Assessment of the Mode of Occurrence and Radiological Impact of Radionuclides in Nigerian Coal and Resultant Post-Combustion Coal Ash Using Scanning Electron Microscopy and Gamma-Ray Spectroscopy
Assessment of the Mode of Occurrence and Radiological Impact of Radionuclides in Nigerian Coal and Resultant Post-Combustion Coal Ash Using Scanning Electron Microscopy and Gamma-Ray Spectroscopy
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DOI：
10.3390/min10030241
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发表时间：
2020-03
期刊：
影响因子：
2.5
通讯作者：
I. Okeme;T. Scott;P. Martin;Yukihiko Satou;T. Ojonimi;M. O. Olaluwoye
中科院分区：
文献类型：
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作者：
I. Okeme;T. Scott;P. Martin;Yukihiko Satou;T. Ojonimi;M. O. Olaluwoye
当煤和煤灰中的天然放射性核素浓度（重新）悬浮或处置到环境中时，其浓度足以引起潜在的健康和环境问题。为了评估这些问题，本研究利用高分辨率伽马能谱结合扫描电子显微镜和能量色散光谱，对从尼日利亚两个煤矿（Okaba 和 Omelewu）获得的煤炭和模拟煤灰样品进行了表征。观察到离散的铀矿颗粒分散在煤灰样品中，旁边还有含有 U 和 Th 的矿物颗粒（独居石和锆石），其中独居石是最丰富的放射性矿物颗粒。这些放射性颗粒（尺寸在 10 μm 至 80 μm 之间）的凹坑和裂纹表面形态表明它们容易分解成更有害且更容易吸入的 PM2.5 气溶胶颗粒，有可能传递局部剂量并导致慢性呼吸道疾病。两个矿井的煤灰样品的活度浓度和放射性危害指数结果比土壤中世界平均水平高出三到五倍，这意味着这些煤灰材料应适当存放在泥浆池中，以防止因长期室内暴露于伽马辐射、氡气和吸入释放的放射性粒子的风险增加而造成危害。
Natural radionuclide concentrations in coal and coal ash can occur at levels sufficient to raise potential health and environmental concerns when (re)suspended or disposed into the environment. To evaluate such concerns, this study characterized coal and simulant coal ash samples obtained from two Nigerian coal mines (Okaba and Omelewu) using high resolution gamma spectroscopy combined with scanning electron microscopy and energy dispersive spectroscopy. Discrete uraninite particles were observed dispersed within the coal ash samples, alongside U and Th containing mineral grains (monazite and zircon) with monazite the most abundant radioactive mineral particles. The pitted and cracked surface morphologies of these radioactive particles (with sizes between 10 μm and 80 μm) indicate their susceptibility for disintegration into more harmful and readily inhalable PM2.5 aerosol particles, with the potential to deliver a localized dose and cause chronic respiratory diseases. The results of activity concentrations and radiological hazard indices for the coal ash samples from both mines were between three and five times higher than world average in soil, which imply that these coal ash materials should be suitably contained in slurry ponds to prevent hazards due to increased risk of prolonged indoor exposure to gamma radiation, radon gas, and inhalation of liberated radioactive particles.