Shrimp species (Macrobrachium felicinum) collected from estuarine mangrove area of the Imo River is an important route of exposure to polycyclic aromatic hydrocarbons (PAHs). The estuarine associated sediment (EAS) composited sample showed higher TPAH, ΣAlkyl, ΣPAH and ΣPAH concentrations (550.84, 172.36, 413.17 and 482.11 ng/g dry weight-dw) than their mean concentrations in shrimp samples (509.39 ± 354.21, 31.38 ± 18.49, 52.10 ± 1.35 and 460.06 ± 330.76 ng/g wet weight-ww), respectively. Among the individual PAHs congeners, phenanthrene was the dominant species detected in the EAS accounting for 21.02 % of the total PAH load and the decreasing order of 3- > 2- > 5- > 4- > 6-ring contamination was found. A different pattern predominated by naphthalene was observed for the shrimp species, suggesting that the organisms have different selectivity for a range of PAHs congeners. These variations may be attributed to different degree of bioavailability of these compounds, characteristic sandy lithology of the EAS and the protective capacity of soot particles associated with liquid fossil fuel combustion masking the uptake of high molecular weight PAHs by the organisms. Cancer risk associated with consumption of shrimps in the region was assessed using estimated daily intake (EDI) and compared with standards. The EDI values for naphthalene, benzo(a)pyrene and ∑PAH were lower than the USEPA benchmarks and EFSA levels of concern values for adult and children population, suggesting low probability of developing cancer.

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-C(12)-n-C(26), maximising at n-C(18), n-C(20) and n-C(22)), n-alk-1-enes (n-C(14:1)-n-C(26:1), maximising at n-C(18:1) and n-C(20:1)), giving rise to Carbon Preference Indices (CPIs) between 0.15 and 0.82. An unresolved complex mixture (UCM) occurring in the range n-C(18)-n-C(35), 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.

Polycyclic aromatic hydrocarbon (PAH) analyses of surface sediments from the Cross River estuary by gas chromatography-mass spectrometry indicated natural diagenetically derived PAHs in the upper estuary, with minor and variable amounts of petrogenic and combustion-derived PAHs from human activities (lower estuary). The occurrence of significant amounts of perylene (average 23% of all PAHs) with the diagenetic natural PAHs in the middle estuary bordered by mangrove forests supports its origin from terrestrial organic matter. The natural PAHs represent the highest percentage (average 76%) of the total PAHs in this tropical environment. The traditional geochemical parameters, including the petrogenic PAHs, confirmed trace petroleum contamination in the estuary. Specific PAH ratios such as Fl/Py and Fl/(Fl+Py) also support this source contribution.

No abstract

No abstract