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Home > Science and research > Geological hazards > Radon risk > Radon risk mapping

Radon risk

Radon risk mapping in the Czech Republic

Scale 1 : 200 000

The first radon maps on a scale 1 : 200 000 covering the regions of the state area were published in 1990. Based on the geological, pedological, radiometric and hydrogeological maps at the same scale and soil gas radon measurements in the major geological and lithological units, radon risk is expressed in three categories of radon index – low, medium and high. The maps were hand-drawn and were not converted for computer processing.

Scale 1 : 500 000

The radon risk map on a scale 1 : 500 000 was included in the Map Atlas of the Czech Republic – GEOČR500 (1998) together with 10 other geoscientific maps, published on CD ROM. The GIS project was built for ArcView with the possibility of downloading ArcExplorer viewer directly from the CD. The vector data are in ESRI format, the tabelar data are connected in the *.dbf format. Topographic raster data use the *.tiff format. Radon risk is characterised by three basic categories (low, medium and high) and one interstage category (typical for the radon risk from low category to medium in the inhomogeneous Quaternary sediments). The data background was based on 7000 soil gas radon measurements, performed by the Czech Geological Survey and companies joined in the Association Radon Risk

Thematic layers can be combined from all 11 maps covering the geoscientific themes and construct the maps after users´ demand (eg. high radon risk sites – topography – radiometric map – hydrogeological map). The sampling data are connected with the databases, whose content can be presented in the form of separate window.

Radon index maps at a scale 1 : 50 000

Since 1999, the Czech Geological Survey uses also the vectorized geological maps at the scale of 1 : 50 000, enabling to construct more detailed radon index maps. The more precise determination of radon risk from bedrock in particular villages and towns is possible. These maps (published during 1999 – 2005) are used by the State Office for Nuclear Safety and municipal authorities for distribution of the track-etch detectors within villages and cities.

Usually at each geological map 40 – 90 rock types were specified. The rock types differ mostly by mineralogical composition or by stratigraphic position, the difference in primary uranium concentrations and subsequently in radon concentration is not so expressive. In combination with results from the radon database the particular rock types were grouped into prevailing categories of radon index. Four categories were used in detailed maps – low, interstage (for inhomogeneous Quaternary sediments), medium and high. Grouping of vectorized geological units was performed in MGE programme and transformed into Microstation programme (Bentley), where the grouped contours of rock units are marked according to the prevailing category of radon index. The test sites´ positions are loaded over the vectorized radon layer and topographic raster files (intravilan plans, road network and watersheds) are attached. Except of web application on map server of the Czech Geological Survey the digital outputs were published on CD ROM (AutoRun, Internet Explorer 4.5 or higher). The CD application was broadly used by municipal authorities for the track – etch detectors´ distribution within the districts and intravilans of villages.

Actualised radon index maps 1 : 50 000

Research activities during 2009 – 2012 enabled to precise the radon index maps with respect to radon potential of deeper geological basement, based on 9 100 data from radon database. The attention was focused on the relationship of radon concentrations in parent basement rock and its Quaternary cover. The close relationship of these two parameters resulted in the division of formerly used intermediate radon index category into three levels low – medium – high according to radon concentrations in deeper basement. The actualised maps are presented on the map server of the Czech Geological Survey.