Toxicity and Bioaccumulation of Heavy Metals and Polycyclic Aromatic Hydrocarbons in Estuarine Fish from the Andoni Estuary, Niger Delta, Nigeria
Okpoji Awajiiroijana U. *
Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Nigeria.
Akpan Nsima A.
Department of Chemical Sciences, Ritman University, Ikot Ekpene, Nigeria.
Eze Victor C.
Department of Chemistry, University of Agriculture and Environmental Science, Umuagwo, Nigeria.
Ijioma Chinonye C.
Department of Chemistry, Alvan Ikoku Federal University of Education, Owerri, Nigeria.
Hassan Dasuki H.
Department of Chemistry, Nigeria Police Academy, Wudil, Kano, Nigeria.
Kareem Muili M.
Department of Science Education, Bayero University, Kano, Nigeria.
Obi Amalachukwu I.
Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Nigeria.
Aningo Gloria N.
Department of Chemistry, Kogi State College of Education, Kabba, Nigeria,
Okoye Peter I.
Department of Industrial Technology Education, Nnamdi Azikiwe University, Awka, Nigeria.
Ogbonnaya Charles N.
Department of Public Health, Madonna College of Health Technology, Umuahia, Nigeria.
Ekwere Ifiok O.
Department of Chemistry, Akwa Ibom State University, Ikot Akpaden, Nigeria.
Okeke Chioma F.
Department of Chemistry, Abubakar Tafawa Balewa University, Yelwa, Nigeria.
Aligwo Michael C.
Department of Chemistry, Alex Ekwueme Federal University, Ndufu-Alike, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Estuarine ecosystems of the Niger Delta are increasingly exposed to contaminants arising from petroleum exploration, gas flaring, artisanal refining, and domestic effluents. This study assessed heavy metals and polycyclic aromatic hydrocarbons (PAHs) in four edible estuarine species—Tilapia sp., Clarias gariepinus, Sarotherodon melanotheron, and Macrobrachium vollenhovenii—collected during the wet season (June–August) from the Andoni Estuary, Rivers State. A total of 24 samples (six per species) were analysed. Muscle tissues were digested and analysed for Pb, Cd, Hg, As, and Cr using atomic absorption spectrophotometry, while naphthalene, anthracene, fluoranthene, and benzo[a]pyrene were quantified using gas chromatography (GC-FID). Bioaccumulation factors (BAF) were calculated from concurrent water measurements. Lead (0.38–0.52 µg/g) and arsenic (0.10–0.15 µg/g) exceeded WHO limits, especially in Clarias gariepinus and Tilapia sp., whereas Cd, Hg, and Cr remained within permissible ranges. ΣPAHs were highest in Clarias gariepinus (0.58 µg/g), with benzo[a]pyrene detected in all species. BAF values exceeded 1 for all contaminants, confirming active bioaccumulation. These findings indicate chronic petroleum-related pollution in the Andoni Estuary and highlight potential human-health risks associated with fish consumption.
Keywords: Heavy metals, PAHs, bioaccumulation, Estuarine fish, Niger Delta