Statistical analysis of the spatial distribution of radionuclides in soils around a coal-fired power plant in Spain

Coal-fired power-plants (CFPP) can be a source of contamination because the coal contains trace amounts of natural radionuclides, such as K-40 and U-238, Th-232 and their decay products. These radionuclides can be released as fly ash from the CFPP and deposited from the atmosphere on the nearby top soils, therefore modifying the natural radioactivity background levels, and subsequently increasing the total radioactive dose received for the nearby population. In this paper, an area of 64 km(2) around the CFPP of Velilla del Rio Carrion (Spain) has been studied by collecting 67 surface soil samples and measuring the activities of one artificial and six natural radionuclides by gamma spectrometry. The found results are similar to the background natural levels and ranged from 0 to 209 for Cs-137, 11 to 50 for U-238, 14 to 67 for Ra-226, 29 to 380 for Pb-210, 15 to 68 for Th-232, 17 to 78 for Ra-224, 97 to 790 for K-40 (all values in Bq kg(-1)). Besides the classical radiochemical tools, Analysis of Variance (ANOVA), Principal Component Analysis (PCA), Hierarchical Clustering Analysis (HCA), and kriging mapping have been used to the experimental dataset, allowing us to find the existence of two different models of spatial distribution around the CFPP. The first, followed by U-238, Ra-226, Th-232, Ra-224 and K-40 can be assigned to 'natural background radioactivity', whereas the second model, followed by Pb-210 and Cs-137, is based on 'atmospheric fallout radioactivity'. The main conclusion of this work is that CFPP has not influence on the radioactivity levels measured in the studied area, with has a mean annual outdoor effective dose E = 71 +/- 22 mu Sv, very close to the average UNSCEAR value of 70 mu Sv, thus confirming the almost non-existent radioactive risk posed by the presence of the CFPP. (C) 2013 Elsevier Ltd. All rights reserved.