–72.58 ± 0.00 mg/L and 48.76 ± 0.21–79.64 ± 0.12 mg/L, respectively. In O. niloticus, Pb ranged from 1.18 ± 0.03 3.62 ± 0.08 mg/kg in the wet season and 1.39 ± 0.04–4.26 ± 0.11 mg/kg in the dry season, while Cd ranged from 0.08 ± 0.01–0.61 ± 0.03 mg/kg and 0.10 ± 0.01–0.76 ± 0.04 mg/kg, respectively. Soil Fe concentrations ranged from 421.58 ± 6.73–758.62 ± 9.17 mg/kg during the wet season and 458.72 ± 7.18–826.47 ± 10.26 mg/kg during the dry season. The BAF was highest for Cd, while PLI values indicated greater contamination at the oil-production-influenced locations, particularly during the dry season. The findings indicate heavy-metal contamination in the study area, with evidence of seasonal variation and accumulation of selected metals in Oreochromis niloticus. The study provides baseline information for environmental monitoring, pollution control and the protection of aquatic and terrestrial resources in Omoku, Rivers State.