Variation of radon progeny concentration over a continental location

Background: The variation of the radon progeny concentration in outdoor environment and meteorological parameters at fine resolution were studied for one year at a continental location, National Atmospheric Research Laboratory, Gadanki, India.  Materials and Methods: The concentrations were measured using Alpha Progeny Meter by collecting air samples at a height of 1 m above the Earth’s surface at a known flow rate. Results: Radon progeny concentration shows temporal variations on diurnal and monthly scales, and is due to mixing in the atmosphere. Peak in the early morning hours and low values during afternoon compared to nighttime are due to differential heat contrast between earth’s surface and its atmosphere. However, the activity during February shows maximum compared to June/July months.  The diurnal variation of radon progeny shows positive correlation with the relative humidity and negative correlation with ambient temperature.  The monthly mean activity of radon progeny for the year 2012 was found to be 4.76 ± 0.73 mWL. Conclusion: The mean concentration of radon progeny in the study region is relatively high compared to the other locations in India and may be due to the rocky terrains and trapping of air-masses near the observation site due to its topography.