Natural analogue studies aim to understand specific processes or to make predictions regrading formation processes or environmental conditions based on information from natural phenomena on Earth. Studying geological environments similar to the disposal system can help evaluate the longterm stability of the disposal system. These studies play a crucial role in evaluating the long-term stability of deep geological repositories (DGRs) for high-level radioactive wastes, which must remain stable for extended periods. In particular, bentonite, as a vital buffer material in DGRs, is mainly composed of montmorillonite and undergoes a transformation into zeolite under specific environmental conditions, resulting in the loss of its role as a buffer material in terms of swelling property and hydraulic conductivity. In this study, bentonite samples from Pohang Basin in Korea were investigated, revealing the presence of montmorillonite and zeolite in both outcrop and drilling core samples. While it has been known that montmorillonite and zeolites can form from volcanic glass through diagenesis or hydrothermal alteration, this study revealed that these minerals are formed under distinct environmental conditions. The outcrop samples primarily consisted of montmorillonite with minor quantities of cristobalite and amorphous silicate minerals. In contrast, the drilling core samples were composed of montmorillonite, zeolites, quartz and feldspar, indicating different mineral assemblages and characteristics between the outcrop and drilling samples. This observation suggests different environmental conditions during the mineral formation process. Therefore, various experiments and analytical methods were employed to gain a deeper understanding of the phase transformation from montmorillonite to zeolites under diverse environmental conditions

Uranium (U) is hazardous material can cause chemical and radiological toxicity, e.g., kidney toxicity and health effects associated with radiation. In Korea, where shallow weathered granitic aquifers are ubiquitous, several previous studies have reported high level of radioactivity in shallow groundwater. This eventually led to the closure of 60 out of 4,140 groundwater production wells in South Korea. Here, we examined aquifers currently dedicated for drinking water supply and investigated the 11,225 dataset of 103 environmental parameters. This dataset includes 80 physical parameters associated with the hydraulic system and 23 chemical parameters associated with waterrock interactions. Among hydraulic parameters, coarse loamy texture in subsoil displayed a notable relation with U concentration level, implied it is controlling the leaching of U from host rocks. Fluorine (F), is one of major products from water-rock interaction in granitic aquifer, exhibited high correlation with U concentration distribution. Positive relation of F concentration with uranium level suggested the dissolved U originated from groundwater interacted with granites. Conclusively, we found that infiltration capacity of soil layers and (2) aqueous speciation in groundwater formulated by interaction of groundwater with local solids, played important role for U concentration in granitic aquifer.