The Path from Geology to Indoor Radon
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Environ Geochem Health https://doi.org/10.1007/s10653-019-00496-z (0123456789().,-volV)(0123456789().,-volV) ORIGINAL PAPER The path from geology to indoor radon S¸ tefan Florica˘ . Bety-Denissa Burghele . Nicoleta Bican-Bris¸an . Robert Begy . Vlad Codrea . Alexandra Cucos¸ . Tiberiu Catalina . Tiberius Dicu . Gabriel Dobrei . Andrei Istrate . Alexandru Lupulescu . Mircea Moldovan . Dan Nit¸a˘ . Botond Papp . Istvan Pap . Kinga Szacsvai . Ancut¸a T¸ enter . Teofana Sferle . Carlos Sainz Received: 28 June 2019 / Accepted: 7 December 2019 Ó Springer Nature B.V. 2020 Abstract It is generally accepted that radon emis- pointed out that the geological foundation can provide sion is strongly influenced by the geological charac- a reasonable explanation for the majority of the values teristics of the bedrock. However, transport in-soil and recorded in both soil and indoor air. Results also entry paths indoors are defined by other factors such as showed that older houses, built with earth-based permeability, building and architectural features, materials, are highly permeable to soil radon. ventilation, occupation patterns, etc. The purpose of Energy-efficient houses, on the other hand, have a this paper is to analyze the contribution of each tendency to disregard the radon potential of the parameter, from natural to man-made, on the radon geological foundation, causing a higher predisposition accumulation indoors and to assess potential patterns, to radon accumulation indoors and decreasing the based on 100 case studies in Romania. The study general indoor air quality. Keywords Geology Á Radon Á Energy-efficient Á & S¸. Florica˘ Á B.-D. Burghele ( ) Á N. Bican-Bris¸an Á Indoor air quality R. Begy Á A. Cucos¸ Á T. Catalina Á T. Dicu Á G. Dobrei Á A. Istrate Á A. Lupulescu Á M. Moldovan Á D. Nit¸a˘ Á B. Papp Á I. Pap Á K. Szacsvai Á A. T¸ enter Á T. Sferle Á C. Sainz Faculty of Environmental Science and Engineering, Introduction Babes¸-Bolyai University, Cluj-Napoca, Romania e-mail: [email protected] Radon is considered a carcinogenic gas, attributed S¸. Florica˘ Á V. Codrea between 9 and 15% of the 14,000 annual cases of lung Department of Geology, Faculty of Biology and Geology, cancer in Europe (Darby et al. 2005; Krewski et al. Babes¸-Bolyai University, Cluj-Napoca, Romania 2005). Worldwide, it is considered to be the second R. Begy leading cause of lung cancer after smoking. Prolonged Interdisciplinary Research Institute on Bio-Nano-Science, exposure to levels exceeding 100 Bq/m3 is treated as a Babes¸-Bolyai University, Cluj-Napoca, Romania serious environmental problem (WHO 2009; T. Catalina Á A. Istrate UNSCEAR 2000). The European Union has stipulated Faculty of Engineering Installations, Technical University in the C.E. 2013/59/Euratom the obligation of Mem- of Civil Engineering of Bucharest, Bucharest, Romania ber States to monitor and report levels of radioactivity from natural and anthropogenic sources. Romania has C. Sainz Department of Medical Physics, Faculty of Medicine, since adopted Law 526/2018, establishing a National University of Cantabria, Santander, Spain Action Plan to tackle the radon issue. 123 Environ Geochem Health Radon (Rn222) is a decay product directly descend- performed in five of the largest municipalities in ing from radium (Ra226) in the natural uranium decay Romania. series. The local geology is the main controlling factor on the sources of radon generation in the atmosphere, and consequently, indoors too (Sachs et al. 1982; Study areas Kemski et al. 2001, 2005, 2009; Ciotoli et al. 2017), since uranium is widely distributed in rocks and soils The five cities considered for the present study, throughout the earth’s crust. It is well known that any Bucharest, Cluj-Napoca, Ias¸i, Sibiu and Timis¸oara, rock may have a higher or lower content of radioactive are scattered throughout the country. Three cities are elements, depending on its genesis (Sachs et al. 1982; located on the east, south and west plains, while the Gundersen et al. 1992; Appleton 2007; Drolet et al. other two are situated within the intra-Carpathian 2013). Magmatic and metamorphic rocks, for exam- depression. The geological background of Romania ple, are known to have a higher content of radioactive and the five cities considered are presented in Fig. 1. elements (U/Ra) than most sedimentary rocks (Stoici From a geological point of view, the city of and Ta˘taru 1988; Cosma and Jurcut¸ 1996). However, Bucharest is located in the central part of the some sedimentary rocks, mainly clastic sedimentary Wallachian sector of the Moesian Platform, involving rocks, consisting of fragments (clasts) of preexisting two major structural units: a metamorphic sole and magmatic or metamorphic rocks, loosened from cross-cutting magmatic rocks, overlain by a sedimen- weathering process, then transported and accumulated tary cover (Mutihac 1990; Ionesi 1994). Quaternary to some sedimentary basins, are also known to have a sedimentary deposits (gravel and sands of Colentina significant radioactive potential (Drolet et al. 2013). Formation and loess deposits of the Upper Middle The causal relationship between the amount of Pleistocene; loess deposits and sands and gravels of radioactive elements in a certain type of rock and the lower terraces of uppermost Pleistocene; detrital radon emanations is not always easy to plot, even if the deposits of the Holocene lower terraces and riverbeds) latter is dependent on uranium concentrations and the are spread on the whole area of Bucharest. Borehole nature of the parental mineral. Certain factors such as data (Liteanu 1952) indicate the presence in subsur- rock granulometry, permeability, fractures, cracks, face of two important Pleistocene litostratigraphic rock weathering and decay characteristics may play an units: The Fra˘¸est ¸ti Formation (Lower Pleistocene) and important role in the generation and migration of Coconi Formation (Middle Pleistocene). The basal radon to the subsurface (Ball et al. 1991; Nazaroff late Pleistocene (Mostis¸tea Fm.) is not cropping out in 1992; Drolet et al. 2013). Besides the geological the studied area (Liteanu 1953, 1956; Andreescu et al. bedding of a building site, the transfer of radon indoor 2011, 2013). is dependent on environmental factors such as venti- Timis¸oara municipality is located on the southeast- lation, occupation patterns or building and architec- ern border of the Pannonian Basin, the Miocene- tural features (Sachs et al. 1982; Gundersen et al. Quaternary back-arch extensional basin, occurred 1992; Kemski et al. 2005; Bossew et al. 2008; after the Styrian phase (sensu Stille). The geological Appleton and Miles 2010). structure of this area consists of the units of the pre- Recent studies have shown that although the Neogene basement (i.e., thrusting nappes, suture variation of the radon levels indoors depends primarily zones, magmatic bodies, sedimentary deposits, etc.), on the physico-chemical characteristics of the sub- bordered by fault systems reactivated successively strate (type of rock and permeability), the parameters during Alpine movements and neo-structures (deep that influence the inlet and transport paths can play a blocks, grabens, horsts, etc.) and controlled by normal decisive role in the accumulation of radon (Demoury faults (Polonic 1985). The Quaternary is largely et al. 2013; Cosma et al. 2013; Bossew 2015; Ciotoli exposed all over this area of the basin and mainly et al. 2017). With this in mind, investigations consists of clastic and clay deposits. The older concerning the radon concentration of in-soil gas, soil Pleistocene fluviatile terrace deposits are covered by permeability, surface radon exhalation (house perme- Holocene alluvial deposits consisting of interbedded ability) and indoor radon concentration were clays, sand and gravels. (Codarcea et al. 1968; Mircescu 1982; Simionescu et al. 1989). 123 Environ Geochem Health 123 Fig. 1 The geological background of Romania and the setting of the five investigated perimeters, after Geological map of Romania, IGR, 1: 200000 (Sheet L-35-XXXIII for Bucharest, Sheet L-34-XII for Cluj-Napoca, Sheet L-35-XIX for Sibiu, Sheet L-35-X; L-35-XI for Ias¸i, Sheet L34-XXII for Timis¸oara) Environ Geochem Health Ias¸i municipality and its surroundings are located in Materials and methods the central-eastern sector of the Moldavian Platform. This platform consists of two major units: a meta- Solid-state nuclear track detectors were placed indoors morphic and magmatic sole, transgressed by a sedi- in 1000 residential buildings for two consecutive mentary cover (Mutihac 1990; Ionesi 1994;Ra˘ileanu campaigns. Each campaign lasted 6 months. In each et al. 2012). Carbonate, terrigenous and clastic building were placed 2 passive detectors; one for each Sarmatian rocks and Quaternary deposits (loess, as of the two most occupied rooms of the house. The well as sand, gravel of the Pleistocene fluvial terraces, working protocol for passive measurements has been as well as Holocene alluvial deposits of the Bahlui previously described elsewhere (Cucos¸ et al. 2012). River) are exposed in Ias¸i and its neighborhoods area Based on passive measurement results, 100 houses (Braˆnzila˘ 1999). with radon concentrations above 200 Bq/m3 in at least The city of Sibiu is situated on the southern border one room were chosen for detailed diagnostics. Only of the Transylvanian Depression, nearby the contact these 100 houses were analyzed in the present study. area with the Carpathians metamorphic rocks. The Soil gas radon concentration was determined basement of the whole area concerns Precambrian in situ, using RM-2 (Radon v.o.s., Czech Republic) metamorphic schists and upper Cretaceous sedimen- portable soil radon monitor and applying the Neznal tary formations, transgressed by Neogene formations, method (Neznal et al. 2004). The method requires on their turn overlapped by Quaternary deposits determining the concentration of radon from soil gas (Mutihac 1990). In Sibiu area, Badenian contains samples extracted from a depth of 80 cm using a metal marls, gravels and sands, Sarmatian contains sandy probe, 15 sampling points for each 800 m2 of bare soil.