Spatial distribution and radiological risk assessment of soil radon (222Rn) and thoron (220Rn) in Gandhinagar city, Gujarat, India

Measurements of radon and thoron concentrations were taken at 70 locations in and around Gandhinagar Gujarat, India. The radon concentration varied between 175 and 14,807 Bq/m 3 , whereas, thoron varied between 28 and 15,033 Bq/m 3 . Maximum concentration of radon and thoron is observed in northern and eastern part of Gandhinagar due to fly ash content of the soil discharged from the Gandhinagar thermal power station. The annual dose rate due to inhalation varied between 0.0013 and 0.1337 mSv/year, below the ICRP recommendation. High radon concentrations are also observed in dumping areas and geological structures with high seismic risk.