Problems of Geography, 2020, Vol.3, DOI: https://doi.org/10.35101/PRG-2020.3.4
Petar Stefanov, Dilyana Stefanova, Karel Turek

There are over 6000 state-owned karst caves in Bulgaria. Some of them represent sites for mass tourism and have been turned into show-caves, which are run by NGOs or executive bodies. The paper presents the results of integrated monitoring (2010-2020) in 13 of the most popular Bulgarian show-caves, which are annually visited by over 0.6 million tourists. The applied model of integrated monitoring of cave systems (Speleo-MIKS) was developed by the Experimental Laboratory of Karstology at the National Institute of Geophysics, Geodesy and Geography – the Bulgarian Academy of Sciences (NUGGG-BAS) in international cooperation. The monitoring covers almost all indicators of the cave environment, susceptible to observations and measurements. The latter are carried out either on an expedition basis (in different months and seasons, including in extreme conditions), or on a continuous instrumental basis (including automatic stations and established monitoring networks). The monitoring covers microclimate (temperature and relative humidity, temperature of cave sediments and waters), gas composition and radiation exposure (CO2 concentration in cave air, 14C activity, Radon activity concentration, gamma radiation / gamma background); hydrochemical monitoring of cave waters; extensometric monitoring. Based on the results of the monitoring, conclusions about the condition and changes in the cave environment, as a result of tourist activity, have been drawn and summarized, while the bio-comfort and the risks for the visitors and the staff of the tourist caves have also been assessed. In 4 of the caves, CO2 concentrations of over 1% were recorded during the high tourist season (summer-autumn). In 7 of the most visited tourist caves, high average annual concentrations of Radon (from 3 to 8 kBq/m³) were also detected. Real effective doses for cave guides were calculated – in the Venetsa cave they exceeded 2.5 to 5.5 times the reference value of 6 mSv. The current state and the existing problems in the management and administration of the tourist caves have been analyzed. Two important conclusions stand out: 1. The Bulgarian legislation has not yet introduced „cave“ as an existing workplace, 2. „Cave guide in a tourist cave“ does not exist in the List of regulated Professions in Bulgaria. Specific measures have been proposed to optimize cave tourism. The results of the monitoring in the tourist caves also confirm the effects of global climate changes on the speleomicroclimate and the gas composition of the cave systems.

karst, karst geosystems, tourist caves, speleomicroclimate, integrated speleomonitoring (Speleo-MIKS), CO2 , radiation exposure, Radon-222, effective doses, gamma background, radiocarbon activity, bioclimatic comfort and bioclimatic risks

The monitoring in the tourist caves is organized through two international research projects, financed by the Bulgarian Research Fund: “Development of an experimental model of complex monitoring for sustainable development and management of protected karst territories” (ProKARSTerra, № DO 02.260 / 18.12. 2008) and “Contemporary impacts of global changes on karst evolution (based on integrated monitoring in model karst geosystems in Bulgaria)” (ProKARSTerra-GlobalChange, № DN 14/10 of 20.12.2017). Preliminary studies of the cave systems have also been carried out with a series of projects of the Fund (NZ-3/91; NZ-432/94; NZ-525/95; SS-905/99).
Monitoring of radon activity is also supported through the projects “Application of Radio-Nuclear investigations and Radio-Nuclear dating in surveying anthropogenic impacts at vulnerable geosystems” (2008-2010), “Radionuclide methods in experimental design of an integrated monitoring of karst geosystems” (2011-2013) and “Application of radiocarbon dating in the research of karst systems” (2014-2016) on bilateral academic cooperation between BAS (NIGGG) and the Academy of Sciences of the Czech Republic (Institute of Nuclear Physics). This cooperation is also the basis for the extensometric monitoring in the tourist caves through 2 projects in partnership with the Institute of Rock Structure and Mechanics: “Tectonic activity of the significant karst systems (development correlation of Central Europe and 94 Mediterranean area)” (2014-2016) and “Plate-wide tectonic pressure pulses (correlation of extensometric monitoring in Mediterranean and Central Europe)” (2017-2019).
We would like to express our gratitude to the tour guides of the tourist caves for their assistance in conducting the monitoring.

Author information:
Author: Petar Stefanov
E-mail: psgeo@abv.bg
Affiliation: National Institute of Geophysics, Geodesy and Geography – BAS, department of Geography, str. Acad. G. Bonchev, bl. 3, Sofia 1113, Bulgaria

Author: Dilyana Stefanova
E-mail: dili_stefanova@abv.bg
Affiliation: National Institute of Geophysics, Geodesy and Geography – BAS, department of Geography, str. Acad. G. Bonchev, bl. 3, Sofia 1113, Bulgaria

Author: Karel Turek
E-mail: turek@ujf.cas.cz
Affiliation: Department of Radiation Dosimetry of the Nuclear Physics Institute – Czech Academy of Sciences

How to cite:
Stefanov, P., Stefanova, D., & Turek, K. (2020). Микроклиматични и радиационни условия и здравни рискове в туристическите пещери в България (на базата на резултати от интегриран мониторинг). Problems of Geography, 2020, Vol.3, p. 47-100. https://doi.org/10.35101/PRG-2020.3.4