Seasonal and geological controls of radon (²²²Rn) in groundwater of Vamanapuram river basin, SW India

Abstract

The study investigates the spatio-temporal variability of radon (²²²Rn) with respect to the geology and hydrogeology of the Vamanapuram River Basin (VRB), SW India. A total of 40 groundwater samples were collected during three seasons of 2019. RAD7, RAD-H₂O accessory (Durridge Co. USA) was used to analyse ²²²Rn, and physico-chemical parameters were measured in situ by Horiba Laqua water quality analyser. The results show that the ²²²Rn activity was in the range of 640–79,940 Bq/m³ in pre-monsoon, 250–36,950 Bq/m³ in monsoon and 420–59,790 Bq/m³ in post-monsoon season and 18% of samples exceeded the permissible limit of USEPA (11,000 Bq/m³) during all seasons. Remarkably, the samples exceeding the permissible limit of ²²²Rn were associated with khondalitic rocks with notable amount of uranium-bearing minerals and NW-SE trending lineaments, the most active type of lineament in the study area. The study shows the considerable influence of seasons and the highest activities were found during pre-monsoon compared to the other two seasons.

Keywords:

• Radon activity
• RAD7
• lineaments
• hard rock terrain
• tropical mountainous river basin

Acknowledgments

The authors thankfully acknowledge Department of Science and Technology (DST) for providing financial assistance under DST-INSPIRE Fellowship for the successful completion of research work. The authors grateful to Central Groundwater Board (CGWB), Kerala region for providing lithology data which helps to interpret the results.

Disclosure statement

The authors declare that they have no known competing financial interest or personal relationships that could have appeared to influence the work reported in this paper.

Ethics approval statement

The manuscript has not been published in any other journal. The manuscript includes original data, acquired during our own research, and is not under consideration for publication elsewhere.