Variation in radon concentration and terrestrial gamma radiation dose rates in relation to the lithology in southern part of Kumaon Himalaya, India

Radon concentrations in groundwater and soil–gas along with the terrestrial gamma radiation dose rate have been measured in the different geological formation of Kumaon Himalaya, India. Radon concentrations were found to vary from 1 to 392 Bq/l with a mean of 50 Bq/l in water and 398Bq/m3 to 25.8kBq/m3 with a mean value of 5.867 kBq/m3 in soil–gas. The radium content in collected groundwater samples from the study area was found to vary from 0.11 to 0.75 Bq/l with a mean value 0.35 Bq/l. The terrestrial gamma radiation dose rate and uranium content in soil were found to vary from 21.67 to 57.50μR/h with a mean value of 36.15μR/h and 0.8 to 15.3 ppm with a mean value 3.4 ppm, respectively, in different lithotectonic units. The emanation of radon in groundwater and soil–gas are found to be controlled by the geological formation of the area. It was also found to be controlled by the tectonic structure of the area. Radon level was found higher in the area consisting of granite, quartz porphyry, schist, phyllites slates and lowest in the area having sedimentary rocks, predominantly dominated by quartzite rocks. The terrestrial gamma radiation dose rate in the area was found positively correlated with radon concentrations in groundwater and soil–gas. A strong positive correlation was observed between uranium content in soil and terrestrial gamma radiation dose rate. Soil–gas radon concentration was also found positively correlated with the uranium content in the soil. However, a weak correlation was found between uranium content in soil and radon concentrations in groundwater samples from the study area. No correlation was observed between radon concentrations in groundwater and soil–gas.