Polycyclic Aromatic Hydrocarbons in Sediment and Tympanotonus fuscatus from the Upper Reaches of the Bonny Estuary

Abstract

Polycyclic aromatic hydrocarbons (PAHs) in sediment and Tympanotonus fuscatus were investigated in the Iwofe River, Rivers State, Nigeria, to assess contamination and bioaccumulation in an estuarine environment affected by anthropogenic activities. Sediment and T. fuscatus samples were collected bimonthly over a twelve-month period, and organisms were handpicked from intertidal swamp areas during low tide. PAHs were extracted and quantified using high-performance liquid chromatography with fluorescence detection. Detected PAHs were classified as individual compounds, low-molecular-weight PAHs, high-molecular-weight PAHs and carcinogenic PAHs. The bio-sediment accumulation factor was calculated to assess uptake from sediment into organism tissues. PAH concentrations recorded across sampling months ranged from 0.010 to 0.288 mg/kg in sediments and from 0.0004 to 0.093 mg/kg in T. fuscatus tissues. Sixteen priority PAHs were detected in both matrices. BSAF values were below one for most compounds, whereas benzo(b)fluoranthene showed a markedly higher value of approximately 15. Carcinogenic PAHs accounted for 2% of total PAHs in sediment and 17% in T. fuscatus. The mixed distribution of low- and high-molecular-weight PAHs suggests possible inputs from both petroleum-related and combustion-related sources. The findings indicate that sediment and T. fuscatus are useful complementary matrices for monitoring PAH contamination in the upper reaches of the Bonny Estuary.