Heavy Metal Contamination and Bioaccumulation of Cadmium, Nickel and Lead in Water and Fish Muscles from the Al-Diwaniyah River, Iraq

Abstract

Freshwater contamination by trace metals is an environmental issue of direct relevance to aquatic organisms and to communities that consume fish. This study examined cadmium (Cd), nickel (Ni), and lead (Pb) in river water and in the muscle of common carp (Cyprinus carpio) and Silurus spp. collected from the Al-Diwaniyah River, Iraq, during two sampling seasons. In each season, 45 water samples and 45 muscle samples from each fish species were examined. Water samples contained 0.016 ± 0.002 and 0.014 ± 0.004 μg/L Cd in the first and second seasons, respectively. Nickel increased from 0.035 ± 0.010 to 0.074 ± 0.040 μg/L, while Pb increased from 0.016 ± 0.010 to 0.061 ± 0.040 μg/L. In common carp muscle, Cd declined from 0.29 ± 0.07 to 0.21 ± 0.10 μg/g dry weight, Ni declined from 2.05 ± 0.38 to 0.72 ± 0.18 μg/g, and Pb declined from 12.91 ± 1.08 to 2.04 ± 0.73 μg/g. In Silurus muscle, Cd changed from 0.14 ± 0.07 to 0.15 ± 0.08 μg/g dry weight, Ni increased from 3.95 ± 1.11 to 8.87 ± 4.12 μg/g, and Pb remained similar at 6.02 ± 2.41 and 5.90 ± 3.57 μg/g. The results indicate that metal accumulation varied according to both species and sampling season. Common carp had the highest Pb concentration during the first season, whereas Silurus had the highest Ni concentration during the second season. Continued monitoring of river water, sediments, and edible fish tissues is warranted to clarify temporal changes in metal exposure and their environmental significance (Kumar et al., 2024).