| Abstrakt: |
Abstract We report the geochemical characterisation of hydrocarbons extracted from surface sediments of the Calabar River and coastal soils, SE Niger Delta, Nigeria using gas chromatography–mass spectrometry (GC–MS). As a result, a special group of organic compounds prevalent in the entire study area was identified. It consists of aliphatic hydrocarbons (7.3–22.2% of the total lipids) with several distinctive chemical features. These include a high abundance of even numbered n-alkanes (n-C12–n-C26, maximising at n-C18, n-C20 and n-C22), n-alk-1-enes (n-C14:1–n-C26:1, maximising at n-C18:1 and n-C20:1), giving rise to Carbon Preference Indices (CPIs) between 0.15 and 0.82. An unresolved complex mixture (UCM) occurring in the range n-C18–n-C35, and the presence of hopanes indicate petroleum contamination. The predominance of even numbered n-alkanes in the Calabar River sediments are thought to be derived from inputs of different microorganisms inhabiting an oil-polluted environment and contributing to the organic matter (OM). This paper, for the first time, gives an account of the unusual predominance of even numbered n-alkanes/alkenes in surface sediments from the Niger Delta of Nigeria and thus contributes to the information on the rare occurrence of such distributions in the geosphere. |
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