Quaternary deposits and weathered bedrock material as a source of dangerous radon emissions in Estonia

Abstract

The risk of dangerous radon emissions in Estonia is high, being among the highest in Europe. In almost 33 per cent of Estonian land area, the content of radon in soil-contained air exceeds the safe limit for unrestricted construction (50 kBq/m 3 ). In such high radon-risk areas the concentration of radon in soil-contained air ranges from 50 to 400 kBq/m 3 , in a few cases reaching up to 2,100 kBq/m 3 exceeding the permitted level for residential areas. The situation is particularly serious in the northernmost part of the country, where uranium-rich graptolite argillite (Dictyonema shale) and the Obolus phosphorite are close to ground surface and their particles are constituent parts of Quaternary deposits. Radon emissions from bedrock have been investigated in detail, but to date Quaternary strata as a source of radon emissions are poorly studied. According to our measurements the highest concentrations of radon are related to tills containing clasts and fines of graptolite argillite and phosphorite. Glacial deposits include also granitoidal material, containing U, Th and K, which have been transported by glaciers from the outcrop areas of crystalline basement rocks in Finland and the Gulf of Finland. Due to weathering, outwash and repeated redeposition other genetic types are poorer in radioactive elements and they are weaker sources of radon.

Accumulation of heavy minerals in the eastern coast of the Gulf of Riga, south-western Estonia

“…The high content of heavy minerals indicates that these sands may have practical importance for the separation of garnets and radioactive minerals. Also, in the sites that have a high concentration of heavy minerals, high levels of radon emissions and radioactivity have been detected and described in other papers (Petersell et al, 2015).…”

“…Elevated radioactive elements' levels of U, K and Th, caused by the content of heavy minerals in the ground, have been detected in various parts of Estonia (Petersell et al, 2015). However, heavy minerals, mainly zircon and monazite, may also be of practical importance.…”

The Prospects of Clay Minerals from the Baltic States for Industrial-Scale Carbon Capture: A Review

“…The Baltic Shield is the exposed Precambrian northwest segment of the East European Craton. The Baltic Shield contains the oldest rocks of the European continent with a lithospheric thickness of 250 to 300 km [258,259]. Generally, in the direction from the northeast to southwest throughout the Baltic States, the stratigraphical layers of the craton are monoclinally deepening from the north of terrestrial Estonia to Lithuania, where the craton reaches a depth of more than 2 km.…”

Environmental factors influencing the spatial distribution of geogenic radon sources (uranium, radium) in a granitic area

“…𝐶 ∞ : maximal radon concentration in soil air at large depth available for transport (Bq m -3 ) 𝐶 𝑅𝑎 : radium activity mass concentration of the material (Bq kg -1 ) 𝜀: emanation coefficient (dimensionless), 𝜌 𝑏𝑢𝑙𝑘 𝑑𝑟𝑦 : bulk density (kg m -3 ) 𝑝 𝑒 : effective porosity This relationship has been widely applied in its original form and with slight variations (Chitra et al, 2018;Cosma et al, 2001;Ielsch et al, 2002;Ishimori et al, 2013;Jiang et al, 2011;Moldrup et al, 1998;Nazaroff and Nero, 1988;Pereira et al, 2017;Petersell et al, 2015;Washington and Rose, 1992;Yakovleva, 2005).…”