Uranium (U) as a trace element in groundwater supply constitutes a major health risk in many regions worldwide. This trace element becomes a public health concern when it exceeds national or international drinking water standards, as it is associated with several diseases (e.g., several types of cancer). In the Mecklenburg-Vorpommern (MV) region of northern Germany, particularly in the shallow aquifer (<30 m), elevated U concentrations have been historically reported. These levels are linked to glacial sediments originating from Scandinavia during the last glaciation. A “roll front” mechanism was postulated to explain U accumulation and migration in the subsurface, which either promotes or limits the mobility of U toward groundwater. This behavior is attributed to redox-driven mobilization processes, where oxidizing agents (e.g., nitrates) alter reducing environments, leading to the release of previously immobilized geogenic U from sediments.

Through an in-depth hydrochemical and geochemical analysis aimed at characterizing the water and soil in the MV area, this study analyzes both historical and recent data (2007-2024) from 6,711 water samples and 1,087 soil samples to assess the current status of U in the region. The results show that U concentrations in groundwater range from below detection limit (0.005 µg L⁻¹) to 104 µg L⁻¹, with 6% of samples exceeding the German drinking water limit in areas such as Schwerin, Wittenburg, Wismar, Anklam, Jarmen, Güstrow, and Greifswald. Groundwater temperatures range from 5.3 to 21.9 °C, with the highest U concentrations observed between 8.5 and 11.5 °C, indicating that temperature plays a role in uranium levels in the water. Redox potential (Eh), ranging from -143 to 806 mV, was found to be a key factor influencing U mobility. The roll front effect was identified, with peak U concentrations occurring between 50 and 425 mV, i.e., in the redox window of nitrate-reducing conditions. Outside this range, U levels in groundwater tend to remain below 10 µg L⁻¹. Soil concentrations range from 0.1 to 8.8 mg kg⁻¹, and a co-occurrence was observed between elevated U levels in sediments (>0.6 µg L⁻¹) and groundwater (>10 µg L⁻¹) in the same hot spot areas. The textural classification based on grain size has shown that soils with high Organic Carbon contents (Ha, Hn; ≈ 1.59 mg kg⁻¹; i.e., peaty soils), clay (Tu, Tl, Ts; ≈1.7 mg kg⁻¹), clay-sandy (Lts; ≈1.21 mg kg⁻¹) and sandy (sl1–sl3; ≈0.6 mg kg⁻¹), collected from depths of 10 to 40 cm, exhibit the highest U contents.

Future activities will include hydrogeochemical analysis (major, minor, and trace elements), and micro-scale studies (using core samples) in the MV area, conducted in collaboration with LUNG. Identifying and characterizing the sediments and groundwater in the MV area is essential for developing a conceptual model to understand the specific U-bearing facies and the mechanisms controlling uranium mobilization, which under certain conditions may either enhance or limit its concentration in groundwater. Continuing with the detailed characterization of the MV area, is essential for identifying the specific U-bearing phases, optimizing the design of mobility tests and water treatment strategies in MV.

Key words: Uranium, Groundwater, soil, Mecklenburg-Vorpommern