Diversité ichtyologique et niveau de contamination des matrices eau-sédiment-poisson par les effluents miniers des rivières Ulindi et Elila en Territoire de Mwenga, Est de la RD Congo
| dc.contributor.author | Mukabo Okito Gabriel, MSc | |
| dc.date.accessioned | 2025-11-05T07:01:32Z | |
| dc.date.available | 2025-11-05T07:01:32Z | |
| dc.date.issued | 2024-02 | |
| dc.description | Thèse présentée et défendue publiquement En vue de l’obtention du grade de Docteur en Sciences Naturelles et Environnement (PhD) Spécialité: Ecotoxicologie et Gestion de l’Environnement Aquatique | |
| dc.description.abstract | In order to understand the impact of mining activities on the quality of the water, sediments and physiology of fish in the Ulindi and Elila rivers and some of their tributaries in the Mwenga Territory, a systematic inventory of fish with identification, The effect of intensive mining on the health of fish living in the upper basins of the Ulindi and Elila rivers was studied between June 2018 and March 2022 by comparing the reproductive, hepatic and gill systems of fish sampled at sites upstream and downstream of mining operations. Water, sediment and fish muscle samples were analysed for total mercury (T-Hg), lead (Pb), cadmium (Cd), nickel (Ni), chromium (Cr), arsenic (As), copper (Cu), zinc (Zn), manganese (Mn) and iron (Fe) using atomic absorption spectrophotometry. Several indices (WQI, LPI, HPI, FC, LPI, IGEO, FBA) were calculated to assess the level of contamination of the water-sediment-fish. Histological changes in organs were studied at two different trophic levels using two fish species Oreochromis niloticus and Labeobarbus pellegreni for which a semi-quantitative assessment was carried out and the results were classified according to the severity of histological responses. The health risk associated with eating fish from these rivers was assessed. The results obtained show the taxonomic presence of 41 species of fish in the study area, divided into 5 orders, 10 families and 20 genera. The best represented orders are Siluriformes, Cypriniformes and Perciformes, with 15, 13 and 9 species respectively. The Cyprinidae family was the most diverse, followed by the Amphilidae, Clariidae and Mochokidae families with 5 species each. 10 species of fish were reported for the first time in this part of the Ulindi river basin. With regard to the distribution of fish, the Shannon and equitability indices indicate sparsely and evenly distributed populations. The distribution of species by station shows that there are links of similarity and/or a complex set of interrelationships between the different variables of several orders that describe the environment of the stations and the species present. In addition, from an ecotoxicological point of view, this study showed that the upper basins of the Ulindi and Elia rivers in the Mwenga territory in eastern DRC are indeed contaminated by mercury, lead, arsenic, cadmium and chromium. The water at the various sampling sites contained levels of TMEs in excess of the thresholds recommended by the WHO and the EU for drinking water. The sediment analysis results showed low concentrations compared with the standards set by the WHO, EU and CCME for freshwater sediments. The study also showed that water contains more TMEs than sediments, while pelagic fish, Oreochromis niloticus, are more contaminated with Cd and Pb than benthic fish, L. pellegreni, which are more contaminated with mercury. And that the concentrations of TMEs found in the gonads and livers of two species of fish studied (Oreochromis niloticus and Labeobarbus pellegrini) were generally above the standards recommended by the WHO for consumption. Cd and Pb were most concentrated in all the organs analysed for both species and exceeded the 0.5 mg/kg limit recommended by the WHO/FAO, while the highest Ni values were found only in the gills and testes, with 0.08 and 0.06 mg/kg respectively. Mercury was most accumulated in the liver, ovaries and testes of L. pellegreni with respectively 0.30, 0.45 and 0.48 mg/kg exceeding the recommended limits for each of these organs. Histopathological results showed that L. pellegrini accumulated more Hg than O. niloticus. Exposure to mercury, a pollutant capable of disrupting reproduction with a high rate (70%) of prevalence of ovotestis in the male gonads in L. pelegrini. Finally, the results of the risk assessment linked to the consumption of polluted fish show that the daily exposure doses (DIE) obtained for each of the TMEs analysed in O. niloticus fish are all below the tolerable daily intake (TDI) for both adults and children. And the hazard quotient calculated for each metallic element considered is less than 1, which indicates that there is no risk of toxic effects linked to the TDEs considered in relation to the consumption of O. niloticus fish from the study area in both adults (TDI = 0.199 < 1) and children (TDI = 0.498 < 1). Education and awareness of optimal levels of heavy metals in fish is crucial and this information must be made available to the public to ensure that nature and human health are not in conflict. To mitigate the impact of mining effluents on the Ulindi and Elila rivers, it is advisable to adopt sustainable mining waste management practices. These practices include pre-treatment of effluent to reduce contaminants before discharge into these rivers, regular monitoring of water and sediment quality, and ongoing ecotoxicological studies to assess the health and diversity of fish populations. | |
| dc.identifier.uri | https://repository.ub.edu.bi/handle/123456789/2127 | |
| dc.language.iso | fr | |
| dc.publisher | UB, ED | |
| dc.title | Diversité ichtyologique et niveau de contamination des matrices eau-sédiment-poisson par les effluents miniers des rivières Ulindi et Elila en Territoire de Mwenga, Est de la RD Congo | |
| dc.type | Thesis |