Displays

Urban air quality is strongly influenced by the atmosphere’s ability to disperse primary emissions and opportunities for secondary pollution formation. In mid- to high-latitude regions that experience enduring winter snow cover or soil freezing, regional subsidence and stagnation associated with persistent anti-cyclonic conditions such as the “Siberian High” can lead to “cold pool” or “persistent inversion” events. These events can result in life-threatening pollution episodes that last for weeks. While often associated with complex topography [1,2], persistent inversion events can also influence the air quality of urban centres in flat, inland regions [3]. This presentation will describe a recently-developed radon-based technique for identifying and characterising synoptic-timescale persistent inversion events, which is proving to be a simple and economical alternative to contemporary meteorological approaches that require regular sonde profiles [1]. Furthermore, key assumptions of the radon-based technique to characterise diurnal-timescale changes in the atmospheric mixing state described by Chambers et al. [4] are violated during persistent inversion conditions. Here we demonstrate how atmospheric class-typing, through successive application of radon-based techniques for identifying synoptic- and diurnal-timescale changes in the atmospheric mixing state, improves understanding of atmospheric controls on urban air quality in non-summer months across the full diurnal cycle. This knowledge translates directly to statistically-robust techniques for assessing public exposure to pollution, and for evaluating the efficacy of pollution mitigation measures. Lastly, we show how atmospheric class-typing can be used to enhance the evaluation of chemical transport models [5].

[1] Baasandorj, M., et al. Environ. Sci. Technol., 51, 5941–5950, https://doi.org/10.1021/acs.est.6b06603, 2017.

[2] Kikaj, D., et al. Atmos. Meas. Tech., 12, 4455–4477, https://doi.org/10.5194/amt-12-4455-2019, 2019.

[3] Chambers, SD and A Podstawczyńska. Atmos. Environ., 219, 117040, https://doi.org/10.1016/j.atmosenv.2019.117040, 2019.

[4] Chambers, S.D., et al. J. Geophys. Res. Atmos. 124, 770–788, https://doi.org/10.1029/2018JD029507, 2019.

[5] Chambers, S.D., et al. Atmosphere 10 (1), 25, doi:10.3390/atmos10010025, 2019.

How to cite: Chambers, S., Kikaj, D., Podstawczyńska, A., Crawford, J., and Williams, A.: Characterising diurnal- and synoptic-timescale changes in urban air quality using Radon-222, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1506, https://doi.org/10.5194/egusphere-egu2020-1506, 2020.

The rather short life time of ²²²Radon of 5.5 days makes this radioactive noble gas an almost ideal tracer of atmospheric transport processes. ²²²Radon, the gaseous progeny of ²²⁶Radium, which is a trace constituent of all soils, can escape the soil grains and make its way from the unsaturated soil zone into the atmosphere. The exhalation rate of ²²²Radon from continental surfaces depends on soil type and permeability, but is orders of magnitude larger than that from ocean surfaces. Therefore, the atmospheric ²²²Radon activity concentration can be used as a measure of the residence time of air over continental surfaces or to distinguish continental from marine air masses. At continental sites, the short-term variability of ²²²Radon is mainly determined by diurnal or synoptic-scale boundary layer mixing processes. If its continental exhalation rate is known, ²²²Radon can even be applied as a quantitative tracer for evaluating regional scale transport model performance. In the present study we use ²²²Radon activity concentration measurements from the ICOS atmospheric station network and STILT transport model results to assess the ability of this routinely used model to correctly simulate the (diurnal) variation of boundary layer transport. This uncertainty assessment is an important step towards reliable estimates of the contribution of transport model error in GHGs inversion studies that aim at providing accurate fluxes from inversion of atmospheric GHGs observations in ICOS.  

How to cite: Karstens, U., Levin, I., Ramonet, M., Gerbig, C., Arnold, S., Conil, S., Della Coletta, J., Frumau, A., Gheusi, F., Kazan, V., Kubistin, D., Lindauer, M., Lopez, M., Maurer, L., Mihalopoulos, N., Pichon, J.-M., and Spain, G.: Assessment of regional atmospheric transport model performance using 222Radon observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10467, https://doi.org/10.5194/egusphere-egu2020-10467, 2020.

Using Safecast data for estimating ambient dose rate in cities around the world

Petr KUČA¹ and Peter Bossew²

¹ National Radiation Protection Institute (SURO), Praha, Czech Republic 

² German Federal Office for Radiation Protection, Berlin

Safecast [1] is a citizen science project, aimed to environmental monitoring. Its main activity is measuring ambient dose rate (ADR) all over the world. Motivated by the Fukushima NPP accident in March 2011, the project started soon after, and since, numerous citizens have contributed, carrying monitors with them.

In this presentation, the Safecast project is introduced together with its standard instrument for ADR measurement, called bGeigie Nano. We discuss matters of quality assurance connected to data generation mainly by citizens who are generally no trained metrologists, and consequently, interpretation problems of Safecast data.

The freely accessible data, currently (January 2020) over 120 million observations, were used to calculate mean ADR in various cities around the world where sufficient data is available. The resulting geographical pattern mainly reflects the variability of dose rate from terrestrial radiation, which is controlled by the one of geochemistry, namely the concentrations of uranium, thorium and potassium. Further influence comes from cosmic radiation, natural radionuclides in the air (a small contribution) and in a few cases, from anthropogenic radiation caused by nuclear fallout.

In some cities at high altitude, such as Cusco (Peru), Nairobi (Kenia) or Denver (USA), secondary cosmic radiation clearly contributes strongly to ADR. In low to medium altitude, cosmic dose rate varies relatively little, so that it contributes little to the geographical pattern. Apart from the regional geological background, ADR is generated by building materials typical for an urban environment. Mean terrestrial ADR in cities around the world ranges between several 10 nSv/h and several 100 nSv/h. Anthropogenic radiation contributes little, except close to areas affected by the Chernobyl and Fukushima accidents. However, one can argue that also radiation from building materials, although originating from natural radionuclides, is anthropogenic, as buildings are anthropogenic objects and the choice of building materials is an anthropogenic one.

We show maps displaying mean ADR for a number of cities. Geology and in some cases, altitude above sea level are clearly reflected in these maps. Besides, we address statistical issues related to spatial dispersion of ADR and of data clustering as resulting from varying and heterogeneous sampling density. Finally, we discuss merits of the Safecast project as well as inevitable limitations.

[1] www.safecast.org ; Brown, A., Franken, P., Bonner, S., Dolezal, N., Moross, J. (2016): Safecast: successful citizen-science for radiation measurement and communication after Fukushima. Journal of Radiological Protection, 36 (2), S82 – S101; doi:10.1088/0952-4746/36/2/s82

How to cite: Kuča, P. and Bossew, P.: Using Safecast data for estimating ambient dose rate in cities around the world, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4944, https://doi.org/10.5194/egusphere-egu2020-4944, 2020.

A detailed investigation of geogenic radon potential (GRP) was carried out using geostatistical analysis on multiple radon-related variables to evaluate natural radiation in an area of Southeast Ireland. The geological setting of the study area includes basal Devonian sandstones and conglomerates overlying an offshoot of the Caledonian Leinster Granite, which intrudes Ordovician sediments. The Ordovician sediments contain traces of autunite (Ca(UO₂)2(PO₄)₂·10–12H₂O), which is a uranium-bearing mineral and a source of radon. To model radon release potential at different locations, a spatial regression model was developed in which soil gas radon concentration measured in-situ using a Radon RM-2 detector was considered as a response value. Proxy variables such as local geology, soil types, terrestrial gamma dose rates, radionuclide concentrations from airborne radiometric surveys, soil gas permeability, distance from major faults and a Digital Terrain Model were used as the main predictors. Furthermore, the distribution of indoor radon concentration was simulated using a soil-indoor transfer factor. Finally, the workability of the proposed GRP model was tested by evaluating the correlation between previously measured indoor radon concentrations and the estimated values by the GRP model at the same measurement locations. This model can also be used to estimate the GRPs of other areas where radon-related proxy values are available.        

Keywords: Natural radiation, geogenic radon potential, geostatistical analysis, spatial regression model, indoor radon simulation

How to cite: Mousavi, M. and Crowley, Q.: Geogenic radon potential mapping using geospatial analysis of multiple radon-related variables: a case study from Southeastern Ireland, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4884, https://doi.org/10.5194/egusphere-egu2020-4884, 2020.

The accident occurring at the Chernobyl Nuclear Power Plant (ChNPP) in 1986 remains the most prolific in the history of civil nuclear power generation. In the decades since the incident, remote characterisation technologies have advanced significantly in their capabilities. Current knowledge of ¹³⁷Cs distribution within the CEZ is provided by extensive ground sampling investigations conducted at the turn of the millennium. Whilst this method has a high degree of accuracy, it does not allow for local-scale variation to be resolved. Furthermore, the physical collection of samples is labour intensive and suffers from inconsistent sampling densities throughout the extent of the surveyed area. Inconsistent data spacing occurs due to time and resource constraints, terrain difficulties and exposure risk from the physical radiation hazard, which all relate to using humans to collect the samples. Airborne monitoring using UASs is a solution to overcoming the drawbacks experienced from ground-based sampling, albeit coming at a loss of absolute measurement accuracy. This method allows for the creation of a consistent network of sampling points at a high resolution, independent from terrain conditions and without exposing the operators to potentially harmful doses of radiation.

This work presents a comprehensive UAS radiation mapping investigation aiming to evaluate the ¹³⁷Cs distribution within the CEZ using two distinct radiation mapping UASs to conduct surveys at different spatial resolutions. The first comprises of a lightweight (8 kg) fixed-wing UAS equipped with a dual detector payload (2 x 32.8 cm³ CsI[Tl] detectors) to map over large areas at a relatively high forward velocity (14 – 18 m s^-1) and a  medium-low spatial resolution (20 – 60 m pixel^-1). A multi-rotor aerial vehicle is preferred for the second system, which was used to monitor smaller areas of interest (highlighted by the fixed-wing survey), at a higher spatial resolution (3 – 10 m pixel^-1) and a much lower forward velocity of approximately 3 m s^-1. This system was heavier than the fixed-wing variant, weighing approximately 11 kg.

In the seven days of active fieldwork in the CEZ, more than 650 km of combined flight distance was covered by the two systems, characterising a total area of approximately 15 km². Through a series of carefully calibrated processing algorithms, both the ¹³⁷Cs activity (in kBq m^-2) and the dose-rate (µSv hr^-1) resulting from ¹³⁷Cs deposition at one metre above ground level are evaluated. Error propagation through this procedure indicates a base-rate error of 11.5-13.9% in the estimation of ¹³⁷Cs activity from the air, while the basal error for the dose-rate estimation is lower at approximately 5.5 – 6.2%. Minimum detectable activity (MDA) was calculated as 98.1 ± 0.4 kBq m^-2 for the fixed-wing system operating at 40 - 60 m altitude and 33.5 ± 0.9 kBq m^-2 for the multi-rotor at 8 - 20 m altitude.

How to cite: Connor, D., Wood, K., Martin, P., Verbelen, Y., Goren, S., Holland, E., Megson-Smith, D., Smith, N., Richardson, T., and Scott, T.: Multiscale UAS Radiation Mapping Within the Chernobyl Exclusion Zone (CEZ)., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5327, https://doi.org/10.5194/egusphere-egu2020-5327, 2020.

Planning and conduct of aircraft- or drone-based gamma-ray spectrometry surveys may raise the need to simulate and explore the radiation flux from the ground for airborne measurement geometries. Presented here is a simple yet powerful approach to simulating the count rates of gamma-rays measured with standard airborne detector systems and processed with the conventional window method.

The window method is based on energy windows within the gamma spectrum that are associated with the three naturally occurring radioelements potassium, uranium, and thorium. Various correction and processing steps are applied to the integral window count rates using system specific calibration parameters such as stripping ratios, sensitivities and background values to finally derive ground concentrations of the three elements. For a simulation of such gamma-ray data, the count rates produced by the sources to be simulated and recorded by a particular measuring system in a particular geometry must be calculated and noise with matching statistical properties be applied to them. This means that the well-known steps for airborne gamma-ray processing, described e.g. in IAEA (2003), have to be performed in reverse order. This approach reveals some interesting insights into the capabilities and limitations of the airborne radiometrics method.

The simulation process itself starts with the design of the simulated survey features. This includes the survey area location and size, the course and spacing of the survey lines and the sampling distance. From these parameters, a dataset is constructed that contains the positions of the sampling points. Also, the relevant system parameters are defined. In the next step, the radiometric conditions of the area are designed. This is done by discretizing the survey area in grid cells and assigning concentration values to each cell according to the desired ground source distribution. Count rates for each grid cell can now be calculated and the count rate grids are subsequently processed using a geometric response filter that simulates the footprint properties of the detector at the selected survey height. Finally, after applying noise of matching statistical properties to the filtered grids, they are scanned along the sampling positions, leading to a dataset that contains the simulated airborne gamma-ray data.

The simulated dataset can be utilized in various ways to explore the influences of survey, system, source and environmental parameters on the recorded window count rates. The benefit of the proposed approach is that common workflow procedures as preferred by the user can be directly applied to the data and the resulting maps can be inspected in the usual way. Furthermore, processing algorithms and methods such as filtering and statistical levelling can be tested and optimised. In this contribution, the way the simulation works is outlined and the results are illustrated by means of various examples.

IAEA, 2003. Guidelines for radioelement mapping using gamma ray spectrometry data. IAEA-TECDOC No. 1363, Vienna.

How to cite: Ibs-von Seht, M.: Simulation of airborne gamma-ray data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4786, https://doi.org/10.5194/egusphere-egu2020-4786, 2020.

*davaakhuu@caesar.elte.hu

The ¹³⁷Cs is a principal radioisotope introduced into the environment through the atmospheric bomb tests (from 50s to 60s) and the major nuclear accidents (Chernobyl, 1986 and Fukushima, 2011).  From atmosphere, ¹³⁷Cs adsorbs to precipitation and returns to lithosphere by wet and dry deposition as radioactive fallout component.  Due to the Chernobyl nuclear accident, the released contaminated air mass contained particles with attached Cs, largely propagated, deposited and distributed across northern and eastern European countries in the ambient environment (Balonov et al., 1996) in case of Fukushima disaster also contributes to the increase, but only by minor amount.  These particles could have reached the houses (e.g. through open windows, doors, fractures, and vents) in urban environment and deposited inside resulting in the exposition of the habitants to ¹³⁷Cs.  In areas that are not accessible for regular cleaning (e.g., attics) physical state and chemical composition of attic dusts remain constant i.e. unchanged in time.

Accordingly, undisturbed attic dust samples from Salgótarján (Hungary), a former heavy industrial city, were collected and studied as past records of anthropogenic pollution, with intention of elucidating the pathways of radioactive contamination in urban environment.

The specific activity of Cs-137 was measured in 36 attic dust samples.  Construction ages of the selected houses range from 1880 to1989, a selection criterion superimposed on the 1x1 km grid design. The Homogenized samples (amount: 1-1.5 g, grain size: <0.125 mm) were analyzed by a well-type HPGe detector placed in a low-background iron chamber at the laboratory of the Hungarian Center for Energy Research.  The obtained ¹³⁷Cs activity ranges from 4.34 ± 0.27 Bq/kg ^-1 to 140.74 ± 1.66 Bq/kg ^-1 (Detection limit: 0.75 Bq/kg ^-1).  Arithmetic mean of the values is 73.32 ± 1.58 Bq/kg ^-1, whereas geometric mean and standard deviation is 59 ± 1.36 Bq/kg ^-1 and 39.83 ± 0.76 Bq/kg ^-1, respectively (all decay corrected into year of sampling, 2016). Specific activity of radionuclide is higher than result published in other regions of Hungary and neighboring countries.  This confirms that attic dust is very effective material for monitoring past fallouts of production from early nuclear weapon testing and nuclear catastrophe(s).

Our results performed that a higher activity concentration of ¹³⁷Cs is found in the oldest houses (1890-1970) were present in the high elevated areas. Thus, it indicates that deposition of ¹³⁷Cs was strongly influenced by local physical conditions (geomorphology and meteorology).  Due to the geostatistical analysis, interpolation was done with ordinary point kriging using the obtained variogram model.  Adjusted model shows a best fit (r²=0.606) with spherical model.  The results of ¹³⁷Cs activity concentration suggest a good spatial dependency verifying our sampling strategy.  Therefore, it can be considered that attic dust remained undisturbed for decades and preserve past records of components of atmospheric pollution.

Keywords: attic dust, ¹³⁷Cs activity concentration, geostatistical analysis, urban environment, high altitude, Hungary

Reference:

Balonov, M., Jacob, P. és Minenko, V. (1996) Pathways, Levels and Trends of Population Exposure after the Chernobyl Accident, Radiological Consequences of the Chernobyl Accident.

How to cite: Tserendorj, D., Völgyesi, P., Szabó, K. Z., Abbaszade, G., Le Tan, D., Salazar, N., Zacháry, D., Cong Nguyen, T. C. N., and Szabó, C.: Spatial variation of Cs-137 activity concentration in urban environment using attic dust samples from city of Salgotarjan in northern part of Hungary, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1195, https://doi.org/10.5194/egusphere-egu2020-1195, 2020.

Radon is a radioactive gas which emanates from rock, soil and water. Radon concentrations in the
atmosphere are generally very low (typically <5 Bq m-3), however it can occur at much higher levels
in soil (typically 10’s-100’s kBq m-3), or enclosed spaces such as buildings and caves (typically 10’s-
100’s Bq m-3). Exposure to radon and its daughter products is associated with an elevated risk of
developing lung cancer. Ireland has a population weighted indoor radon concentration of 98 Bq m-3
resulting in an estimated 300 annual lung cancer cases per year, representing approximately 12% of
the annual lung cancer cases. A national-scale legislative radon-risk map has a 10 x 10 km spatial
resolution and is based exclusively on indoor radon measurements (i.e. it does not contain any
geological information). The legislative map satisfies the European Council Directive
2013/59/EURATOM Basic Safety Standard, in that it defines “high radon” areas as those where >10%
of homes are estimated to exceed the national reference level of 200 Bq m-3. New buildings in such
areas are legally required to have a barrier, with low radon permeability installed.

This research focuses on a karstic region of SE Ireland, which features some exceptionally high
indoor radon concentrations (65,000 Bq m-3), even though it is not classified as a “high radon” area
on the national legislative map. Here we demonstrate the use of measuring sub-soil radon
concentrations and sub-soil permeability, in order to construct a radon potential (RP) map of the
area. Extremely high sub-soil radon concentrations (>1443 kBqm-3) and radon potential values
(>200) are spatially associated with Namurian shales, interbedded with limestone. Overall, we
classify the study area as high radon potential (RP >35) using this technique. We suggest all areas
underlain by Namurian shales in Ireland should undergo similar radon potential mapping, and if
necessary, should be re-designated as “high radon” areas. If deemed appropriate (i.e. where RP
>35), such a designation will help to protect the general public from the harmful effects of indoor
radon exposure, and will help to lower the incidence of radon-related lung cancer in these areas.

How to cite: Hughes, M. and Crowley, Q.: Using geogenic radon potential to assess designation of radon priority areas in Ireland, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4672, https://doi.org/10.5194/egusphere-egu2020-4672, 2020.

Legacies from uranium mining pose an acute risk to human health and the environment in Central Asia in the countries of Kyrgyzstan, Tajikistan, Uzbekistan and Kazakhstan. This risk is due to the emission of radioactive radiation and the potential contamination of groundwater with radionuclides from the mining residues. A precise knowledge of the location and the contained concentrations of these contaminated sites is necessary in order to obtain an assessment of the hazard and to define areas with the highest remediation priority.

The Federal Institute for Geosciences and Natural Resources in Germany (BGR) currently carries out the project DUB-GEM (Development of a UAV-based Gamma spectrometry for the Exploration and Monitoring of Uranium Mining Legacies), funded by the German Federal Ministry of Education and Research. Within the project, an Unmanned Aerial Vehicle (UAV) based system is to be developed with which the exploration of contaminated sites can be carried out both with low risk for the measurement technician and quickly and cheaply. The challenge lies in the nuclide-specific determination and differentiation of heap and tailing materials with airborne measurements and scintillation detectors. Due to the low spectral resolution of such detectors, this was not possible for a long time. However, with new technologies, scintillation materials and better computer algorithms there is now a potential to solve the problem.

In the DUB-GEM project, one of the detectors to be used will be a large volume (600 ml) CeBr3-detector. In preparation for the field campaign in 2021, we calculated theoretical gamma spectra for this detector using Monte Carlo simulations with the program MCNP6. The simulations were done for varying survey parameters such as flying height and speed, as well as for varying source parameters such as nuclide-specific composition and ground distribution of the mining residues to be mapped. The results of the theoretical investigations will be used to design and optimize survey parameters and to estimate minimum detectable activities.

How to cite: Preugschat, B. and Ibs-von Seht, M.: Gamma spectra from uranium mining residues simulated for airborne geometries and detectors, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5074, https://doi.org/10.5194/egusphere-egu2020-5074, 2020.

The Canary Islands are an archipelago with an area of 7,447 km² comprising seven main islands and some islets, located about 90 km off the northwest coast of Africa. La Palma is the most active volcanic island of the Canarian archipelago in historical times (after XV Century), with an area of 706 km² and about 83,000 inhabitants. From the geochemical point of view, La Palma is characterized by alkaline rocks ranging from basanites and alkali picrites to phonolites. Despite the different geological units essentially overlap in their bulk chemical compositions, there are significant differences.

Measurements of natural gamma radiation were carried out in 71 sites randomly selected on a predefined 3x3 km sampling grid covering the whole island in 2013. Total outdoor gamma radiation levels were measured at 1 m above the ground. Air gamma radiation was measured by means of a MINI 6-80 (Mini-Instruments) monitor equipped with an energy-compensated Geiger-Müller MC-71 probe and FH 40 GL 10 (ThermoFischer Scientific) dosimeter equipped with a proportional-gas detector. The background radiation was calculated for each sampling site and subtracted for each dose measurement. Additionally, 25 soil samples were collected at a depth of 0-15 cm in uncultivated fields. Radiometric measurements for ⁴⁰K, ²²⁶Ra and ²³²Th radioisotopes were performed by low-level gamma spectrometry with coaxial-type germanium detectors (Canberra Industries Inc., USA).

The gamma absorbed dose rates showed a log-normal distribution, ranging from 37.2 up to 134.0 nGy·h^-1, with a geometric mean of 64.5 nGy·h^-1. The observed mean gamma absorbed dose rate in La Palma Island was higher than those measured in La Gomera Island (43.9 nGy·h^-1), and lower than those measured in Tenerife (89.2 nGy·h^-1) and El Hierro islands (93.3 nGy·h^-1) (publication in preparation). The geometric means of ⁴⁰K, ²²⁶Ra and ²³²Th activity concentration were 216.1 Bq·Kg^-1, 22.0 Bq·Kg^-1 and 23.6 Bq·Kg^-1, respectively.

Maps with the spatial distribution of the terrestrial natural gamma radiation and ⁴⁰K, ²²⁶Ra and ²³²Th radioisotopes were also prepared and compared with the geochemical composition of soils. Contour maps for the terrestrial radiation component of the absorbed dose rate and radioisotope distributions were obtained using ordinary Kriging interpolation. Lower absorbed dose rates (between 45 and 70 nGy h^-1) were observed in the oldest northern part of the island, corresponding to the Taburiente and Garafía basaltic shields. Two anomalies were found with absorbed dose rate values between 80 and 110 nGy h^-1. The first one is located at the Bejenado stratovolcano, extending north to the Caldera de Taburiente, and south to the Aridane Valley. The second anomaly was found in the southeastern part of the Cumbre Vieja ridge. This last volcanic edifice corresponds to the youngest part of the island, where several historical eruptions have occurred. These anomalies might be related to phonotrephritic and phonolitic rocks identified at the upper part of the Bejenado sequence and Cumbre Vieja edifice.

How to cite: López-Pérez, M., Salazar-Carballo, P. Á., Martín-Luis, M. C., Lorenzo-Salazar, J. M., Duarte-Rodríguez, X., Catalán-Acosta, A., Gijón-Aguado, Á., and Hernández-Armas, J.: Natural gamma radiation in La Palma Island, Canary Islands, Spain, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8436, https://doi.org/10.5194/egusphere-egu2020-8436, 2020.

In this paper, six typical adsorption materials (activated carbon, kaolin, montmorillonite, bentonite, zeolite, and attapulgite) were used to investigate the effects of adsorption time, initial concentration, pH, and temperature on the adsorption of cesium (Cs) contained in wastewater. A combination of kinetics and isotherms was used. The results revealed that, for the same adsorption time, the adsorption efficiencies of the six materials for Cs were as follows: zeolite>attapulgite>bentonite>montmorillonite>activated carbon>kaolin. The adsorption rate of zeolite to Cs ions was almost independent of the initial concentration and temperature. The removal effect of other materials improved in alkaline environments at 30℃. Attapulgite, montmorillonite, activated carbon, and kaolin could be used for the removal of Cs at low initial concentrations. The adsorptive processes utilized by the six adsorption materials were the result of a combination of various adsorption mechanisms. Among the six typical adsorption materials, zeolite, attapulgite, and bentonite had clear removal effects and could be used in practical application in which radioactive wastewater containing Cs needs to be disposed of. Our results suggest that zeolite is the best adsorption material for this purpose.

How to cite: Du, C., Wang, J., Liu, X., and Niu, J.: A comparative study of the adsorption efficiency of typical adsorption materials for wastewater containing cesium, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12275, https://doi.org/10.5194/egusphere-egu2020-12275, 2020.

In the Central Asian countries of Kyrgyzstan, Tajikistan, Uzbekistan and Kazakhstan, uranium production activities during the Soviet era have led to a large number of mining legacies. The mining residues can show significant levels of radioactive contamination. Due to the mountainous landscape and the geotechnical conditions at these sites, there is a risk of uncontrolled release of radioactive contaminants into the environment and into cross-border rivers in the region. The situation is exacerbated further by the fact that the countries are prone to natural hazards such as earthquakes, floods, mudflows and landslides. There is an urgent need to map locations, extent and inventory of the contaminated areas in order to be able to support remediation measures and monitor the long-term stability of the remediated legacies.
The research project DUB-GEM funded by the German Federal Ministry of Education and Research (grant no. 01LZ106A-C) deals with the development of a UAV-based gamma spectrometry for the exploration and monitoring of uranium mining legacies. The aim of the three-year project is to develop and apply a method that allows regulatory authorities and operators to map contaminated sites rapidly and economically using gamma spectrometers mounted on a UAV (unmanned aerial vehicle). The main tasks of the project are to select and configure suitable detectors, to develop flight, measurement, and data processing strategies and to design an airframe that is ideally suited to carry out the surveys. In this contribution we present the current status of the project, including the design of the UAV prototype, results of the first test and calibration measurements with the selected gamma spectrometers and an outlook on upcoming project activities.

How to cite: Altfelder, S., Arndt, R., Ibs-von Seht, M., Kunze, C., Preugschat, B., Schröder, M., Schulz, H., and Wiens, B.: UAV-based mapping of radioactive contamination of uranium mining legacies in Central Asia , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13503, https://doi.org/10.5194/egusphere-egu2020-13503, 2020.

It is necessary to develop environmentally benign methods for removing uranium from various environments due to its high toxicity and radioactivity. Among the methods, we used fungal biosoprtion using newly isolated Cladosporium sp. strain F1. Extensive absorption of presynthesized nanoplates of uranium-phosphate minerals was observed on the hyphae of the Cladosporium sp. strain F1. In addition, once soluble UO₂²⁺ species was added to the culture of Cladosporium sp. strain F1, uranium mineral plates were also observed on the surface of the fungus hyphae over a range of pH. This was confirmed by EDX analyses, and SEM, AFM, and thin sectional TEM image analyses. The maximum biosorption capacity of uranyl ions was 74.3 mg g⁻¹ at pH 6.0. In general, biosorption capacity of Cladosporium sp. strain F1 was better than that of Aspergillus niger strain to uranium minerals. In conclusion, this study showed that the newly isolated fungus Cladosporium sp. strain F1 could be a cost-effective and environmentally friendly biosorbent to remove toxic uranium from aqueous environments.

How to cite: Lee, J. and Hur, H.-G.: Uranium phosphate mineral adsorption to newly isolated fungus Cladosporium sp. strain F1, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22387, https://doi.org/10.5194/egusphere-egu2020-22387, 2020.

The CORSAIR (Cloud Oriented Radiation Sensor for Advanced Investigation of Rocks) project was born to meet the EU guidelines 2013/59/EURATOM on safety standards for protection against ionizing radiations. The project designed an automated system capable of providing a real-time measurement of the radioactive activity concentration index for building materials according to regulations of more than 20 different countries. Measurements are conducted through in situ gamma-ray spectroscopy techniques on 3 x 3 x 3 m³ blocks of rock at quarries and processing centers, and quantify the activities, the abundances and the related effective dose-rates of natural radionuclides (⁴⁰K, ²³²Th, ²³⁸U and their progenies) in stone materials for the building industry. The detector comprises a 2” x 2” cylindric CeBr₃ crystal having a 2.5% energy resolution at 1461 keV. A lateral lead shield of 1.3 cm enables a ~60% reduction of the gamma signal coming from above and beside the detector. The system is designed for providing the radiometric index in less than 30 min with an overall uncertainty of the order of 5%.

The innovative aspects of the detector are in its autonomous operation and the easy fruition of the results of the material characterization. Energy calibration and peak recognition are automatically performed on‑board through an innovative stochastic method based on simulated annealing. The computation of the results is fully-automated and requires no intervention of the operator. The battery-powered detector is equipped with GPS, LoRa, Bluetooth and Wi-Fi connectivity and can be remotely controlled thanks to a dedicated Android app. Acquired data and activity indexes are synced through LoRa connectivity to a cloud database, where they can be easily accessed by sellers and buyers, thus preventing the placing on the market of blocks hazardous to public health.

How to cite: Serafini, A., Alberi, M., Carconi, P., Chiarelli, E., De Felice, P., Deserventi, A., Donati, M., Fanchini, E., Giordano, F., Grignani, P., Iovene, A., Luciani, L., Manessi, G., Mantovani, F., Marini, M., Morichi, M., Pepperosa, A., Raptis, K. G. C., Rogo, F., and Strati, V. and the CORSAIR: Making radioactivity measurements on building materials accessible to everyone, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1149, https://doi.org/10.5194/egusphere-egu2020-1149, 2020.

In groundwater, the soluble members of the uranium decay chain such as uranium, radium, and radon can be found in significant concentration. Their distribution is affected by physicochemical properties such as pH, redox potential and chemical composition of the groundwater. Uranium can be mobilised under oxidising conditions especially in the water where the pH is near neutral and has high alkalinity. In contrast, radium is mobile in reducing environment, enhanced by the presence of carbonate, sulphate, chloride. These parameters vary along the groundwater flow paths and with regard to the change of regime characteristics. Areas with recharge regime and discharge points of local flow systems are characterised by oxidising environment while discharge areas of higher-order systems tend to be reducing. The natural radioactivity of groundwater, as a possible threat for human health, has been investigated for a few decades as groundwater is a very common drinking water source. In Hungary, 96% of the water supply relies upon groundwater. Following the Euratom Drinking Water Directive the radioactivity of drinking water is screened in Hungary by gross alpha and gross beta activity measurements. Whenever the measured concentrations surpass the limit values the long-term consumption of the water can lead to health issues. High values of gross alpha activity can be found in the foreland of Lake Velence. Previous studies have already shown high uranium concentration values (compared to average crust values) related to the Velence Granite Formation in Velence Hills and to the carbonatic and organic-rich beds of the Ujfalu Formation in the foreland of Lake Velence. Until recently no observations and measurements were made regarding the radioactivity of the groundwater. Therefore, uranium, radium, and radon concentration measurements were carried out in the adjacent area and interpreted in flow system context. A total of 53 samples were taken from surface water as well as from groundwater. Alpha spectrometry applied on Nucfilm discs was used to measure the uranium (U-234, U-238) and radium (Ra-226) activity while radon (Rn-222) activity was determined by TriCarb 1000 TR liquid scintillation detection. Pressure-elevation profiles, hydraulic cross-sections, tomographic potential maps were compiled to understand the groundwater flow directions and regime characteristics in the wider area. The areal distribution of the activity concentration values was interpreted regarding the groundwater flow system, physicochemical parameters measured onsite and in the laboratory. Those areas can be delineated where according to the flow conditions and the related geochemical environment the mobility of the uranium or radium and thus elevated activity concentration can be expected in groundwater. The results of the study have proved that the areal variability of the natural radioactivity of the groundwater is strongly affected by the groundwater flow conditions along with geological features. This flow system approach and its methodology may facilitate the safe water management of drinking water supply systems.

This study was supported by the ÚNKP-17-4 and ÚNKP-18-3 New National Excellence Program of the Ministry of Human Capacities and it has also received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 810980.

How to cite: Baják, P., Csondor, K., Surbeck, H., Izsák, B., Vargha, M., Horváth, Á., Pándics, T., and Erőss, A.: How can flow system approach help to understand the natural radionuclide content of the drinking water originated from groundwater sources? Case study in the vicinity of a granitic complex, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1181, https://doi.org/10.5194/egusphere-egu2020-1181, 2020.

The SMEAR Estonia is a Station for Measuring Ecosystem-Atmosphere Relations (SMEAR). It is built on the same concept as the Finnish SMEAR stations ^[1] and belongs to the same measurement network. It is located in a hemiboreal forest at Järvselja, South-Eastern Estonia (58.2714 N, 27.2703 E at 36 m a.s.l.) ^[2]. The Estonian University of Life Sciences runs long-term measurements on meteorological parameters, trace gases and fluxes at the station. Atmospheric aerosol and air ions measurements are deployed by the University of Tartu (UT). 

Our main interest at UT lies in characterising atmospheric ions and aerosols, studying their connections to atmospheric new particle formation and cloud processes, and understanding the impacts of these processes on air quality, local weather and climate. Air ions are known to participate in forming atmospheric new particles ^[3]. Newly formed aerosol particles have the potential to modify cloud properties, once they reach big enough sizes via condensational and coagulational growth^[4]. Air ions are primarily produced by the ionisation of air molecules, with the ionisation energy provided by natural radioactivity present in the atmosphere. The initial ionisation produces are subject to different dynamic processes, including charge transfer, clustering, coagulation and condensational growth ^[5]. At UT, we are launching a five-year project, starting from Jan. 2020, to investigate how atmosphere transforms the new-born air ions to climatically relevant aerosol particles. In order to get insights into the transformation process, atmospheric radioactivity measurements are crucial together with air ion and aerosol measurements.

In the lower troposphere, ionization of the atmospheric originates from the decay of radon and other radioactive nuclides in the air and the Earth's crust as well as cosmic radiation. In collaboration with the Finnish Meteorological Institute, we initiated atmospheric radioactivity measurements at the SMEAR Estonia. The total gamma radiation (50 keV to 1.3 MeV) is measured with a gamma radiation meter (RADOS RD-02L) (since June 2019). The atmospheric radon is monitored using a filter-based Geiger-Müller counter (since Nov. 2019), which is a one-counter variation of an earlier design^[6]. Atmospheric radon concentration is determined based on deposited beta activity. Preliminary results show that SMEAR Estonia (mean gamma dose rate = 0.03 uSv/h, mean radon conc. = 2.5 Bq/m³) has less ionization than SMEAR II station in Finland (mean gamma dose rate = 0.08 uSv/h, mean radon conc. = 2 Bq/m³). The linkage of this observation to air ion properties is under progress.

References:

[1]       Hari P., Kulmala M., Boreal Environ. Res. 2005, 10, 315-322.

[2]       Noe S. M. et al., Forestry Studies 2015, 63.

[3]       Tammet H. et al., Atmospheric Research 2014, 135-136, 263-273.

[4]       Merikanto J. et al., Atmos. Chem. Phys. 2009, 9, 8601-8616.

[5]       Chen X. et al. Atmos. Chem. Phys. 2016, 16, 14297-14315.

[6]       Paatero J. et al., Radiat. Prot. Dosim. 1994, 54, 33-39.

How to cite: Junninen, H., Paatero, J., Hõrrak, U., and Chen, X.: Atmospheric radioactivity measurements at the SMEAR Estonia Station, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19757, https://doi.org/10.5194/egusphere-egu2020-19757, 2020.

Radon is newly considered a risk factor for lung cancer. Traditionally, radon is used as a curative in spa. One way of balneation is radon inhalation in mines (eg Bad Gastein in Austria and Boulder mine in USA), where patients are exposed for several tens of minutes to hours to air activity in the order 10^3 to 10^4 Bq m-3 222Rn. Even higher activities can be found in abandoned uranium mines, often in the order 10^4 to 10^5 Bq m-3 222Rn in the poorly ventilated parts. These underground spaces are often visited by mineral collectors and montanists. In two abandoned uranium mines, the progression of surface beta activity of hair during the stay was monitored and the value and shape of the gamma dose-rate field was measured immediately after mine leaving.

Beta activity increases irregularly, due to the walking between areas with a different radon activity. The highest surface beta activity of hairs was at the end of the stay, with a maximum of 320 Bq cm-2. After leaving the mine, activity decreases exponentially with an effective half-life of about half an hour. Gamma activity was measured after a two-hour stay in an environment with radon activities ranging from 3.7*10^4 to 2.3*10^5 Bq m-3. The gamma field has the shape of a human figure. Especially the lungs and abdominal fat showed increased gamma. The highest gamma dose-rate was measured on hairs, up to 9 µGy h-1. Thus, a combination of surface activation, Rn-product deposition in the lungs, and dissolution of radon in the blood and its redistribution in the body were observed.

How to cite: Golias, V.: Activation of the human body exposed to high radon activity, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17988, https://doi.org/10.5194/egusphere-egu2020-17988, 2020.

Recent studies demonstrated how accurate beryllium 7 can be used as proxy to predict seasonal weather, in particular Indian monsoons, climate change patterns such as tropopause height changes, tropopause breathing and Jet Stream stalling.

Beryllium 7 studies also prove that climate change phenomena are not driven by solar flux or earth magnetic field but are only partially influenced by them.

In this work we will compare recent tropopause height data with Beryllium 7 in order to build a comparative scale between the 2 parameters, including a focus on QBO (quasi-biennual oscillation) to quantify the effect of QBO on the analysed beryllium 7 data.

How to cite: Terzi, L., Wotawa, G., Staten, P. W., Luan, L., Gabriel, A., and Kalinowski, M.: A new comparative scale between tropopause height and beryllium 7 and the weight of quasi-biennial oscillation (QBO) effect., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7978, https://doi.org/10.5194/egusphere-egu2020-7978, 2020.

Radon-222 is a progeny of Uranium-238, naturally present in the Earth’s crust. After its migration through the soil, it reaches the atmosphere. The Radon progenies are then adsorbated to aerosol particles. The particles are scavenged by falling rain drops, leading a large amount of radon progenies to the ground. This sudden addition of radon progenies explains to the gamma dose rate peaks occurring during rainfall events.

An atmospheric radon modelling chain was developed. It is based on the IRSN long-range atmospheric transport modelling, and can be used to forecast or to reanalyze these events. The peaks are observed hundreds times a year on radioactivity monitoring networks in France. Then, a comprehensive statistical comparison can be achieved to evaluate the modelling, in particular its atmospheric transport component.

Less than half of the gamma dose rate peaks simulated matches the observed ones. We considered false positive – peaks simulated but not observed – and false negative – peaks observed but not simulated. Radon exhalation spatial distribution and seasons seem to have a major impact on the model capability to reproduce these peaks. The choice of rain data is also essential for a better simulation.

Beyond other validation cases, IRSN now has a validation tool, the database of which is populating on a daily basis, to evaluate the long-range atmospheric transport model used for emergency purposes. The quality of this response is a critical issue and has to be constantly improved. The statistics on the gamma dose rate peaks will improve our understanding of the phenomena. It will also be used to validate the improvement made on the accuracy of the radon exhalation spatial distribution.

How to cite: Quérel, A., Quélo, D., Doursout, T., and Gréau, C.: Lessons learned on atmospheric radon modelling by statistical model-to-data comparison on gamma dose rate peaks, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14940, https://doi.org/10.5194/egusphere-egu2020-14940, 2020.