Assessment of water quality and time accumulation of heavy metals in the sediments of tropical urban rivers: Case of Bumbu River and Kokolo Canal, Kinshasa City, Democratic Republic of the Congo

The highest concentrations of heavy metals in sediments reached the values of (in mg.kg−1) 190.2 (Cu), 58.6 (Cr), 1117.9 (Zn), 1.2(Cd), 149.2 (Pb), and 11.8 (Hg). The results indicate high variability in metal concentrations in surface sediments according to sampling period and sites. In general, all metal concentrations showed a gradual increase with time, e.g. Cd and Pb consistently increased during the three sampling years. All analysed metals were above SQGs during the year 2017 and 2 to 4 times higher than PELs. EF and Igeo showed severe enrichment to extremely severe enrichment, and moderate to extremely polluted by Zn and Pb. Correlation analysis suggested that the metal contamination in the studied sites is caused by the anthropogenic activities as well as the influence of urban effluents discharge into the river receiving systems. The results of the present study will be helpful to assess and intervening effective management strategies at the local input source pollution level and similar environments.