Environmental Assessment by Metallic Trace Elements of Gold Soils – Case of Chami (Dakhlet Nouadhibou, Mauritania)

Abstract

In the Inchiri region of northern Mauritania, the discovery of new artisanal methods for extracting gold has made the town of Chami a strategic location for gold miners and their mining operations. Despite the importance of this activity in the country's economy, to the significant revenues it provides, it is still likely to have a negative impact on the various environmental compartments. The objective of this study was to assess the environmental impact of trace metal elements (ETM) from gold panning in the soils of Chami area. For this purpose, forty soil samples were collected during a field mission in May 2022. The geochemical analyses of the ETM (As, Co, Cr, Cu, Hg, Pb, Ni and Zn) were carried out at the ALS laboratory in Dublin, using the inductively coupled plasma -atomic emission spectroscopy (ICP-AES) technique. The results show that the concentrations of ETM in soils differ according to the sampling station and the considered metal. These concentrations sometimes exceed the normal thresholds. The average value of the pollution index is higher than 1, revealing soil contamination by several elements (As, Cu, Hg and Pb). The geo-accumulation index varying between 0 and 4 shows a medium to high soil pollution class. The correlation matrix obtained shows positive correlations between the studied elements, which suggest that they have the same anthropic origin. These results show an accumulation of metals in soils that can persist in the environment, especially Hg, the most toxic element that is easy to diffuse and change speciation, in addition to being capable of causing risks to the environment and human health.