Radionuclides and trace metal pollution in sediments from the Upper Bonny Estuary in Southern, Nigeria.

Abstract

Surface Sediment cores collected from the Upper Bonny Estuary, located in Southwest Nigeria were analyzed by radiometric techniques. Gamma emitting radionuclides such as ²²⁶ Ra and ²²⁸Ra were measured using gamma-ray spectrometer to determine spatio-temporal and vertical distributions of radionuclide activities expressed in Bq·kg^-1 dry weight. The results of activities of naturally occurring radionuclide such as ²²⁶Ra (15.37 ± 02 to 34.06 ± 03 Bq·kg^-1), ²²⁸Ra (32.60 ± 05 to 48.57 ± 06 Bq·kg^-1) were all found to be within the range of typical values reported for coastal regions. Total ²¹⁰Pb in surface samples were determined via its daughter ²¹⁰Po by alpha spectrometry. The results ranged from 57.83 Bq.kg^-1 dw to 131.69 Bq.kg^-1 dw for the various stations. Ratios of ²²⁶Ra to ²²⁸Ra suggested accretion for all samples with low sediment accumulation registered during rainy season. The concentrations of trace metals (Ca, Mg, K, Zn, Pb, Cd, Co, Cr, Cu, Fe, Ni and Na) were determined using a Varian Atomic Absorption Spectrophotometer. Cr varied significantly (p < 0.05) with its range of mean values presented in mg/kg along with variations at statistically significant level.