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Natural radioactivity and radon exhalation rate of Sardinian dimension stones
Get PDFDue to the ever-growing public concern about radon risk arising from building materials, the radon exhalation rates and the natural radioactivity of eighteen dimension stones mostly used in Sardinia and widely exported worldwide have been estimated by means of laboratory tests. Some of the quarrying companies that operate within the Sardinian territory provided the samples to be tested, which include twelve granitoids, four pyroclastic rocks and two basalts. The Activity Concentration Index (Iɤ), the External Radiation Hazard Index (Hex) and the Radium equivalent activity (Raeq) were calculated for each rock sample under investigation, based on the estimated values of 222Rn exhalation rate and 226Ra, 232Th and 40K radioactivity concentration. A poor correlation between radon release rates and 226Ra radioactivity concentrations was found. The contribution to indoor radon accumulation was also simulated for the stone with the highest 222Rn exhalation rate and the resulting concentration compared with the limit value establish by the 2013/59/Euratom Directive. These findings can be extended to rocks formed in similar geodynamic settings that are likely to produce igneous rocks with similar petrographic and geochemical features
Measurements of Indoor Radon Levels and Gamma Dose Rates
No full textIn order to estimate indoor natural radioactivity levels, long and short-term radon tests and ambient gamma dose rate measurements have been performed in several environments of the Faculty of Engineering and in the student canteen of Cagliari University. The measured values were found below the recommended reference levels issued by Directive 2013/59/Euratom. Consistent information about building characteristics, living habits and exposure times were recorded, to be taken into account in the UNSCEAR model. The annual effective dose calculated for each room ranges from 0.004 to 0.628 mSvy−1. The levels of radon concentration measured until now did not exceed the recommended threshold values; additional testing will be performed to ensure full compliance of indoor air quality requirements
MODELLING OF GEOGENIC RADON IN SARDINIA AND HEALTH RISK ASSESSMENT
Get PDFEnhanced level of radon in indoor environments such as homes, schools, public buildings and workplaces is considered an important health issue. Provided that radon is responsible for about 3–14 percent of all lung cancers, governments and inter-governmental institutions have issued several rules in the field of radioprotection of people from exposure to radon and its progenies. As one of the main preventive measures in Europe, the 2013/59/EURATOM BSS Directive requires the member states countries to prepare an action plan to address the radon potential source and identify Radon Prone Areas (RPAs), where the radon concentration is expected to exceed the national threshold level (as annual average of 300 Bq m-3 for both residential and workplaces).
Following this directive, the work to be discussed here focuses on the preparation of a radon potential map of Sardinia according to the “Vast Area” approach and based on the use of literature derived geogenic data (e.g. lithological and geological types, U and Ra content, soil-gas radon, permeability and tectonics). As one of the main results of this thesis work, a predictive Geogenic Radon Potential (GRP) map expressing the radon potentials in ordinal categories was developed.
The produced GRP map has merit because 1) it doesn't depend on the anthropogenic factors (e.g. building material, ventilation rate and living habits); 2) it can be used for the estimation of the radon hazard of both existing buildings and future construction sites, thus for the land-use planning.
Complementary field and laboratory-based experiments were conducted to examine the predictive power of the proposed GRP map. Through the validation tests, we tried to answer three main questions; 1) considering the effect of radon anthropogenic factors, is it possible to use the GRP levels to estimate the indoor radon concentration for an area? 2) Do the results of real-time pilot tests in an area identified as RPA correlate with the category of radon potential predicted by the GRP map? And 3) is it possible to use the GRP map to justify the occurrence of enhanced levels of radon in closed spaces?
In general, the correlations between examination test results and the predicted radon potential by the GRP map showed that the proposed map can address the major source of indoor radon in Sardinia. Besides, the radon emanation potential and natural radioactivity of the building material, the second major contributor to the indoor radon activity, was also investigated in detail parallel to the GRP mapping. The application of radon is not limited to addressing the health hazard. Radon monitoring coupled with natural radioactivity detection can be used as a tool for radiogenic assessments. This application was investigated in an area that consists of heavy mineral placer deposits in South-Eastern Sardinia. Through this experiment, the natural radioactive characteristics and radon-related behaviors of studied formations were well-distinguished
The last year of the Ph.D. programme was carried out at Trinity College of Dublin, where the primary purpose of the study was to evaluate in detail the radon and thoron potential in an area with complex geology. Data obtained from radiometric surveys, geochemical measurements and indoor radon concentrations were used to distinguish radon and thoron release from different geo formations and soil types. To aim this, a set of samples were collected from selected geo types and radon/thoron exhalation rates were estimated through laboratory experiments. As a result, radon and thoron potential maps were developed. In the next step, a detailed investigation of soil gas radon concentrations was considered in a radon priority area identified through the potential maps. As a result of the second investigation, a geostatistical model was built to estimate the GRPs with higher accuracy
Detailed Geogenic Radon Potential Mapping Using Geospatial Analysis of Multiple Geo-Variables—A Case Study from a High-Risk Area in SE Ireland
Get PDFA detailed investigation of geogenic radon potential (GRP) was carried out near Graiguenamanagh town (County Kilkenny, Ireland) by performing a spatial regression analysis on radon-related variables to evaluate the exposure of people to natural radiation (i.e., radon, thoron and gamma radiation). The study area includes an offshoot of the Caledonian Leinster Granite, which is locally intruded into Ordovician metasediments. To model radon release potential at different points, an ordinary least squared (OLS) regression model was developed in which soil gas radon (SGR) concentrations were considered as the response value. Proxy variables such as radionuclide concentrations obtained from airborne radiometric surveys, soil gas permeability, distance from major faults and a digital terrain model were used as the input predictors. ArcGIS and QGIS software together with XLSTAT statistical software were used to visualise, analyse and validate the data and models. The proposed GRP models were validated through diagnostic tests. Empirical Bayesian kriging (EBK) was used to produce the map of the spatial distribution of predicted GRP values and to estimate the prediction uncertainty. The methodology described here can be extended for larger areas and the models could be utilised to estimate the GRPs of other areas where radon-related proxy values are available
A Study of Natural Radioactivity Levels and Radon/Thoron Release Potential of Bedrock and Soil in Southeastern Ireland
Get PDFRadon (222Rn) and thoron (220Rn) account for almost two-thirds of the annual average radiation dose received by the Irish population. A detailed study of natural radioactivity levels and radon and thoron exhalation rates was carried out in a legislatively designated “high radon” area, as based on existing indoor radon measurements. Indoor radon concentrations, airborne radiometric data and stream sediment geochemistry were collated, and a set of soil samples were taken from the study area. The exhalation rates of radon (E222Rn) and thoron (E220Rn) for collected samples were determined in the laboratory. The resultant data were classified based on geological and soil type parameters. Geological boundaries were found to be robust classifiers for radon exhalation rates and radon-related variables, whilst soil type classification better differentiates thoron exhalation rates and correlated variables. Linear models were developed to predict the radon and thoron exhalation rates of the study area. Distribution maps of radon and thoron exhalation rates (range: E222Rn [0.15–1.84] and E220Rn [475–3029] Bq m−2 h−1) and annual effective dose (with a mean value of 0.84 mSv y−1) are presented. For some parts of the study area, the calculated annual effective dose exceeds the recommended level of 1 mSv y−1, illustrating a significant radiation risk. Airborne radiometric data were found to be a powerful and fast tool for the prediction of geogenic radon and thoron risk. This robust method can be used for other areas where airborne radiometric data are available
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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