Heavy Metals Pollution of Water and Sediment in Mada River, Nigeria

Abstract

Sediment acts as a sink for heavy metals, which may be remobilized into the water column. The research was carried out to assess seasonal distribution and impact of heavy metals (Zn, Mn, Ni, Fe, Cu, Cr, Cd) concentrations in sediment on the overlying water. Water and bed sediment samples were collected from Mada River during rainy and dry seasons and analyzed for the heavy metal concentrations, using atomic absorption spectrophotometer (AAS). Metal levels in water were higher during the dry season, except for the decrease in Fe (3.79±0.94 mg/L) and Mn (0.20±0.12 mg/L) concentrations. Metal levels in sediment decreased during the dry season, however, Zn (0.25±0.02 mg/kg) and Ni (0.025±0.02 mg/kg) showed an increase in concentrations. Metal levels were higher in water and sediment during dry and rainy seasons respectively. Sediment contained higher metal concentrations compared to water. Partition coefficients (Kd) values during the dry season were less than 1 except for Mn (1.35), but greater than 1 during rainy season, excluding Zn (0.39) and Ni (0.77). Correlations between metal concentrations in sediment and water were positively strong for Cu (0.7825) and Mn (0.9428). Cr, Fe and Mn levels in water and sediment were significantly different (P = .05) for both seasons. Remobilization of metals from sediment surfaces onto overlying water might account for the low Kd values and higher metal levels in water during the dry season.