[en] In order to determine physical location of contaminants in soil, solidified soil 'thin' sections, which preserve the undisturbed structural characteristics of the original soil, were prepared. This paper describes an application of different autoradiographic methods to identify the distribution of selected nuclides along key structural features of sample soils and sizes of 'hot particles' of contaminant. These autoradiographic methods included contact autoradiography using CR-39 (Homalite Plastics) plastic alpha track detectors and neutron-induced autoradiography that produced fission fragment tracks in Lexan (Thrust Industries, Inc.) plastic detectors. Intact soil samples containing weapons-grade plutonium from Rocky Flats Environmental Test Site and control samples from outside the site location were used in thin soil section preparation. Distribution of particles of actinides was observed and analyzed through the soil section depth profile from the surface to the 15-cm depth. The combination of two autoradiographic methods allowed to distinguish alpha- emitting particles of natural U, ^239+240Pu and non-fissile alpha-emitters. Locations of 990 alpha 'stars' caused by ^239+240Pu and ²⁴¹Am 'hot particles' were recorded, particles were sized, their size-frequency, depth and activity distributions were analyzed. Several large colloidal conglomerates of ^239+240Pu and ²⁴¹Am 'hot particles' were found in soil profile. Their alpha and fission fragment 'star' images were micro photographed. (author)