keywords: Contamination factor, heavy metal, sediments, pollution indices, surface water
The pollution of surface water in recent time impairs its quality. Deleterious effect of sediment contamination with heavy metals could be associated with their toxicity and accumulative capacity in biota. Information on sediment pollution with heavy metals of Gbalegbe River is limited. This study therefore seeks to evaluate the degree of sediment contamination of Gbalegbe River through the application of sediment pollution indices. Spatially, Gbalegbe River (12.5 km) was stratified into eight stations (S1, S2, S3, S4, S5, S6, S7, and S8) based on proximity to key anthropogenic activities. At each station, three sampling points were randomly chosen. Temporal stratification covered wet (March - October) and dry (November – February) seasons. Sediment samples were collected from each station forth – nightly for 24 months following standard methods. Sediment samples were analysed for Cadmium, Nickel and Chromium according to standard methods. Pollution load index (PLI), modified degree of contamination (mCd) and geoaccumulation (Igeo) were calculated. Data were analysed by using descriptive statistics and ANOVA at α0.05.Spatially, Cadmium ranged from 0.10±0.01 to 0.34±0.12; Nickel (0.06±0.01, 0.24±0.04) in S 1 and S 6, while highest (0.34±0.01) and least (0.06±0.02) concentrations of Chromium were recorded in S 2 and S 1, respectively. Seasonally, Cadmium ranged from 0.15±0.12 to 0.27±0.01; Nickel (0.12±0.05, 0.13±0.05) in dry and wet seasons, while Chromium ranged from 0.13±0.02 to 0.14±0.01 in wet and dry seasons, respectively. Spatially, the values of PLI and mCd were 0.121 and 0.150. Seasonally, the highest (0.140) and least (0.110) of PLI; mCd (0.350, 0.210) were recorded in dry and wet seasons. Spatially, Igeo ranged from -0.502 to 0.163 for Zinc and Chromium, while the highest (0.970) and least (0.060) were recorded for Lead and Chromium in wet and dry seasons, respectively. Hence, Gbalegbe River rich fauna abundance and diversity could be threatened.