Estimation of uranium migration parameters in sandstone aquifers

The chemical composition and isotopes of carbon and uranium were investigated in groundwater samples that were collected from 16 wells and 2 sources in the Northern Dvina Basin, Northwest Russia. Across the dataset, the temperatures in the groundwater ranged from 3.6 to 6.9 °C, the pH ranged from 7.6 to 9.0, the Eh ranged from -137 to +128 mV, the total dissolved solids (TDS) ranged from 209 to 22,000 mg L^-1, and the dissolved oxygen (DO) ranged from 0 to 9.9 ppm. The 14C activity ranged from 0 to 69.96 ± 0.69 percent modern carbon (pmC). The uranium content in the groundwater ranged from 0.006 to 16 ppb, and the 234U:238U activity ratio ranged from 1.35 ± 0.21 to 8.61 ± 1.35. The uranium concentration and 234U:238U activity ratio increased from the recharge area to the redox barrier; behind the barrier, the uranium content is minimal. The results were systematized by creating a conceptual model of the Northern Dvina Basin's hydrogeological system. The use of uranium isotope dating in conjunction with radiocarbon dating allowed the determination of important water-rock interaction parameters, such as the dissolution rate:recoil loss factor ratio and the uranium retardation factor:recoil loss factor ratio in the aquifer. The 14C age of the water was estimated to be between modern and >35,000 years. The 234U:238U age of the water was estimated to be between 260 and 582,000 years.