Abstract
The radon-prone area of the Adamawa region in Cameroon is characterized by high natural radiation background resulting from the high concentrations of radium-226, thorium-232, and indoor radon. To produce a radon-risk map, radon measurements in soil were carried out in the city of Ngaoundere. The radon activity concentration in soil gas ranged from 256 to 166 kBq m−3 with a mean of 80 kBq m−3 and a standard deviation of 38 kBq m−3. The area is mostly classified as high risk (80%) according to the Swedish classification, and 20% as medium risk. A low-risk area was not observed. Granite-like geology sites were characterized by higher radon concentration. A ratio of about 295:1 was obtained for soil radon gas to indoor radon concentrations, with a positive correlation (R = 0.40), and a transfer factor of 3 per mil. These results demonstrate that in situ measurements of radon concentration in soil can provide accurate information on the level of indoor radon concentrations. Geostatistical and deterministic interpolation techniques have been used to obtain a radon map by comparing the suitability of ordinary kriging and inverse-distance-weighted (IDW) interpolation methods. It turned out that there is not much difference in the prediction errors of the two techniques (Root Mean Square Error = 34.4 for ordinary kriging and 34.3 for IDW). It is concluded that both methods give acceptable results. In situ measurements and geostatistical analysis allow assessment of expected indoor radon exposure in a given area at reduced costs and time required. However, for the investigated area, more research is needed to produce reliable radon-risk maps.
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Acknowledgements
The authors are grateful to the Abdus Salam ICTP for its support through the OEA-AF-12 project at CEPAMOQ. The Environmental Radioactivity Network Center (ERAN) is thanked for project acceptance and funding through FY-21-14. The International Atomic Energy Agency (IAEA) is thanked for funding and technical support through the CMR9009 TC Project. The Ministry of Scientific Research and Innovation of Cameroon is acknowledged for funding the field works through the Public Investment Budget 2020 allocated to the Institute of Geological and Mining Research. The Institute of Geological and Mining Research (IRGM) is thanked for the support to carry out field work. The Local Material Promotion Authority (MIPROMALO) is thanked for the various internships granted.
Funding
This work was supported by ERAN [FY-21-14], the International Atomic Energy Agency [CMR9009], Abdus Salam International Centre for Theoretical Physics [OEA-AF-12], and the Ministry of Scientific Research and Innovation of Cameroon [Public Investment Budget 2020].
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All authors contributed to the study conception and design. Data collection was performed by SB, NN II, and HYA. Data analysis was performed by SB, Saïdou, CK, MH, and BD. The first draft of the manuscript was written by SB, supervised by Saïdou, KN, and ST. All authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
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Bachirou, S., Saïdou, Kranrod, C. et al. Mapping in a radon-prone area in Adamawa region, Cameroon, by measurement of radon activity concentration in soil. Radiat Environ Biophys 62, 427–439 (2023). https://doi.org/10.1007/s00411-023-01042-3
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DOI: https://doi.org/10.1007/s00411-023-01042-3