This paper presents the results pertaining to studying the properties of the photocatalytically active composition of strontium bismuthate SrBi_2.70O_5.05, SrBi_2.90O_5.35, and SrBi_3.25O_5.88 and bismuth carbonate (BiO)₂CO₃ in molar ratios 1/0.67, 1/0.56, and 1/0.37, respectively. These compositions are obtained through pyrolytic synthesis from organic precursor complexes of strontium and bismuth with sorbitol. It has been established that the synthesised powder materials absorb the light of the visible range up to 500 nm owing to the presence of a narrow-gap semiconductor strontium bismuthate. The presence of a wide-band semiconductor (BiO)₂CO₃ ensures an effective separation of electron-hole pairs. The diffuse reflection spectra (DRS) of compositions differ from the analogous spectra of a mechanical mixture of these semiconductor phases with the same composition, which allows one to assume the heterostructural structure of the semiconductor system. The same heterostructure is confirmed by the results of mapping. Catalytic particles that are synthesised at a temperature of 500°C containing 27 mass% (BiO)₂CO₃ (corresponding to SrBi_2.9O_5.35/(BiO)₂CO₃ = 1/0.56) have the greatest activity with respect to the photodecomposition of methylene blue (MB). The possibility of controlling the optical properties and photocatalytic activity of the composition is depicted due to the joint formation of the strontium bismuthate phase and the bismuth carbonate phase.

The photocatalytic activity of heterostructural α-Bi₂O₃/Bi compositions obtained by low-temperature pyrolysis of bismuth complexes with sorbite has been investigated. The efficiency of catalysts has been estimated based on the decomposition rate of methylene blue under illumination by visible light. The obtained catalysts are characterized by different contents of metallic Bi and different degrees of imperfection of the α-Bi₂O₃ lattice, which was obtained by changing the amount of sorbite in the composition of the precursor organomineral bismuth complex and varying the synthesis temperature. It is established that isothermal annealing of the α-Bi₂O₃/Bi compositions in air in the range of 400–600°C leads to relaxation of defects and an increase in the α-Bi₂O₃ lattice volume. An increase in the annealing temperature to 550°C is accompanied by a rise in the α-Bi₂O₃/Bi catalytic activity. However, the heterostructure degrades at higher temperatures as a result of metallic bismuth oxidation, while the catalytic activity decreases.

This work is devoted to the study of the content of mineral forms of nitrogen in the water of small rivers in Khabarovsk and its surroundings, represented by the Bolshekhekhtsirsky Nature Reserve, during the winter low water of 2017-2021, which lasts from December to February. The dynamics of quantitative distribution of ammo-nium, nitrite, and nitrate nitrogen in relation to different groups of watercourses were considered. The correlation analysis enabled to reveal the probable reasons for such correlations of their content.