Natia Gigauri

According to observational data, experimental measurements and numerical modeling, is assessed pollution of one of the industrial centers of Georgia, Rustavi city’s atmosphere with microaerosols. Monthly, daily and hourly changes of the concentrations of PM2.5 and PM10 in the city atmosphere are analyzed. It is accepted that PM2.5 concentrations are always lower than PM10 concentrations, but their change curve is the same. In addition, it has been noted that the maximum concentrations of particles in the atmosphere of Rustavi city will be reached at any part of the day, which is determined by the total impact of the traffic flow and industrial facilities. By numerical modeling has calculated the influence of background western light air, gentle and fresh breeze on the distribution of PM particles in the atmosphere. Calculations showed that background light air and gentle breeze lead to an increase the concentrations of microaerosols in the city's atmosphere, while fresh breeze contribute to the dispersion of dusty clouds. As a result, the level of dust in the city is decreasing, but the distribution area is expanding.

The study of ecological problems has a great role in modern life. Micro particles are particularly dangerous for human health. That's why we study the features of the distribution of dust particles in the atmosphere. Based on the monitoring data, the concentrations of PM2.5 and PM10 microparticles in the atmospheric air of the Rustavi city (Georgia) have been investigated. Their concentrations are also determined experimentally using a mobile device in the city and its surroundings. The main pollution areas have been identified. The diurnal picture of the spatial distribution of PM10 and the features of its distribution during the northern background wind have been obtained by numerical modelling. For this, a three-dimensional regional model of atmospheric processes and the integration of the equation of admixtures’ transfer-diffusion are used. The spatial distribution of PM10 is determined by the background wind speed and direction, it is also greatly influenced by the relief and the local circulation systems formed by the diurnal change of the subsurface temperature.

The subject of our study is atmospheric air pollution with numerical modeling. In the presented article, as the object of research there is chosen city Tbilisi, the capital of Georgia, with a population of one and a half million and a difficult terrain. Main source of pollution in Tbilisi is currently vehicles and construction dust. The concentrations of dust and PM (Particulate Matter) were determined in the air of Tbilisi and in its vicinity.There are estimated their monthly maximum, minimum and average concentrations. Processes of dust propagation in the atmosphere of the city and its surrounding territory are modelled using 3D regional model of atmospheric processes and an admixture transfer-diffusion equation. There were taken figures of distribution of the polluted cloud and dust concentrations in different areas of the city at different heights and at different time intervals with the background stationary eastern wind. It is accepted that the difficult terrain and mountain-bar circulation affect the deformation of the cloud and its spread, there are determined time periods when the dust concentration in the city is greater than MAC (Maximum Allowable Concentration, MAC=0.5 mg/m3).

The concentrations of PM2.5 and PM10 in the atmospheric air of Tbilisi and the adjacent territory during the COVID-19 pandemic was studied. A decrease of the PM concentrations in the atmosphere of the city was revealed and it was found that the main contribution to the pollution of the atmosphere of Tbilisi with PM2.5 and PM10 is made by motor vehicles. The concentration of PM2.5 in the atmosphere of Tbilisi is usually lower than the concentration of PM10 by about 2-4 times, but the character of the curve of their changes is the same. The maximum dust pollution is reached in the evening hours, after 19:00. At a height of 2 m from the surface layer, the high concentration of PM10 (1.0-2.5 MAC) is formed in the interval from 16:00 to 21:00 in the central and southern parts of the city and on relatively flat areas.

Tbilisi, a large city of the South Caucasus, is a junction point connecting Asia and Europe, Russia and republics of the Asia Minor. Over the last years, its atmosphere has been experienced an increasing anthropogenic load. Numerical modeling method is used for study of Tbilisi atmospheric air pollution. By means of 3D non-linear non-steady numerical model a peculiarity of city atmosphere pollution is investigated during background western light air. Dust concentration spatial and time changes are determined. There are identified the zones of high, average and less pollution, dust accumulation areas, transfer directions etc.  By numerical modeling, there is shown that the process of air pollution by the dust proceeds in four stages, and they depend on the intensity of motor traffic, the micro-relief of the city, and the location of city mains. In the interval of time 06:00 - 09:00 the intensive growth, 09:00 - 15:00 - a constancy or weak decrease, 18:00 -21:00 an increase, and from 21:00 to 06:00 a reduction of the dust concentrations take place. The highly polluted areas are located in the vicinity of the city center and at some peripherical territories of the city, where the maximum dust concentration at 9PM is equal to 2 maximum allowable concentrations. The similar investigations conducted in case of various meteorological situations will enable us to compile the map of background urban pollution and to elaborate practical measures for ambient air protection.

Pollution of the Tbilisi atmospheric air with PM2.5 and PM10 in usual and pandemic situations by using the data of 5 stationary observation points is investigated. The values of the statistical characteristic parameters of PM in the atmosphere of Tbilisi are analyzed and trend graphs are constructed. By means of analysis of pollution levels in the quarantine and usual periods the proportion of vehicle traffic in pollution of city is estimated. Experimental measurements of PM2.5, PM10 in the atmosphere have been carried out in different districts of the city and map of the distribution of their concentrations were constructed. It is shown that maximum pollution values are recorded in the city center and along major motorways. It is shown that the average monthly concentrations vary in the range of 0.6-1.6 Maximum Permissible Concentration (MPC). Average daily values of concentration vary at 2-4 days intervals. The distribution of PM10 generated as a result of traffic is numerical modeled. The modeling results are compared with the observation data.

PM2.5 propagation at Tbilisi territory in winter period in case of background north light wind is numerically modeled and analyzed through combined integration of 3D regional model of atmospheric processes evolution and equation of admixtures transfer-diffusion. Motor transport moving at city streets and trunk lines is a main source of atmosphere pollution. There are investigated the main peculiarities, which characterize the process of microaerosols spatial distribution under rugged terrain conditions. PM2.5 high concentration zones are established at the territory of city, time intervals, when high air pollution forms or air self-purification takes place, are determined. Temporal and spatial variations of PM2.5 concentration in the lower part of atmospheric boundary layer are studied. It is established that 25 mkg/m3 and higher concentration is obtained from 11AM to 1PM and from 7PM to 10PM in the surroundings of Ponichala situated in the eastern part of the city. 

Temporal and spatial variations of PM2.5 distribution originated resulting from motor transport traffic during background south light wind are studied via numerical modeling. PM2.5 high concentration zones at the territory of the city are established, and time intervals, where air high pollution forms or air self-purification process occurs, are determined. There is established a difference, which exists between PM2.5 spatial distributions in case of background south and north winds. 

Dust distribution of the difficult relief town Tbilisi, located in the complex territory of Georgia in case of basic meteorological situations and stationary pollution sources is studied with the use of regional model of atmospheric process development in the Caucasus and non-stationary three dimensional equation of transfer-diffusion of passive admixtures. Terrain - following coordinate system is used with the purpose of taking into account the impact of very complicated relief on the atmosphere pollution process. It is shown, that in case of meso-scale process, the dust dissipated from city in the atmosphere is basically concentrated in the boundary layer. Maximum values of dust concentration are obtained in the lower 100 m surface air layer. A dust concentration equal to 0.01-1 Maximum Allowable Concentration (MAC = 0.5 mg/m3) is obtained at a height of 2 m at a distance of 10 km from the city, at a height of 100 m – at a distance of 15-18 km and a height of 600 m – at a distance of 40 km. A change in the direction of dust transfer is related to daily variation of dynamical and thermal meteorological fields in the atmosphere surface layer and formation of local vertical vortex. Modelling of dust micro-scale diffusion process showed that the city air pollution depends on spatial distribution of the main sources of city pollution, i.e. on vehicle traffic intensity, as well as on spatial distribution of highways, and micro-orography of city and surrounding territories. It is shown that the dust pollution level in the surface layer of the atmosphere is minimal at 6 a.m. Ground-level concentration rapidly grows with increase of vehicle traffic intensity and by 12 a.m. reaches MAC in the vicinity of central city mains. From 12 a.m. to

9 p.m. maximum dust concentration values are within the limits of 0.9-1.2 MAC.

Microscale processes of dust dispersion in the atmosphere of Tbilisi with complex orography are studied by numerical modeling of the 3-dimensional regional model of dust distribution in the environment and the equation of transfer-diffusion of impurities. A system of terrain coordinates is used to account for the impact of complex terrain on air pollution. For modeling, a horizontal step with respect to latitude and longitude is taken as 300 and 400 m, respectively. A case of weak background wind from the east is discussed. The model considers the vehicle as a stationary source of dust emissions into the atmosphere.

 Modeling of the micro-scale dust diffusion process has shown that the pollution of the city atmosphere depends on the sources of pollution or the intensity of traffic and the spatial layout of roads, as well as the orography of the city and its surrounding area. It is shown that the level of pollution of the terrestrial atmosphere is minimal at 6 o'clock in the morning. Then along the central highway of the city, the dust concentration in the terrestrial layer increases rapidly with the increase of traffic intensity and reaches the value of 1 ZDC (0.5 mg / m3) in 12 hours. The maximum dust concentration in the 12-21 h interval ranges from 0.9-1.2 ZDC. During this period, the maximum zone of pollutants is formed, with a weak increase in their area and terrestrial concentration. These zones are located in both the central and suburban areas of the city. Their location and area depend on the spatial distribution of wind speed, formed by the influence of complex terrain and turbulent and advective transfer of dust. At 21-24 hrs, dust pollution and groundwater concentrations decrease. After midnight in the city this process takes place quasi-periodically.

Defined concentrations of PM-particles and dust in the air of Tbilisi and its surrounding area. Their monthly maximum and minimum values ​​are estimated. The dust propagation process is modeled in the case of a background stationary westerly wind. The source of pollution is vehicles moving in the city. Visual images of dust distribution area and concentrations were obtained.

Microscale processes of dust distribution in the city of Tbilisi with a very

complex topography are modeled using a 3D regional model of atmospheric

processes and numerical integration of the transport-diffusion equation of the

impurity. The Terrain-following coordinate system is used to take into account the influence of a very complex relief on the process of atmospheric pollution.

Modeling is carried out using horizontal grid steps of 300 m and 400 m along

latitude and longitude, respectively. The cases of the stationary background eastern and western weak winds are considered. In the model, motor transport is considered as a nonstationary source of pollution from which dust is emitted into the atmosphere.

Modelling of dust micro-scale diffusion process showed that the city air

pollution depends on spatial distribution of the main sources of city pollution, i.e. on vehicle traffic intensity, as well as on spatial distribution of highways, and micro orography of city and surrounding territories. It is shown that the dust pollution level in the surface layer of the atmosphere is minimal at 6 a.m. Ground-level concentration rapidly grows with increase of vehicle traffic intensity and by 12 a.m. reaches maximum allowable concentration (MAC = 0.5 mg/m3) in the vicinity of central city mains. From 12 a.m. to 9 p.m. maximum dust concentration values are within the limits of 0.9-1.2 MAC. In the mentioned time interval formation of the highly dusty zones, and slow growth of their areas and value of ground-level concentrations take place. These zones are located in both central and peripheral parts of the city. Their disposition and area sizes depend on spatial distribution of local wind generated under action of complex terrain, as well as on the processes of turbulent and advective dust transfer. From 9 to 12 p.m. reduction of dust pollution and ground-level concentration takes place. After the midnight city dust pollution process continues quasi-periodically.

Numerical modeling studies the kinetics of the dispersion of 10 μm dust particles into the atmosphere from aeration lamps of Georgian Manganese Ltd. №1 and № 4's workshops in the case of steel.

Modeling has shown that thermal convection significantly reduces the concentration of dust in the vicinity of the source near the subsoil surface of the atmosphere. In the vicinity of the source of the eruption, dust is transferred from the lower levels to the higher levels and their further advectional distribution. At this time a zone of wind speed convergence is formed in the vicinity of the aeration lanterns. This zone gradually decreases with increasing altitude and transforms into a divergence zone in the upper part of the Earth's surface layer. An ascending convective flow of air and dust is received on top of each source.

The kinetics of anthropogenic dust scattering in the atmosphere of large cities by separate sources using numerical integration of a system of three-dimensional nonlinear quasi-static and non-static equations of the atmosphere. It is accepted by modeling that the dust propagation kinematics obtained by quasi-static and non-static equations have both common and different characteristics. In the case of beta-mesoscale diffusion, described by quasistatic equations, advection diffusion plays a major role in the dust transfer process. In the case of gamma-scale diffusion, described by non-static equations, convection diffusion plays a major role in the dust transfer process.

The part of Georgian population living on the rural territory is approximately 46%, and 66% of the territory of Georgia consists of high mountainous regions inhabited by 6.5% of the country’s population. The high mountainous regions of Georgia are characterized by relatively structural weaknesses: non-diversified economy, outmigration, extreme poverty, underdeveloped infrastructure, limited access to health care and other public services such as waste management and sewerage. All these lead to increased formation of illegal dumpsites and latrines, which in turn impact on climate change.

The aim of the research was to determine impact of illegal dumpsite and latrines on climate change using IPCC methodology and experimental data about quantity and morphological composition of municipal solid waste and statistical data of amount of latrines in High Mountainous Rural Regions of Georgia.

The results of illegal dumpsites and latrines study shows that methane emissions from illegal dumpsites generated by high-mountainous rural regions of Georgia is 0.01% of emissions from the waste sector, while methane emissions from latrines amount is 0.01% of emissions from all sectors of Georgia.

A numerical model of the propagation of dust emitted into the atmosphere is based on a three-dimensional nonlinear nonquasistatic equation for thermal convection in the atmosphere. The model uses a digital grid with high resolution capability. The kinetics of the distribution of 10 μm dust particles emitted from two high sources into the atmosphere are studied using numerical modeling. Two meteorological situations are considered - calm and background northwest wind. By modeling, it is obtained that the kinematics of the distribution of dust emitted into the atmosphere are substantially different from each other in the case of quiet and background movement. Spatial dust distribution occurs as a result of both ordered horizontal and vertical flows as well as diffuse movements. Diffusion of advection, convection and turbulent dust under the influence of background wind creates a cloud-shaped vertical zone of dust pollution. No diffusion motion is obtained in the received zone

The main characteristics of the diffusion of industrial dust in the industrial region of

Georgia - Zestafoni in cases of background, weak and strong westerly and east winds are studied.

The calculations were carried out using the regional model fог the development of atmospheric pro cesses in the Caucasus and the transfer equation of a passive admixture.

Dust distribution of the industrial town Zestafoni located in the complex territory of Georgia in case of basic meteorological situations and stationary pollution sources is studied with the use of regional model of atmospheric process development in the Caucasus and non-stationary three-dimensional equation of transfer-diffusion of passive admixtures.

Distribution patterns of dust dissipated in the atmosphere are obtained at different level from the surface. It is shown that dust dissipated from cities in the atmosphere is basically concentrated in the boundary layer. Maximum values of dust concentration are obtained in the lower 100 m surface air layer. Spatial dust distribution region increases and concentration decreases along with height increase. An influence of local orography on the pollution cloud is investigated. During a background western Light Air Likhi and Racha ridges impede dust transfer to the east and cause dust cloud deformation. Dust spreads along the valleys of Kvirila and Chkherimela rivers located between the ridges. In case of Gentle and Fresh Breezes the impact of local orography on the dust dispersion process is insignificant. Dust is basically transferred in the direction of background flows.

The zone of influence of industrial town dust on the environmental pollution is determined. A width of this area varies from 5 to 20 km in dependence of the background wind velocity. 

Kinematics of dust propagation is studied. It is determined that in 2-100 m layer of atmosphere the process of turbulent diffusion take precedence in the process of dust spreading. From 100 m to 1 km the processes of diffusive and advective transfers are identical, while above 1 km the preference is given to advective transfer.

Numerically modeled and studied dust distribution in industrial cities of Georgia in case of weak westerly wind. Images of spatial distribution of dust are obtained, the influence of orography, horizontal and vertical turbulence and advection processes on the distribution of dust in the atmosphere is analyzed.

By using the regional model for the development of atmospheric processes in the Caucasus and the passive impurity transference equation, the diffusion of urban dust is simulated in cases of background, weak and strong west winds. The main characteristics of dust diffusion in the industrial region of Georgia – c.Zestafoni and its environs are studied. Areas of urban dust distribution, the vertical structure of a dust cloud, the surface density of deposited dust, etc. have been determined.

Discussed changes in the concentrations of aerosol emissions from the Zestaponi Ferroalloy Plant according to the 2018 seasonal changes and their ecochemical assessment.

Using a non-linear, non-stationary three-dimensional and continuous environment of impurity transfer-diffusion equations in atmospheric hydrothermodynamics, a numerical model of the evolution and distribution of impurities of β-scale atmospheric processes for a separate region of Georgia has been developed. The model studies the distribution of dust in Kakheti in the case of four main weather conditions and stationary sources of pollution. Images of the distribution of dust emitted into the atmosphere at different levels from the earth's surface are obtained. It is shown that dust scattered in the atmosphere from cities is mainly concentrated in the boundary layer of the atmosphere. Maximum values ​​of dust concentration are obtained in the air surface 100 m layer. Areas of influence of cities are defined. It is 20-30 km for Tbilisi, about 10 km for Rustavi, and no more than 2-4 km for other cities.

Mathematical models for the distribution of pollutants in the atmosphere and river in a separate region of Georgia are developed using the non-stationary linear equation of atmospheric hydrothermodynamics and the transfer-diffusion of matter into a continuous environment. The purpose of creating models and scientific studies conducted through them is to develop mathematical models that will be able to determine the level of air pollution and major rivers in certain regions of Georgia in the event of the release of large amounts of pollutants in them. The presented work discusses the creation of the following 2 types of models:

    Model 1. Development of a numerical model for the development of beta-meso-scale atmospheric processes for the region of Georgia, the spread of passive and non-passive substances in the atmosphere and sedimentation on the soil.

    Model 2. Establish a numerical model for the distribution of spilled material in the Mtkvari River and investigate pollution. The model is intended to study the spread of pollutants in the Mtkvari River in the first approach. The river is divided into 10 conditionally homogeneous linear sites and the average annual values ​​of the characteristic hydrological parameters of the river are used for each site. The results of the calculations show that the discussed models qualitatively accurately describe the distribution of pollutants in the terrain and rivers of the mountainous region.

It is shown, that the relief of the Caucasus significantly influences on the trajectory of the pollution distribution. The North West orientation of the Main Caucasian Range resists air motion to the north, constrains the radioactive pollution in the boundary layer to flow around the Main Caucasian Range from the west or east sides. It is obtained that the 48 hours are necessary for the radioactive cloud to overflow the South Caucasus and distribute over the territory of the North Caucasus. The radioactive pollution is falling out mainly in the central, southeast and northwest parts of the South Caucasus. The zone of the radioactive deposition is extended along the background wind and deformed by the influence of the relief. The maximum length of the zone of significant deposition of radioactive substance equals approximately 750 km in case of the background South East wind and 350 km in other cases. The maximum width of the zone approximately equals 150 km. It is obtained that the surface density of the deposited radioactive nuclide in the zone of significant radioactivity decreases from 360 a.u./m2 down to 1 a.u./m2 when the concentration of 10 aerosol 131I in emission plume during during 6 hours are equal to 100 a.u./m3.

Using the regional numerical model for the development of atmospheric processes in the Caucasus, the distribution of the radioactive element iodine-131 emitted as a result of a hypothetical possible accident into the atmosphere from the Armenian nuclear power plant in the case of background south, southwest and southeast winds has been studied. Radioactive decay and aerosol sedimentation processes are considered. The distribution of only 10 μm diameter radioactive nuclide is considered.

Doctoral Thesis Referee

Master Theses Supervisor

Doctoral Thesis Supervisor/Co-supervisor

Scientific editor of monographs in foreign languages

Scientific editor of a monograph in Georgian

Editor-in-Chief of a peer-reviewed or professional journal / proceedings

Review of a scientific professional journal / proceedings

Member of the editorial board of a peer-reviewed scientific or professional journal / proceedings

Participation in a project / grant funded by an international organization

Participation in a project / grant funded from the state budget

Patent authorship

Membership of the Georgian National Academy of Science or Georgian Academy of Agricultural Sciences

Membership of an international professional organization

Membership of the Conference Organizing / Program Committee

National Award / Sectoral Award, Order, Medal, etc.

Honorary title

Monograph

Handbook

Research articles in high impact factor and local Scientific Journals

Publication in Scientific Conference Proceedings Indexed in Web of Science and Scopus