Uptake of polycyclic aromatic hydrocarbans by the fingerlinks of Oreochromis niloticus (Linneaus, 1757) from the dispersed phase of bonny light crude oil

K.E. Lelei, F.D. Sikoki


In many crude oil spill sites, dispersants are widely applied during clean-up operations without adequate consideration of their environmental effects. This is despite the fact that the water accommodated fractions of these mixtures contain toxic components. This study investigated the uptake of polycyclic aromatic hydrocarbons (PAHs) from the water accommodated fractions (WAF) of a mixture of a dispersant, Goldcrew and Bonny Light crude oil using a tilapian fish, Oreochromis niloticus. The aim was to determine the critical body residue (CBR) of the PAHs in the fish exposed to the dispersed, dispersant and crude oil in water (DCOWAF-PAH) and undispersed, crude oil in water only (COWAF-PAH) regimes of the mixtures in the WAF. The control experiment had water only. The concentrations for both regimes of exposure were at sub-lethal levels of 0.2, 0.4, 0.8 and 1.6ml/L for fifty days using renewal static bioassay. The types and total concentrations of PAHs were analyzed for in the crude oil, fish feed administered, preexposed fish sample, dispersant and test water before exposure. The sixteen known carcinogenic PAHs were found in the crude oil (1916.4ppm), eleven in the fish feed (0.57ppm), three in the pre-exposed fish
(0.007ppm), and none in the dispersant and test medium (water). The concentration of the PAHs in the fish from the DCOWAF-PAH ranged from 3.6128-7.9744ppm while that of the COWAF-PAH ranged from 3.4114-
3.9693ppm. The concentrations of individual PAHs recovered in the fish showed that napthalene had the highest CRB level of 6.7780ppm and 3.2610ppm, anthracene was 0.6590ppm and not detected (N.D) while acenaphthene had the lowest CBR of 0.00001ppm and below the limit of quantification (<LOQ) for
the DCOWAF-PAH and COWAF-PAH exposure phases respectively. The results showed the order of the CBR level as NAP>FL>BaF>BaP>BaA>FLU>PHE in the COWAF-PAH irrespective of exposure concentration, while for the DCOWAF-PAH, it was NAP>FLU>BaF>BaP>B(ghi)P>BaA>BkF>PHE. The results demonstrated that the presence of the dispersant, Goldcrew increased the critical body residue of the PAHs irrespective of the concentration in the fish samples. This was especially so for the low molecular weight PAHs (<200). Thus, the application of dispersants for crude oil spills need to be done with utmost care particularly in fishing grounds

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