Content of radionuclides (²²⁶Ra, ²³²Th, ⁴⁰K, ¹³⁷Cs) in soils of the North-West region of Russia formed on three types of soil forming rocks

¹ The Dokuchaev Central Soil Science Museum, Birzhevoy proezd, 6, 199034, St.Petersburg, Russia
² Russian Institute of Radiology and Agroecology, Kievskoye Rd., 109 km, 249032, Obninsk, Kaluga region, Russia
³ Peter the Great St.Petersburg Polytechnic University, Polytechnicheskaya Str. 29, 195251, St.Petersburg, Russia

^* Corresponding author: coolhabit@yandex.ru

Abstract

The results of a study of the content of natural radionuclides (NR) (²²⁶Ra, ²³²Th, ⁴⁰K) and technogenic ¹³⁷Cs in soil samples formed on the most common types of soil-forming rocks of the North-West: lakeglacial (non-boulder and tape clay), glacial and water-glacial deposits are presented. Soil sections laid in the Pskov, Novgorod and Leningrad regions. The granulometric composition in the upper part of the soil profile is lighter than in the parent rock. This is reflected in the NR content in the profile of these soils: with a decrease in the fractions of physical clay and silt, the content of ²²⁶Ra, ²³²Th and ⁴⁰K decreases. This is due to the fixation of natural radionuclides by secondary clay minerals. According to the increase in the average specific activity of all NRs, the soils form the following sequence: soils on water-glacial deposits soils on moraines - soils on lake-glacial deposits. A comparison of the average specific activity of natural radionuclides and their ranges in the upper part of the soil (0-5, 5-10 and 10-20 cm) and in the parent rock (90-100 cm) revealed a higher content of radionuclides in parent rocks (lake-glacial and moraine deposits). In the soils on water-glacial deposits, no significant difference was found.