Bioavailability of polycyclic aromatic hydrocarbons (PAHs) and Environmental Risk (ER) Assessment: The case of the Ogbese river, Nigeria (original) (raw)
h i g h l i g h t s • Greater influence of sediment clay particles in partitioning of PAHs over other factors. • High molecular weight PAHs were more sensitive to the OC changes than low molecular weight PAHs. • Variability in specific interactions and unequal partition efficiencies with sediment organic matter under natural condition. • Partition effect of PAHs with SOM increases more rapidly with increasing molecular weight. • Natural organic matter is an important sedimentary hydrophobic domain in PAH assessment. a b s t r a c t Pollution from PAHs in porewater and surficial sediments of the rapidly contaminated Ogbese River, Ondo State, Nigeria was investigated. Samples were extracted using Hexane/methylene chloride mixture and the complex PAH mixtures were analyzed by gas chromatography-mass spectrometry. There was greater influence of sediment fine particles (R 2 = 0.978) in partitioning of PAHs over other factors. Total concentration of PAHs in the sediments and porewater ranged 14.45 µg g −1 to 26.78 µg g −1 (n = 8, dry weight) and 6.25 µg L −1 to 13.93 µg L −1 (n = 8) respectively. The measured partition coefficients (i.e., K oc values) of the individual PAHs between sediment organic matter (SOM) and porewater across all locations ranged from 5.027 (±0.157 SD) to 5.074 (±0.169 SD). The correlation in log K oc (observed vs predicted) for high molecular weight/low molecular weight-PAHs suggests variability in specific interactions and unequal partition efficiencies with SOM under natural condition. Based on equilibrium partitioning and narcosis model, three PAHs {benzo(b)fluoranthene, benzo(a)pyrene and dibenz(a,h)anthracene }has toxic unit (TU) values of concern. These results represent a baseline report for future monitoring programs of PAHs.
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