## 4 Results and Discussion
### Estimation of biogeochemical Mineral Neoprecipitation
The effective sorption sites of rocks and the formation of new bioorganic bonding sites in the polysaccharide matrix of biofilms may overlap. In our case, the K\({}_{\text{d}}\) value of uranium increased by 30.5% in the most polluted well (6169 mg/L NO\({}_{\text{3}}\)\({}^{-}\)). * Changes in Eh and pH values, affecting the distribution of uranium forms, the solubility of mineral phases, including clay phases, and the bacterial community itself. Abiogenic and biogenic reduction processes contribute to Eh reduction and pH growth, which are sometimes above the optimal values for denitrification bacteria (2-4): [-CH\({}_{2}\)O] + 2 NO\({}_{\text{3}}\)\({}^{-}\) + 2H\({}^{+}\) = 2.5 CO\({}_{2}\) + \(N_{\text{2(gas)}}\) + 3.5H\({}_{2}\)O (2) [-CH\({}_{2}\)O] + Fe(OOH) + 2H\({}^{+}\) = 0.25 CO\({}_{2}\) + 1.75H\({}_{2}\)O + Fe\({}^{2+}\) (3) [-CH\({}_{2}\)O] + 0.5 SO\({}_{4}\)\({}^{2-}\). + 0.5H\({}^{+}\) = 0.5H\({}^{-}\) + CO\({}_{2}\) + \(H_{2}\)O (4)
* The formation of carbonate species in solution and carbonate mineral phases during the oxidation of organics (2-4) can enhance the mobility of uranium due to stable carbonate complexes or modify the sorption properties of host rocks. * The formation of microbial metabolites that, on the one hand, inhibit nuclide migration when accumulating in biofilms and, on the other hand, enhance migration in the form of biocolloids (pseudocolloids), which mobilize uranium. In addition to the above factors, the hydrogeochemical conditions at each facility play a crucial role. The maximum number of denitriying and sulphate-reducing bacteria (Table 2) was found in Sample 3, which was taken from the most contaminated well. Moreover, uranium, like many other metals, can be used in enzymatic reactions as an oxidizer. The question is, at what concentration does nitrate lead to a decrease in the biological efficiency of uranium reduction? This question should be solved experimentally. In particular, in the laboratory experiments, after the addition of 50, 500, and 3000 mg/L of NO\({}_{\text{3}}\)\({}^{-}\) and 50, 100, and 200 mg/L of uranium to clean groundwater (Sample 1, Table 1), we observed that at nitrate concentrations of up to 500 mg/L, the microbial reduction efficiency of nitrate ions increased within 7 days. At high concentrations of NO\({}_{\text{3}}\)\({}^{-}\) and 200 mg/L of U(VI), pronounced retardation was recorded, up to 1.2%. contains a wide variety of functional groups, primarily hydroxyl, carboxyl, carbonyl, and sometimes amino groups. In one of our publications, we performed a detailed analysis of the interaction of uranyl ions with the functional groups of o-polysaccharides isolated from the bacterium Pseudomonas veronii, a common biofilm inhabitant. Carbonyl groups have been found to play a major role at neutral pH values [41]. [PERSON] et al. [42] provided evidence of uranium bonding with the extracellular polysaccharides (EPS) produced by _Pseudomonas aeruginosa_ strain BU2 involving carboxylic groups at pH 5.0, whereas at lower pH values, amino and hydroxyl groups played a major role. It is worth noting that biofilms are a condition for the immobilization of other compounds, primarily iron, calcium, and chromium, that contribute to the formation of new mineral phases in biofilms (calcites, ferrihydrites, etc.) [43] that are known for their high sorption capacity for many actinides [44]. Taking into account the possibility of stimulating microbial processes, microbial growth on rocks can therefore be an important factor in the immobilization of uranium in the form of organic and organomineral deposits in local areas. Calculating the SIs of solutions with respect to certain minerals in a wide range of redox conditions is important for the development of remediation practices since SI reveals how microbial activity changes Eh (Figure 3). Recall that in the model calculations, 10 mg/L of uranium was added, corresponding to the simulated, not natural, solutions. Phosphates appeared due to the addition of whey to stimulate biota development.