Significant radioactive contamination of soil around a coal-fired thermal power plant

Soil samples were collected around a coal-fired power plant from 81 different locations. Brown coal, unusually rich in uranium, is burnt in this plant that lies inside the confines of a small industrial town and has been operational since 1943. Activity concentrations of the radionuclides U-238, Ra-226, Th-232, Cs-137 and K-40 were determined in the samples. Considerably elevated concentrations of U-238 and Ra-226 have been found in most samples collected within the inhabited area. Concentrations of U-238 and Ra-226 in soil decreased regularly with increasing depth at many locations, which can be explained by fly-ash fallout. Concentrations of U-238 and Ra-226 in the top (0-5 cm depth) layer of soil in public areas inside the town are 4.7 times higher, on average, than those in the uncontaminated deeper layers, which means there is about 108 Bq kg(-1) surplus activity concentration above the geological background. A high emanation rate of Rn-222 from the contaminated soil layers and significant disequilibrium between U-238 and Ra-226 activities in some kinds of samples have been found. (C) 2002 Elsevier Science Ltd. All rights reserved.