Geochemical Speciation and Ecological Risk of Heavy Metals in Estuarine Sediments of the Qua Iboe River, Nigeria

Abstract

This study investigated the chemical properties of marine sediments and the distribution of heavy metals in a river estuary in Akwa Ibom State. Sediments were collected from 10 geo-referenced points using a standard steel grab sampler. Physical parameters were analysed with standard laboratory instruments, while hydrometer methods determined grain size, metal analysis was performed using were determined using an Inductive Coupled Plasma-Mass Spectrometry and pollution levels were assessed. The sediment pH ranged from 6.32 to 7.88, with a moderate level of organic carbon (1.45 - 3.62%), and fine particles such as salt (42.7%) and clay (20.7%), which favour metal retention. The concentration of heavy metals (mg/kg) followed the order of Fe > Mn > Zn > Cu > Cr > Pb > Ni > Cd. Pollution indices identified Cd and Pb as the major contaminants, with Cd exhibiting a high ecological risk (Er=143). The estuary displays a moderate level of contamination influenced by petroleum activities and domestic discharge.