The Correlation Graph between Gamma Radiation and Radon Concentration in soil of oil Exploration Areas in Thenzawl Village of Mizoram

Abstract

The Ground level Gamma Radiation and Radon gas concentration at different depth beneath the ground surface of oil exploration areas in Mizoram, India is studied and correlation graph is drawn. The oil exploration area at Thenzawl(TZ) site in Serchhip district, is studied. The main instrument utilized for the study was RnDuo machine devised to survey Radon 222 (222Rn) connected to soil probe of 1mtr long to be baptized at different depth. Background gamma radiation survey at ground level is conducted with Russian base Gamma Survey Meter (PM 1405). The background gamma radiation at ground level varies from 168 nSv/hr at TZ-1 to 176 nSv/h at TZ-3 location with an average of 173.3 nSv/h. An in-situ measurement of soil gas was carried out at three different spots at four different depths each namely 10cm, 30cm, 50cm and 70cm. The radon gas concentration beneath the soil, within the study area ranges from 0.14 kBq/m3 at TZ-3 to 1.37 kBq/m3 at TZ-2 location. A correlation graph between ground level gamma radiation and the radon concentration in soil at different dept shows that the correlation coefficient is highest at 10cm with R2=0.238 and lowest at 70cm with R2=0.005. The Radon gas concentration obtained is below the worldwide average of 35-40 kBq/m3 .(UNSCEAR 2000).

Introduction

This study investigates radon concentration in soil gas at different depths and its relationship with background gamma radiation in the Thenzawl oil exploration area of Serchhip district, Mizoram, India.

Earth contains naturally occurring radionuclides such as uranium, thorium, radium, and potassium, which produce natural background radiation. Among these, radon (^222Rn), a decay product of uranium (^238U), is a significant contributor to human radiation exposure. Radon movement in soil depends on geological characteristics, and its concentration generally increases with depth.

The study aimed to measure radon concentrations at 10 cm, 30 cm, 50 cm, and 70 cm depths and examine their correlation with ground-level gamma radiation. Background gamma radiation was measured using the PM-1405 Gamma Survey Meter, while soil gas radon was measured in situ using the Smart RnDuo detector at three sampling locations.

The results showed that ground-level gamma radiation ranged from 168 to 176 nSv/h. Radon concentrations increased consistently with depth, ranging from 0.14–0.81 kBq/m³ at 10 cm to 0.22–1.37 kBq/m³ at 70 cm. Measurements were conducted in January 2020 under dry weather conditions with moisture-free soil, minimizing environmental effects on radon levels.

Conclusion

The Radon concentration in soil gas of oil exploration area in Serchhip district of Mizoram is studied. An in situ measurement was taken at four different depth such as 10cm, 30cm, 50cm and 70cm with the help of a Smart RnDuo and a stainless steel probe. The study was carried out during winter season in the month of January 2020. The soil has no moisture content. It has been observed that the concentration of radon gas increases as we baptize the soil probe deeper and deeper. This means that for every spot chosen, the radon gas concentration at 10cm deep is lowest and the radon gas concentration at 70cm is highest and the concentration at 30cm and 50 cm lie in between. But, the correlation coefficient (R2) obtained from the graph was best at 10cm with R² = 0.238 while it is least at 70cm deep with R² = 0.0.005. This indicates that the gamma radiation had a better correlation close to the ground surface. The correlations observed are not that good. The possible reason for this poor correlation may be due to the contributing factor. Whereas the radon concentration at different baptism depth is contributed by Uranium 238, on the other hand, the background gamma radiation at ground level is contributed by many cosmic and terrestrial sources like Uranium, potassium, thorium etc. The radon gas concentration obtained in these locations are far below the world average of 35-40 kBq/m3 (UNSCEAR 2000).

References

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Copyright

Copyright © 2026 Lalnunpuia ., Remlalsiama , Lalmuanawma Chhangte. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.