Mapping the geogenic radon potential for Germany by machine learning

The radioactive gas radon (Rn) is considered as an indoor air pollutant due to its detrimental effects on humanhealth. In fact, exposure to Rn belongs to the most important causes for lung cancer after tobacco smoking. Thedominant source of indoor Rn is the ground beneath the house. The geogenic Rn potential (GRP) - a functionof soil gas Rn concentration and soil gas permeability - quantifies what“earth delivers in terms of Rn”and rep-resents a hazard indicator for elevated indoor Rn concentration. In this study, we aim at developing an improvedspatial continuous GRP map based on 4448field measurements of GRP distributed across Germany. Wefittedthree different machine learning algorithms, multivariate adaptive regression splines, random forest and supportvector machines utilizing 36 candidate predictors. Predictor selection, hyperparameter tuning and performanceassessment were conducted using a spatial cross-validation where the data was iteratively left out by spatialblocks of 40 km*40 km. Thisprocedure counteracts the effectofspatial auto-correlation in predictorand responsedata and minimizes dependence of training and test data. The spatial cross-validated performance statistics re-vealed that random forest provided the most accurate predictions. The predictors selected as informative reflectgeology, climate (temperature,precipitation and soil moisture), soil hydraulic, soilphysical (field capacity, coarsefraction) and soil chemical properties (potassium and nitrogen concentration). Model interpretation techniquessuch as predictor importance as well as partial and spatial dependence plots confirmed the hypothesized domi-nant effect of geology on GRP, but also revealed significant contributions of the other predictors. Partial and spa-tial dependence plots gave further valuable insight into the quantitative predictor-response relationship and itsspatial distribution. A comparison with a previous version of the German GRP map using 1359 independent testdata indicates a significantly better performance of the random forest based map

European radon abatement policy: state and ongoing discussion

Radon is a hazardous air pollutant which can cause detriment to individuals and to the society. Thus, the natural consequence is avoiding it or in practice, limiting exposure. This has led to regulation on national and international level whose objective is reduction of radon exposure. In Europe, the Basic Safety Standards (BSS) issued in 2013, whose implementation is mandatory for EU Member States, caused a boost to efforts towards radon regulation as well as to radon research since a number of components of radon abatement policy appeared not resolved sufficiently reliable in the sense of quality assurance. In this contribution, we present the state of implementation of EURATOM Basic Safety Standards in Europe and in Germany, as a particular example. We also address a number of topics currently discussed

Analysis of specific radionuclides activity variations in soil within geotectonic units of Republic of North Macedonia

To establish baseline values for concentrations of terrestrial radionuclides for the Republic of North Macedonia, a survey covering the entire territory was performed. The 213 soil samples were collected from regions around the major settlements and cities, approximately evenly distributed over the geotectonic units which constitute the country's geological foundation. The specific activities of radionuclides were measured by gamma spectrometry. The following geometric mean values and geometric standard deviations were obtained: 550 Bqkg(-1) (1.47) for K-40, (37) Bqkg(-1) (1.33) for Ra-226, 38 Bqkg(-1) for U-238, and 38 Bqkg(-1) (1.53) for Th-232 in dry soil. The relation between specific activities of natural radionuclides and geology was investigated. Correlation between radionuclides, which may serve as additional geochemical indicators, and geology could not be found convincingly,. Mutual correlations between Ra-226, U-238, and Th-232 activities were found to be high (Spearman rho about 0.8), whereas the ones between these and K-40 are a bit lower, somewhat above rho = 0.6

The first version of the Pan-European Indoor Radon Map

A hypothetical Pan-European Indoor Radon Map has been developed using summary statistics estimated from 1.2 million indoor radon samples. In this study we have used the arithmetic mean (AM) over grid cells of 10 km10 km to predict a mean indoor radon concentration at ground-floor level of buildings in the grid cells where no or few data (N < 30) are available. Four interpolation techniques have been tested: inverse distance weighting (IDW), ordinary kriging (OK), collocated cokriging with uranium concentration as a secondary variable (CCK), and regression kriging with topsoil geochemistry and bedrock geology as secondary variables (RK). Cross-validation exercises have been carried out to assess the uncertainties associated with each method. Of the four methods tested, RK has proven to be the best one for predicting mean indoor radon concentrations; and by combining the RK predictions with theAMof the grids with 30 or more measurements, a Pan-European Indoor Radon Map has been produced. This map represents a first step towards a European radon exposure map and, in the future, a radon dose map

Some results of a radon survey in 207 Serbian schools

In this paper the results of radon concentration measurements performed in 207 schools in 7 communities of Southern Serbia are presented. The annual radon concentration varied from 17 Bqm-3 to 428 Bq m-3 with a median value of 96 Bq m-3. The arithmetic mean (AM) of the 207 annual averages was 118 Bq m-3 with a standard deviation (SD) of 78 Bq m-3. The best distribution fitting of radon concentration by log-normal function was obtained. The log-normal parameters are the following: geometric mean (GM) = Bq m-3, geometric standard deviation (GSD) = 1.9. In addition, a spatial distribution of the indoor radon concentration over the investigated areas is observed.JRC.E.8-Nuclear securit

Comparison of radon mapping methods for the delineation of radon priority areas - an exercise

Background: Many different methods are applied for radon mapping depending on the purpose of the map and the data that are available. In addition, the definitions of radon priority areas (RPA) in EU Member States, as requested in the new European EURATOM BSS (1), are diverse. Objective: 1) Comparison of methods for mapping geogenic and indoor radon, 2) the possible transferability of a mapping method developed in one region to other regions and 3) the evaluation of the impact of different mapping methods on the delineation of RPAs. Design: Different mapping methods and several RPA definitions were applied to the same data sets from six municipalities in Austria and Cantabria, Spain. Results: Some mapping methods revealed a satisfying degree of agreement, but relevant differences were also observed. The chosen threshold for RPA classification has a major impact, depending on the level of radon concentration in the area. The resulting maps were compared regarding the spatial estimates and the delineation of RPAs. Conclusions: Not every mapping method is suitable for every available data set. Data robustness and harmonisation are the main requirements, especially if the used data set is not designed for a specific technique. Different mapping methods often deliver similar results in RPA classification. The definition of thresholds for the classification and delineation of RPAs is a guidance factor in the mapping process and is as relevant as harmonising mapping methods depending on the radon levels in the area.Funding: This work is supported by the European Metrology Programme for Innovation and Research (EMPIR), JRPContract 16ENV10 MetroRADON (www.euramet.com). The EMPIR initiative is co-funded by the European Union’s Horizon 2020 research and innovation programme and the EMPIR Participating States

Design, Analysis, and Fabrication of a Snake-Inspired Robot with a Rectilinear Gait

Snake-inspired robots display promise in areas such as search, rescue and reconnaissance due to their ability to locomote through tight spaces. However, several specific issues regarding the design and analysis must be addressed in order to better design them. This thesis develops kinematic and dynamic models for a class of snake-inspired gait known as a rectilinear gait, where mechanism topology changes over the course of the gait. A model using an Eulerian framework and Coulomb friction yields torque expressions for the joints of the robot. B-spline curves are then used to generate a parametric optimization formulation for joint trajectory generation. Exact gradient computation of the torque functions is presented. A parametric model is used to describe the performance effects of changing system parameters such as mass, length, and motor speed. Finally, a snake-inspired robot is designed and fabricated in order to demonstrate both the vertical rectilinear gait and a modular, molded design aimed at reducing the cost of fabrication

Similarities and differences between radon surveys across Europe: results from MetroRADON questionnaire

Background: As a major cause of lung cancer after smoking, indoor radon is a hazard for human health. Key steps of radon surveys are numerous and include metrology, survey design, development of maps, communication of results to stakeholders, etc. The Council Directive 2013/59/EURATOM introduced new challenges for European Union Member States, such as the identification of radon priority areas, which calls for efforts to improve all the key steps involved in radon surveys. Objective: This study aims to compare existing radon measurement procedures between different European countries and to use the results to optimize the consistency of indoor radon data across Europe. Design: A questionnaire was developed and sent to more than 70 European institutions working in this field to collect information on indoor radon surveys carried out in the respective countries, in order to identify the rationale and methodologies used. Results: A total of 56 questionnaire forms on indoor radon surveys were completed and returned by universities, research institutions, and competent authorities on national and regional surveys from 24 European countries. The replies have been analyzed, and the main findings have been reported, although these replies did not allow to answer all the questions about comparability. Conclusions: From the replies given by the respondents, there is evidence that European indoor radon surveys are comparable regarding measurement methods but not comparable regarding the survey design. Comparability regarding data management, statistical treatment, aggregation, and mapping is unclear on the basis of the replies putting in evidence the need of further information

Radon levels in dwellings and workplaces: a comparison with data from some European countries

Background: According to 2013 European Basic Safety Standards (EU BSS), legal and administrative consequences of having an area declared as radon priority area (RPA) concern workplaces (WP) and public buildings, as well as dwellings (DW). However, RPAs in many cases are defined as higher levels of indoor radon in DW. The reason is that most data are available for DW. So far, indoor radon data for WP (except for schools) and public buildings are scarce. Objective: The objective of this study was to compare indoor radon levels in DW and WP in a given area and to evaluate whether they have different distributions and different average levels. Design: Austria, Finland, Germany, and Italy provided indoor radon data on DW and WP. Data related to WP were aggregated in the same grid, as already done for data on DW, to update the European Indoor Radon Map. Based on 10 km × 10 km grid cells, the same statistics are computed for both datasets. Thus, two structurally equal datasets for each country were generated to be statistically compared. Results and conclusions: Generally, there are numerous indoor radon data on DW than data on WP. Statistical analysis suggests that in all the countries, indoor radon levels – in terms of arithmetic mean (AM) of the natural logarithm-transformed data – in WP and DW are statistically different (P < 0.05), as well as from those referring to schools. The difference in distributions is neither attributable to the effect of geology nor to the effect of different sample sizes. The correlation between aggregated data is positive in the sense that if the mean (over grid cells) radon concentration increases in DW, it increases in WP as well. Compared with DW, in all countries indoor radon levels in WP seem to be statistically different, but the results are not enough to draw final conclusions: on-purpose designed surveys could be a useful tool to better understand this phenomenon