Radiological impacts of phosphogypsum
2011
Al Attar, Lina | Al-Oudat, Mohammad | Kanakri, Salwa | Budeir, Youssef | Khalily, Hussam | Al Hamwi, Ahmad
This study was carried out to assess the radiological impact of Syrian phosphogypsum (PG) piles in the compartments of the surrounding ecosystem. Estimating the distribution of naturally occurring radionuclides (i.e. ²²⁶Ra, ²³⁸U, ²³²Th, ²¹⁰Po and ²¹⁰Pb) in the raw materials, product and by-product of the Syrian phosphate fertilizer industry was essential. The data revealed that the concentrations of the radionuclides were enhanced in the treated phosphate ore. In PG, ²²⁶Ra content had a mean activity of 318Bqkg⁻¹. The uranium content in PG was low, ca. 33Bqkg⁻¹, because uranium remained in the phosphoric acid produced. Over 80% of ²³²Th, ²¹⁰Po and ²¹⁰Pb present partitioned in PG. The presence of PG piles did not increase significantly the concentration of ²²²Rn or gamma rays exposure dose in the area studied. The annual effective dose was only 0.082mSvy⁻¹. The geometric mean of total suspended air particulates (TSP) ca. 85μgm⁻³. The activity concentration of the radionuclides in filtrates and runoff waters were below the detection limits (ca. 0.15mBqL⁻¹ for ²³⁸U, 0.1mBqL⁻¹ for ²³²Th and 0.18mBqL⁻¹ for both of ²¹⁰Po and ²¹⁰Pb); the concentration of the radionuclides in ground water samples and Qattina Lake were less than the permissible limits set for drinking water by the World Health Organisation, WHO, (10, 1 and 0.1Bq L⁻¹ for ²³⁸U, ²³²Th and both of ²¹⁰Po and ²¹⁰Pb, respectively). Eastern sites soil samples of PG piles recorded the highest activity concentrations, i.e. 26, 33, 28, 61 and 40Bqkg⁻¹ for ²²⁶Ra, ²³⁸U, ²³²Th, ²¹⁰Po and ²¹⁰Pb, respectively, due to the prevailing western and north-western wind in the area, but remained within the natural levels reported in Syrian soil (13–32Bqkg⁻¹ for ²²⁶Ra, 24.9–62.2Bqkg⁻¹ for ²³⁸U and 10–32Bqkg⁻¹ for ²³²Th). The impact of PG piles on plants varied upon the plant species. Higher concentrations of the radionuclides were recorded for grass in comparison to broad-leaved plants. Among the species that grow naturally on PG piles, Inula, Ecballium and Polygonium may be radionuclides accumulators. A determined effort is needed at a national level to achieve a common and coherent approach to regulate PG piles or to consider it a resource material rather than waste or residue.
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