ИСТИНА

In the 20th century, several deposits of radioactive minerals were developed at the Khibiny Mountains. Now the excavations are closed. Sealed radioactive mines and their tailings are gradually destroying presenting a NORM source. In the Southern Khibiny, near the lovchorrite mine, the distribution of Th-232 series radionuclides in loose sediments was explored. A field dosimetry was performed, 100 sedimentary samples along the valley including the near-mine zone and 26 samples of rocks were obtained. The acquired results indicate a systematic distribution of Th-232 radionuclides in the loose deposits. Mainly it relates to two factors: the initial uneven content of radionuclides in the rocks that the valley cuts in and the exogenous processes transporting eluvium. We found that in the most radioactive samples there is an inverse relationship between the grain size and Th-content. It was determined for the grain-size fractions less than 2 mm. The sequential extraction survey and alfa-spectometry indicated the majority (>90%) of Th-232 and Th-228 being in the mineral form. The spatial distribution analysis of radionuclides allows estimating an impact of such potentially dangerous industrial objects on the environmental radiation conditions as well as examining the modern dynamics of natural environment.