卷 43, 编号 6 (2024)

Benzene is one of the most common classes of chemicals in industry. As a rule, it enters the atmosphere as a result of man-made accidents, during the evaporation of solvents, etc. Benzene and its derivatives are toxic and have a negative impact on the environment and the human body. Therefore, issues of benzene transformation in the atmosphere are of increased interest. In present work, the structures and electronic energies of equilibrium configurations and transition complexes of the C₆H₆ F and C₆H₆F⁺ systems are calculated using the density functional theory. It has been shown that the interaction of benzene with atomic fluorine can proceed through two channels, i.e. the elimination of hydrogen with the formation of a phenyl radical and the addition of a fluorine atom with the formation of an ipso-fluorocyclohexadienyl radical. It has been established that for the dissociation of ipso-fluorocyclohexadienyl radical into fluorobenzene and atomic hydrogen, it is necessary to expend about 27 kcal/mol. This indicates a low probability of this process occurring at low temperatures. Under experimental conditions, when the temperature of fluorine atoms is about 1000 K, the ipso-fluorocyclohexadienyl radical decomposes to form fluorobenzene. In this case, the occurrence of secondary reactions is unlikely. The conclusions drawn from the analysis of the results of quantum chemical calculations are in good agreement with the experimental data.

By the method of resonant fluorescence (RF) of chlorine atoms, the reaction rate constant of a chlorine atom with dimethyl sulfide (DMS) was measured in the temperature range 308–366 K. It is shown that the reaction rate constant decreases during experiments at a higher temperature. At a temperature of 308 K, the rate constant of this reaction was measured at different ratios of the reaction time and the diffusion time of chlorine atoms to the reactor wall. The data of these experiments showed that with an increase in the diffusion time of the active centers to the surface of the reactor, compared with the contact time of the reagents, a decrease in the measured reaction rate constant is observed. This allowed us to assert that the reaction is heterogeneous and the interaction of the chlorine atom with the DMC occurs on the surface of the reactor.

A series of probe measurements to determine the electron concentration in a gas ahead of a strong shock wave front was carried out using a double-diaphragm shock tube DDST-M of the Institute of Mechanics, Moscow State University. At the same time, the light flux from the region of the shock-heated gas was recorded, which made it possible to calculate the electron concentration behind the shock wave using the spectroscopic method. The experiments were carried out in air, oxygen, and nitrogen at shock wave velocities from 8.3 to 11.3 km/s and an initial pressure of 0.25 Torr in the low-pressure chamber. The dependences of the electron concentration on the shock wave velocity and the distance from the observation point to the shock wave are obtained. Spectroscopic measurements made it possible to determine the dependence of the electron concentration on the composition of the gaseous medium. The obtained data are compared with the experimental data of other authors.

Every year, metallurgical plants emit hundreds of thousands of tons of harmful substances into the atmosphere. Remote sensing of flue gases from chimneys of metallurgical plants is an urgent task for both industrial enterprises themselves and environmental control systems of nearby settlements. In this work, based on the results of remote optical monitoring of emissions from chimneys of metallurgical plants of the MMC “Norilsk Nickel’s”, Polar Division, the concentration of sulfur dioxide in the flue gases was estimated. The measurements were carried out using Infrared Fourier Transform Spectrometers operating in the range 7–13 µm with 4 cm^-1 spectral resolution. A new technology for remote optical sensing in a passive mode of flue gases from metallurgical plants is proposed, including measurements both on cross sections of chimneys and plumes.

Using a coated-insert flow tube reactor coupled to mass spectrometer with molecular beam sampling, the uptake of O₃ on a salt film coating of MgCl₂·6H₂O was studied under variation in the reactant concentration ([O₃] = 2.5 ‧ 10¹³ – 1.6 ‧ 10¹⁴ cm⁻³), humidity ([RH] = 0–24%), and reactor temperatures of 254 and 295 K. The time-dependent character of the uptake coefficient g(t) = γ_r exp(−t/τ) was obtained, the γ_r and t parameters being dependent on [O₃]. Using the method of mathematical modeling, based on the shape of the dependence of the uptake coefficient on ozone concentration and its time history, the uptake mechanism was proposed and the elementary kinetic parameters were assessed, on the basis of which it is possible to extrapolate the temporal behavior of the uptake coefficient to tropospheric conditions at arbitrary ozone concentrations. Based on their obtained dependencies, at room temperature the uptake occurs according to the reaction mechanism of an adsorbed molecule on the surface of the substrate: the mechanism includes the stage of reversible adsorption, formation of an adsorbed complex followed by its unimolecular decomposition with the release of molecular chlorine into the gas phase. At low temperatures, the uptake proceeds through recombination via the Eley–Ridil’s reaction mechanism: it includes reversible adsorption, formation of a surface complex, its reaction with an ozone molecule from the gas phase followed by the release of an oxygen molecule into the gas phase. In this case, no chlorine is formed. No dependence of the uptake coefficient on relative humidity was found in the range of RH from 0 to 24% at T = 254 K.

Due to the increase in radon emanation, the conductivity in the surface layer of air increases, which causes variations in the electric fields in the low atmosphere and according to some hypotheses in the ionosphere. There are known proposals on the possibility of using such ionospheric disturbances as precursors of earthquakes. We simulate the ionospheric electric fields in the framework of a quasi-stationary model of the conductor consisting of the atmosphere including the ionosphere. The consequences of the paradoxical point of view about a decrease in the conductivity of surface air with an increase in radon content are also considered. Even with extreme radon emanation, disturbances of the ionospheric electric field are obtained three to four orders of magnitude smaller than the supposed precursors of earthquakes.

The influence of atmospheric waves generated by a tropospheric convective source on the state of the upper atmosphere and ionosphere during the recovery phase of the geomagnetic storm on May 27–28, 2017 was studied. A new approach to accounting for atmospheric waves generated by tropospheric convective sources in large-scale atmospheric models without using wave parameterization is proposed and implemented. The developed approach makes it possible to comprehensively study the effects generated by atmospheric waves against the background of various geophysical events, including geomagnetic storms. The multimodel study has shown that the proposed approach allows us to reproduce perturbations of the critical frequency ionosphere F₂ layer caused by the propagation of atmospheric waves generated by a tropospheric meteorological source. It is shown that the inclusion of a heat inflow source simulating the propagation of atmospheric waves from the lower atmosphere in the global model enhances the effects of a geomagnetic storm, which manifests itself as an additional decrease in the critical frequency of the F₂ layer, which can reach 7 % of absolute values.