Studies of Natural Soil Radioactivity in the Kirchhoff Hill (the Leningrad Region, the Russian Federation)

From the geoecological point of view, a special place in the geological section of the Kirchhoff Hill is occupied by highly radioactive geological bodies – dictyonema oil shales. As a result of glacial tectonic dislocations and due to numerous local elevations and depressions in the relief, dictyonema oil shales can come into direct contact with the soil over relatively large areas here. Based on the results of the route survey of the gamma field over the soils of the Kirchhoff Hill in the zone of anomalously high exposure dose rate, we laid a pit. Seven samples were taken and analyzed from the depth of 0 to 85 cm. The first two samples (0– 25 cm) correspond to the gray-humus dark-profile soil on dictyonema oil shales type. Here, the average value of the specific effective activity (Aeff) makes 1,750 Bq/kg. The average Aeff of the next 5 samples of dictyonema oil shales (25–85 cm) makes 1,870 Bq/kg. Such radioactivity values belong to the environmental hazard class IV and impose significant restrictions on building and construction in the area of studies.