In this investigation, the level of toxic metals (Cd, Pb, Hg, Cu, Ni, Al, Zn and U) was determined in sediment samples from two watersheds (Kienké and Tchangué) in the Abiete-Toko gold district, southern Cameroon. The potential contamination and toxicity of studied metals was determined by evaluating enrichment factor (EF), geo-accumulation index (Igeo) and ecological risk assessment (ERA). Considering the spatial distribution patterns, metal concentrations were lower than the average shale values, except for Cu and Ni of site 4 in the Kienké watershed and only Ni in the Tchangué watershed. In this study, the EF and Igeo values revealed that sediments were moderately polluted by Ni and Cu and unpolluted by other metals. The evaluation of the ERA based on ecological risk index (RI), ecological risk factor (Er), contamination factor (CF) and pollution load index (PLI) revealed that the sediments from the Abiete-Toko watersheds have significant to very high ecological risk assessment and are generally unpolluted by trace metals and U, except for Ni and Cu. Little quantities of heavy metals with low U levels and distribution were found at the sites close to the vicinity of artisanal mining and peri-urban areas. This proximity reveals that artisanal gold mining activities, agricultural runoff, and other anthropogenic inputs in the study area are probable sources of slight metal contamination. However, the non-use of toxic effluents for gold mining and pesticides for agriculture can be an advantage of the unpolluted status of the watersheds. The physical degradation of the ecosystem through excavations, wells and other stream diversion methods is expanding in the zone. Appropriate measures should be taken by artisans to rehabilitate the gold mining sites, to ensure appropriate treatment of wastewater and non-use of toxic effluents into nearby tributaries.

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Mining is an activity that involves the use of chemicals and results in unsustainable and dangerous conditions for the miners, their families, the community and the surrounding ecosystem. This study was done to assess metallic contamination of soils and sediments in the Bétaré-Oya gold artisanal mine district, East-Cameroon. A total of thirty (30) samples of exploited soils, control soils and sediments were taken from the mining sites of Lom, Mbal and Mali. The concentrations of heavy metals and metalloids (Fe, Sr, Cu, As, Pb and Zn) were determined by Inductive Plasma Ionisation Source Atomic Emission Spectrometry. The results show that in the sediments metals such as: As (1.82), Cu (24.22), Pb (18.04) and Zn (65.69) have average concentrations slightly higher than the UCC and Average Shale reference values. In the exploited soil As (1.93), Cu (16.86) and Zn (96.22) have average concentrations slightly higher than the UCC and Average Shale reference values.While in the cotrol soils only As (1.62) and Zn (59.72) shows an average concentration slightly above the UCC reference values. The average concentrations of the different heavy metals and metalloids were then used to calculate the intensity of contamination in soils and sediments.  The results of this calculation indicate that the Enrichment Factor (EF) of As, Sr, Zn and Pb indicate an extremely high enrichment in these elements. The geo-accumulation Index (Igeo) (22.85-25), the Contamination (CF) (1.47), the low values of the ecological risk indices suggest a low potential ecological risk and Pollution load index (PLI) (0.67) indicates extreme contamination with these elements in the soils and sediments. However, only As indicates a slight contamination (class 1) in soils and sediments. Gold panning activities and untreated mine tailings discharges would be considered as the main sources of sediment and soil pollution in Bétaré-Oya.

The purpose of this work is to characterize the sediments of the Babouri-Figuil Basin from a diagenetic point of view, the protolith context and weathering conditions, using major element geochemistry and mineralogy of the sedimentary rocks. Microscopic observations of diagenetic phenomena (on and around detrital grains of the basin), and the study of precipitation of the cement show that these sediments have undergone phenomena of compaction, dissolution, recrystallization and cementation. Cementation of quartz by silica is controlled by the rate of precipitation of silica, which is closely related to temperature than pressure. Thus, the sediments of the basin could be influenced by hydrothermalism during diagenesis, which would have inhibited their reservoir quality by generalized cementation phenomena. Geochemical features of the sediments show high contents in SiO 2 (47.49 wt% -90.79 wt%), Al 2 O 3 (2.92 wt% -23.18 wt%), Fe 2 O 3 (0.2 wt% -6.22 wt%) and alkali and alkaline earth metals (>3%). The chemical alteration index varies between 30.92% and 95.08%. This variation in the CIA values reflects the variation in the proportion of feldspars and different clay minerals in these sediments. However, the ICV calculation and the ICV versus CIA show compositional immature to mature sediments, with low to intense weathering character of these sediments. Petrographic and geochemical characteristics of sediments of the basin are compatible with the composition of the granitic and gneissic surrounding bedrocks.

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