EGU25-1777, updated on 14 Mar 2025
https://doi.org/10.5194/egusphere-egu25-1777
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Determination of environmental Cs-137 levels from standard airborne gamma-ray spectrometry data
Malte Ibs-von Seht
Malte Ibs-von Seht
  • BGR, Geophysical Exploration, Hannover, Germany (m.ibs@bgr.de)

Atmospheric nuclear tests until 1980 and in particular the Chernobyl nuclear accident in April 1986 left considerable amounts of caesium in the environment of Eastern, Northern, and Central Europe. Regional information on the current distribution of caesium is very limited. Airborne gamma-ray spectrometry or radiometry is routinely used to investigate the regional distribution of the naturally occurring radio-elements K-40, U-238 and Th-232 in the rocks and soils of the earth’s surface and to derive compositional and geological information. Due to the large source-receiver distance and the low activity sources, large-volume scintillation detectors are used for this purpose. The spectral resolution of these instruments is low compared to laboratory setups. Therefore, the identification of photo peaks of artificial isotopes in airborne gamma-ray spectra is not straight forward and attempts to routinely determine Cs-137 signals are rare.

In this study, helicopter radiometry data that was originally collected for soil science applications in northern Germany was examined with regard to its Cs-137 information content. The spectra were acquired with a 4x4 litre NaI, 1024 channel instrument (Radiation Solutions). The overlap of the Cs-137 photo peak at 662 keV with Tl-208 and Bi-214 photo peaks from the uranium and thorium decay chains led to the development of a spectral unfolding method. In the spectra corrected in this way the intensity of the Cs-137 signal could be determined. These Cs-137 intensity values were then compared with measurements on the ground, so that a calibration of the airborne system for absolute ground activities of Cs-137 was possible. Applied to large airborne data sets covering areas in the order of 100 km2 resulted in activity maps that give interesting insights into the present day Cs-137 levels in the environment of Northern Germany.

How to cite: Ibs-von Seht, M.: Determination of environmental Cs-137 levels from standard airborne gamma-ray spectrometry data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1777, https://doi.org/10.5194/egusphere-egu25-1777, 2025.