Mitra Arijeet, Pandit S A, Azad Shams, Halliday Alex N, Jindal Manoj K, Srinivasan R, Schilling Kathrin, Basu Anirban
Department Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York 10032, United States.
Divecha Centre for Climate Change, Indian Institute of Science, Bangalore 560012, India.
Environ Sci Technol. 2025 Jul 1;59(25):12967-12977. doi: 10.1021/acs.est.5c01913. Epub 2025 Jun 15.
Uranium (U) contamination in groundwater becomes a critical concern when its concentration exceeds permissible limits. Groundwater samples ( = 46) from Eastern Karnataka exhibit U concentrations ranging from 1.9 to 2744 μg/L, with 78% and 66% of sites exceeding the United States Environmental Protection Agency (USEPA) and Atomic Energy Regulatory Board (AERB), India thresholds, respectively. These high U levels are primarily geogenic. The δU and U activity ratios (U/U) were determined on the same set of samples to understand the redox processes governing groundwater U cycling. The δU isoscape displays a variation of 1.3‰ from -0.95‰ to 0.3‰, providing evidence of a generally oxidizing groundwater environment, with localized U-reducing conditions in the southern part of the study area. The (U/U) of groundwater varies from 1.2 to 5.4, indicating a dynamic interplay of α-recoil effects, preferential leaching of U, and the dissolution of high U zone(s) in granitic rocks. Statistical analysis of geochemical and field parameters reveals three distinct redox environments: oxidized, intermediate, and U(VI) reducing, across the study area. Integrating U isotope compositions and additional redox indicators with statistical analysis in this manner provides a robust approach to understand the subsurface environment controlling U cycling in large, data-limited regions.
当地下水中铀（U）的浓度超过允许限值时，其污染就成为一个关键问题。来自卡纳塔克邦东部的地下水样本（n = 46）显示，铀浓度范围为1.9至2744μg/L，分别有78%和66%的采样点超过了美国环境保护局（USEPA）和印度原子能管理委员会（AERB）的阈值。这些高铀含量主要是地质成因的。对同一组样本测定了δU和铀活度比（U/U），以了解控制地下水铀循环的氧化还原过程。δU等浓度线显示出从-0.95‰到0.3‰变化了1.3‰，这证明了地下水环境总体上呈氧化状态，而在研究区域南部存在局部的铀还原条件。地下水的（U/U）从1.2到5.4不等，表明α反冲效应、铀的优先淋滤以及花岗岩中高铀区的溶解之间存在动态相互作用。对地球化学和现场参数的统计分析揭示了整个研究区域存在三种不同的氧化还原环境：氧化环境、中间环境和U(VI)还原环境。以这种方式将铀同位素组成和其他氧化还原指标与统计分析相结合，为理解数据有限的大区域中控制铀循环的地下环境提供了一种强有力的方法。
