Geochemical modelling of uranium speciation in the subsurface aquatic environment of Punjab State in India

This research paper investigates the geochemical modeling of uranium speciation in the subsurface aquatic environment of Punjab State, India. The primary objective is to assess the influence of redox conditions and complexant concentration on uranium speciation in groundwater. Utilizing geochemical models such as MEDUSA and PRHEEQC versions 2, various groundwater samples, including bore well and hand pump sources, were analyzed for geochemical parameters, particularly uranium concentration. Through the application of a Piper diagram, groundwater was categorized into four types, indicating diverse geological conditions. The results revealed an alarming mean concentration of uranium at 99.96 µg/L, significantly above the EPA guideline limits of 30 µg/L. The study found that low redox potential in groundwater predominantly keeps uranium in the U (IV) oxidation state, complicating predictions of its behavior amidst fluctuations in redox potential, pH, and ligand concentration. Key uranium species controlling groundwater concentrations included U4O9(c), UO2(c), and UO2(CO3)34-. The solubility of hexavalent UO22+ was noted as high due to carbonate complex formation, leading to critical implications for the management of groundwater quality and ecological risks in the region.