Elevated uranium in drinking water sources in basement aquifers of southern India

Abstract

Groundwater resources in the crystalline basement complex of India are crucial for supplying drinking water in both rural and urban settings. Groundwater depletion is recognised as a challenge across parts of India due to over-abstraction, but groundwater quality constraints are perhaps even more widespread and often overlooked at the local scale. Uranium contamination in basement aquifers has been reported in many parts of India, locally exceeding WHO drinking water guideline values of 30 μg/L and posing a potential health risk. In this study 130 water samples were collected across three crystalline basement catchments to assess hydrochemical, geological and anthropogenic controls on uranium mobility and occurrence in drinking water sources. Groundwaters with uranium concentrations exceeding 30 μg/L were found in all three study catchments (30% of samples overall), with concentrations up to 589 μg/L detected. There appears to be a geological control on the occurrence of uranium in groundwater with the granitic gneiss of the Halli and Bengaluru study areas having higher mean uranium concentrations (51 and 68 μg/L respectively) compared to the sheared gneiss of the Berambadi catchment (6.4 μg/L). Uraniumnitrate relationships indicate that fertiliser sources are not a major control on uranium occurrence in these case studies which include two catchments with a long legacy of intense agricultural land use. Geochemical modelling confirmed uranium speciation was dominated by uranyl carbonate species, particularly ternary complexes with calcium, consistent with uranium mobility being affected by redox controls and the presence of carbonates. Urban leakage in Bengaluru led to low pH and low bicarbonate groundwater hydrochemistry, reducing uranium mobility and altering uranium speciation. Since the majority of inhabitants in Karnataka depend on groundwater abstraction from basement aquifers for drinking water and domestic use, exposure to elevated uranium is a public health concern. Improved monitoring, understanding and treatment of high uranium drinking water sources in this region is essential to safeguard public health.

Estimation of Natural Uranium and Its Risk-Assessment in Groundwater of Bangalore Urban District of Karnataka, India

“…As reported by Lapworth et al [34] urban leakage in Bangalore led to a low-pH and low-bicarbonate groundwater hydrochemistry, thus reducing uranium's mobility and altering uranium's speciation. The local geology and physico-chemical environment may be responsible for the differences in the uranium concentrations at various distances.…”

“…The study region is situated on the tonalitic biotite gneisses-dominated Archean gneiss complex of Peninsular India. Along with a few tanks and lift-irrigation schemes, groundwater is the district's main source of irrigation water [34]. The two main crops that are farmed in the district are paddy and ragi, and the supporting crops including maize, cereals, and groundnuts.…”

“…After analyzing the uranium along with the other water-quality parameters, its significance with the different water-quality parameters was studied further [34]. The association between uranium and other water-quality parameters was assessed using the Number Cruncher Statistical System (NCSS).…”

Geochemical evaluation and the mechanism controlling groundwater chemistry using chemometric approach and groundwater pollution index (GPI) in the Kishangarh city of Rajasthan

“…India is one of the most populated countries and is the third largest country in groundwater abstraction worldwide (Lapworth et al, 2021). An increased freshwater demand to ful ll drinking, irrigation, and industrial purposes is frequently observed in this country (Sulaiman et al, 2023).…”

Predicted uranium and radon concentrations in New Hampshire (USA) groundwater—Using Multi Order Hydrologic Position as predictors

“…Studies identifying elevated U are found, for example, in locations in Mongolia (Nriagu et al, 2012), South Korea (Shin et al, 2016), United Arab Emirates (Xiong et al, 2020), Turkey (Simsek, 2008), Australia (Brown et al, 1998), Finland (Suutarinen et al, 1991), the United States (Lopez et al, 2021), and southern India. In southern India, elevated U concentrations have been encountered as greater depths have been drilled in response to dwindling water supplies (Lapworth et al, 2021). Similarly, studies identifying elevated Rn are found for locations in Austria (Schubert et al, 2010), Switzerland (Gainon et al, 2007), South Korea (Cho et al, 2019), Japan (Tsunomori et al, 2017), the United States (Ayotte et al, 2007), the India Himalayas (Prasad et al, 2018), and many more countries.…”