Phase formation in the NaF-KF-AlF3 system, in the vicinity of the K2NaAl3F12 composition, has been studied. The samples have been prepared by melting the starting components at 650 °C. A new phase has been revealed, which appeared to be a low-temperature form of the well-known K2NaAl3F12 ternary fluoride obtained by the hydrothermal synthesis method. The high-temperature form melts at 598 °C and is stable in a narrow temperature region of about 15 deg below the melting point. Thermal analysis, high temperature X-ray diffraction, IR-spectroscopy, X-ray fluorescence, and X-ray powder diffraction crystal structure analysis have been applied to study the composition, crystal structure, and thermal properties of the low-temperature phase. The crystal structure consists of trigonal-hexagonal two-dimensional (2D) grids built from the [AlF6] octahedra connected via vertices. The 2D grids have a specific wave-like conformation with a wavelength of 11.88 Å and an amplitude of 0.46 Å. There is a shift of the adjacent grids relative to each other. Because of this shift, the space between the grids changes. The shift leads to the formation of pores adapted to potassium and sodium ions. The reasons for the wave-like structure of layers are discussed. It is shown that the two polymorphic forms differ in the order of cation occupations.
The extent to which northern peatlands respond to or influence climate change is an unresolved question in Arctic science. Recent studies in Alaska, Canada, and Fennoscandia have raised concerns that northern peatlands, while currently a net sink or minor source of atmospheric CO2 , may become a significant CO2 source under a warming climate.
Expanding peatlands emit methane but sequester atmospheric carbon through long‐term accumulation of undecomposed plant matter. Drier conditions may reverse this process by increasing temperatures and lowering the peatland water table, causing anaerobic decomposition of stored peat and subsequent outgassing of CO2.While this process would likely reduce methane emissions and possibly enhance C uptake from increased soil nutrient mineralization rates [Oechel and Vourlitis, 1994], many scientists now believe that warming and drying of northern peatlands will liberate stored C for uptake by the atmosphere and biosphere.
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