Environmental and Geochemical Characteristics of Heavy Metals in Soils Around the Former Mining Area of Zeïda (High Moulouya, Morocco)

Abstract

The Zeïda mining center, closed in the mid-1980s, was once intensively exploited for lead concentrates. Throughout its activity, more than 12 Mt of tailings were generated and, to this day, they are still abandoned in the open air, exposed to weathering conditions without any rehabilitation. The purpose of the present study is to evaluate the environmental and geochemical characteristics of the soils, combining physicochemical, mineralogical, sequential, and kinetic extraction analyses, as well as the metallic spatial distribution and pollution indices of heavy metals (Pb, Cd, Cu, As, and Zn), levels, and risks. The results showed that the abandoned tailings had the highest concentrations of heavy metals, far exceeding their equivalents in the international and local guidelines. The soils spatial distribution maps showed that the levels of heavy metals decreased with distance from the tailings. Based on the pollution indices results, the soils located on and near the tailings are highly contaminated mainly by Pb. While downstream of the tailings, this contamination intensity decreased until becoming null. The sequential extraction results indicated that Pb, Zn, and Cd were primarily associated with the exchangeable fraction in tailings and soils. Therefore, they were more mobile and environmentally hazardous in the study area. The As was mainly associated with the residual fraction, and was thus immobile. Cu was more mobile in tailings as long as it was associated with the reducible fraction while it became immobile in the downstream soils. The kinetic extractions using EDTA and H 2 O revealed that the labile and less labile fractions were very significant in tailing for the majority of heavy metals. The methodology applied in this study may constitute a valuable tool to develop appropriate mine reclamation solutions.

Investigation of the usability of industrial mining wastes in agriculture

“…It was determined that heavy metal values of all mixtures were below the heavy metal limit values allowed in the soil. Thus, it was understood that heavy metals in the content of the waste would not cause harm to human health, as in similar studies using different mine waste (Chen et al, 2019;Samsuri et al, 2019;Esteves-Aguilar et al, 2023;Jayapal et al, 2023;Nassiri et al, 2023;Tibane and Mamba, 2023;Zhang et al, 2023).…”

Sediments as Sentinels of Pollution Episodes in the Middle Estuary of the Tinto River (SW Spain)

“…Numerous anthropogenic activities (e.g., industrial effluents, mining waste, agricultural residues, urban inputs), the natural erosion of geological formations or even high-energy events (river floods, storms, tsunamis, etc.) leave their mark on the geochemical levels of sediments and soils [1][2][3][4][5][6][7]. One of the most common effects is the increase in concentrations of certain elements, among which heavy metals are commonly used as a reference to measure the level of pollution [8][9][10][11].…”