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—A quantitative assessment of the fractionation of elements during sedimentation is made based on long-term comprehensive studies with the participation of geochemists, hydrobiologists, soil scientists, and chemists. Analytical studies of the chemical composition of water, soil, bottom sediments, and biota were carried out at the Center for Collective Use of Scientific Equipment for Multielement and Isotope Studies and at the Institute of Catalysis, Novosibirsk. Based on a mineralogical and geochemical approach, we chose lakes with different types of biogenetic formation and different classes of organomineral sediments and performed detailed studies of the relationship between the organic and mineral parts of the sediments. It has been established that the organomineral sediments of different classes and biogenetic types of formation differ not only in the contents of major elements (Si, Ca, C, and O) but also in the group composition of organic matter. The direct effect of the transformation of organic matter on the mineral composition of bottom sediments has been revealed. The contents of other elements vary in a narrow range of values. At the same time, the difference in the contents of elements between organomineral sediments of different types and classes is comparable with their difference within a class. The leading role in the formation of the geochemical and mineral compositions of the organomineral sediments of small lakes belongs to intricate biological, biochemical, and physicochemical processes depending mainly on azonal factors and occurring under prolonged freezing-up (anaerobic conditions).

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The selectivity of Fe-MFI catalysts to partial peroxide oxidation of methane to methanol and formic acid was studied depending on their topology (Nanocrystals, Microcrystals, and bulk Commercial) and activation with oxalic acid. The catalysts were characterized by XRD, ICP-OES, SEM, UV-vis DR, NH 3-TPD, N 2 adsorption. TOF of methane oxidation increased in the series: Nanocrystals < Microcrystals << Commercial. The selectivity to methanol depended mainly on the crystallite size and increased in the same series. The increase in TOF and selectivity to formic acid, as well as a sharp decrease in the selectivity to CO 2 over all the activated catalysts were accounted for by an increase in the total acidity of the catalysts and the number of oligomeric Fe oxo-clusters. Different pathways to the formation of methanol/CO 2 (via free radical mechanism) and formic acid (via heterogeneous route) over Fe-MFI catalysts were suggested.

The process of synthesis of formic acid via partial peroxide oxidation of methane over Fe-MFI zeolites, as well as the influence of the catalyst activation by oxalic acid on the process parameters (conversion and selectivity) was studied. XRD, ICP-OES, SEM, UV-vis DR, ESR, NH 3 -TPD, 27 Al MAS NMR, N 2 adsorption techniques were used for the catalyst characterization. The observed increase in TOF, selectivity to formic acid and efficiency of H 2 O 2 utilization upon the catalyst activation with oxalic acid was accounted for by the formation of oligomeric oxo-clusters of Fe-ions and by an increase in the total acidity of the catalysts. The process of oxidation of main intermediates of the reaction, such as methanol and formic acid, was studied in the presence and in the absence of methane that allowed the mechanism of methane oxidation to formic acid to be suggested.