Contamination by heavy metals from mining activities: An ecological impact assessment of Mura and Kimpulande Rivers, Democratic Republic of the Congo

The contamination levels and distribution of heavy metals were assessed in riverbed sediments and water column samples from Mura and Kimpulande Rivers, both impacted by copper-cobalt and gold mining activities. Analyses were performed using inductively coupled plasma-mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS), and atomic fluorescence spectrometry (AFS). Results showed high concentrations of Ni, Cu, Zn, As, Cd, and Hg in water samples. The concentrations of As, Cd, and Hg in water from both rivers exceeded the limits set in Democratic Republic of the Congo (DRC) legislation on requirements for mine water discharges. High concentrations were found also for Cu, Cr, Zn, As, Cd, Pb, and Hg in river sediments and were assessed against sediment quality guidelines for the protection of aquatic life. The Enrichment factor (EF) and the Geoaccumulation index (Igeo) values revealed extremely severe enrichment of Cu, Co, As, and Cd and extreme pollution by Cu and Co in sediment samples demonstrating high contamination of these rivers. The results from calculated ecologic risk factors revealed that aquatic ecosystems in the investigated rivers are at risk. Therefore, a review of current mining practices is needed and the urgent enforcement of good practices is recommended in order to protect the environment and public health.