| Abstract |
The territory of Sofia Valley is about 1,200 sq.km. Tectonically, it represents a graben separated by bordering faults from the surrounding mountain ridges. Major geothermal reservoirs are of Mesozoic age (sediments and volcanic rocks) as well as Neogene age (sand layers). The thermo-mineral waters in the frame of this region are essential factor for originated and development of the capital of Bulgaria - the city of Sofia. All over the valley, there are some groundwater sources with a total flow-rate of up to 110 L/s and a temperature from 21°C to 81°C (B-1, Kazichene). The thermo-mineral sources are mainly used in balneology, bottling, heating energy, spa tourism etc. Through a comparative analysis of data on the registered contents of metals in thermo-mineral sources in Sofia Valley are represented differences in chemical composition of waters in the geothermal fields (sites). The results of water samples from the sources obtained in the laboratory of the University of Antwerp (Belgium) as well unpublished data from the laboratory of the Scientific Institute (NIKFR) - Ovcha Kupel (Bulgaria) were used. Possible connections between the specific natural conditions, the temperature, pH and the concentration of metals in the waters of each source are considered. An assessment has been made of the suitability of the extracted waters in accordance with the current rules for the content of metals in the mineral waters used for bottling potable water. |