Geochemical assessment and transfer of potential effects of metallic trace elements around abandoned mining sites in Kettara region (Morocco)

Abstract

The degradation of environmental quality due to pollution is a pressing concern worldwide, particularly in areas that have been abandoned after mining activities. One significant aspect of this degradation is the contamination of soil and water resources by Metallic Trace Elements (MTE). These elements, originating from mining operations, pose serious environmental and human health risks, necessitating urgent attention and remediation efforts. Understanding the characteristics and extent of MTE contamination in abandoned mining areas is crucial for effective environmental management and sustainable development. In this context, this study aims to investigate the patterns, distribution, and impacts of MTE contamination in soil and water resources within Kettara abandoned mining areas (Morocco), offering insights into potential mitigation strategies and policy interventions to address this critical environmental issue. Stream and groundwater samples were collected in the Kettara region where the abandoned tailings constitute with Acid Mine Drainage (AMD), the principal source of this contamination. Stream samples were collected in 2018 at fourteen points near sixteen hydrogeological wells and situated at different distance from the pollution source.

This study addresses an environmental concern, focusing on the dispersion of MTE such as Arsenic, Zinc, and Nickel in both streams and groundwater. Through geochemical analysis, it is revealed that Arsenic is particularly prevalent, with higher concentrations detected in streams, especially those proximate to mining waste sites. The main sampling water near the abandoned mine shows several anomalies (As, Ni and Zn). The higher As concentration in the stream samples E1 and E2 with 179.55 and 96.63 ppm and near the mine wastes. The concentration of As is also higer in the water samples especially in the hydrogeological well P21 and P2 with 9.665 and 7.798 ppm.

The presence of MTE in groundwater is linked to various factors, including the direction of flow (vertical or lateral) from soil to groundwater and the hydraulic conditions (presence of the drainage axis that is materialized by the convergence of the groundwater flow from the upstream to the downstream, generally from the hydrogeological wells P1 to P23). The hydraulic relationship between streams and groundwater, hydrogeological properties such as aquifer porpermeability (vertical scale 2.5 × 10^–14 to 1.31 × 10^–12 m/s and horizontal scale 9 × 10^–14 to 0.37 × 10^–9 m/s) and transmissivity (about 10⁻² m²/s), and the configuration of the piezometric geometry (including the presence of drainage axes and divisional boundaries within the Ketarra groundwater) are factors that contribute to the mobility and distribution of MTE within the water resources of the Kettara basin.