Uranium isotopes in groundwater occurring at Amazonas State, Brazil

Area of Science:

• Environmental Science
• Geochemistry
• Radiochemistry

Background:

• Groundwater quality is crucial for human consumption.
• Understanding uranium isotope behavior provides insights into hydrogeochemical processes.

Purpose of the Study:

• To investigate the behavior of dissolved uranium isotopes (238)U and (234)U in groundwater from Amazonas State, Brazil.
• To assess the radiological implications of uranium concentrations for drinking water suitability.

Main Methods:

• Isotope dilution technique for precise uranium quantification.
• Alpha spectrometry for determining uranium isotope activity ratios (AR).

Main Results:

• Dissolved uranium concentrations ranged from 0.01-1.4 µg/L.
• Uranium activity ratios ((234)U/(238)U) varied between 1.0-3.5.
• Groundwater likely circulates in reducing environments with low-grade uranium leaching.
• Increasing AR trends observed with groundwater flow, particularly in Manaus, and along SW-NE directions, potentially linked to increasing water acidity.

Conclusions:

• The hydrogeochemical conditions favor uranium leaching from low-concentration mineral strata.
• Groundwater in the studied region is safe for human consumption based on radiological parameters, as uranium levels are below WHO guidelines.