Radon variability in groundwater from the lesser Himalayas to the gangetic alluvial plain, with hydrogeochemical and isotopic insights from Tehri Garhwal

Abstract

Groundwater radon (222Rn) poses radiological risks in Himalayan regions dominated by fractured crystalline aquifers. This study evaluates radon variability in groundwater from Tehri Garhwal (Lesser Himalayas) and compares it with previously published groundwater data from 27 sites (post-monsoon 2022) in the Siwalik foothills (Dehradun) and Gangetic alluvial plains (Haridwar). In the present study, ten groundwater samples from Tehri Garhwal were analyzed for radon, while hydro chemical and stable isotope (δ18O and δD) analyses were conducted on 13 water samples, including the ten analyzed for radon. Radon concentrations ranged from 2 to 43 Bq L⁻1, with 70% exceeding the recommended drinking-water guideline .