Heavy Metal Speciation by Tessier Sequential Extraction Applied to Artisanal Gold Mine Tailings in Eastern Cameroon

The Betare Oya gold district is situated in the Lom Basin, one of Cameroon's Neoproterozoic volcano-sedimentary basins. The aim of this study was to evaluate the speciation, bioavailability and potential risk of metals in mine tailing of Betare Oya gold district. The metal content of the mine tailing samples collected is evaluated using an Inductive Coupled Plasma-Optical Emission Spectrometer. Speciation was performed according to the Tessier sequential extraction procedure. The low presence of clay in the tailings of the study area reduces the adsorption and mobilization of metals. Pyrite was the dominant sulphide mineral present in the study area. Metal speciation shows that greater portion of metals are bound to Fe-Mn oxide, and decrease progressively to inert fraction, organic fraction, carbonate and exchangeable forms. Relatively high mobility factors observed for Cd, Pb, Co, Fe, Zn and Mn at all sampling sites indicate high mobility, reactivity, susceptibility and bioavailability of these metals in the mine tailings studied. The enrichment of Ni, Cd, Cu, Pb, Co, Fe, Zn and Mn in soil and sediments when compared to metal bioavailability in mine tailings can be attributed to intense oxidation and dissolution of sulphide minerals linked to primary gold mineralization, intense weathering and anthropogenic activities. Contamination index, contamination degree, enrichment factor and geo-accumulation index indicate that Cd, La, As, Hg, and Pb may pose an ecological risk. The potential ecological risk assessment shows a low to very high level of ecological risk. The evaluation of metals content and chemical speciation in the study area is necessary to predict their mobility, bioavailability and potential risk to the ecosystem and this study represents the first metal speciation study in gold mines in Cameroon.