Levels of PAHs in shrimps, Penaeus monodon from Jones Creek southern Nigeria
Polycyclic aromatic hydrocarbons (PAHs) were measured in shrimp samples (Penaeus monodon) of Jones Creek southern Nigeria during the rainy and dry seasons and analysed for 16 priority PAHs. The ΣPAHs ranged from 0.073 to 0.800 mg/kg for shrimp samples collected for the 18 month duration of this study. Fluorene and anthracene were the most dominant PAH observed with concentrations of 0.084 ± 0.010 mg/kg and 0.059 ± 0.007 mg/kg respectively. Fluorene was also the most detected PAH comprising 21.91% of the 16 PAHs detected while benzo(g,h,i)perylene was the least with 0.02%. The source of contamination is closely related to human activities such as domestic and industrial discharges, refining activities and street runoff. High concentrations were recorded during the rainy season and during the first quarter of the year. The investigated samples were classified as minimally contaminated when compared with FDA levels of PAHs in shrimp samples. Distribution patterns showed that PAHs with 3 and 4 rings dominated confirming the pyrogenic source of the detected PAH. Diagnostic ratios such as phenanthrene/anthracene and benzo(a)anthracene/chrysene were achieved to evaluate the emission sources of PAHs. These ratios indicated a pyrolytic source of PAHs for sediments, as well as a pyrolytic or pyrogenic origin of the PAHs detected in the shrimp samples obtained within the study area.
Key words: PAHs, sediment, shrimps, cancer risk, diagnostic ratio.