Ecological and Geochemical Features of Manganese Distribution in Groundwaters of Ukraine

Abstract

The results of hydrogeochemical studies on the identification of the features of manganese distribution in drinking groundwater of conditionally clean and technologically polluted territories of Ukraine are presented, as well as the assessment of the influence of inorganic ligands characteristic of the investigated groundwater on the behavior of Mn2+ depending on the initial conditions of the water environment. The Kyiv city, as well as Zhytomyr, Vinnytsia, and Rivne regions were selected as conditionally clean territories; Kyiv and Dnipropetrovsk regions — as technologically polluted territories. According to domestic and foreign literary data, the range of medical, biological, and toxicological properties of manganese is outlined, and the key features of the element prevalence in natural aqueous solutions and underground waters are clarified. Manganese and ferrum concentrations in the samples of the studied groundwater were determined using the high-precision method of mass spectrometry with inductively coupled plasma (ICP-MS). As a result of the statistical processing of the studied samples, it was established that the median manganese content for most of the examined territories does not exceed the maximum permissible concentration. The exception is the underground water of the Pidhirtsi village (Kyiv region), where the concentration of the element exceeds the standard by almost 4 times. A comparative analysis to determine the relationship between the manganese and ferrum concentrations and the depth of water intake structures did not show any regularities characteristic of natural waters undisturbed by technogenic activity. It was revealed that the largest deviations from the background values for manganese are typical for the Dnipropetrovsk region, and for ferrum — for the Kyiv city. Statistically significant relationships between the concentrations of manganese and ferrum in the examined samples were not found, which indicates the different geochemical nature of the elements concentration processes in the studied groundwater. Using the specialized software tools Hydra and Medusa, the finding forms of manganese depending on the pH of the water environment in studied samples were calculated. The obtained ratios of the element soluble forms for conditionally clean and technologically polluted territories of Ukraine made it possible to establish that in the water of conditionally clean territories, manganese migrates mainly in the form of free Mn2+ ion, and to a much lesser extent (11%) in the form of MnSO4. On the other hand, within the technologically polluted territories, the key role belongs to the inorganic ligand SO42–, the ratio of soluble compounds MnSO4 and Mn2+ is, respectively, 56% to 44%. The obtained results can serve as a basis for the selection of criteria when performing biogeochemical zoning of the territory of Ukraine.