Abstract

The distributions and concentrations of extractable fatty acids (FAs) and alcohols (FALs) in surface sediments of the Imo River were determined to estimate the relative proportion of terrigenous and autochthonous fractions of organic matter (OM) input to the river. The range of total organic carbon (TOC) content (2.10-4.58%) is typical for coastal environments and comparable to those of other river systems within the Niger Delta region. This may be a reflection of the sheltered basin morphology and high energy conditions of the river, characterized by overwhelming sand fraction. The contribution from terrestrial vegetation appears to predominate the distribution of FAs (21.17-75.16%) and alcohols (38.7-81.7%), in contrast to many aquatic sediments whose distributions are either phytoplankton or bacteria dominated. This may be linked to the relatively shallow water depth, oxic and refractory nature of the sedimentary organic carbon of the area as well as proximity of most sampling points to terrigenous source. Utilization of ratios confirmed this pattern and indicated that the OM deposited at the time of sampling was not fresh. The dominance of 19:0 acids in some samples is associated to an input from a certain consortium of bacteria with a different physiological structure inhabiting petroleum contaminated environment.

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