Anita Erőss

Biofilm Bacterial Communities Inhabiting the Cave Walls of the Buda Thermal Karst System, Hungary

The diversity of biofilm bacterial communities associated with cave walls of the Buda Thermal Karst System (BTKS) located in Hungary was studied by scanning electron microscopy and molecular cloning based on 16S rRNA genes. Samples from two sites, the Molnár János cave (MJB) and the Rudas-Török spring cave (RTB), respectively, were analyzed and compared. The presence of iron precipitates was typical at both study sites, despite the fact that the cell morphological structure of the biofilms observed by SEM was characteristically different. Clones analyzed from BTKS were found to belong to 10 common phyla (Thermodesulfobacteria, Chloroflexi, Nitrospirae, Chlorobi, Proteobacteria, Firmicutes, Actinobacteria, Planctomycetes, Bacteroidetes, Verrucomicrobia) within the domain Bacteria. Moreover, sequences related to Aquificeae, Acidobacteria and Gemmatimonadetes were exclusive to MJB, while Cyanobacteria were found in RTB only. The phylogenetic distribution of the dominant bacterial clones was quite dissimilar between the two sites. In the biofilm from MJB clones affiliated with Firmicutes, whereas in the RTB clones related to Deltaproteobacteria were found in the highest number. In addition, substantially larger numbers of clone sequences related to thermophilic bacteria were recovered from MJB. On the basis of sequences of known microorganisms corresponding to our clone sequences, it is assumed that aerobic as well as anaerobic iron and sulfur transformation performed by different bacterial communities might be important biogenic processes in both caves.

Diversity and morphological structure of bacterial communities inhabiting the Diana-Hygieia Thermal Spring (Budapest, Hungary)

The Buda Thermal Karst System is an active hypogenic karst area that offers possibility for the analysis of biogenic cave formation. The aim of the present study was to gain information about morphological structure and genetic diversity of bacterial communities inhabiting the Diana-Hygieia Thermal Spring (DHTS). Using scanning electron microscopy, metal accumulating and unusual reticulated filaments were detected in large numbers in the DHTS biofilm samples. The phyla Actinobacteria, Firmicutes and Proteobacteria were represented by both bacterial strains and molecular clones but phyla Acidobacteria, Chlorobi, Chlorofexi, Gemmatimonadetes, Nitrospirae and Thermotogae only by molecular clones which showed the highest similarity to uncultured clone sequences originating from different environmental sources. The biofilm bacterial community proved to be somewhat more diverse than that of the water sample and the distribution of the dominant bacterial clones was different between biofilm and water samples. The majority of biofilm clones was affiliated with Deltaproteobacteria and Nitrospirae while the largest group of water clones was related to Betaproteobacteria. Considering the metabolic properties of known species related to the strains and molecular clones from DHTS, it can be assumed that these bacterial communities may participate in the local sulphur and iron cycles, and contribute to biogenic cave formation.

The chemical characterization of the thermal waters in Budapest, Hungary by using multivariate exploratory techniques

Europe’s largest naturally flowing thermal water system can be found in Budapest, Hungary. The thermal waters are used mainly for balneological purposes, and hence a huge database is available about the chemical status of these waters at the bath company. This study has been prepared with the purpose of characterizing the chemical composition of the thermal waters of Budapest through descriptive statistics and multivariate exploratory techniques. A further objective was to determine the factors influencing the physico-chemical parameters and to investigate the temporal changes in water quality. The characterization was based on a database containing regular quarterly water chemical analyses of wells and springs collected over several decades (1960–2009).

Hydraulic evaluation of the hypogenic karst area in Budapest (Hungary)

The Buda Thermal Karst area, in central Hungary, is in the focus of research interest because of its thermal water resources and the on-going hypogenic karstification processes at the boundary of unconfined and confined carbonates. Understanding of the discharge phenomena and the karstification processes requires clarification of the groundwater flow conditions in the area. Accordingly, the aim of the present study was to present a hydraulic evaluation of the flow systems based on analyses of the archival measured hydraulic data of wells. Pressure vs. elevation profiles, tomographic fluid-potential maps and hydraulic cross sections were constructed, based on the data distribution. As a result, gravitational flow systems, hydraulic continuity, and the modifying effects of aquitard units and faults were identified in the karst area. The location of natural discharge areas could be explained and the hydraulic behavior of the Northeastern Margin Fault of the Buda Hills could be determined. The flow pattern determines the differences in the discharge distribution (one- and two-component) and related cave-forming processes between the Central System (Rózsadomb area) and Southern System (Gellért Hill area) natural discharge areas. Among the premises of hypogenic karstification, regional upward flow conditions were confirmed along the main discharge zone of the River Danube.RésuméL e de l’intérêt de la recherche à cause de ses ressources en eau thermale et des processus de karstification hypogénique en cours à la limite des carbonates libres et captifs. La compréhension des phénomènes de décharge et des procédés de karstification nécessite une clarification des conditions d’écoulement des eaux souterraines dans la zone. Le but de la présente étude était ainsi de présenter une évaluation hydraulique des systèmes d’écoulement basée sur les analyses des données hydrauliques mesurées sur des puits disponibles dans les archives. Des profils de pression en fonction de l’altitude, des cartes d’imagerie du potentiel de fluide et des coupes transversales hydrauliques ont été élaborés à partir de la distribution spatiale des données. En conséquence, les systèmes d’écoulement gravitaire, la continuité hydraulique, et les effets modificateurs des unités aquitards et des failles ont été identifiés dans la région karstique. La localisation des zones de décharge naturelle pourrait être expliquée et le comportement hydraulique de la faille de la marge nord-est. des collines de Buda pourrait être déterminé. Le mode d’écoulement détermine les différences dans la distribution de la décharge (à une ou deux composantes) et les processus de formation des cavités entre les zones de décharge naturelle du Système Central (région de Rózsadomb) et le Système du Sud (zone des collines de Gellért). Parmi les hypothèses relatives à la karstification hypogénique, les conditions d’écoulement régional ascensionnel ont été confirmées le long de la zone de principale décharge du Danube.ResumenLa zona de Buda Thermal Karst, en el centro de Hungría, está en el foco de interés de la investigación debido a sus recursos de agua termal y los procesos de karstificación hipogénica en curso en el límite de carbonatos confinados y no confinados. La comprensión de los fenómenos de descarga y de los procesos de karstificación requiere aclarar las condiciones de flujo de agua subterránea en la zona. En consecuencia, el objetivo del presente estudio fue presentar una evaluación hidráulica de los sistemas de flujo basados en el análisis de los datos hidráulicos de archivos en pozos. Se construyeron perfiles de presión vs elevación, mapas tomográficos de fluido potencial y secciones transversales hidráulicas, basados en la distribución de datos. Como resultado se identificaron los sistemas de flujo gravitatorio, la continuidad hidráulica y los efectos modificadores de las unidades de acuitardas y de las fallas en el área kárstica. La ubicación de las áreas de descarga natural podría ser explicada y el comportamiento hidráulico de la falla de Margen Noreste de las Colinas de Buda podría ser determinado. El esquema de flujo determina las diferencias en la distribución de la descarga (uno y dos componentes) y los procesos de formación de cuevas relacionados entre las áreas de descarga natural del Sistema Central (área de Rózsadomb) y del Sistema Sur (área de Gellért Hill). Entre las premisas de karstificación hipogénica, se confirmaron las condiciones regionales de flujo ascendente a lo largo de la zona de descarga principal del río Danubio.摘要匈牙利中部的布达热岩溶地区由于其热水资源及非承压和承压碳酸盐边界持续的深成岩溶化过程而成为研究兴趣的焦点。了解补给现象和岩溶化过程需要弄清楚本地区地下水流状况。因此,目前的研究目的就是根据井过去档案记载的水力资料对水流系统的水力状况进行评估。基于资料的分布,绘制了压力对高程的剖面、层析成像液体-潜力图和水力横断面。因此,确认了岩溶区的重力水流系统、水力连续性及弱透水层单元和断层的改性效果。天然补给区的位置可以解释,布达山东北边缘断层的水力特性可以确定。水流模式决定了中部系统(Rózsadomb地区)和南部系统(Gellért山地区)天然排泄区之间排泄分布(一个和两个组分)和相关的洞穴形成过程方面的差异。在存在着深成岩溶化前提下,确定了沿多瑙河主要排泄带的区域向上水流条件。Tartalmi kivonatA Budai Termálkarszt Magyarország középső régiójában, fedett és fedetlen karbonátos kőzetek határzónájában húzódik. Termálvíz készletének, valamint a határzónában zajló hipogén karsztosodási folyamatoknak köszönhetően, intenzíven kutatott terület. A megcsapolódási jelenségek és a karsztosodási folyamatok megértéséhez a terület felszínalatti áramlási rendszereinek vizsgálata szükséges. Jelen tanulmány célja az áramlási rendszerek hidraulikai feldolgozása archív kútadatok alapján. A munka során az adateloszlás figyelembevételével nyomás-eleváció profilok, tomografikus folyadék-potenciál térképek és hidraulikai keresztszelvények készültek. Az alkalmazott módszerek eredményeként gravitáció által vezérelt áramlási rendszerek és a hidraulikus folytonosság jelenléte, valamint a vízfogó képződmények és vetők áramlást módosító hatása került kimutatásra a területen. Sikerült meghatározni továbbá a természetes megcsapolódási területek elhelyezkedésének okát, valamint a Budai-hegység Északkeleti peremvetőjének hidraulikai szerepét is. A kimutatott áramlási mintázat meghatározza a megcsapolódási területek (egy- illetve két-komponensű) jellegét és az ehhez kapcsolódó barlangképződési folyamatokat a Rózsadombi és Gellért-hegyi területeken. Végül, a Duna menti megcsapolódási zónában bizonyítást nyert a hipogén karsztosodás egyik elengedhetetlen feltétele, a regionális feláramlás.ResumoA área Buda Thermal Karst, na região central da Hungria, está em foco quanto ao interesse de pesquisa devido aos seus recursos hídricos hidrotermais e aos processos de carstificação hipogênica atualmente em curso no limite entre carbonatos confinados e não confinados. A compreensão dos processos de carstificação e do fenômeno de descarga exige o esclarecimento das condições de fluxo das águas subterrâneas da área. Consequentemente, o objetivo do presente estudo foi apresentar uma avaliação hidráulica dos sistemas de fluxo com base nos registros de dados hidráulicos de poços. Foram desenhados perfis de pressão vs. elevação, mapas tomográficos de potencial de fluido e seções transversais hidráulicas, baseados na distribuição de dados. Como resultados foram identificados sistemas de fluxo gravitacional, continuidade hidráulica, e o efeito modificador de falhas e de unidades aquitardes do carste da área. A localização das áreas de descarga natural pôde ser explicada e o comportamento hidráulico no Northeastern Margin Fault do Buda Hills pôde ser determinado. O padrão de fluxo determina as diferenças na distribuição da descarga (um e dois componentes) e a formação relacionada de cavernas entre o Sistema Central (área de Rózsadomb) e o Sistema Sul (área de Gellért Hill). Dentre as premissas da carstificação hipogênica, as condições regionais de fluxo ascendente ao longo da área de descarga do Rio Danúbio foram confirmadas.

Fluid Flow Systems and Hypogene Karst of the Transdanubian Range, Hungary—With Special Emphasis on Buda Thermal Karst

Carbonate regions have great economic importance for water supply, oil and gas reservoirs, geothermal fluids and also Mississippi Valley-type ore deposits. Therefore, the understanding and consequences of flow pattern in carbonates require special interest. The hypogene and epigene karst areas of carbonate sequences were distinguished and associated with different orders of groundwater flow. However, the effect of confinement on flow pattern of carbonate aquifers was not fully considered in previous studies. We demonstrated the most important prerequisites and consequences of the application of the gravity-driven regional groundwater flow concept for carbonate sequences at different degrees of confinement. The results put into a frame the distribution of different springs and caves (epigene and hypogene) of the carbonate system of the Transdanubian Range, Hungary, and provide insights for better understanding of the hydrogeology of areas with similar unconfined and confined settings. Relationship among different flow regimes, distribution and character of springs and hypogene karstification processes, in addition to natural discharge-related phenomena, such as mineral and microbial precipitates, were recognized in the area of Buda Thermal Karst. This area is a natural laboratory where the connection between groundwater flow and karstification processes can be studied.

Radon as a natural tracer for underwater cave exploration

The Molnár János cave is one of the largest hypogenic caves of the Buda Thermal Karst (Budapest, Hungary) and mainly characterized by water-filled passages. The major outflow point of the waters of the cave system is the Boltív spring, which feeds the artificial Malom Lake. Previous radon measurements in the cave system and in the spring established the highest radon concentration (71 BqL-1) in the springwater. According to previous studies, the origin of radon was identified as iron-hydroxide containing biofilms, which form where there is mixing of cold and thermal waters, and these biofilms efficiently adsorb radium from the thermal water component. Since mixing of waters is responsible for the formation of the cave as well, these iron-hydroxide containing biofilms and the consequent high radon concentrations mark the active cave forming zones. Based on previous radon measurements, it is supposed that the active mixing and cave forming zone has to be close to the spring, since the highest radon concentration was measured there. Therefore radon mapping was carried out with the help of divers in order to get a spatial distribution of radon in the cave passages closest to the spring. Based on our measurements, the highest radon activity concentration (84 BqL-1) was found in the springwater. Based on the distribution of radon activity concentrations, direct connection was established between the spring and the István-room of the cave, which was verified by an artificial tracer. However, the distribution of radon in the cave passages shows lower concentrations (18-46 BqL-1) compared to the spring, therefore an additional deep inflow from hitherto unknown cave passages is assumed, from which waters with high radon content arrive to the spring. These passages are assumed to be in the active cave formation zone. This study proved that radon activity concentration distribution is a useful tool in underwater cave exploration.

Heat potential evaluation of effluent and used thermal waters in Budapest, Hungary

Europe’s largest thermal water system can be found in the capital of Hungary. The springs and wells that supply the famous baths of Budapest discharge mainly from a regional Triassic carbonate rock...

Radionuclides in the waters of the Bükk region, Hungary

The aim of the present study is to characterize the distribution of the 238U decay series radionuclides, focusing on uranium, radium, in the cold, lukewarm and thermal karst waters in the Bükk region. This is a novel approach to characterize fluids and understand their mixing in regional discharge zones of carbonate aquifers. Based on the measurements, simple flow system, without mixing, is supposed, and the elevated radium content might be connected to hydrocarbon reservoir fluids. The results may support the improvement of protection strategies of springs and wells involved in water supply.

CONCLUSIONS FROM A NEGATIVE TRACER TEST IN THE URBAN THERMAL KARST AREA, BUDAPEST, HUNGARY

To prove the hydraulic connection between the urban Rózsadomb recharge area (Buda Thermal Karst System, Budapest, Hungary) – through its hydrothermal inactive caves – and the springs at the foothills has been an important question since the 1980s. These cold and lukewarm springs have been utilized as thermal baths since Roman times, and in modern times, occasionally, chemical and bacterial contaminants of human origin have been detected in them. It is hence of considerable importance to know whether these contaminants originated from the Rózsadomb recharge area or from close to the discharge points. According to the results of a previous test in a cave passage high upon the hill, it was tempting to suppose direct connection between the Rózsadomb area and the Boltív Spring in the foothills. The expected breakthrough-time predicted from this previous study was between 10 hours and 42 days. The tracer test documented in this present work showed that no breakthrough occurred. It is proposed therefore that the risk of the Boltív Spring being contaminated by infiltration in the Rózsadomb recharge area is low as compared with the possible contamination from sources near the discharge area. We suggest that in this case the negative tracer test clearly helped to prove and to understand better the role of “natural attenuation” in the Rózsadomb area. The efficient dilution observed in the tracer test facilitated the prediction of a hitherto unknown, large, phreatic cave-system as well.

Uranium in groundwater – The importance of hydraulic regime and groundwater flow system's understanding

Uranium and other natural radionuclides are common components in groundwater, but they are not routinely measured. In drinking water their total activity is screened, but in the evaluation of the measured values usually the aquifer material is only considered. However, the occurrence of radionuclides in groundwater is strongly affected by flow systems and their geochemical characteristics. Therefore hydrogeology and flow systems evaluation is crucial to understand natural radioactivity. Areas of different hydraulic regimes - recharge, throughflow and discharge - even within the same aquifer are characterized by different geochemical environment. In the present study pressure-elevation profiles were generated based on existing basic hydraulic data of wells in order to determine the flow regimes and associated vertical groundwater flow directions. 24-753 mBq L-1 uranium activity concentrations were found in groundwater and surface water showing great areal variability. High uranium values correspond to recharge regimes with downward flow directions. Uranium mobility is enhanced by high bicarbonate content and circumneutral pH. The study emphasize the importance of groundwater flow systems understanding in those areas, where elevated background radioactivity may exist.