2. Materials and methods

In September 2018, employees of the Laboratory of Environmental Radiology at the Institute of Geodynamics and Geology, N. LaverovFederal Centre for Integrated Arctic Research of the Ural Branch of Russian Academy of Sciences carried out expeditions to study the natural and technogenic radioactivity of bottom sediments in the upper reaches of the Zolotitsa river. To accomplish this task, 50 samples were taken. Sampling of bottom sediments from the river was carried out from a boat with a bottom grab bucket, the appearance of which is shown in Fig. 1 with the sampling scheme shown in Fig. 2. For laboratory conditions, the samples were air dried in a cabinet at a temperature of 105°C to constant weight. After weighing, the samples were placed in a Marinelli vessel to measure the specific activity of isotopes by gamma spectrometry. Registration of gamma radiation from a counting soil sample, as well as processing of spectra, was carried out using the “Progress-gamma” software and hardware complex. The energy calibration of the gamma spectrometer to control the safety of the setup parameters was carried out after each measurement using a combined control source in a Marinelli vessel. The minimum exposure time of the counting sample was 3600 seconds. However, depending on the activity of the sample, the exposure time in individual samples with weak activity increased. The fractional composition was determined after grinding the samples in a PM100 planetary ball mill (Retsch, Germany) using an AS200 sieving machine (Retsch, Germany) with a set of sieves from 45 µm to 10 mm (Methodology..., 2016).

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