Aspects of Regional Geothermal Water Use in Bulgaria

ABSTRACT Geothermal water in Bulgaria has only direct applications. Major types of direct utilization include balneology, space heating and air-conditioning, geothermal heat pumps, direct thermal water supply, greenhouses, and bottling of potable water and soft drinks. Electricity generation from geothermal water is not currently available in the country

Tracing groundwater recharge conditions based on environmental isotopes and noble gases, Lom depression, Bulgaria

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Characterization of the Karst water regime in the Danube catchment area (Bulgaria)

The purpose of study is to estimate the role of karst springs in the formation of the flow of the Bulgarian rivers that are right tributaries of the Danube River. The study area includes the region from the Danube River to the main ridge of the Balkan (Stara Planina), representing a major water divide that separates the Black Sea catchment area from the Aegean one. The eastern border represents the watershed between the Danube and the Black Sea hydrological zones. From a geological point of view, the northern part of the area is located on the Moesian platform and the southern part belongs to the Fore Balkan and Balkan areas where various types of rocks of different geologic age outcrop. In some of them, there are conditions for the formation of karst water. In the northern part of the area they form distinct aquifers that gradually sink to the north; this is so called "platform" type of karst. In the southern mountainous part there are numerous karst basins. The most significant of karst springs are included in the national groundwater monitoring network. The hydrographs of karst springs are analyzed in view of the specific features of karstification. To classify the studied springs with respect to their regime, several indicators are used. Furthermore, the role of karst waters in the river runoff of the Bulgarian tributaries of the Danube River is assessed

Hydraulic constructions and facilities on karst in Bulgaria: repercussions influence and problems

The safety and accident free exploitation of hydraulic facilities depends on geological and hydrogeological conditions of terrains where they are built. Such facilities have one of the most serious problems when they are located in a karst environment. In Bulgaria, there have been a number of cases of refusal to build dam walls at the preliminary exploration, as well as complication of the initial projects after clarification of the karst features in the affected areas. In many cases, after the construction of the facilities, changes are identified in the hydrogeological conditions which, besides the karst water regime, also affect the activity of the karst processes. Selected examples of hydraulic facilities on the territory of Bulgaria, the problems encountered, and the implemented engineering solutions are presented. The accomplished studies, construction and exploitation of hydraulic facilities in the karst terrains of Bulgaria are a serious experience that can be used in future similar activities

ARSENIC IN THE THERMAL WATERS OF SOTHERN BULGARIA

The research is based on water samples from thermal mineral waters and individual water sources associated with confined fractured aquifers in Southern Bulgaria. The analysis indicated that more than 65% of them contain arsenic below the drinking water standard of 0.01 mg/l, as defined in Regulation No. 9 from 2001 for the drinking water quality. In 3.5% of the samples (11 water sources), the arsenic concentration exceeds 0.05mg/l, which was the quality standard before the adoption of Regulation No. 9. Some of the thermal waters with highest arsenic concentration come from Triassic limestones and dolomites (Kazichene, Starozagorski Bani, Slivesnki Bani, Ovcha Kupel), individual sources are associated to gneiss (Kozhuh, Gotsedelchevski Bani), granites (Yakoruda), andesites (Merichleri). In some cases, thermal water of elevated arsenic concentration from fractured hydrothermal systems discharge in younger unconsolidated deposits, where they come into contact with freshwater (Ravno Pole, Sandanski, Merichleri). In such environments, if drinking water abstractions are overexploited, it is possible to compromise them by drawing in mineral water of naturally elevated arsenic concentration. Such risk depends on the hydrodynamic conditions, the physicochemical conditions, and the forms of arsenic in the water

Analysis of the spatial variation of indoor radon concentrations (national survey in Bulgaria)

This paper presents the methodology and results of the national radon survey in Bulgaria and its spatial variability. The measurements were carried out in 2778 dwellings using CR-39 track detectors over two successive 9 and 3-month periods from April 2015 to March 2016. The arithmetic (AM) and geometric (GM) means of annual indoor radon concentration were 111 ± 105 Bq/m3 and 81 Bq/m3 (GSD = 2.15), respectively. The distribution of data has been accepted to be log-normal. Two hypotheses have been investigated in the paper. The first one was a spatial variation of indoor radon concentration and the second was spatiality of the factor that influences radon variation. The indoor radon concentrations in the 28 districts have been significantly different, which prove the first hypothesis. The influence of the factors, geology (geotectonic unit, type of rock, and faults distance of the measuring site), type of the region, and the presence of the basement in the building on radon spatial variation, was examined. The analyses have been shown that they significantly affect radon variations but with a relatively small contribution in comparison to the radon variation between district. Furthermore, the significance and contribution of the investigated factors were different in each district, which confirmed the second hypothesis for their spatiality

Exotic rock block from the Koshava gypsum mine, Northwest Bulgaria: Petrography, geochemistry, mineralogy and melting phenomena

The described exotic rock block (60×80×13–15 cm) was found at 290 m depth in a lower–middle Badenian gypsum layer in the Koshava mine, NW Bulgaria, near the Danube River. It is greyish-black, granular, with layered structure and layers composed of α-quartz rosettes covered with organic matter (kerogen-like type with high contents of Ge, Mo and B), wood relicts with chalcedony replacement, and porous lenses with compact accumulation of organic matter. The block is coated with quartz crust, up to 2 cm thick, with regmaglypt-like forms, also replaced by quartz. Aside from the surface, melting phenomena were also observed inside the quartz rosettes and especially in the wood relicts and porous lenses. The melted drops are actually crystallized chalcedony. The organic matter accumulations contain Si-organic zoned micrometre-sized spherules. Fe silicides were found in the organic matter of all parts of the block, in which hapkeite was determined by X-ray analysis. Other detected minerals include graphite, cristobalite, coesite, skeletal and framboidal pyrite, moassanite, magnetite, suessite, sphalerite and minerals formed in the gypsum lagoon (gypsum, celestine, barite, calcite, halite and clays). The geological position of the block in the gypsum without any other sediments, the extensive melting phenomena with melted spherules, crushed quartz, its enrichment in 18O isotope and the presence of coesite suggest that it is shock ejecta, in certain aspects resembling the large Muong Nong-type tektites, but its characteristics could be the basis for distinguishing it as a new tektite type. The fact that it was found in a gypsum layer of early–middle Badenian age points to its probable association with the Ries-Steinheim impact event, despite the long distance between them (~1100 km)

მიწისძვრებთან დაკავშირებული წყლის დონის ვარიაციების შესწავლა წრფივი მეთოდებით

სტატიაში განხილულია ჰიდროდინამიური დაკვირვების სპეციალური მეთოდები,რომლებიც გამოიყენება რეალურ დროში, ტექტონიკური პროცესების მონიტორინგისა და სეისმური მდგენელების გამოყოფის მიზნით. შემუშავებული მეთოდიკა გამოიყენება დიდ ფართობზე ძლიერი მიწისძვრის მომზადების პროცესში ,დაკვირვების მონაცემებიდან გეოდინამიკური მდგენელის გამოყოფისა და მისი დროსა და სივრცეში განაწილების კანონზომიერების დადგენის მიზნით

Interdisciplinary studies on the technical and economic feasibility of deep underground coal gasification with CO₂ storage in Bulgaria

This paper presents the outcome of a feasibility study on underground coal gasification (UCG) combined with direct carbon dioxide (CO₂) capture and storage (CCS) at a selected site in Bulgaria with deep coal seams (>1,200 m). A series of state-of-the-art geological, geo-mechanical, hydrogeological and computational models supported by experimental tests and techno-economical assessments have been developed for the evaluation of UCG-CCS schemes. Research efforts have been focused on the development of site selection requirements for UCG-CCS, estimation of CO₂ storage volumes, review of the practical engineering requirements for developing a commercial UCG-CCS storage site, consideration of drilling and completion issues, and assessments of economic feasibility and environmental impacts of the scheme. In addition, the risks of subsidence and groundwater contamination have been assessed in order to pave the way for a full-scale trial and commercial applications. The current research confirms that cleaner and cheaper energy with reduced emissions can be achieved and the economics are competitive in the future European energy market. However the current research has established that rigorous design and monitor schemes are essential for productivity and safety and the minimisation of the potential environmental impacts. A platform has been established serving to inform policy-makers and aiding strategies devised to alleviate local and global impacts on climate change, while ensuring that energy resources are optimally harnessed