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Five trace metals in Leptodius exarata, epipellic sediments and surface water from an intertidal ecosystem in the Niger Delta (Nigeria) were studied to evaluate their spatial distributions, degrees of contamination, and associated ecological and health risks. The results show that the Cd (cadmium), Cr (chromium), Ni (nickel), Pb (lead) and Zn (zinc) concentrations in sediment range from 0.

Polycyclic aromatic hydrocarbon (PAH)–degrading bacteria were isolated from aviation fuel contaminated soil at Inua Eyet Ikot in Ibeno, Nigeria. PAH-degrading bacteria in the contaminated soil were isolated by enrichment culture technique. Isolates with high PAH degrading potential characterized by their extensive growth on PAH-supplemented minimal salt medium were screened for their naphthalene, phenanthrene and chrysene degradability. The screening medium which contained selected PAHs as the sole source of carbon and energy showed that Micrococcus varians AFS-2, Pseudomonas putida AFS-3 and Alcaligenes faecalis AFS-5 exhibited a concentration–dependent growth in all the PAH–compounds tested. There were visible changes in the color of growth medium suggesting the production of different metabolites. Their acclimation to different PAH substrates was also evident as A. faecalis AFS-5 isolated from chrysene grew well on other less complex aromatic compounds. The isolate exhibited best growth (0.44 OD 600 ) when exposed to 10 ppm of chrysene for 5 days and could utilize up to 90 ppm of chrysene. This isolate and others with strong PAH-degrading potentials are recommended for bioremediation of PAHs in aviation fuel-contaminated sites in the tropics.

The concentrations and distribution of selected heavy metals in epipelic and benthic sediments of Cross River Estuary mangrove swamp were studied to determine the extent of anthropogenic inputs from industrial activities and to estimate the effects of seasonal variations on geochemical processes in this tropical estuarine ecosystem. The analysis shows that the mean concentrations (mg/kg, dw) of Cu, Cr, Fe, Ni, Pb, V and Zn vary from 24. 1-32.4, 19.9-27.4, 666.7-943.5, 15.2-30.3, 8.8-24.7, 2.2-6.9 and 140.1-188.9, respectively. An important observation is that, in general, lowest metal concentrations are found during the dry season, compared to wet season. Pollution load index (PLI) and index of geoaccumulation (I geo ) revealed overall low values but the enrichment factors (EFs) for Cr, Zn, and V were high, and this reflects the intensity of anthropogenic inputs related to industrial discharge into the estuary. The mean concentrations of Zn, Cu and to some extent Ni exceeded the Effects Range-Low (ERL) and Threshold Effect Level (TEL) values in majority of the samples studied, indicating that there may be some ecotoxicological risk to organisms living in these sediments. The inter-element relationship revealed the identical source of elements in the sediments of the studied area. The concentration of heavy metals reported in this work will be useful as baselines for comparison in future sediment quality studies.