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.
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