Multi‐Isotope Based Identification and Quantification of Oxygen Consuming Processes in Uranium Hosting Aquifers With CO 2  + O 2 In Situ Leaching

• Published in: Water resources research 2023-03, Vol.59 (3)
• Main Authors: Lu, Chongsheng, Xiu, Wei, Guo, Huaming, Lian, Guoxi, Yang, Bing, Zhang, Tianjing, Bi, Erping, Shi, Zheming
• Format: Article
• Language: English
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1029/2022WR033980

Although neutral in situ leaching through CO 2  + O 2 is employed to extract uranium (U) in sandstone by in situ leaching (ISL), mechanisms of U mobilization and O 2 consumption remained unclear. To address this gap, 18 groundwater samples were taken from the Qianjiadian sandstone U ore field, including seven samples from production wells in mining area M1 (mining for 5 years), six samples from production wells in mining area M2 (mining for 4 years), and five samples from monitoring wells (GC), to quantify U‐mobilizing processes in the mining aquifer by employing hydrogeochemical compositions and multi‐isotopes. The introduction of O 2 and CO 2 efficiently stimulated U mobilization in the mining aquifer. The injected CO 2 critically promoted the dissolution of carbonate minerals, which enhanced the formation of uranyl carbonate (predominantly CaUO 2 (CO 3 ) 2 2− and Ca 2 UO 2 (CO 3 ) 3 (aq)) and thus facilitated U mobility. Generally, δ 34 S SO4 and δ 18 O SO4 in M2 and M1 were significantly lower than those in GC ( p