Speciation of Some Heavy Metals in Sediments of the Pennington River, Bayelsa State, Nigeria
Speciation helps in the identifications and quantification of the defined geochemical fractions, forms or phases in which an element exists in the environment. Speciation in sediment compartment is a significant step to understand the potential environmental risk, distribution, mobility and bioavailability of pollutants. The total heavy metal concentrations of some environmentally toxic metals in sediments of the Pennington River System, Bayelsa state, Nigeria was examined. The concentrations of heavy metals in each fraction were determined using a ANALYST 400 Perkin-Elmer AAS. The mean concentrations (mg/kg) for the six metals in dry season sediment samples were: 0.14±0.17(As), 0.39±0.55(Co), 2.43±5.06(Cu), 26.82±22.19(Fe), 0.69±1.10(Pb), and 1.22±1.19(Zn), while the mean metal concentrations (mg/kg) in wet season samples were:0.11±0.18(As),0.37±0.6(Co), 2.07±4.35(Cu), 26.65±24.79(Fe), 0.61±1.08(Pb), and 1.11±1.00(Zn) respectively. Speciation study applying the five-stage sequential extraction scheme revealed that As, Co, and Pb in sediment prevails mostly in exchangeable fraction. Cu and Zn were more prevalent in residual fraction, while Fe was found more in residual and Fe/Mn-Oxide fractions. In an attempt to infer anthropogenic input from natural input, comparison with sediment quality guideline (SQGs) and ecotoxicological sense of heavy metal contamination was employed. The concentration of the studied heavy metals in Pennington River System does not pose a threat to the sediment dwelling fauna and anyone who consumes aquatic animals, particularly fish, from the Pennington River. According to SQGs, the studied heavy metals of the Pennington River sediments were under the category of non-polluted. Speciation is a powerful and versatile technique for predicting the degree of contamination risk of a river system. In this present study, all heavy metals investigated are relatively stable under normal conditions of Pennington River system. This means that there is a low source of pollution arriving to the Pennington River system. Iron was found to be the highest occurring heavy metal and arsenic was the least occurring heavy metal in this study. Furthermore, there is no heavy metal pollution threat pose to sediments dwelling fauna and anyone who consume aquatic animals, particularly fish from the Pennington River system. To preserve the unpolluted state of the Pennington River system it remains important that allochthonous inputs are devoid of heavy metals.
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