Heavy metal contamination and ecological risk in Kabompo River, Northwestern Zambia

Abstract

Rivers are vital water sources that support aquaculture, agriculture, and domestic use, particularly in rural communities. Assessing heavy metal contamination and ecological risks is essential for sustaining these functions. This study assessed heavy metal contamination and ecological risks in the Kabompo River, Northwestern Zambia, by analysing water and sediment samples across ten sites. Water quality analysis revealed that Cadmium (Cd), Chromium (Cr), Cobalt (Co), Copper (Cu), Iron (Fe), Lead (Pb), and Zinc (Zn) concentrations were all within permissible limits set by the Zambia Bureau of Standards (ZS 190:2010), while nickel remained undetected. In sediments, the highest concentrations of zinc (23.56 ± 0.83 mg/kg), copper (31.43 ± 0.64 mg/kg), lead (4.50 ± 0.49 mg/kg), and cobalt (15.55 ± 0.58 mg/kg) occurred at the Kabompo–Lunga River confluence, while lower levels were observed at Chikalakala and Kauchimba. Enrichment factor analysis indicated severe enrichment of zinc, copper, and lead (EF > 10) at Chikalakala, Christella, and the confluence. Geoaccumulation index (Igeo) values were generally below zero, indicating no contamination, although copper approached moderate pollution levels at Christella and the confluence. Ecological risk indices (ERI) and contamination degrees (CD) indicated minimal ecological risk overall, though elevated metal levels at the confluence and Kalende warrant periodic monitoring. These findings suggest that the Kabompo River remains ecologically viable for aquaculture and other uses, but localised enrichment at selected sites highlights the need for routine monitoring and targeted pollution control to ensure sustainable use, particularly in regions influenced by mining activities.