Groundwater radon (222Rn) assessment of a coastal city in the high background radiation area (HBRA), India

In this study, radon (222Rn) concentration in groundwater sampled from the phreatic aquifers of urban and peri-urban ensemble of Kozhikode District, Kerala, Southern India, was assessed using RAD-7 detector with RAD H2O accessory. The 222Rn concentration in the urban zone varied from 0.66 to 35.1 Bq/L with an average value of 6.2 Bq/L, whereas in the peri-urban zone, it ranged between 0.18 and 25.13 Bq/L with an average concentration of 5.1 Bq/L. All the measured radon (222Rn) activity is well within the EPA’s maximum contaminant level (MCL) except at three locations. Neither the spatial variation of 222Rn nor the correlations with depth to groundwater level, pH, or TDS of the groundwater samples were significant in the study area. However, thickness of the weathered sediments, proximity of lineaments, and interactions with host rock were significantly associated with the occurrence of 222Rn in groundwater. The residence time of groundwater in the alluvial aquifers was also found out. The study confirmed the influence of hydrogeological properties on the spatial distribution of radon activity in the urban and peri-urban zones of Kozhikode District. © 2021, Saudi Society for Geosciences.