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1.3 Radon & Geology
by Rouwen Lehné1 & Eric Petermann2
1: HLNUG, Germany; 2: BfS, Germany
The radioactive gas radon belongs, together with terrestric and cosmic radiation, to the natural sources of radioactive radiation. For Germany e.g. the average exposure coming from radon is about 1.1 mSv/a (Bundesamt für Strahlenschutz, 2016), which makes up more than 50 % of the total natural radiation exposure.
With the 2013/59/EURATOM directive of the EU-Commission, the EU member states were urged to update their radiation protection laws to account for the health risk of the exposure to elevated indoor radon levels and to prepare National Radon Action Plans (EC 2014). The EU member states have to provide information on so called “radon priority areas” by the end of 2020. The basis for the identification of those areas will be the map of geogenic radon potential (a function of radon soil gas concentration and soil gas permeability). In many cases (i.e. for many countries or regions) the currently available data is not sufficient to provide a satisfying accuracy, leading to the need of additional field measurements. The selection of sampling sites ideally reflects both 1) the administrative level on which radon-priority area will be delineated and 2) available knowledge about variability of landscape characteristics governing the geogenic radon potential (rock, soil, water characteristics, etc.). However, while the influence of soil and rock on the radon concentration is fairly understood, the impact of tectonic inventory and hydrogeological aspects (e.g. origin, flow direction and flow velocity) cannot be considered schematically but require site-specific awareness and treatment. This session therefore is inviting contributions from the large field of action related to radon & geology. The topics include but are not limited to:
5:50pm - 6:05pm
Impact of Geological Conditions and Constructional Features on Indoor Radon
TTK University of Applied Sciences, Estonia
Radon is quite widespread in Estonia, due to complicated geological conditions caused by the appearance of tectonic cracks, graptolitic argillite, phosphorite and also uranium in some places. Geological Survey of Estonia mapped radon priority areas and Radon Risk Atlas was published, according to this 1/3 of the entire territory is a radon risk area. For the most part of Estonia radon concentrations in soil air varies 23–75 kBq/m³, however in some areas it exceeds the value of 500 kBq/m³. Estonia, in terms of average levels of its indoor radon concentrations, is among the five highest radon-risk countries in Europe, with the Czech Republic, Sweden, Luxemburg and Finland.
Unfortunately, indoor radon measurements in Estonia were not obligated until 2018, previous requirements were set only for kindergartens and schools. According to EURATOM 58/2013, all European countries must apply radon action plane and adopt requirements expanded for all working places. All though directive measurements are prescribed at basement floors and first floors, according to construction peculiarities these measurements need to be in consideration also at upper floors.
The current study was carried out in public university building located in the city centre of Tallinn. In this study radon measurement results will be introduced with locations, detailed geological data and maps. For the measurements, fifteen Radon Eye Plus 2 devices were used. Simultaneously radon activity concentrations were recorded at all building five floors above horizontal and vertical directions, following geological cross-section. One-week short-term continuous measurement methodology was used according to local guidelines “Measurement of radon activity concentration”. As a result, radon risk map of the building was made up with identified radon movements. Indoor radon concentration can be hold at a safe level during working hours by enhancing the building ventilation system.
6:05pm - 6:20pm
Radon potential and gamma radiation
Institute of Geological Sciences, University of Wroclaw, Poland
The research aimed to evaluate the relation between radon potential and gamma dose rate.
The survey was carried out on two granitic massifs in SW Poland: Kakonosze and Strzelin. In each region 10 measurement points were located, where measurements of radon in the atmosphere; radon in soil gas; gamma dose rate; U, Th and K content in soil were performed trough one year.
The measurements of radon concentration in the atmosphere and in soil were carried out using passive detectors LR-115. The detectors exposed in the atmosphere were exchanged seasonally, whereas detectors exposed in soil gas were exchanged twice during one season. The uranium, thorium and potassium contents in soil were measured in-situ by Gama-Ray Spectrometer RS-320 BGO Super-SPEC, whereas gamma dose rate by the radiometer.
The averages of radon in the atmosphere, radon in soil, gamma dose rate, U, Th and K contents were higher in Karkonosze than in Strzelin Massif.
The seasonal variations of radon concentration in the atmosphere, radon concentration in soil gas and gamma dose rate were observed. The results of U, Th and K seemed to be unrelated with seasonal weather changes. The strong influence on the results of uranium content had rain.
The calculated correlation coefficients between radon concentration in the atmosphere, radon in soil gas and gamma dose rate indicate good relations between those parameters. However, more research in other geological bedrock and structures should be performed to confirm the usefulness of gamma dose rate to evaluate geogenic radon potential.
This research was supported by the National Science Centre, Poland. Dec.2017/01/X/ST10/00288
6:20pm - 6:35pm
CANCELLED | Bivariate wavelet analysis applied to one-year time series of radon concentration in Pál-völgy cave, Hungary
1Department of Applied Chemistry, Szent István University, Villányi út 35-43, 1118 Budapest, Hungary; 2Department of Physics and Process Control, Szent István University, Páter Károly utca 1, 2100, Gödöllő, Hungary; 3Lithosphere Fluid Research Lab, Eötvös University, Budapest, Hungary
Since the variability of radon concentration depends on multiple factors such as meteorological conditions, it is important to identify their interaction for a better understanding of radon time-dependent dynamics. In this study, one-year radon concentration time series measured in a Hungarian cave in 2010 by Nagy et al., 2012, were evaluated by univariate and bivariate wavelet analysis to determine the effect of ambient meteorological conditions on the temporal series of radon concentration inside the cave.
The Pálvölgy cave is part of the Buda Thermal Karst System located in Buda Hills, Budapest, Hungary. The sampling point is located 200 m far from the show cave path to ensure undisturbed conditions. Radon concentration, temperature, relative humidity and pressure inside the Pálvölgy cave were measured by Nagy et al., 2012 with AlphaGUARD active radon monitor at one-hour sampling frequency in 2010. The ambient meteorological conditions correspond to the hourly records of the Budapest Central Hungarian Meteorological Station (2.57 Km from the measurement point).
The time series were evaluated individually at first and subsequently a bivariate analysis was performed. Continuous and discrete wavelet analysis were executed to identify the temporal dependency of radon with ambient temperature, relative humidity and pressure. Results show that radon activity concentration measured within the studied cave has a temporally variable dependence with the ambient atmospheric conditions such as temperature and pressure.
Nagy, H.É., Szabó, Z., Jordán, G., Szabó, C., Horváth, Á., Kiss, A., 2012. Time variations of 222Rn concentration and air exchange rates in a Hungarian cave. Isotopes Environ. Health Stud. 48, 464–472.
6:35pm - 6:50pm
Assessment of thoron and radon exhalation in rock samples collected in the southwest region of Angola
1University of Coimbra, LRN – Laboratory of Natural Radioactivity, Department of Earth Sciences, Portugal; 2CITEUC – Center for Earth and Space Research, Department of Earth Sciences, University of Coimbra, Portugal; 3MARE – Marine and Environmental Sciences Centre, Department of Earth Sciences, University of Coimbra, Portugal
The assessment of the thoron (220Rn) exhalation and emanation rates has been generally underrated due to its short half-life. However, the contribution of 220Rn to the inhaled dose rate can be similar or higher than the contribution of radon (222Rn). Improving existing knowledge of the 220Rn exhalation rate from bedrock is therefore imperative.
We collected 30 samples from igneous (n = 17) and metasedimentary (n = 13) units in the southwestern region of the Angolan Shield. Whole-rock geochemistry analysis were performed by X-Ray Fluorescence. 226Ra and 208Tl activity concentrations were determined by gamma-ray spectrometry with an Ortec NaI(Tl) detector. 222Rn and 220Rn exhalation rates were measured simultaneously with an AlphaGuard DF2000 monitor (Bertin Instruments) and the 222Rn and 220Rn emanation coefficients computed.
208Tl activity is generally higher than 226Ra activity, however, 220Rn and 222Rn exhalation rates and emanation coefficients have the same order of magnitude. On average, igneous rocks present higher 208Tl and 226Ra activity, 220Rn and 222Rn exhalation rates and emanation coefficients compared to metasedimentary rocks. Igneous rocks should therefore be assigned a higher level of risk in terms of radiation exposure. 220Rn and 222Rn exhalation rates are correlated, however, the underlying causes are seemingly different between metasedimentary and igneous rocks. In metasedimentary rocks, the correlation between 220Rn and 222Rn exhalation rates is linked to a correlation between 208Tl and 226Ra activity while in igneous rocks the correlation between the exhalation rates is linked to a correlation between 220Rn and 222Rn emanation coefficients.
6:50pm - 7:05pm
Radon anomalies along faults in Jiroft Aquifer, Iran
1Shahid Bahonar University of Kerman, Kerman, Iran; 2Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands
Radon, a radioactive gas, that is considered as a hazardous element to life and one of the known causes of lung cancer, is a geological tracer for earthquakes and fault zones. The purpose of this study was to measure the concentration of radon in groundwater of the Jiroft plain and to determine its relationship with fault zones in the region. In this regard, 40 samples were collected from the groundwater and the RAD7 was used to measure the amount of dissolved radon in them. According to the results, Radon levels were high in 67% of the samples. The zoning map of the radon gas concentration was prepared by performing an interpolation operation. The study area was classified into four classes: very high, high, medium and low in terms of radon concentration. In order to determine the relationship between the high concentrations of radon and faults in the region, the weights of evidence method were used. The results of this method show that there is a relatively high correlation between water-wells with high and very high radon contamination and the main faults of the region. The highest correlation was obtained at a distance of 1000 meters from the faults, and by increasing the distance the radon emanation decreased.
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