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This study is focused on the environmental geochemistry of potentially toxic metals (PTMs)-bearing products and wastes in a mining area in Djebel Onk (NE Algeria) and their potential ecological and health risk assessment. Representative samples from (i) commercial products and (ii) grain size classes of wastes were mineralogically characterized using X-ray diffraction. The major and PTMs elements in the samples were chemically analyzed via ICP-AES and ICP-MS, respectively. The results reveal that the samples were mostly composed of carbonate fluorapatite (P2O5 > 24 wt %) and yielded PTM concentrations within the average range of phosphorites in neighboring countries and worldwide deposits as well. The concentrations of V, Cd, As, Ni, and Pb in the products were found to be within the acceptable values according to various standards, such as the Canadian and German Fertilizer Ordinance policies. Geochemically, PTMs distribution is linked to the main sub-composition of phosphate rock (apatite, clay, and dolomite). The Enrichment Factors (EF) display very-high-to-extremely-high enrichment of PTMs (Cr, Zn, As, Sr, Mo, Cd, Sb, Tl, Th, and U), while V, Co, Cu, Ni, Zr, Ga, Nb, and Pb show minor and moderate-to-high enrichments. Among all the PTMs, Cd, Tl, and U display a very high ecological risk (PERI) and contribute most to the total risk index (RI). The human health risk assessment of PTMs represented by the Hazard Index (HI) indicates that the non-carcinogenic risks are below the threshold values (HI < 1), while the HI values are higher for children than they are for adults. However, the cancer index (life time cancer risk) for Cr, Ni, As, and Cd for children and Cd for adults is greater than the acceptable threshold. These results are useful for phosphate beneficiation via removing these PTMs from the commercial product for efficient waste management.

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Research relevance. Phosphate mining activities are one of the main sources of contamination by heavy metals since they harmfully affect the soil and lead to the degradation of the ecosphere. Research aim. This study aims at characterizing and evaluating the metallic contamination of soils in the vicinity of the Djebel Onk mine in the town of Bir El Ater (Wilaya of Tébessa) in eastern Algeria, and particularly focusing on estimating the spatial variability of this contamination and the extent of the contaminated area. Methodology. The physicochemical characteristic (pH) was determined by pH-meter, whereas AAS was used for the determination of heavy metals (Pb, Cu, Zn, Cd) in the examined soil Research results. The results reveal that soils that are close to the mine site studied and even those that are far away are heavily contaminated with heavy metals — lead (Pb), zinc (Zn), copper (Cu) and cadmium (Cd); the results also point out to a high variability of concentrations not only between sampling sites but also within the same mine site. The analysed soil pollution index is generally high even for soils sampled downstream more than 30 km from the mine site, whereas it is extremely high on the surface of the tailings slopes, underlining the fact that tailings are considered perennial sources of heavy metal contamination in their current state. Conclusion. The unhealthy area affected by metal pollution from mining sites in the Djebel Onk is very large as a result of the dispersion, by wind and water transport, of residual pollutants from the mine wastes abandoned on site. Remediation measures must be put into place to immobilize the pollutants and limit their spread to the environment Keywords: Soil contamination, Algeria, heavy metals, phosphate mine, pollution index.