Nikolay Stoyanov

• PhD
• University of Mining and Geology "Saint Ivan Rilski"

A specific type of landfill, a tailings dam (or pond), is typically an earth-fill embankment dam used to store the byproducts of mining operations after the ore has been separated from the gangue. The primary threat posed by a tailings pond is the potential for leachate generated by the slurry to penetrate the soil and contaminate the aquifer. Base...

This study presents the potential of the ERT (Electrical Resistivity Tomography) method for mapping the spatial boundaries of old landfills, differentiating the hydrogeological units containing landfill bodies of various rank, and assessing the extent and degree of groundwater pollution caused by liquid emissions. The method’s effectiveness is due...

Предложен е общ методичен подход за математическо моделиране на замърсяването на подземни води от минни обекти, депа за отпадъци, селскостопански обекти, големи инженерни съоръжения и др. Направен е аргументиран избор на ключови замърсители, които е необходимо да бъдат изследвани при количествени оценки и прогнози. Дефинирани са границите и компоне...

A general methodological approach is proposed for the preliminary assessment of the potential impact on groundwater during the operation of quarries for aggregates. The practical application and effectiveness of this approach are by using a numerical model to predict groundwater and soil contamination during the implementation of a project in the r...

Until the end of the 20th century, the uncontrolled discharge of highly polluted emissions from the non-ferrous metals companies in Bulgaria was the cause of heavy contamination in vast areas around these industrial sites. In the last two decades, after the introduction of good environmental practices and the closure of polluting industries, a dece...

The presented study examines the problem caused by the groundwater pollution in the alluvial aquifer complex formed in the terrace of the Vacha River. Two working hypotheses are considered. In the first one is accepted that the aquitard is regionally well sustained and limits the penetration of Mn-contaminated waters into the lower aquifer. In the...

The regional hydrogeological conditions in Northern Bulgaria determine the existence of a large artesian basin consisting of layered aquifers. The groundwater temperature increase with depth and the conditions in the deeper layers are favourable for the formation of stratified hydrothermal reservoirs with potential for heat extraction. Although it...

This paper is targeted to the development of methodology, data sources and extraction from the archives of the parameters considering the soil ground conditions. The integral parameter reflecting the properties of the surface ground layers is so called Vs_30. This parameter is an integral characteristic of the ground conditions used in almost all p...

Even after the implementation of eco-protective measures, the Eleshnitsa tailings pond continues to contaminate the Quaternary aquifer, formed in the alluvial deposits of Mesta River. A three-dimensional model of mass transport of selected key pollutants is developed on the basis of hydrochemical studies, geophysical surveys, and processing and sys...

The presented study is aimed towards determining the reasons for manganese pollution of drinking water extracted from the terrace of Vacha River. The results show that this is due to the seepage of from the artificial lake, formed after the construction of a small hydropower plant. Another possible reason is the natural accumulation in the upper pa...

An identification method for determining the aquifer’s mass transport parameters is proposed, based on data from field tracer tests with a pulse or a continuous source and an arbitrary position of the observation well in respect to the tracer entry point. The method is also applicable in the presence of a representative set of data on changes in th...

Sofia, the capital of Bulgaria, is situated in a region rich in thermal waters, which were a major factor for the establishment and development of the city. The thermal spring in the city center of Sofia has been in use since ancient times. As the city expanded rapidly in the 19th and 20th centuries, it absorbed many other sources of thermal water....

One of the many environmental problems resulting from electricity generation in thermal power plants is the release of large amounts of solid wastes (coal combustion products). In the absence of effective eco-friendly disposal practices, this waste is accumulated in the form of coal ash embankments or in the excavated parts of the open-cast mines....

Conventional engineering geological survey methods are often difficult to apply when studying high and steep rock slopes. In such conditions, the use of drilling equipment is difficult and even dangerous, especially when there are weak, strongly weathered sections on the slopes, creating a potential danger of self-collapse of rock fragments. In man...

Resume. This is a presentation of the methodology, data sources and extraction from the archives of the parameters considering the soil ground conditions reflected by the parameter V s_30. This parameter is an integral characteristic of the ground conditions used in almost all procedures of the seismic hazard mapping software. The V s_30 means the...

Geophysical surveying, ERT method, mapping of karst terrains, geoelectrical model, Balkan Stream gas pipeline

The Repository for Radioactive Waste in Novi Han, Lozen Mountain (Bulgaria), dates from the early 1960s. In the present study, the complex geoenvironmental setting of the repository site was analysed from the viewpoint of assessment of potential radionuclide migration from the repository to the geosphere. Thus, components of the mass transport fiel...

Bulgaria is relatively rich in geothermal water of temperature in the range of 25ºC-100ºC and the total flow-rate exceeds 3,000 L/s. Generally, there are more than 170 geothermal fields: 102 of them are state-owned and the rest of them – belong to some municipalities. Up to 72% of the total known flow-rate from the reservoirs has a comparatively lo...

A brief review of the European legislation related to groundwater protection and the legislation’s transposition in Bulgaria has been made. The existence of the necessary regulatory framework for ensuring groundwater protection has been pointed out. The basic guidance documents that help to meet the requirements set out in the Water Framework Direc...

A generalized conceptual scheme of the hydrogeological conditions in the region of the Krasnovo thermomineral field is developed. This concept is implemented in a three-dimensional model of the flow structure. The modeled area includes the upper part of the thermomineral reservoir to a depth of 400 m and covers a territory of about 72 km2. Within t...

The Dobrudzha Coal Deposit is characterized by complex geological, tectonic and hydrogeological conditions. The formed aquifers and complexes, on the one hand, hinder the possible exploitation of the coal deposit, on the other hand they are important for drinking water supply in the area. The aim of the present study is to develop a 3D hydrodynamic...

Significant parts of important aquifers in Bulgaria are affected by the long-term in-situ leaching of uranium, using acid in borehole systems with reinjection. This is the case with the Momino uranium deposit formed in the lower part of the Neogene-Quaternary sedimentary complex, filling the Thracian depression. In this complex is formed one of the...

Through a comparative analysis of data on the registered contents of metals in the thermal sources in the town of Velingrad are represented differences in chemical composition of the waters in the four fields – Chepino, Ladzhene, Kamenitsa, and Draginovo. The results of water samples from 19 water sources obtained in the laboratory of the Universit...

The conditions for spreading of a fast-moving contaminant in the subsurface were studied at an industrial site where large amounts of contaminated water had been discharged over a relatively long period of time. The site is located in the eastern part of the town of Karlovo in Southern Bulgaria. Several hydrogeological units were distinguished in t...

The efficiency of the application of electrical resistivity tomography (ERT) for detailed geoelectrical mapping of near-surface geological section is illustrated by a descriptive example. The options for differentiation of the section according to electrical resistivity, provided by the method, are discussed. The application of electrical resistivi...

Mineral processing tailings ponds, if improperly managed, could be a significant source of the environment pollution. The paper presents a methodology developed to assess the impact of a tailings pond on the surface and groundwater, as well as on the soil in the nearby area. A case-study of the methodology application to a tailings pond of a real l...

The area of Kamchiya River's inflow into the Black Sea has an important role not only as a natural landmark, but also as a leading factor for the national economy. It has been subjected for many years to oil and gas exploration, as well as to extraction of deep, highly mineralized waters containing chemical elements of industrial value. There are c...

Coal mining is the cause of significant changes in the geotechnical and hydrogeological conditions in the subsurface areas affected by it. This creates serious problems with the ground stability, rapid rise of groundwater level and concentrated or scattered water surface inflows. The proposed geophysical approach for mapping of abandoned mining wor...

A generalized conceptual scheme of the thermo-mineral field "Merichleri" is presented that is based on data from its exploitation and on the contemporary ideas for the geological and tectonic characteristics of its imbedding structures. This concept is implemented in the composed three-dimensional model of the flow field in the studied region. The...

The studied area is located in the vicinity of Rashid branch, part of the Nile Delta. This region is part of one of the most important aquifers in the world. The review of published information indicates that the existing zone of interaction between groundwater and sea salt water is complicated by the variable lithological composition in vertical a...

The major results from the hydrogeological study of “Zheleznitsa” and “Kresna” tunnels are presented including the boundaries of the main hydrogeological units, the ranges of the average values for the permeability coefficients, the depth of the GWL’s and the distribution of the hydraulic heads and gradients in the massif. The expected rates of wat...

The proposed geoelectrical approach for determination and characterization of prominent areas for extraction of groundwater is based on the different electrical resistivity properties of these zones in comparison to those of the remaining parts of the rock massif. The same characteristic can be applied with high credibility for the differentiation...

A comprehensive approach for modeling the subsurface space and groundwater pollution caused by landfills in karst areas is applied. An electrical tomography surveying was performed in order to study the karst areas and to obtain a detailed picture of the hydrogeological conditions in the area of the old and the new landfill of Pazardzhik. Two-dimen...

A general conceptual model of the hydrogeological conditions within the proposed alternative sites for the construction of a new nuclear power facility - Block 7 of NPP "Kozloduy" is presented. The model is developed after a systematization of the collected climatic, geological, tectonic, hydrological, hydrogeological, and technogenic information a...

The territory of Northern Bulgaria is an object for searching oil and natural gas. Essential aspect of these activities is prediction and estimation of impact on groundwater and its protection. Many factors and all sources should be studied in detail in order to avoid any negative impact on groundwater during study and exploitation of oil and natur...

The territory of Northern Bulgaria is an object for searching oil and natural gas. Essential aspect of these activities is prediction and estimation of impact on groundwater and its protection. Many factors and all sources should be studied in detail in order to avoid any negative impact on groundwater during study and exploitation of oil and natur...

In the process of detailed mapping of near-surface geological section, along with the traditional drilling methods, can be successfully applied the electrical tomography methods. The advantage of the latter is determined by the ability to obtain data from continuous sequences at specified intervals or volumes in the sub-surface area. The efficiency...

A three-dimensional numerical mathematical model of the flow field in the region of the geothermal site "Haskovo mineral baths" is composed. The modeled area covers the sub-surface space to a depth of 1300 m along a territory of about 35 km2. Within this framework fall four high rank hydrogeological units: the Upper-Eocene thermal water-bearing sed...

Mathematical two-dimensional (2D) and three-dimensional (3D) hydrological models are applied in order to obtain a quantitative forecast for a possible pollution of the sub-surface space by liquid emissions from the new landfill near the town of Samokov. The models are developed by using the computer programs VS2DTI, Modflow and MT3D-MS. The 2D mode...

The appropriate sites for construction of monitoring wells in rock complexes characterized by low water-bearing characteristics are zones with active water exchange which have higher permeability and have direct hydraulic links with other water-permeable parts in the sub-surface space. Such zones are formed in heavily cracked, tectonically disturbe...

Sofia, the capital of Bulgaria is undergoing significant development in recent years. The number of residents has increased significantly during the last decades, which has given a significant impact on the expansion of the urban environment. The water and particularly groundwater have important implications for the city since its founding until no...

2013 г. На база на извършените търсещо-оценъчни работи и сравнителен анализ на допълнителни материали, авторите са набелязали перспективни участъци за търсене на термални и минерални води, които могат да се използват за добив на геотермална енергия и развитие на курортното дело в района. Препоръчани са основни методики и последователност за провежд...

. The high efficiency of electrical tomography method for mapping of near-surface section is based on the good differentiation of the environment in respect to its specific electrical resistivity. The variation of this physical characteristic is associated with differences in lithological composition, porosity, water-saturation, and composition of...

One basecase and two predicitive local 3D models are developed in order to assess the current state and the possible future changes in the groundwater flow structure in the areas affected by the coal mining near the city of Pernik. The models are developed using the computer program Modflow and taking into account the results of prior regional mode...

The conditions for the formation and the movement of groundwater in the Pernik mines area after termination of underground coal mining are simulated by a regional mathematical three-dimensional (3D) model. It is development using the computer program Modflow. The model takes into account the natural and technogenic factors that led to the current s...

The presence of non-compacted and water-permeable zones in the walls of surface water bodies violates their normal functioning and could lead to a compromising (destruction) of these facilities. The proposed integrated geophysical approach for locating the problematic areas include the application of two geoelectrical methods-GPR and resistivity to...

A general approach is proposed for calculating the parameters and the mode of exploitation for a discrete well system for extraction of geothermal energy. The hydrodynamic design of the production and the injection wells is based on a numerical 3D flow model of the affected subsurface area. The temperature of the obtained water is predicted by one-...

Generally, the landslides study is aimed towards determination of their physical- geological characteristics and the peculiarities of their structure. The main tasks are detection of zones characterized by different degree of water-saturation, mapping of landslide surfaces and contact zones, along which is performed the rock mass movement, determin...

The spatial boundaries and the quantitative characteristics of the basic components of the potential pollutant transport media are determined for the area of the designed national disposal facility for storage of radioactive waste near NPS “Kozlodui”. From the radionuclides that will be disposed are defined those that are regarded as key factor in...

ELECTROTOMOGRAPHIC SURVEYING IN THE REGION OF THE ZOGRAF MONASTERY ON MOUNT ATHOS The performed geophysical surveying reveals the efficiency of the electrotomographic techniques for a complex study of different problems in the field of hydrogeology and engineering geology. The geoelectrical sections, created on the basis of data from the performed...

The high piezometric levels and the big groundwater storage capacity of the Neogen-Quaternary aquifer complex are causing serious difficulties during the subway construction in the central part of Sofia, Bulgaria. The main problem is connected to the groundwater drawdown in the excavations for deep foundation constructions (subway stations and vent...

Mathematical models are developed in order to prognosticate the mass-transport of radionuclides in the loess complex in the region of NPS “Kozlodui”. The conditions for mass transport of the isotopes of 90Sr, 137Cs, 60Co, 63Ni, and 241Am in the unsaturated zone (zone of aeration) are simulated. The applied scheme of convective and diffusive mass tr...

Generally, the landslides study is aimed towards determination of their physical-geological characteristics and the peculiarities of their structure. The main tasks are determination of the landslide surfaces and the contact zones, along which is performed the rock mass movement, determination of the shape, the dimensions, and the spatial situation...

Vadose zone sensors provide more complete spatial monitoring for possible landfills leaks than wells alone, so they allow fewer leaks to go unnoticed. Detected leaks can be managed earlier than would have been possible if they were discovered only when they reached the monitoring wells. In many situations, the rate of migration of leachate through...

Contaminants penetrating aquifers lead to substantial changes in the groundwater content. These changes could be indirectly registered with adequate precision by the geoelectrical resistivity methods. The most suitable technique for estimating of groundwater contamination is the 2D resistivity survey with pole-dipole array. The advantages of this m...

A mathematical model of groundwater pollution processes caused by Plovdiv sanitary landfill is developed. The model is based on the simplified approach and is used in the initial stage of the study of this potential ecological problem. The simplified approach is based on the assumption that migration of pollutants takes place in a relatively homoge...

Today Bulgaria heads for a long term perspective regarding its landfills. So solutions are searched for possibilities to leave the landfill areas, after closure, in such conditions that the environment will not be adversely affected in the future. Presently there are a large number of different landfills in operation, and lots have earlier been com...

The fresh groundwater in the coastal aquifers is in direct contact with the sea salt water. The existing fragile equilibrium between them is oftentimes disturbed by the influence of natural or technogeneous factors. The broken equilibrium is causing a process of salt water intrusion in the coastal aquifers. As a result, the fresh/saline water inter...

The present groundwater map of Bulgaria is intended for a wide range of users - hydrogeologists, non-professionals in the field of hydrogeology, investors, students, etc. who wish to get a general idea of the distribution and type of main groundwater and mineral water reservoirs in Bulgaria. Four classes according to groundwater productivity and fo...

1) , nts@mgu.bg (2) ABSTRACT Aim of the study is to development a lithofacial and fluvial-architectural model of the deposits from the area of the sanitary landfill Plovdiv, which to allow the compila-tion of a reliable mathematical model for estimation and prognoses of the range and the scale of ground water contamination as result of the landfill...

Development of precise models for predicting and managing processes of groundwater contamination as a result of a number of natural and technogenic factors (mining activity, industry, agriculture, sanitary landfills, etc.) requires more detailed knowledge on the structure and morphology of aquifers. Some of the aquifers are located in sediments and...