Environmental Dominance and Potential Impacts of Endocrine Disruptors On the Surficial Sediments of Calabar River, South Eastern Nigeria

Abstract

Endocrine disrupting chemicals (EDCs) are persistent toxic organic and inorganic chemicals that enter the aquatic environment through point and non-point sources and alter the physico chemical nature of water and the physiology of aquatic organisms. Of significance are the organochlorine pesticides (OCPs) and the polychlorinated biphenyl (PCBs) contamination of aquatic ecosystems. The study was conducted to provide baseline data and information on the extent of surface sediments contamination by the EDCs in the Calabar river, Nigeria. Surficial sediments from five in equidistant locations were sampled using the Van Veen sediment sampler in the dry and wet seasons of 2014 and 2015. The TOC in the surface sediments for the dry and wet seasons were 33.84 ±0.21 and 54.44±0.14 % respectively. The EDCs were highest during the wet season than the dry season suggesting the desorption and re-mobilization of organochlorines from contaminated soils into the riverine system. The ∑OCP residues ranged from 12.93±0.06µg/kg dry wt in the dry season to 23.50±0.01µg/kg dry wt in the wet season. The ∑PCB concentrations, 4.02± 0.2µg/kg dry wt (dry season) and 7.26± 0.11µg/kg dry wt (wet season) were however lower than the OCPs during the study period. Most of the EDC values were above the permissible limits and maximum contaminant levels of USEPA, indicating that the Calabar river sediments are potentially contaminated as a result of anthropogenic activities entering the system. The implications of the observed seasonal trend with respect to contamination of sea foods and posing of ecological risks to humans are discussed. This study forms part of the ongoing environmental assessment of the pollution status of Nigeria’s marine and coastal ecosystems.