Emission Of Toxic Substances Research Articles

RETENTION OF FIRE WATER USED DURING FIREFIGHTING OPERATIONS BY THE FIRE BRIGADE

The article presents the issue of wastewater circulation after firefighting activities executedby fire brigades and the lack of research on the composition of water entering the city sewagesystem as well as the potential impact on the environment to which it is disposed of. It wasnoted that fire brigades use biodegradable foam agents during typical fire-fighting operations,both in sewage treatment plants and in the natural environment, but the main problem is theselection of fire-fighting techniques and extinguishing agents and the subsequent consequencesin the environment. Consideration was given to deciding whether to use water, which dissolvesflammable substances, foam containing surfactants, or completely refraining from extinguishingdue to the possibility of sewage entering the surrounding waters. To this end, it outlines the courseof fires where firefighting operations have resulted in the contamination of watercourses andbodies of water, contamination of the ground or long-term emission of toxic substances into theatmosphere. Due to the lack of guidelines for dealing with fire-water in urban conditions, attentionwas paid to absolute protection of watercourses and water bodies against the infiltration of postfiresewage in its original form and the use of mechanical dams and embankments to stop them atthe scene of the incident. Attention was also drawn to the proper operation of dosing equipmentand the environmental burden caused by using foam concentrates in higher concentrations thanrecommended by the manufacturer was presented.

Hydrotreated vegetable oil migrates through soil and degrades faster than fossil diesel and hydrotreated vegetable oil-fossil diesel blend

HVO has been noted as a more sustainable fuel, not only leading to lower total CO2 emissions, but also resulting in lower emissions of toxic substances upon fuel burning. The environmental impact of HVO and HVO diesel blends when accidentally spilled into the soil and ground water has, however, received little attention. While HVO and diesel exhibit nearly identical viscosity and density, their behavior in soils differs due to varying water solubility and fuel additives. In laboratory- and pilot-scale soil columns and lysimeters, we compared the migration and biostimulation-enhanced degradation of HVO, HVO-diesel blend (HVO15), and fossil diesel over 120 days. Additionally, we investigated the impact of fuel additives on migration by comparing HVO without additives to HVO15 and diesel in wet and dry soil columns over 21 days. Notably, HVO migrated through soil more rapidly and in greater quantities than diesel. In wet soil, 69% of added HVO, 8.4% of HVO15, and 21% of diesel leached through as light non-aqueous phase liquid (LNAPL). Dry soil showed smaller differences in fuel migration, but HVO did not mobilize when water was added, unlike HVO15 and diesel. Biostimulation reduced HVO leaching by 15% more than HVO15 and 48% more than diesel. Overall, HVO’s behavior in soil differs significantly from fossil diesel, with factors like lower water solubility, reduced mobilization from dry soil, and higher in situ degradability contributing to its reduced environmental risk compared to fossil fuel alternatives in accident scenarios.

Electronic cigarettes - harmful substances contained in e-cigarette liquids and smoke

Electronic cigarettes and electronic cigarette liquids are increasingly popular in society, especially among young people. However, despite the widespread belief that they are a safe alternative to traditional cigarettes, many scientific studies confirm that electronic cigarettes can be equally, if not more, harmful to health. There are many chemicals in electronic cigarette liquids, such as nicotine, propylene glycol, glycerol, flavors and fragrances. Some of these substances are toxic and can cause a number of negative health effects, such as irritation of the respiratory tract, the onset of lung disease, neurological disorders and increased risk of cardiovascular disease. In addition, electronic cigarettes can be harmful to the environment due to the emission of toxic substances into the air and improper disposal of used batteries. Therefore, an informed approach to the use of electronic cigarettes and an understanding of the potential health risks associated with them is necessary. Further scientific research and education of the public about the harms of electronic cigarettes are key to preventing the negative consequences associated with their use.

Methodology for assessing the level of development and efficiency of the functioning of the traffic management system, taking into account the environmental factor

The scientific article presents a methodology for assessing the level of development and efficiency of traffic management systems, taking into account environmental factors. The order and algorithms for all calculations to assess the level of effectiveness for road traffic management systems of motor transport, while taking into account the impact of environmental factors, are provided. The methodology for assessing the current state of the traffic management system relies on the degree of deviation of each individual indicator from its target value. The resulting value of the composite indicator for the system’s condition is then compared to its standard value, and an estimated overall state for the system is determined. According to some indicators, there has been an increase in emissions of toxic substances in the city's streets and roads, which are assessed as “poor”. To improve the state of the environment, an immediate set of organizational and technical measures has been proposed for the rational development of the traffic management system.

АНАЛІЗ НАСЛІДКІВ ЕКСТРЕМАЛЬНИХ СИТУАЦІЙ НА БАЗІ ЧИСЕЛЬНИХ МОДЕЛЕЙ

The report considers some classes of numerical models that were built to predict the consequences of emergencies at industrial enterprises. The first class of models has been developed to predict chemical air pollution in case of accidental emissions of toxic substances. Modeling is carried out on the basis of the fundamental equations of aerodynamics and mass transfer. Difference splitting schemes are used for the numerical solution of the modeling equations. The second class of CFD models is designed to assess the risk of thermal damage to people in the event of thermal pollution of the air environment. The third class of models was developed to assess the risk of injury to people when a shock wave moves. To solve this problem Euler equations were used. Computer codes were developed on the base of proposed numerical models.

Assessing life cycle impacts from toxic substance emissions in major crop production systems in Thailand

Toxicity-related impacts are often omitted or poorly represented in environmental performance assessments of agricultural production systems. Existing studies usually focus on selected aspects, such as pesticides, and rely on the wider range of relevant emissions and life cycle operations, hampering decision support that considers trade-offs and regional characteristics. The present study comprehensively assesses life cycle toxicity impacts of major crop production systems in Thailand, considering all relevant supply chain operations, farm-level field operations, and downstream crop residue burning. Impact characterization factors for farm-level and downstream processes have been specifically parameterized for Thai conditions. All impacts were translated into damage costs for different scenarios based on Thailand's action plans for agricultural production, air pollution control and energy consumption, to facilitate targeted decision support at the national level. Toxicity-related impacts vary considerably across Thai crop production systems, ranging from a few hours (cassava, sugarcane, palm oil) to 1.5 months (rice) of average individual human lifetime loss, and from 15 (sugarcane) to 147 (rice) million species fraction lost over time and water volume. Combined, these crop systems caused damage equivalent to >3.5 trillion Thai Baht in 2019, dominated by pesticide and manure/fertilizer-related farm-level emissions due to human health damage, and by fertilizer and fuel-related supply chain operations due to ecosystem quality damage. The scenarios could substantially reduce toxicity-related impacts on humans and ecosystems across almost all considered crop production systems, mainly through adopting integrated approaches, including optimal use of crop residues and swine manure, and reducing pesticide use and diesel consumption for field operations. Our results demonstrate that including all life cycle operations and regionalized impact factors is crucial to respectively identify major trade-offs across production scenarios and account for country-specific characteristics. The proposed approach is suitable to inform national strategies supporting more sustainable crop production, and can be adapted to consider other production systems and regions.

Evaluation of Ecological Parameters of a Compression Ignition Engine Fueled by Diesel Oil with an Eco Fuel Shot Liquid Catalyst

This article discusses the potential applications of the Fuel Shot liquid catalyst in compression ignition (CI) engines for reducing toxic substances in exhaust gases. Incorporating catalysts into fuel can optimize the combustion process, consequently reducing the emission of toxic substances into the atmosphere. Toxic compounds, such as nitrogen oxides, particulate matter, and hydrocarbons, adversely affect flora and fauna. Various methods are known for reducing their concentration in engine exhaust gases, one of which is the Fuel Shot liquid catalyst. The authors conducted experiments on a Fiat 1.3 JTD engine with a Common Rail system. The results indicate that the application of the liquid catalyst reduces the content of nitrogen oxides and hydrocarbons in the exhaust gases and slightly decreases fuel consumption. Additionally, investigations were carried out on the engine’s injection apparatus, which was fueled with modified fuel. The findings demonstrate that the fuel additive does not affect the wear of precision parts of fuel injectors and high-pressure pumps.

An Overview of Lignocellulose and Its Biotechnological Importance in High-Value Product Production

Lignocellulose consists of cellulose, hemicellulose, and lignin and is a sustainable feedstock for a biorefinery to generate marketable biomaterials like biofuels and platform chemicals. Enormous tons of lignocellulose are obtained from agricultural waste, but a few tons are utilized due to a lack of awareness of the biotechnological importance of lignocellulose. Underutilizing lignocellulose could also be linked to the incomplete use of cellulose and hemicellulose in biotransformation into new products. Utilizing lignocellulose in producing value-added products alleviates agricultural waste disposal management challenges. It also reduces the emission of toxic substances into the environment, which promotes a sustainable development goal and contributes to circular economy development and economic growth. This review broadly focused on lignocellulose in the production of high-value products. The aspects that were discussed included: (i) sources of lignocellulosic biomass; (ii) conversion of lignocellulosic biomass into value-added products; and (iii) various bio-based products obtained from lignocellulose. Additionally, several challenges in upcycling lignocellulose and alleviation strategies were discussed. This review also suggested prospects using lignocellulose to replace polystyrene packaging with lignin-based packaging products, the production of crafts and interior decorations using lignin, nanolignin in producing environmental biosensors and biomimetic sensors, and processing cellulose and hemicellulose with the addition of nutritional supplements to meet dietary requirements in animal feeding.

Research on the presence of cigarette butts and their leaching of chemical pollutants and microparticles: the case of Dalian, China

Cigarette butts (CBs) can contain high amounts of toxic substances such as heavy metals, polycyclic aromatic hydrocarbons (PAHs) and microplastics, all of them can result from the incomplete decomposition of CBs. However, limited research exists on the pollution caused by littered CBs in China and the emissions of toxic substances from different Chinese cigarette brands.Therefore, the main objective of this study was to assess the quantity of CBs littered in Dalian city, China, and to evaluate the emissions of heavy metals, PAHs, and microplastics from different cigarette brands. During the survey, a total of 10,591 CBs items and 35 cigarette brands were collected. ICP-MS analysis confirmed the presence of 17 types of heavy metals in the highest abundance brand of CBs, with concentrations ranging from 0.02 μg/L (U and La) to 395 μg/L (Mn). In the lowest abundance brand of CBs, 15 types of heavy metals were detected, with concentrations ranging from 0.08 μg/L (U) to 297 μg/L (Mn). Additionally, a total of 9 PAHs, including compounds such as naphthalene and acenaphthylene, were detected in both the highest and lowest abundance brands of CBs using HPLC-MS/MS, with concentrations ranging from 0.40 ng/L (Anthracene) to 92.12 ng/L (Naphthalence). Microplastics and particles were also identified by light microscopy and SEM. Based on cigarette consumption data in China, it is estimated that annually 360,000 tons of plastic waste are generated by CBs in the environment. Considering the presence of CBs in urban and beach environments, the release of these toxic substances poses a threat to water resources.

Optimizing natural rubber blends for examination gloves: Vacuum radiation for mechanical strength and solvent barrier

AbstractNatural rubber (NR) is emblematic of sustainability compared to synthetic rubber. However, the tradition of adding sulfur as a vulcanization ingredient results in the release of toxic substances and the potential for health issues. In this study, a feasible strategy was proposed to replace sulfur and discover a safe bulk modification process for NR films. The results have shown that the NR particle size was disintegrated to below 10 nm by gamma irradiation. High tension strength up to 24.45 MPa was observed in the vulcanized NR blend film, which could be elongated up to 800% strain after exposure to an optimum dose of 14 kGy. In comparison to commercial NR latex and nitrile gloves, the vulcanized NR/ SIS films exhibited better chemical resistance ability against hexane, methanol, toluene, and acetone, as revealed by the permeation test. The appearance of amorphous regions and highly oriented NR crystallites was observed through transmission electron microscopy. Findings from this study propose the vacuum radiation strategy that can replace conventional vulcanization methods, resulting in NR films with high mechanical and barrier performance. Furthermore, the emission of toxic substances is reduced by this green process, making it practically useful for potential chemical‐resistant examination glove applications.

Spatial Analysis of the Impact of Motor Vehicle Fires on the Urban Environment using the Example of Warsaw

Abstract This scientific article is dedicated to the analysis of the impact of vehicle fires on the urban environment. In the context of the dynamic processes of urbanization and societal mobilization, understanding the consequences of vehicle fires becomes exceedingly important for ensuring sustainable urban development and improving residents’ quality of life. The article presents the results of spatial analyses of vehicle fires that occurred within the Warsaw area between 2010 and 2021. In the analytical section, an attempt was made to identify the parts of the city where residents were most exposed to the emission of toxic substances. According to the presented calculations, almost 3 tons of toxic substances are released into the atmosphere every year as a result of vehicle fires in Warsaw. The article also provides information about the materials used in motor vehicles and assesses their environmental impact through the emission of hazardous substances in the event of a vehicle fire. Proposed changes that could minimize the number of vehicle fires in the future are also indicated in the article, thereby contributing to increased road safety levels in the city and positively influencing the environment.

Environmental Impacts Assessment in Suspension PVC Production Process Using Computer-Aided Process Engineering

The new demands for sustainable operation in the chemical industry due to increasing environmental regulations and agreements have generated the need to adapt existing processes to more intelligent production. The plastics sector is in a complex position due to its contribution to economic development and the climate crisis. Therefore, environmental assessment has become an important tool due to the benefits it provides by quantifying the environmental performance of processes, allowing it to balance operational and environmental needs. Polyvinyl chloride (PVC) is one of the most globally used polymers thanks to its resistance, flexibility, and cost-effectiveness. The polymer is synthetized by suspension polymerization, which is characterized by high productivity and controllability. However, it presents problems associated with intensive energy consumption and the emission of toxic substances and greenhouse gases. Therefore, an environmental assessment of the suspension PVC production process was performed using the waste reduction algorithm (WAR). The potential environmental impact (PEI) was quantified using the generation rate and the output velocity for four cases and three different fuels. It was found that the process transforms raw materials with high impacts, such as VCM, into substances with lower PEI, such as PVC. However, the process has a high generation of PEI due to the effects of energy consumption (−2860, −2410, 3020, and 3410 for cases 1–4, respectively). The evaluation of the toxicological impacts shows that the ATP category is the only one that presents a positive generation value (75 PEI/day); the product contributes to the formation and emission of impacts. The atmospheric categories showed that the energy consumption of the process is the most critical aspect with a contribution of 91% of the total impacts emitted. The AP and GWP categories presented the highest values. It was determined that the most suitable fuel is natural gas; it has lower impacts than liquid and solid fuels (coal). Additionally, it can be concluded that the PVC production process by suspension is environmentally acceptable compared to the polyethylene or polypropylene processes, with output impacts 228 and 2561 times lower, respectively.

An Overview of Small Nuclear Power Plants for Clean Energy Production: Comparative Analysis of Distributed Generation Technologies and Future Perspectives

There is a steady trend in the world to increase the share of distributed generation. The volume of self-generated energy commissioning is constantly growing, with projected increases in growth rates in the future. At the same time, demands for efficiency and environmental safety in new power plants are constantly increasing. In this regard, one of the promising areas for the development of distributed energy is the transition to small nuclear power plants (SNPPs). As in the case of wind and solar power plants, SNPP operations are not accompanied by emissions of toxic substances or greenhouse gases into the atmosphere. In addition, SNPPs consume a much smaller volume and mass of fuel compared to conventional small-capacity fossil fuel power plants. This paper describes the characteristics of the main types of distributed generation. The key technical and economic characteristics of existing and prospective small-capacity nuclear fuel facilities are systematized. The results of a comparative analysis of the cost of electricity produced by SNPPs and competing power plants are also presented. In addition, a number of promising regions of the Russian Federation for the introduction of SNPPS have been identified, and a review of the methods of energy storage for SNPPS, which are necessary when working in an isolated power system, has been carried out.

Occurrence and formation of environmentally persistent free radicals in incineration and their impact on soil and water

Incineration is a thermal waste treatment technique that can be understood as a controlled combustion process with the primary objective of volume reduction of waste mass. Combustible waste including gaseous, aqueous, muddy, molten, and solid waste is typically deal with incineration at temperature ranges from 750 to 1200 °C. End products of incineration include a considerable amount of particulate matter (PM) and pollutants. Particulate matter released from the incineration process plays an important role in forming environmentally persistent free radicals (EPFRs) which are the most toxic and stable substance emitted from the incinerator. Other major compounds released during the incineration process are dioxins, polychlorinated biphenyls, polychlorinated naphthalene, chlorinated benzenes, and polycyclic aromatic hydrocarbons (PAH). Although incineration is significantly used to control the waste crisis but emissions of toxic substances from an incinerator have various health impacts on the environment and humans. Long exposures to these hazardous compounds lead to respiratory and cardiovascular diseases. These toxic compounds participate in various redox activities as well as metal complexation events and deteriorate the physiochemical parameter of soil and water. The aim of the present study is to summarize the existing knowledge regarding the formation of harmful compounds released during waste incineration and major environmental challenges associated with them.

Emissions of Toxic Substances from Biomass Burning: A Review of Methods and Technical Influencing Factors

In the perspective of energy sustainability, biomass is the widely used renewable domestic energy with low cost and easy availability. Increasing studies have reported the health impacts of toxic substances from biomass burning emissions. To make proper use of biomass as residential solid energy, the evaluation of its health risks and environmental impacts is of necessity. Empirical studies on the characteristics of toxic emissions from biomass burning would provide scientific data and drive the development of advanced technologies. This review focuses on the emission of four toxic substances, including heavy metals, polycyclic aromatic hydrocarbons (PAHs), elemental carbon (EC), and volatile organic compounds (VOCs) emitted from biomass burning, which have received increasing attention in recent studies worldwide. We focus on the developments in empirical studies, methods of measurements, and technical factors. The influences of key technical factors on biomass burning emissions are combustion technology and the type of biomass. The methods of sampling and testing are summarized and associated with various corresponding parameters, as there are no standard sampling methods for the biomass burning sector. Integration of the findings from previous studies indicated that modern combustion technologies result in a 2–4 times reduction, compared with traditional stoves. Types of biomass burning are dominant contributors to certain toxic substances, which may help with the invention or implementation of targeted control technologies. The implications of previous studies would provide scientific evidence to push the improvements of control technologies and establish appropriate strategies to improve the prevention of health hazards.

Healthcare Waste-A Serious Problem for Global Health.

Healthcare waste (HCW) is generated in different healthcare facilities (HCFs), such as hospitals, laboratories, veterinary clinics, research centres and nursing homes. It has been assessed that the majority of medical waste does not pose a risk to humans. It is estimated that 15% of the total amount of produced HCW is hazardous and can be infectious, toxic or radioactive. Hazardous waste is a special type of waste which, if not properly treated, can pose a risk to human health and to the environment. HCW contains potentially harmful microorganisms that can be spread among healthcare personnel, hospital patients and the general public, causing serious illnesses. Healthcare personnel are the specialists especially exposed to this risk. The most common medical procedure, which pose the highest risk, is injection (i.e, intramuscular, subcutaneous, intravenous, taking blood samples). The World Health Organization (WHO) estimates that around 16 billion injections are administered worldwide each year. However, if safety precautions are not followed, and needles and syringes are not properly disposed of, the risk of sharps injuries increases among medical staff, waste handlers and waste collectors. What is more, sharps injuries increase the risk of human immunodeficiency virus (HIV), hepatitis B and C viruses (HBV/HCV), tuberculosis (TB), diphtheria, malaria, syphilis, brucellosis and other transmissions. Disposing of medical waste in a landfill without segregation and processing will result in the entry of harmful microorganisms, chemicals or pharmaceuticals into soil and groundwater, causing their contamination. Open burning or incinerator malfunctioning will result in the emission of toxic substances, such as dioxins and furans, into the air. In order to reduce the negative impact of medical waste, waste management principles should be formulated. To minimize health risks, it is also important to build awareness among health professionals and the general public through various communication and educational methods. The aim of this paper is to present a general overwiev of medical waste, its categories, the principles of its management and the risks to human health and the environment resulting from inappropriate waste management.

Http://journal.insat.org.ua/?page_id=5149&lang=uk

The purpose of the work was to identify environmental climatic impacts resulting from the biodiesel fuel use for vehicles (Vs). The methods are based on computation of natural resource consumption and toxic substances emission with the help of environmental footprint calculator being a software program. The results of integral assessment of the environmental impact (namely, consumption of water, pow basic traction trucks as VOLVO FM, FH, FE, and FL) were computed for biodiesel fuel types В0, В7, В30, В100 depending upon different standards of EURO propellants. Both positive and negative environmental impact factors have been determined for consuming biofuels during full lifecycle of Vs. It has been defined that minor decrease in СО2 emission owing to the use of standard modern biodiesel fuel was followed by significant increase in NOx emission, as well as power and water consumption in terms of first-generation biodiesel fuel utilization. Similar tendencies were recognized. Moreover, opportunity to apply biodiesel fuels along with other measures decreasing СО2 emission was analyzed. Originality it is stipulated by the use of the integrated assessment of impact of vehicles on climate change, as well as the use of natural resources while applying biodiesel fuel for vehicles. Keywords: greenhouse effect, biodiesel fuel, life cycle of Vs, nitrogen oxides.

Hydration mechanism and environmental impacts of blended cements containing co-combustion ash of sewage sludge and rice husk: Compared with blended cements containing sewage sludge ash

In this study, the hydration mechanism and environmental impacts of blended cements with the co-combustion ash of rice husk and sewage sludge (CCA) were investigated and compared to those of blended cements with sewage sludge ash (SSA). CCA possesses lower phosphate contents than SSA, leading to lower inhibition effects on early hydration of cement clinker. Moreover, the pozzolanic activity of CCA is higher than that of SSA. Thus, more hydration products from the pozzolanic reaction of CCA are generated in CCA-based blended cements. Compared to the matrix of SSA-based blended cements, that of their CCA-based counterpart is filled with more hydration products, which promotes porosity refinement and strength development of CCA-based blended cements at later ages. CCA-based blended cements exhibit greater environmental benefits than SSA-based blended cements because fossil consumption and toxic substance emissions during the co-combustion of rice husk and sewage sludge is lower than that during the mono-combustion of sewage sludge.

Assessment of human exposure to food crops contaminated with lead and cadmium in Owerri, South-eastern Nigeria

BackgroundFood safety and security have remained an emerging global challenge amidst increasing human activities that potentially contaminate the food chain. With the rapid population growth, urbanisation and unrestrained emission of toxic substances, urban-dwelling Nigerians are particularly vulnerable to consuming contaminated food crops. Materials and methodThis study presents a framework for critical analysis of human exposure patterns to potentially contaminated food crops using the city of Owerri (Nigeria) as case study. It systematically assessed the metal burden of soil and staple food crops and the potential health risk associated with dietary exposure of humans to contaminated food crops. Samples of soil, cassava (Manihot esculenta) tubers and fluted pumpkin (Telfairia occidentalis) leaves were collected from household gardens and analysed for concentration of selected metals (Al, As, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb and Zn) using ICP-OES. A risk assessment of human exposure to Pb contamination using both the Target Hazard Quotient (THQ) and Hazard Index (HI) was estimated. ResultsThe majority of metals measured below the respective health-based maximum concentration limits of the Nigerian Department of Petroleum Resources target value, except for Pb in soil, which was above the limit of 85 µg g−1 in 0.9 % of sampled soils. However, Pb measured above the threshold of 0.3 µg g−1 stipulated by the FAO/WHO Codex Alimentarius in 46 % of sampled pumpkin leaves with no correlation established with soil Pb concentrations. This suggests possible Pb contamination via atmospheric deposition, and that human ingestion of pumpkin leaves presents the greatest health risks. ConclusionThe findings revealed that children and toddlers are more prone to Pb contamination via food crop ingestion than adults based on the THQ and HI evaluations; hence need for relevant policies to ensure food safety. This study provides background data for epidemiological investigation of relationships between contaminated food crop ingestion and blood Pb.

USE OF MATHEMATICAL MODELS IN THE PROBLEMS OF ASSESSING THE CONSEQUENCES OF EXTREME SITUATIONS ON INDUSTRIAL FACILITIES

The report considers some classes of numerical models that were built to predict the consequences of emergencies at industrial enterprises. The first class of models has been developed to predict chemical air pollution in case of accidental emissions of toxic substances. Modeling is carried out on the basis of the fundamental equations of aerodynamics and mass transfer. Difference splitting schemes are used for the numerical solution of the modeling equations. The second class of numerical models has been developed to assess the risk of chemical injury to people in industrial rooms. The third class of models was developed to assess the risk of injury to people when a shock wave moves. To solve this problem Euler equations were used. The fourth class of models was developed to predict river pollution in case of accident chemical pollution. The fifth class of models was developed to assess the influence of protection barriers to reduce air pollution Computer codes were developed on the base of proposed numerical models.