Study of variation of radon with depth of the soil and its concentration in the atmosphere in some areas of Tumkur district, Karnataka state, India

Background radiations are from cosmic and terrestrial origin. Radon gas, a decay product of 226Ra is present in the soil, rock, water and in atmosphere. Being ubiquitous, their concentrations in air contribute more than half of the natural radiation exposure of the public. Radon, thoron and their progeny are present in indoor and outdoor atmosphere. In the present study, the indoor and outdoor gamma radiation level near the study areas have been measured using Scintillometer (Type SM 141D) which were found to be highest (1.41 mSv/y) in Pavagada and lowest in Sira (0.62 mSv/y). The radon concentrations in soil gas were determined using solid state nuclear track detectors (SSNTDs). (alpha sensitive films, LR-115 type-2). Radon concentrations for different depths, 30 cm, 60 cm, 90 cm and 120 cm from the ground surface were found to be, 1.19, 1.61, 1.71 and 1.85 mSv/y respectively. The concentration radon in the atmosphere were highest near Pavagada (43.25 Bqm-3) and Madhugiri (40.70 Bqm-3). The effective gamma doses and inhalation doses were determined using UNSCEAR conversion factors. The results from the study showed that, the concentrations of radon in soil gas increased with depth. The average dose measured is found to be lower than global average. (author)