| Summary: | The purpose of the study. To identify the features of humic acids of soils of different formation conditions using quantitative indicators of fluorescence spectra. Place and time of the event. The research was carried out on the territory of Siberia, where in the period 2000-2021, key areas with different natural conditions were identified in different regions. Methodology. Humic acids (HA) are considered as an independent component of the system of humus substances (SHS) of soils, the properties of which depend on the ecological conditions of formation. Soil samples were taken during the period of the most stable state of the system of humus substances in a continuous column every 5–10 cm and (or) less within the visible boundaries of genetic horizons. The HA preparations were isolated with 0.1 n NaOH after preliminary soil decalcification followed by precipitation with 2 n HCl. Additional purification from ash elements was not carried out. Fluorescence spectra of humic acid solutions with the same concentration of the substance (0.01 % HA) at pH of 13 were recorded in the wavelength range of 300–650 nm on an Agilen Cary Eclipse Fluorescence Spectrophotometer at an excitation wavelength of 330 nm. The main results. The average statistical quantitative indicators of the fluorescence spectra of humic acids of soils formed under different natural conditions were calculated: the position of the fluorescence maximum (λmax), the value of the first moment (M1), and the ratio of the integral fluorescence intensities in the areas of its maximum manifestation in the red and blue parts of the spectrum (coefficient α). The results showed that soils formed in different natural conditions have different ranges of values of all quantitative indicators of the fluorescent properties of humic acids. They differ significantly in tundra soils of plain and mountainous conditions, within the same mountainous country due to vertical zonality, within the same territory with ring zonality due to the change of humidification areas, and ...
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