Multivariate analysis of potentially toxic metals in sediments of a tropical coastal lagoon
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Surface sediments collected from the Lagos Lagoon, Nigeria, and three adjoining rivers were analysed for their physicochemical properties and pseudototal concentration of the potentially toxic metals (PTM) Cd, Cr, Cu, Pb and Zn. The concentration of the PTM varied seasonally and spatially. Odo-Iyaalaro was observed to be the most polluted river, with highest concentrations of 42.1 mg kg-1, 102 mg kg-1, 185 mg kg-1, 154 mg kg-1 and 1040 mg kg-1 of Cd, Cr, Cu, Pb and Zn respectively, while Ibeshe River was the least contaminated, apart from a site affected by Cu from a textile industry. Some of the sediments were found to be above the consensus-based probable effect concentrations and Dutch sediment guideline for metals. Overall metal concentrations were similar to those reported for other tropical lagoon and estuarine systems affected by anthropogenic inputs as a result of rapid urbanisation. Generally high concentrations of Pb were observed at sites close to a bridge, and this highlights the critical need for a phase-out of Pb in petrol in Nigeria. Due to the large number of samples, principal component analysis was used to examine relationships within the data set. Generally, sediments collected during the dry season were observed to have higher concentration of PTM compared to those collected during the rainy season. This means that PTM could accumulate over a prolonged period and then be released relatively rapidly, on an annual basis, into tropical lagoon systems.
Lagos Lagoon , Potentially toxic metals , sediments , principal component analysis
A. O. Oyeyiola, C.M. Davidson, K.O. Olayinka, T.O. Oluseyi and B.I. Alo (2013). Multivariate analysis of potentially toxic metals in sediments of a tropical coastal lagoon. Environmental Monitoring and AssessmentVolume 185(3), pages 2167-2177.