Distribution of potentially toxic metal and radionuclide contamination in soils related to phosphogypsum waste stockpiling in the Eshidiya Mine, Jordan

Prior to this study, phosphogypsum (PG) stockpiles at the Eshidiya mine in Jordan were thought to be potentially enriched with potentially toxic metals and radionuclides, resulting in possible environmental degradation of the surrounding ecosystem. In order to investigate this phenomenon, enrichment levels and distribution patterns of metals (e.g. Zn, Cd, V) and radionuclides in the underlying soils, alluvium, and yellow marl bedrock were determined and compared against those in the PG stockpiles. The Ra-226, Pb-210, and U-238 in soil reached peak concentrations of 1.5 pCi/g, 2.0 pCi/g, and 1.1 pCi/g, respectively. These elemental concentrations are similar to their concetrations in the uncontaminated soils, whereas the concentrations of these elements exhibit higher concentrations in PG and are as follows: Ra-226= 18 pCi/g, Pb-210= 19 pCi/g, and U-238= 4 pCi/g. The elements Cd, Zn, and V have maximum concentrations of 3 mg kg(-1), 69 mg kg(-1) and 62 mg kg(-1), respectively, in the soil's layer. These elemental concentrations are relatively lower than in uncontaminated soil and the PG. The degrees of mobility of the determined elements in soils were classified into three categories: elements with high mobility are Se, Mn, Pb, and Cr; those with moderate mobility are Co, Ni, As, Hg, Cu, V, and Zn; and those with low mobility are U, Cd, Pb-210, Ra-226, and U-238. Following correlation analysis, R-mode factor analysis was applied in conjunction with mineralogy to understand the geochemical variability of the soil. Four main meaningful factors were extracted: a detrital quartz factor, a clay minerals factor, a carbonate factor, and a terrigenous minerals factor. To investigate the spatial distribution patterns of the elements, a contour mapping technique was applied, allowing the following conclusions: (1) The elements Pb-210, Ra-226, and U exhibit similar distribution patterns; (2) Cd and Cu show similar distribution patterns; (3) As and V exhibit similar distribution patterns; and (4) no observed trend was observed for Cr. Generally, the results revealed that potentially toxic metals and radionuclides are not contaminated in soils related to the phosphogypsum stockpiles, and the soils of the Eshidiya area do not contain potentially toxic metals and radionuclide concentrations that threaten the surrounding ecosystem.