Appraising the factors favouring uranium mobilization and associated health risk assessment in groundwaters of north-western India

• Published in: Ecotoxicology and environmental safety Vol. 229; p. 113086
• Main Authors: Sharma, Diana A., Keesari, Tirumalesh, Pant, Diksha, Rishi, Madhuri S., Sangwan, Priyanka, Thakur, Nandini, Sinha, U.K.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01-01-2022; Elsevier
• Subjects: Activity ratio; Environmental isotopes; Groundwater; Groundwater contamination; India; Leaching; Punjab; Radon - analysis; Risk Assessment; Uranium - analysis; Uranium isotopes; Water Pollutants, Radioactive - analysis; India; Groundwater contamination; Punjab; Environmental isotopes; Leaching; Activity ratio; Uranium isotopes
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2021.113086

An attempt has been made in this study to evaluate the factors favoring the uranium mobilization into the groundwater of Northwest India using uranium isotope activity ratio (234U/238U), radon (222Rn) and environmental isotopes of water (2H, 18O and 3H). The values range from 23 - 597 µg/L for total uranium and 634–3210 Bq/m3 for radon and the corresponding annual effective dose is estimated to be 18.9–490 µSv/a and 6.2–31.5 μSv/a respectively. Uranium activity ratio (UAR) varies from 0.68 - 1.17 and maximum samples indicate secular equilibrium. Environmental isotopic data indicates that the source to groundwater is vertical percolation of rainwater in the case of shallow zone while regional flows from outcrop areas recharge the deep groundwater. A wide scatter is noticed in environmental 3H content (0.23–6.62 TU) indicating both fast and sluggish water flows. The UAR phase diagram suggests that leaching process controls the uranium mobilization into the groundwater. The correlations among UAR, uranium and Uexcess further indicate oxidative nature of leaching process. Statistical treatment of the obtained data along with available geochemical and isotope evidences suggest that source of uranium is common but the driving processes are different for shallow and deep zone. Influences of root zone CO2, oxic species from irrigation return flows and water level fluctuations are also evaluated. Low uranium, low UAR, low 3H and high 222Rn activity in deep zone suggest uranium being released from the roll front as well as transported from outcrop regions. This study highlights the application of uranium isotope ratio, radon and environmental isotopes in assessing vulnerability of alluvial aquifers towards uranium contamination.
•Uranium isotopic ratio, radon and water isotopes were used to understand U mobilization.•Uranium activity ratio (UAR) vary from 0.69 to 1.17 and conform to secular equilibrium.•Uranium and radon exhibit contrasting trends in shallow and deep aquifers.•Oxidative leaching of sediments facilitate uranium mobilization into aquifers.•Isotope tracers and UAR support the geogenic nature of uranium contamination.