Water Quality and Ecotoxicological Impacts of Surfactants and Heavy Metals in Urban Rivers of Benin City, Niger Delta, Nigeria
Okpoji Awajiiroijana U. *
Department of Pure and Industrial Chemistry, University of Port Harcourt, Choba, Nigeria.
Orji-Azuka Loveth N.
Department of Zoology, University of Ibadan, Nigeria.
Igwegbe Kelvin C.
Forensic Toxicology Laboratory, National Counter Terrorism Centre, Abuja, Nigeria.
Ekwere Ifiok O.
Department of Chemistry, Akwa Ibom State University, Ikot Akpaden, Nigeria.
Ewuola Akinola A.
Department of Chemistry, Federal University of Technology, Akure, Nigeria.
Garuba Muhammed H.
Department of Chemistry and Industrial Chemistry, Kwara State University, Malete, Nigeria and Department of Science Education, Bayero University, Kano, Nigeria.
Etukudo Esther W.
Department of Chemistry, Akwa Ibom State University, Ikot Akpaden, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Urban rivers in Nigeria are increasingly affected by detergent residues, domestic wastewater, and trace-metal inputs associated with rapid urbanisation. This study assessed the physicochemical characteristics, surfactant concentrations, and selected heavy metals in three urban rivers in Benin City, Edo State. Water samples were collected once from midstream points in each river and analysed for pH, dissolved oxygen (DO), biological oxygen demand (BOD), chemical oxygen demand (COD), turbidity, linear alkylbenzene sulfonates (LAS), sodium dodecyl sulfate (SDS), and metals (Ni, Cu, Zn, Mn, Fe) using APHA, MBAS, and AAS methods. pH ranged from 6.5 to 6.9, DO from 4.8 to 5.5 mg/L, BOD from 18 to 22 mg/L, COD from 40 to 50 mg/L, and turbidity from 10 to 15 NTU, with River B consistently exhibiting the poorest water quality. Surfactant concentrations were highest in River B, where LAS reached 0.22 mg/L and SDS 0.12 mg/L. Heavy metals followed the same spatial pattern, with River B recording the highest values of Ni (25 µg/L), Cu (17 µg/L), Zn (60 µg/L), Mn (110 µg/L), and Fe (350 µg/L), the latter exceeding WHO limits. The combined occurrence of organic enrichment, elevated surfactants, and trace metals indicates substantial anthropogenic influence and potential ecological stress, although biological impacts were not directly measured. These findings highlight the need for strengthened wastewater management, regulation of detergent-rich effluents, and routine monitoring to protect vulnerable urban freshwater ecosystems.
Keywords: Surfactants, heavy metals, urban rivers, water quality, Benin City