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Radon (222Rn) is a natural gas produced by the radioactive decay of uranium-bearing rocks and soils in the Earth?s crust. Geology is one of the main factors controlling source and distribution of radon. Most rocks and soils possess small amount of uranium, but there are particular types of bedrocks and unconsolidated deposits characterized by higher than average uranium contents. These lithological types include some granites, light-colored volcanic rocks, phosphatic rocks, ironstones, limestones and shales rich i...

In the XX century many drillings for exploration and exploration of oil and gas were conducted in Northern Bulgaria. Up to 1500 boreholes with a depth of several hundred meters to more than 5000 m have been drilled on its territory so far. During drilling, aquifers with different hydrochemical properties have been registered. The aim of the present study is to assess the current ecological status of the old oil boreholes in Central Northern Bulgaria. As a result of the field activities a catalogue with information...

The ?Druzhba? uranium mine, near village of Eleshnitsa, Southwestern Bulgaria, was in operation from 1955 to 1992. During excavation work three different confined aquifers were registered ? at altitude of 805, 730 and 630 m. The original groundwater table was at 815 m and during the operation period it was reduced down to 520 m. After cessation of mining activities, the dewatering pumps (with approximate flow-rate of 300 m3/h) were stopped in December 1995, and then the deep mine galleries started to be flooded by...