TITLE:
Determination, Speciation and Bioavailability of Trace Metals Elements in Sabodala Mine Tailings
AUTHORS:
Mor Diop, Yacine Diouf, Babacar Diouf, Tidiane Diop
KEYWORDS:
Tailings, Contamination, Trace Metals Elements, Sabodala Gold Operations
JOURNAL NAME:
Journal of Environmental Protection,
Vol.16 No.3,
March
12,
2025
ABSTRACT: The risk of ecotoxicity from mine tailings depends on the bioavailable fraction of heavy metals in the soil, which is closely related to the biological and physico-chemical environment of the soils. The behavior, bioavailability and toxicity of heavy metals in soil depend essentially on their chemical composition. This paper seeks to quantify trace metal elements (TMEs) in mine tailings and to estimate the bioavailability and speciation of TMEs in mine tailings from the Sabodala mine using Tessier sequential extraction. The high metal levels found in the mine tailings revealed clear metallic contamination, with significant enrichment in certain elements such as arsenic (408.1 ppm), antimony (79.46 ppm), nickel (156.42 ppm) and Cd (4.16 ppm). These levels are well above the local geochemical background. This large difference is the result of human mining activity, mainly due to the geological nature of the rocks mined. Speciation studies revealed that 95% of the antimony is retained in the residual fraction, reflecting the limited toxicity of this metalloid. The average concentrations of arsenic, nickel and cadmium in the residual fractions are significant (61%, 51% and 52% respectively). This is followed by the sulphide phase, the carbonate phase, the iron and manganese oxide phase and finally the exchangeable phase. These last four phases, representing the labile fraction, contain relatively high levels of metallic elements, likely to contaminate the water and plants in the region. This labile fraction results in a high potential for mobility if conditions become more acidic. The potential mobility factors for arsenic and antimony are 5% and 2% respectively. These two metalloids (As, Sb) associated with crystalline and non-crystalline oxide, hydroxide or sulphide minerals, are considered immobile and have a low risk of polluting groundwater. Cadmium and nickel can be considered the most mobile elements in mine tailings, as around 12% and 10% respectively are found in the exchangeable and carbonate fractions.