Radon In Samples Research Articles

Determination of compactly supported functions in shift-invariant space by single-angle Radon samples

While traditionally the computerized tomography of a function f∈L2(R2) depends on the samples of its Radon transform at multiple angles, the real-time imaging sometimes requires the reconstruction of f by the samples of its Radon transform Rpf at a single angle θ, where p=(cos⁡θ,sin⁡θ) is the direction vector. This naturally leads to the question of identifying those functions that can be determined by their Radon samples at a single angle θ. The shift-invariant space V(φ,Z2) generated by φ is a type of function space that has been widely considered in many fields including wavelet analysis and signal processing. In this paper we examine the single-angle reconstruction problem for compactly supported functions f∈V(φ,Z2). The central issue for the problem is to identify the eligible p and sampling set Xp⊆R such that f can be determined by its single-angle Radon (w.r.t. p) samples at Xp. For the general generator φ, we address the eligible p for the two cases: (1) φ being nonvanishing (∫R2φ(x)dx≠0) and (2) being vanishing (∫R2φ(x)dx=0). We prove that eligible Xp exists for general φ. In particular, Xp can be explicitly constructed if φ∈C1(R2). Positive definite functions form an important class of functions that have been widely applied in scattered data interpolation. For the case that φ is positive definite, the corresponding single-angle problem in SIS V(φ,Z2) is addressed such that Xp can be constructed easily. Besides using the samples of the single-angle Radon transform, another common feature for our recovery results is that the number of the required samples is minimum.

Radon sampling methodologies: A case for accurate, accessible measurements using household instruments

ABSTRACT Radon is a prevalent carcinogenic gas and the leading cause of lung cancer in the United States besides smoking. As the residential environment is the primary source of radon exposure, accessible and accurate measurements of radon in this environment are essential. However, no radon monitors have been evaluated that are inexpensive enough for regular household use. In this study, we examine two household-grade, continuous monitoring devices, the Ecosense RadonEye and EcoQube. We compare them to two research-grade instruments, the Durridge Company Rad7 and the Rad Elec Inc. E-PERM. In our study, the Ecosense household radon monitors performed accurately and can be used by homeowners and researchers alike as an affordable and reliable radon sensor. Implications: The ability of homeowners and renters to regularly monitor the radon levels inside their home is an important preventative health measure. However, low-cost instrumentation is needed that can provide accurate radon measurements. In this study, we show that the affordable Ecosense continuous monitors produce results that are in line with expensive research-grade instruments in a residential environment, over a range of concentrations. The Ecosense monitors may be suitable for home use, and they may provide a solution that can be used by policymakers and home-dwellers alike to improve regular radon monitoring in residences.

Quantifying indoor radon levels and determinants in schools: A case study in the radon-prone area Galicia–Norte de Portugal Euroregion

Radon is a carcinogenic compound, and is particularly concerning in the education sector, where children and teachers may be exposed even longer than at home. Thus, this study intended to characterise radon in the indoor air of scholar environments in different provinces/districts of the Euroregion Galicia–Norte de Portugal. With a pioneering approach, this study evaluated the influence of specific factors/characteristics (location, type of management, construction material, season and floor within the building) and quantified their relative contribution to indoor radon levels. Radon was continuously monitored in 416 classrooms from school buildings located in urban and rural sites from different provinces/districts both in the regions of Galicia (A Coruña and Lugo provinces) and Portugal (Porto and Bragança districts), considering rooms for different age groups (from nursery schools to universities). Single and multivariate linear regression models were built considering the radon concentrations as the outcome variable and different room/building characteristics as predictor variables. Mean and median radon concentrations were 332 Bq·m−3 and 181 Bq·m−3, respectively. The radon concentrations observed are a public health concern, as almost 1/3 of the places monitored exceeded the reference limit value of the European legislation (300 Bq·m−3). Moreover, around 50 % of the indoor levels measured could be attributed to room/building characteristics: the building's location and the main construction material, as well as the occupants' age group, the floor within the building and the school's type of management (public/private). This study concluded that radon testing is needed in all school buildings and classrooms without exceptions. Thus, public administrations are urged to dedicate funds for testing, mitigation and public dissemination initiatives in schools. A special protocol for radon sampling in school buildings should also be developed.

Metrology aspects (sampling, storage, transportation, and measurement) of radon in water

Background: Radon can enter homes using water during normal household activities, and it contributes to increasing the radon concentration of the adjacent space. Because of its gaseous form, it can easily escape during one of the procedures preceding its measurement (sampling, transport, and storage) and during its measurement resulting in its underestimation, which could lead to an underestimated dose calculation.
 Objectives: This study focused on quantifying and evaluating radon losses during sampling, transporting, and storing radon in water samples. Also, in terms of measuring radon in water activity concentration, two emanometry methods were compared to the direct method of gamma-ray spectrometry.
 Design and Methods: In terms of sampling, two methods were examined and compared. Road transport effect on radon losses was studied by measuring the radon in water concentration of radon-rich samples before and after their transportation at different ambient temperatures. Different materials (PET, glass, aluminum) were examined for their radon tightness by repetitive measurements and interpolation of the recorded data. Also, the effect of ambient temperature (1 to 40°C) on radon losses was studied during the storage phase. To compare radon in water measuring methods, water from the original bottle was poured carefully into the different sample containers that each method requires and measured by each method.
 Results and Conclusions: Sampling is the factor that can cause the most significant radon losses. Radon tightness investigation of different materials showed no significant differences in their ability to preserve radon inside the container, as their fitting curves followed the literature radon decay curve. Ambient temperature (1 to 40 °C) did not appear to affect radon losses during the storage phase. Unlike the storage phase, significant radon losses were observed during road transport at ambient temperatures of 31°C and above. Therefore, measures should be taken to avoid radon losses for ambient temperatures of 31°C and above when road transport is considered (e.g., using thermally insulated boxes and cooling elements). From the comparison of the two emanometry methods with gamma-ray spectrometry, it was found that all methods provide equal results within standard uncertainties.

IMPROVING THE ASSESSMENT OF OCCUPATIONAL EXPOSURE TO RADON IN ABOVE-GROUND WORKPLACES

Representative sampling of radon in indoor air is difficult because the concentration often exhibits unpredictable spatial and temporal variation. In workplaces, temporal variation may be rapid, and the minimum and maximum concentration can differ by a factor of 100. In this paper, we compare methods for assessing the radon concentration in workplaces utilising the results of an initial investigation with a track-etch detector and the results of an additional continuous measurement. The recommended method is as follows: the mean radon concentration during the working hours of 1 week, as well as the weekly mean, is calculated from the continuous measurement. The ratio between these mean concentrations is multiplied by the result from the track-etch detector. The coefficient of variation of this method is assessed as 19%. If the result of 1 week of continuous measurement is used alone, the coefficient of variation is assessed as 32%.

Development of a Sensitive Radon in Breath Analyzer for Exposure Assessment to Uranium Ore Constituents

Currently only imprecise metrics are available to assign lifetime exposure to uranium ore constituents, such as living in proximity to sources of exposure. The purpose of this project is to develop a radon in breath analyzer sensitive enough to measure radon in the breath of people exposed to uranium ore. Radon is exhaled from decaying radium stored in the bones. We are exploring the use of traditional Lucas cells as the radon detection method. To date, background levels in the range of 0.02 to 0.05 CPM have been achieved through careful choice of the ZnS(Ag) scintillator, the method of deposition and an optimized detector operating point. We are also using liquid nitrogen to collect and focus small amounts of radon from large volumes of breath (50 L). To do this, radon samples are passed through a processing system consisting of a CO2 trap, a water trap employing dry ice/acetone, and a liquid nitrogen trap where the radon is collected. To date, approximately 75% of the radon in the initial sample is collected and transferred to the Lucas cell for analysis. Assuming a breath sample of liters (10 minutes breathing for a measurement), a 75% collection and transfer efficiency to the Lucas cell, and a background level of 0.02 to 0.05 CPM in the Lucas cell, the projected sensitivity of the instrument will be 0.00005 to 0.0005 pCi/l. This level of sensitivity was targeted to provide exposure assessment for people exposed to lower levels than historical underground uranium miners. If this instrument has necessary detection limit and is feasible in the field, future epidemiology studies can assign historical exposure with much greater accuracy. The instrument may also be useful for screening people for clinical purposes to assess their health risk.

Two-decade variations of fresh submarine groundwater discharge to Tolo Harbour and their ecological significance by coupled remote sensing and radon-222 model

Although submarine groundwater discharge (SGD) comprises an insignificant proportion of the global hydrologic cycle, it contributes significantly to chemical fluxes into the coastal waters due to concentrated constituents in coastal groundwater. Large nutrient loadings derived from SGD can lead to a series of environmental and ecological problems such as algal blooms, resulting in water discoloration, severe dissolved oxygen depletion, and eventually beach closures and massive fish kills. Previous studies have demonstrated the relationship between algal blooms and SGD obtained from direct measurement with seepage meters or from geo-tracer (i.e., radon and radium) based models; these traditional methods are time-consuming, laborious and point monitoring, and can hardly achieve a high spatiotemporal resolution SGD estimation, which is vital in revealing the effects of SGD to algal blooms over a long period. Alternatively, remote sensing methods for high spatiotemporal resolution SGD localization and quantification are applicable and effective. The temperature difference or anomaly between groundwater and coastal water extracted from satellite thermal images can be used as the indicator to localize and detect SGD especially its fresh component (or fresh SGD). In this study, multi-year (2005, 2011 and 2018) radon samples in Tolo Harbour were used to train regression models between in-situ radon (Rn) activity and the temperature anomaly by Landsat satellite thermal images. The models were used to estimate two-decade variations of fresh SGD in Tolo Harbour. The synergistic analysis between the time series of fresh SGD derived from regression models and high spatiotemporal resolution ecological metrics (chlorophyll-a, algal cell counts, and E.coli) leads to the findings that the increase of the fresh SGD associated with high nutrient concentrations is witnessed 10–20 days before the observations of algal bloom events. This study makes the first attempt to demonstrate the strong relation between the SGD and algal blooms over a vicennial span, and also provides a cost effective and robust technique to estimate SGD on a bay scale.

The first version of the Pan-European Indoor Radon Map

Abstract. 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 km × 10 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 the AM of 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.

Noise-robust Mojette reconstruction using sparse-view CT projections.

Sparse-view Computed Tomography (CT) has important significance in industrial inspection and medical diagnosis. Mojette transform is a kind of discrete Radon transform that can yield exact reconstructions instead of an approximate solution due to finite Radon sampling. However, the image is iteratively reconstructed pixel by pixel from corner to center, and the image error is proportional to the number of iterations. In this paper, we propose that there exist different sets of projection combinations to recover the original image within the close-to-minimal iterations. And a scheme is given to obtain multiple projection sets, each of which has the same number of minimum iterations and can recover a CT image with a similar level of small noise but different distributions. These images can be used further to restore the final CT image by counteracting noise with each other. The accuracy and validity of the proposed algorithm are verified by comparison with both other Mojette inversion algorithms and the classical SART algorithm.

Detection of radon with biosensors based on the lead(II)-induced conformational change of aptamer HTG and malachite green fluorescence probe

The aim of this paper is to assemble a new biosensor for detecting the accumulated radon dose in the environment to achieve rapid monitor of radon. Based on the correlation between radon and its stable decay daughter 210Pb, a biosensor using the lead-induced specific aptamer HTG conformational changes, and the organic dye malachite green (MG) as a fluorescent probe was assembled. In these studies, we explored a novel, sensitive, label-free, fluorescence biosensing method for the detection of both radon and lead. The fluorescence intensity difference has a linear relationship with Pb2+ and the accumulated radon concentration from 6.87 × 103 Bq·h/m3 to 3.49 × 105 Bq·h/m3. The lead and radon detection limits of this method are 6.7 nmol/L and 2.06 × 103 Bq·h/m3, respectively. The student's t-test results indicated that the new method was reliable and stable. The detection method is sensitive, accurate, easy to operate, has a wide linear range and is highly selective. In the sampling and determination processes of radon, the radiation harm to human health can be effectively avoided.

Laboratory Experimental Laws for the Radon Exhalation of Similar Uranium Samples with Low-Frequency Vibrations

It is the fact that there are lots of hazard incidents in underground uranium mines caused by radon but in-suit uranium samples were difficult to collect. Based on closed chamber method, three similar samples in different sealed ways were made in a laboratory with different material rations, namely uranium tailings, quartz sand, cement, iron powder and silicon powder to measure the radon concentrations with and without low-frequency vibrations, which was used by the experimental device for low-frequency vibration diffusion of radon. The results showed that the radon exhalation coming from the similar samples was influenced by the low frequency vibration; the results are presented as two-stage variations compared with the blank group. The radon exhalation increased with the rising vibration frequency when the frequency was 50 to 70 Hz, but fell slowly after reaching the peak radon exhalation rate. Analyses of the relations between the rock damage degree, changes in porosity and the occurrence of an inflection point in the radon exhalation rate in the samples found that they also increased when the frequency was between 0 to 80 in sample 3. The maximum porosity of the third samples was about 4.8% with a low-frequency vibration 60 Hz, while the maximum damage degree was about 0.07 at 50 Hz.

Amplified colorimetric sensor for detecting radon by its daughter lead based on the free-fixed auto-assembly structure of Duplex-hemin/G-quadruplex

A novel signal amplification strategy based on a Pb2+-dependent DNAzyme is proposed for detecting Pb2+ and radon through Pb2+-induced DNAzyme cleavage and the auto-assembly of a duplex-hemin/G-quadruplex with two loop-stem structures and enzyme-mimicking catalytic activity. First, the Pb2+-specific DNAzyme cleaves a primer sequence, which induces assembly of the hairpin probe Hp1/Hp2 into a double helix structure. Subsequently, a G-quadruplex forms after the insertion of hemin into the free G-rich sequences; this G-quadruplex possesses the catalytic activity of horseradish peroxidase and changes colorless TMB to its deeply colored oxidized state. lead-dependent DNAzymes were constantly sheared by Pb2+, and the free primer strands were continuously assembled into double chains by hybridization with hairpin probes, providing amplification for the detection of lead (II) and radon. Under the optimum conditions, there was a good linear relationship between ΔA and the lead concentration for Pb2+ concentrations ranging from 2.58 to 18 nM, and the detection limit was 0.77 nM. Analysis of actual samples indicated that when the radon concentration was in the range of 5.41 × 103– 1.65 × 105 Bq·h/m3, the radon concentration and the absorbance were linearly correlated with a detection limit of 1.62 × 103 Bq·h/m3. During the process of radon sampling and detection, radiation damage from the radioactive gas radon can be avoided.In this study, the primer dissociated by the DNAzyme was in a free state. Compared with the fixed-state primer chain, this system will be more convenient for the biological analysis of ultratrace metal ions. Therefore, this strategy has good application prospects for biosensors and is expected to become a novel platform for the amplification and detection of metal ion signals.

Tectonic and geologic influences on soil gas radon emission along the western extension of Damascus fault, Syria

The main purpose of this work is to demonstrate the possibility of using soil gas radon survey as a promising technique for locating the trend of western extension of Damascus fault, where it is hidden under a cover of Pliocene unconsolidated deposits. The normal level of radon background was established in a stationary area away from the tectonic influence of the fault zone. The sites of radon measurements were chosen according to the accessibility and suitability of the area, besides some indicative geologic and tectonic evidences. A total of 81 radon sampling points were analyzed, and the results revealed some reasonable spatial increases, with peak values of 2–3 times higher than the background level, trending in accordance with what is believed to be the general direction of the fault in the bedrock. However, permeability properties rather than geotectonic activities seemed to be the main causes controlling the variations of radon concentration over the concerned fault zone. Yet, the moderate level of the observed radon values could be attributed to the nature of the prevailing rock types, as well as the probable effect of locked tectonic structure due to the action of high regional compressive regime which typically originates such reverse faulting. Further, the accumulation of fill materials due to rock alteration along the plane of such dormant fault, through long geologic time, possibly led to increase in the ratio of clay minerals which may affect soil gas mobility through the medium.

On the error behaviour of the filtered back projection

AbstractThe filtered back projection (FBP) formula allows us to reconstruct bivariate functions from given Radon samples. However, the FBP formula is numerically unstable and low‐pass filters with finite bandwidth and a compactly supported window function are employed to make the reconstruction by FBP less sensitive to noise. In this paper we analyse the inherent reconstruction error which is incurred by the application of a low‐pass filter with finite bandwidth. We present L2‐error estimates on Sobolev spaces of fractional order along with asymptotic convergence rates, where the filter's bandwidth goes to infinity. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Improved CT Image Reconstruction Through Partial Fourier Sampling

A novel CT imaging structure based on compressive sensing (CS) is proposed. The main goal is to mitigate the CT imaging time and thus x-ray radiation dosage without compromising the image quality. The utilized compressive sensing approach is based on radial Fourier sampling. Thanks to the intrinsic relation between captured radon samples in a CT imaging process and the radial Fourier samples, partial Fourier sampling could be implemented systematically. This systematic compressive sampling helps in better control of required conditions such as incoherence and sparsity to guarantee adequate image quality in comparison to previous CS based CT imaging structures. Simulation results prove the superior quality of the proposed approach (about 4% better PSNR), achieving the smallest CT scan time and the best image quality.

Geographically weighted regression and geostatistical techniques to construct the geogenic radon potential map of the Lazio region: A methodological proposal for the European Atlas of Natural Radiation

In many countries, assessment programmes are carried out to identify areas where people may be exposed to high radon levels. These programmes often involve detailed mapping, followed by spatial interpolation and extrapolation of the results based on the correlation of indoor radon values with other parameters (e.g., lithology, permeability and airborne total gamma radiation) to optimise the radon hazard maps at the municipal and/or regional scale. In the present work, Geographical Weighted Regression and geostatistics are used to estimate the Geogenic Radon Potential (GRP) of the Lazio Region, assuming that the radon risk only depends on the geological and environmental characteristics of the study area. A wide geodatabase has been organised including about 8000 samples of soil-gas radon, as well as other proxy variables, such as radium and uranium content of homogeneous geological units, rock permeability, and faults and topography often associated with radon production/migration in the shallow environment. All these data have been processed in a Geographic Information System (GIS) using geospatial analysis and geostatistics to produce base thematic maps in a 1000 m × 1000 m grid format. Global Ordinary Least Squared (OLS) regression and local Geographical Weighted Regression (GWR) have been applied and compared assuming that the relationships between radon activities and the environmental variables are not spatially stationary, but vary locally according to the GRP. The spatial regression model has been elaborated considering soil-gas radon concentrations as the response variable and developing proxy variables as predictors through the use of a training dataset. Then a validation procedure was used to predict soil-gas radon values using a test dataset. Finally, the predicted values were interpolated using the kriging algorithm to obtain the GRP map of the Lazio region. The map shows some high GRP areas corresponding to the volcanic terrains (central-northern sector of Lazio region) and to faulted and fractured carbonate rocks (central-southern and eastern sectors of the Lazio region). This typical local variability of autocorrelated phenomena can only be taken into account by using local methods for spatial data analysis. The constructed GRP map can be a useful tool to implement radon policies at both the national and local levels, providing critical data for land use and planning purposes.

Early results of a study on improving energy efficiency of housing stock, IEQ and public health in North-East Europe

BACKGROUND/AIMS: The INSULAtE project aims to demonstrate the effects of improving energy efficiency (EE) of dwellings on indoor environmental quality (IEQ) and public health, and to develop a common protocol for assessment of these effects related to national policies and programs implementing the European Energy Performance of Buildings Directive. METHODS: In the first phase, 20 case and control buildings from both Finland and Lithuania are included. The case buildings are multifamily buildings undergoing renovation improving EE, such as adding thermal insulation or changing windows. Measurement data on IEQ parameters (inc. 24h monitoring of PM, CO, and CO2; 1wk passive sampling of VOCs, formaldehyde, and NO2; 2mo monitoring of T and RH; 2mo passive sampling of radon and settled dust) and questionnaire data on occupant health are collected from 5 apartments per building both before and after renovation. Since the winter of 2011-2012, data have been collected from 65 (before) and 7 (after) apartments from Finland, and 82 (before) and 4 (after) apartments from Lithuania. RESULTS/CONCLUSIONS: At this point, data are available (i.e. samples analyzed and data entered in the database) from 22 apartments from Finland and 32 - 82 apartments from Lithuania before renovation. We interpret the findings relative to national reference or guideline values. Preliminary screening of the data reveals thermal index values below recommended (TI = 65) in 11 of 22 apartments in Finland and 34 of 82 in Lithuania. In Lithuania, recommended level of CO2 (1200 ppm) was exceeded in 22 of 76 apartments, formaldehyde concentration was > 0.01 mg/m3 in 32 of 39 apartments, NO2 > 0.04 mg/m3 in one of 61 apartments, and ethylbenzene > 0.02 mg/m3 in one of 39 apartments. All other values (inc. RH, CO, TVOC, and radon) were within recommended limits or data not yet analyzed (inc. microbial levels and mineral fibers in settled dust as well as occupant questionnaire data) in both countries. We will present preliminary results from before and after renovation measurements, and discuss the implications on the assessment protocol development.

Measurement of radon potential from soil using a special method of sampling

Soil radon gas and/or its exhalation rate are used as indicators for some applications, such as uranium exploration, indoor radon concentration, seismic activity, location of subsurface faults, etc., and also in the studies where the main interest is the field verification of radon transport models. This work proposes a versatile method for the soil radon sampling using a special manner of pumping. The soil gas is passed through a column of charcoal by using passive pumping. A plastic bottle filled with water is coupled to an activated charcoal column and the flow of water through an adjustable hole made at the bottom of bottle assures a controlled gas flow from the soil. The results obtained for the activity of activated charcoal are in the range of 20-40 kBq/m 3 , for a depth of approximately 0.8 m. The results obtained by this method were confirmed by simultaneous measurements using LUK 3C device for soil radon measurements. Possible applications for the estimation of radon soil potential are discussed.

The role of soil gas radon survey in exploring unknown subsurface faults at Afamia B dam, Syria

The purpose of this work is to determine a possible connection between anomalous radon values and some expected subsurface geological faults at Afamia B dam which is currently suffering a serious problem of large leakage through its bedrocks. A total of 82 soil gas radon sampling points were measured, using direct active method, over an area of 300 × 300 m which almost covers the entire surface of the reservoir basin. The results revealed a reasonable correlation between the geometric pattern of radon anomalies and the probable orientation of some underlying tectonic lineaments. Abnormal radon values, with peak signals of about 2–5 times higher than the background level, led to the detection of two probable fractured zones, denoted as F 1 and F 2. The data analysis suggests that the leakage of water from Afamia B dam almost runs vertically downwards along N60E trending fault zone F 2. Such a fault is very likely extending down within the Neogene formation to reach the permeable karstic carbonate rocks of Cretaceous at depth, forming large conduits through which the water of the reservoir is possibly drained off. This suggestion was in agreement with the general direction of the groundwater flow in the study area which indicates clearly that the supposed fractured zone F 2 may represent a catchment area for groundwater, and thereby it may constitute the most important structural element concerning the leakage problem of Afamia B reservoir.

An active radon sampling device for high humidity places

An active radon measurement device has been developed to be used in workplaces with a relative humidity of 100% for spot measurements of radon concentration. A mathematical model based on the convective–diffusive transport equation is used in the design of this system, which has been used to measure the radon concentration in the Pozalagua cave (Biscay, at Northern of Spain). From the obtained radon values the public and workers doses have been obtained.