VZTAH MEZI PŘIROZENOU RADIOAKTIVITOU HORNIN A PŮD NA NICH VYTVOŘENÝCH – ZÁKLADNÍ PROBLÉM INTERPRETACE DAT ZÍSKANÝCH LETECKOU A TERÉNNÍ GAMASPEKTROMETRIÍ

Jiří Zimák

doi:10.5817/GVMS2015-1-2-80

The relationship between the natural radioactivity of rocks and soils formed on them – the basic problem of the interpretation of data gathered by airborne and field gamma-ray spectrometry

Vol.22,No.1-2(2015)

Jiří Zimák

https://doi.org/10.5817/GVMS2015-1-2-80

PDF (Czech)

Abstract

The objective of this study was to assess the amount of natural radionuclides in fresh parent rocks and their effect on natural radioactivity of soils developed from them. Forty-five fresh rocks consisting mainly of granitoids, syenitoids, acid to basic metavolcanites, mica schists, gneisses, quartzites, serpentinites, sandstones, graywackes, and limestones and their corresponding overlying soils were sampled for laboratory gamma-ray spectrometric analysis. Contents of potassium, uranium and thorium were converted to mass activity of 226Ra equivalent (am) and terrestrial gamma radiation dose rate (D). Data are tabled and discussed. The highest am values occured in syenitoids (386–441 Bq·kg-1) followed by granitoids, mica schists, greywackes and gneisses, whereas the lowest am values were found in quartzose sandstones (15–36 Bq·kg-1) followed by limestones (less than 15 Bq·kg-1) and serpentinites (less than 6 Bq·kg-1). The natural radioactivity of soils is usually slightly lower than that of parent rocks due to the lower content of potassium, uranium and thorium in soils. This is typical for granitoids, syenitoids and rocks of similar mineralogical composition. In soils developed on granitoids and syenitoids were found increased concentrations of all three elements in the grain size fraction below 0.063 mm. Soils developed on rocks with low natural radioactivity (such as limestones and serpentinites) tend to have significantly higher natural radioactivity than their parent rocks. This may complicate the interpretation of data obtained by airborne gamma-ray spectrometry.

Keywords:
soils; rocks; gamma-spectrometry; natural radioactivity; gamma dose rate

References

Gong, Q. – Deng, J. – Wang, Ch. – Wang, Z. – Zhou, L. (2013): Element behaviors due to rock weathering and its implication to geochemical anomaly recognition: A case study on Linglong biotite granite in Jiaodong peninsula, China. – Journal of Geochemical Exploration 128, 14–24. https://doi.org/10.1016/j.gexplo.2013.01.004">https://doi.org/10.1016/j.gexplo.2013.01.004

Matolín, M. – Chlupáčová, M. (1997): Radioaktivní vlastnosti hornin. – In: Kobr, M. et al.: Petrofyzika, 109–126. Vydavatelství Karolinum, Praha.

Ngachin, M. – Garavaglia, M. – Giovani, C. – Kwato Njock, M. G. – Nourreddine, A. (2007): Assessment of natural radioactivity and associated radiation hazards in some Cameroonian building materials. – Radiation Measurements, 42, 61–67. https://doi.org/10.1016/j.radmeas.2006.07.007">https://doi.org/10.1016/j.radmeas.2006.07.007

Taboada, T. – Cortizas, A. M. – García, C. – García-Rodeja, E. (2006): Uranium and thorium in weathering and pedogenetic profi les developed on granitic rocks from NW Spain. – Science of the Total Environment, 356, 192–206. https://doi.org/10.1016/j.scitotenv.2005.03.030">https://doi.org/10.1016/j.scitotenv.2005.03.030

UNSCEAR, United Nations Scientifi c Committee on the Effects of Atomic Radiation (1988): Exposures from natural sources of radiation. Report to the General Assembly. – U. N., New York, USA.

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