Distribution of naturally occurring radionuclides in soil around a coal-based power plant and their potential radiological risk assessment

Coal-fly-ash is one of the major byproducts of coal-based power plant in which naturally occurring radioactive materials (NORMs) are drastically enriched compared to those of feed coals. Thus, improper management of fly-ash may introduce additional radioactivity to the surrounding environment and cause radiological risk. So, in order to study the distribution of radionuclides in soil around a coal-based power plant and to evaluate their radiological risk, soil, coal and fly-ash samples were analyzed by using a HPGe detector for U-238, Ra-226, Th-232 and K-40 radioactivity concentrations. Furthermore, soil minerals were also studied by X-ray diffractometer to assess the mineralogical provenance of the radionuclides. Mean radioactivity concentrations (in Bq . kg(-1)) of U-238, Ra-226, Th-232 and K-40 in soil samples are 102.9 +/- 41.4, 63.6 +/- 7.4, 103.4 +/- 13.9 and 494.2 +/- 107.5, respectively which are comparatively higher than the typical world mean value. Elevated levels of radioactivity are likely due to the presence of illite, kaolinite, monazite, rutile and zircon minerals in the soil samples rather than technogenic contributions from the power plant. Furthermore, mean soil contamination factor (CF) are close to unity and mean pollution load index (PLI) is below unity while the average radium equivalent activity (Ra-eq in Bq . kg(-1)), external hazard index (H-ex), absorbed ( )gamma dose rate (D in nGyh(-1)), annual effective dose rate (E in mSv . y(-1)) and excess lifetime cancer risk (ELCR in Sv(-1)) are 249.5 +/- 21.7, 0.67 +/- 0.06, 114.2 +/- 9.4, 0.20 +/- 0.02, 4.9 x 10(-4) +/- 0.4 x 10(-4) , respectively, which are within the permissible limit. Thus, in terms of radioactivity concentrations and associated environmental and radiological indices, the effect of the power plant is insignificant.