Assessment of heavy metalcontamination and ecological risks in cultivated wetlands of Northern Akwa Ibom State, Nigeria

The study aim to access the ecological health risks of heavy metals in water and sediments of cultivated wetlands of Northern, Akwa Ibom State, Nigeria. Water samples were collected using Polyethylene bottles, while a modified van-veen grab sampler was used for the sediment, and analyzed based on standard laboratory methods. The indices used where heavy metal pollution index (HPI), comprehensive pollution index (CPI),contamination index (Cd), contamination factor (CF), degree of contamination (DC), geo-accumulation index (Igeo), quantification of contamination (QoC), ecological risk factor (Er), and potential ecological risk index (PERI).The results showed that the mean value of Ni, Cd, and Zn across the locations, Cu (1 and 3), and Pb (2 and 3) in water exceeded the permissible limits. The HPI values across the locations exceeded the threshold, ranging from 374.8 to 512.7, Cd ranged from 31.3 to 49.3, while CPI ranged between 5.473 and 8.042, indicating heavy contaminated water. Cadmium levels in sediments exceeded Australian and New Zealand sediment standards, while Arsenic (2 and 3), and Cadmium exceeded permissible limits. The sediment indices indicated that Cd, Cu, and Pb were the major metallic pollutants. The indices indicated the following-CF: Cu (moderate, and Cd (very high); CD (very high); Igeo: Cd (very highly polluted); QoC: Cd, Mn, Zn, Cu, and Fe (anthropogenic); Er: Cu (3) was high, while Er levels for Pb was very high, and PERI (high). The study revealed that the wetlands were contaminated due to agricultural activities. Constants monitoring and remediation processes are strongly recommended to salvage the wetland ecosystem.