Petar Stefanov – INTEGRATED MONITORING OF THE SAEVA DUPKA CAVE SYSTEM (“SAEVA DUPKA” SPELEO-MIКS)

https://doi.org/10.35101/prg-2020.4.1

There are over 6000 karst caves known to exist in Bulgaria, 15 out of which have a tourist status (show caves). But even in those show caves, no monitoring has been organized or is currently conducted. Since 2009, the Experimental Laboratory of Karstology at the Institute of Geophysics, Geodesy and Geography – the Bulgarian Academy of Sciences (NIGGG-BAS) has been developing a model for integrated monitoring of karst geosystems (MIKS), which also includes monitoring of underground (cave) systems (Speleo-MIKS). The monitoring covers almost all indicators of the cave environment, susceptible to observations and measurements. The structure of the experimentally developed “Saeva Dupka” Speleo- MIKS model includes (Fig. 2):

1. A system for continuous instrumental monitoring:Meteorological – with the use 2 automatic meteorological stations in the cave and 1 meteorological station outside the cave;Temperature of rocks, cave sediments and water in sinter lakes; Cave air gas concentration (CO₂ concentration and Radon activity concentration); Intensity of infiltration cave waters; Extensometric monitoring of active fault structures (with the use of dilatometer TM-71); Automatic monitoring of the number of visitors and duration of stay. The monitoring is carried out with the use of a professional set of instruments, resilient to the cave environment.

2. Regular field monitoring of:

A. In the cave: speleoclimatic and gas composition of the cave air (CO₂ concentration; radiocarbon activity, ¹⁴С; Radon activity concentration – passive measurements with alphatrack detectors);

The regular field monitoring also includes Sampling (of infiltration cave waters and of freshwater calcite) and Experiments (so as to determine the aggressiveness of karst waters in the cave system).

B. On the surface above the cave: Temperature and humidity of the soil; Gas composition of soil air (CO2 concentration and Radon activity concentration);Lysimetric monitoring (of soil solutions); Hydrochemical monitoring of precipitation water (rain and snow); Socio-economic monitoring (SIM).

Speleo-MIKS also includes periodic sampling and analysis of the samples in specialized laboratories.

Based on the original results of the integrated monitoring, several major conclusions can be summarized as follows:

– well-defined seasonal dynamics of the ventilation regime and the parameters of the speleoclimate, and of the cave air gas composition;

– proven active condensation processes and their role in the speleogenesis and the volume growth of the cave;

– fossil carbon participation in the cave atmosphere, which dilutes the radiocarbon content (Δ¹⁴C);

– two extensometric periods can be distinguished: active – exhibiting a very clear tectonic pressure pulse, which ended in 2015-2016, and passive – of relative tectonic calm, which continues into 2020;

– a confirmed role of the cave air CO₂ concentration variations in the intensity of calcite deposition from infiltration cave waters.

– observation of some effects of global climate change on modern speleo- andkarstogenesis. Saeva Dupka is one of the most visited show caves in Bulgaria, which is open for visitors all year round. It also has the status of a protected area (Natural landmark). Therefore, the results of Speleo-MIKS are being analyzed in two practical aspects:

1. Impact of tourism on the cave environment: proven visitors’ thermal effects on the speleological climate and disturbance of the natural balance of CO₂ in the cave air as a result of the visitors’ breathing; established year-round pollution of the cave environment and of the infiltration cave waters from the tourist infrastructure.

2. Bio-comfort and health risks for visitors and staff of the cave (cave guides): proven dangerously high CO₂ and radon-222 concentrations during the high tourist season.

Special attention is being paid to the experimental inclusion of Saeva Dupka with its monitoring system in innovative forms of education on / through karst. The results of Speleo-MIKS are expected to serve as a basis for harmonization of the research methodology for studying the caves in Bulgaria, and for development of a unified system for cave environment assessment in line with the karst geosystems concept.

Key words: karst, karst geosystems, show caves, Saeva Dupka, the Brestnitsa karst geosystem, integrated speleomonitoring (Speleo-MIKS), speleoclimate, concentrations of CO₂ and radon-222, radiation risk, gamma background, radiocarbon activity, hydrochemical monitoring of karst waters, condensation, anthropogenic pressure and global changes

Marian Varbanov, Atanas Kitev, Stefan Genchev, Kristina Gartsiyanova – ASSESSMENT OF OXYGEN BALANCE OF WATER IN THE TOPOLNITSA AND LUDA YANA RIVER BASINS

https://doi.org/10.35101/prg-2020.4.2

This article analyzes and evaluates the current changes in the quality of river waters in the basins of Topolnitsa and Luda Yana. The rivers are experiencing significant anthropogenic impact of various origins and nature. To assess the impact and condition of water quality index used in many countries around the world has been used. Respective Bulgarian normative documents give the opportunity to obtain representative results and to be compared with the reference values of the indicators in the index. The critical condition of the river sections of the rivers Topolnitsa, Mativir and Luda Yana near large settlements has been determinate. Local pollution is usually caused by frequent discharges of wastewater from livestock farms. In the lower reaches of the main rivers there is a gradual change to improvement of water quality in terms of physical and chemical parameters used.

Key words: oxygen balance, water quality, pollution, index assessment

Georgi Zhelezov – DYNAMIC OF WETLAND SYSTEMS IN ARCHARO-ORSOYSKA LOWLAND

https://doi.org/10.35101/prg-2020.4.3

The present research is related to the problem of dynamic in development of the Archaro-Orsoyska wetland system. The scientific results in the investigation are based on the information generated from old maps covering different time periods. Using these data dynamic and transformation of the wetland system have been developed. The spatial models and structures are also realized as a part of the research.

Key words: wetland, system, dynamic

Georgi Zhelezov, Aleksey Benderev, Sava Kolev, Kostadin Nikolov – RELATIONSHIP OF THE SPATIAL DISTRIBUTION OF HEAVY METALS IN THE SOIL WITH THE MORPHOLOGY OF CONTAMINATED RIVER FLOODPLAINS (TOPOMET)

https://doi.org/10.35101/prg-2020.4.4

Concentrations of heavy metals in the soils of contaminated river floodplains can vary greatly over short distances, making it difficult for spatial modeling with the usual approaches. Linking the trace metal contents to the morphography of the terrain using modern geostatistical methods, applied in digital soil mapping, would allow the creation of a predictive model for spatial distribution of pollutants. The research in the project “Relationship of the spatial distribution of heavy metals in the soil with the morphology of polluted floodplains (TOPOMET)” aims to perform predictive modeling of the spatial distribution of certain heavy metals in polluted alluvial deposits and floodplain soils in selected sections of the Danube river valleys – Archaro-Orsoyska lowland, Ogosta and Lom rivers catchments, using remote sensing methods, spatial data analysis and geostatistics. They will be used for GISbased analysis of a set of morphometric parameters of the topography of the valleys. The information on the parameters and contents of heavy metals in nearly 400 soil samples will be processed using Regression-Kriging Techniques and Generalized Linear Models (GLM) to reveal the dependencies between them and to fit regression models. With the help of the latter, an attempt will be made to predict the spatial distribution of selected heavy metals in the soils of the studied areas. As a result of the project, it is expected to establish morphometric parameters that the best describes spatial variation of heavy metal contents in soils and can be used in different predictive models. An attempt will be made to develop a technology for the spatial modeling of heavy metal content in the soils of floodplain terraces. This will make it possible to identify and detail the extent of pollution in river valleys as a result of mining extraction and metallurgical production and to take measures to minimize the health risk for the local population.

Key words: heavy metals, space, pollution, river terraces