Statistical Approach of Selected Heavy Metals in the Sediments of the Mfouati River (South of Congo Brazzaville)

Abstract

Aims: The general objective of this study was to evaluate heavy metals [Molybdenum (Mo), Cobalt (Co), Cadmium (Cd), Nickel (Ni), Antimony (Sb), Bismuth (Bi)] in the sediments of the Mfouati River near the area impacted by the mining operation. Study Design: The sediments were collected in the area near the abandoned plant and in the vicinity. At the end of the sampling, the samples were analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Place and Duration of Study: Sediments were collected in the Mfouati River near the area impacted by the mining operation, these samples were taken in September 2021. Methodology: X-ray diffraction was performed on the sediments of the Mfouati River, the physico-chemical parameters were measured with a Hanna type apparatus. The contents of heavy metals (Mo, Co, Cd, Ni, Sb, Bi) in the sediments were measured by optical emission spectroscopy (ICP-OES). The level of metallic contamination, the indices of evaluation of the contamination (FC, FE, Igeo) were calculated by using the expressions which exist in the literature. Results: The results obtained show that the physical-chemical parameters (pH, EC and TDS) measured are within the standards (WHO). Only the pH which presents a slightly acid character at the stations (S4, S5, S6). The heavy metal contents found (mg/Kg) vary between Mo: [0,05-23] ; Co:[10-39] ; Cd[0,1-63] ; Ni[7-36] ; Bi[0,164-0,169] ; Sb[1-29]. X-ray diffraction showed the presence of the following minerals: Talc and Kaolinite. The results of contamination factor showed the following order:FC(Cd)> FC(Sb) >FC(Mo) >FC(Co) >FC(Bi) >FC(Ni);enrichment factor the order is as follows: FE(Cd)>FE(Sb)>FE(Fe) >FE(Bi) >FE(Mo); geo accumulation index the order is as follows:Igeo(Ni)>Igeo(Co) >Igeo(Mo) >Igeo(Sb) >Igeo(Cd) >Igeo(Bi). Conclusion: The levels of metals Co, Cd, Ni, Sb, Mo in the sediments of the Mfouati River are higher than the concentrations in the terrestrial crust.