222Rn Measurements Research Articles

Indications for solar influence on radon and thoron in the atmosphere, Arad, Romania

Radon (Rn-222; Rn) and Thoron (Rn-220; Tn) from the lowermost atmosphere in Arad, Romania, were investigated from 1993 to 2015. Daytime and night-time measurements exhibit (i) systematic differences; (ii) large annual variations; (iii) semi-annual and possibly ternary annual periodicities; (iv) amplitudes of the annual and semi-annual periodicities differ between daytime and night-time measurements. The day of year of the summer peak time (SPT) of the annual variation of composite Rn and Tn data depict smoothly covarying SPT patterns separated around 50 days. SPT patterns of daytime and night-time of Rn and Tn depict additional separations of gradually varying multi-year patterns. For both radionuclides, the night-time SPT precedes the daytime SPT—by around 105 days for Tn and around 60 days for Rn. In the case of temperature, the SPT of daytime and night-time measurements overlap at around day 195. Thus, for Rn and Tn, daytime and night-time differences depend on the time of measurement within the 24 h cycle. This implies that Rn and Tn measurements are influenced by the rotation of the Earth around its axis. It is suggested that these relations, observed in coexisting Rn and Tn, are a further indication for a solar (extraterrestrial) influence on nuclear radiation, previously suggested for radon.

Evaluation of different LSC methods for 222Rn determination in waters

Monitoring of 222Rn in drinking or surface waters, as well as in groundwater has been performed regularly in connection with geological, hydrogeological and hydrological surveys and health hazard studies. Liquid scintillation counting (LSC) is often preferred analytical method for 222Rn measurements in waters as it allows multiple-sample automatic analysis. LSC method implies mixing of water samples with organic scintillation cocktail, which triggers radon diffusion from the aqueous into an organic phase for which it has a much greater affinity, eliminating the possibility of radon emanation in that manner.The main aim of this paper is calibration of the liquid scintillation counter Qunatulus 1220™ for measuring of radon in water and evaluation of two different methods (one-phase and two-phase) in order to obtain the most suitable LSC technique for radon in water measurement. In this study four different scintillation cocktails were tested: one miscible (Ultima Gold AB) and three immiscible (High Efficiency Mineral Oil Scintillator, Opti-Fluor O and Ultima Gold F). Evaluation of presented methods was based on obtained detection efficiency and achieved Minimal Detectable Activity (MDA) values. Comparison of presented methods, accuracy and precision, as well as different scintillation cocktail's performance, was considered from results of measurements of 226Ra spiked water samples with known activity and environmental samples. LSC results were compared with the results of radon in water measurement obtained by alpha spectrometer RAD7. Calibration was done as a dependence of calibration factor (CF) from Pulse Shape Analysis (PSA).According to the obtained results, with proper adjustment of calibration parameters, both methods could be used for radon in water measurements. The obtained MDA values for all four scintillation cocktails are very low, less than 0.1 Bq l−1 for measuring time of 300 min.

A satellite stand-alone procedure for deriving net radiation by using SEVIRI and MODIS products

In this study, a new stand-alone satellite approach for the estimation of net surface radiation (Rn) has been implemented and validated for the Italian territory. The method uses the MODIS and MSG-SEVIRI time series products and it is independent of the use of ancillary data (i.e. ground measurements). A database of daily measurements of Rn, provided by 9 stations of the FLUXNET network, was used to validate the method in different ecological scenarios in the period 2010-12.The Rn modelled by the proposed approach and the corresponding FLUXNET measurements were in good agreement, with RMSE and R2 of 19.8 Wm−2 and 0.87, respectively, at 8-days scale, and 23.3 Wm−2 and 0.92, respectively, at daily scale.Therefore, the proposed approach can be considered effective for the estimation of spatial and temporal variability of Rn, which is a key variable related to the management of water resources, agriculture, ecology and climate change.

Radon‐traced pore‐water as a potential source of CO2 and CH4 to receding black and clear water environments in the Amazon Basin

AbstractGroundwater is a primary source of dissolved CO2 and CH4 in Amazonian headwaters, yet in higher order rivers, a groundwater/pore‐water source is difficult to constrain due to the high spatial and temporal heterogeneity of pore‐water exchange. Here, we report coupled, high resolution measurements of pCO2, CH4, and 222Rn (a natural pore‐water and groundwater tracer) during receding waters in the three major water types of the Central Amazon Basin: black (Negro River); clear (Tapajós River); white (Madeira River). Considerable spatial heterogeneity was observed in pCO2, CH4, and 222Rn concentrations ranging from 460 μatm to 8030 μatm, 7 nM to 281 nM, and 713 dpm m−3 to 8516 dpm m−3, respectively. The significant correlations between pCO2 and CH4 to 222Rn in the black and clear waters suggests that pore‐water further enhanced CO2 supersaturation by 18–47% and is a driver of CH4 dynamics in these waters.

Environmentally Friendly Measurement of Airborne Radon Using a Nonvolatile Liquid Scintillation Absorbent.

The practicality of using a liquid scintillation method with a nonvolatile liquid scintillation absorbent for the measurement of airborne Rn (radon) in a residence was examined. The relationship between the radioactivity absorbed by the liquid scintillation absorbent and the radon concentration in the air was investigated in a calibrated walk-in radon chamber. The equivalent radioactivity of radon was calculated for Po radioactivity immediately after radioactive equilibrium was attained using successive decay equations via alpha-particle spectrometry based on the 1 h, indirect, selective measurement of the Po alpha-particle spectrum generated after sampling radon. We confirmed that the amounts of radon absorbed in the liquid scintillation absorbent were proportional to the radon concentration in the air. The calibration curve that exhibited reliable quantitative linearity from 500 to 8,000 Bq m in air was extrapolated to the region between 0 and 500 Bq m using the least-squares method with data from 500 to 8,000 Bq m. The validity of the extrapolated curve at less than 500 Bq m was confirmed by comparison of the measured radon concentrations in the room and atmosphere with those determined using an existing ionization chamber. Variations in the absorption of radon were observed due to changes in temperature and humidity. The health and environmental safety of nonvolatile liquid scintillation absorbent was also considered.

Optimization of a portable liquid scintillation counting device for determining 222Rn in water

The new EU Council Directive 2013/51/Euratom of 22 October 2013 introduced limits for the content of 222Rn in drinking water. Radon analysis in water requires a lengthy task of collection, storage, transport and subsequent measurement in a laboratory. A portable liquid scintillation counting device allows rapid sampling with significant savings of time, space, and cost compared with the commonly used techniques of gamma spectrometry or methods based on the desorption of radon dissolved in water. In this study, we describe a calibration procedure for a portable liquid scintillation counting device that allows measurements of 222Rn in water by the direct method, and we also consider the case of 226Ra being present in the sample. The results obtained with this portable device are compared with those obtained by standard laboratory techniques (gamma spectrometry with a high-purity Ge detector, gamma spectrometry with a NaI detector, and desorption followed by ionization chamber detection).

Evaluation of groundwater discharge into surface water by using Radon-222 in the Source Area of the Yellow River, Qinghai-Tibet Plateau

Understanding hydrological processes in the Source Area of the Yellow River (SAYR), Qinghai-Tibet Plateau, is vital for protection and management of groundwater and surface water resources in the region. In situ water measurements of exchange rates between surface water and groundwater are, however, hard to conduct because of the harsh natural conditions of the SAYR. We here present an indirect method using in situ 222Rn measurements to estimate groundwater discharge into rivers and lakes in the SAYR. 222Rn was measured in rivers, lakes, groundwater and springs during three sampling periods (2014–2016), and the results indicate large variability in the concentration of the isotope. The data also indicate decreasing 222Rn trends in groundwater in the cold season (the Feb-2015 sampling period) which may be linked to frequency of capturing 222Rn in the frozen ground caused by geocryogenic processes. In addition, permafrost spatial extent and freeze-thaw processes have strongly affected the hydrological conditions in the region.

Applicability of radon emanometry in lithologically discontinuous sites contaminated by organic chemicals.

The applicability of radon (222Rn) measurements to delineate non-aqueous phase liquids (NAPL) contamination in subsoil is discussed at a site with lithological discontinuities through a blind test. Three alpha spectroscopy monitors were used to measure radon in soil air in a 25,000-m2 area, following a regular sampling design with a 20-m2 grid. Repeatability and reproducibility of the results were assessed by means of duplicate measurements in six sampling positions. Furthermore, three points not affected by oil spills were sampled to estimate radon background concentration in soil air. Data histograms, Q-Q plots, variograms, and cluster analysis allowed to recognize two data populations, associated with the possible path of a fault and a lithological discontinuity. Even though the concentration of radon in soil air was dominated by this discontinuity, the characterization of the background emanation in each lithological unit allowed to distinguish areas potentially affected by NAPL, thus justifying the application of radon emanometry as a screening technique for the delineation of NAPL plumes in sites with lithological discontinuities.

Chaotic correlation dimension analysis of 222Rn gas measurements received from soil

Time series obtained from dynamic system must be examined to learn about the variable parameters of a dynamic system. Chaotic time series analysis is very advantageous signal processing methods. These methods are used to determine the nonlinear behaviour of dynamic system. In this study, nonlinear characteristic of 222Rn, which is a radioactive gas, was examined with correlation dimension method. Nonlinear analyses methods are useful for analyses of complex dynamic system behaviour. Correlation dimension analysis is most used chaotic analysis methods. Chaotic time series analyses applications based on 35,136 measurement data from the Nurdagi region in Turkey. In this study, the nonlinear analysis techniques are applied to recorded data for the year 2007 and the persistent 222Rn measurements are received at 15-min times for 12 months in regions. Chaotic correlation dimension analysis results for 222Rn data was have seen chaotic properties.

Indoor and tap water radon (222Rn) concentration measurements at Giresun University campus areas

In this study, indoor (air) and tap water Radon (222Rn) measurements were performed at various campus areas of Giresun University. The measurement and analysis results were compared with the values recommended by international and national organizations and those reported in literature studies. The measured and calculated values were found to be under the recommended limits. Also, annual effective dose values were evaluated to determine the annual radon exposure of an individual working in the measurement area. Indoor radon concentration values measured by CR-39 detectors were in the range of 76 Bq/m3–504 Bq/m3 and the mean concentration value was obtained as 193.7 Bq/m3. The radon concentrations in tap water samples were found to be in the range of 0.98 Bq/L–27.28 Bq/L. The annual mean effective doses (EWig) of drinking water samples were calculated in the range of 9.9–150.4 (μSv/y) for ingestion and 0.97–14.84 (μSv/y) for inhalation calculations. Excess life time cancer risk (ELCR) was estimated as 0.54%. Radon dose rate in terms of mean annual working level month was calculated as 0.246 WLM/year. The study was performed with a view to contribute to further studies in the related field and constitute a basis for the measurements conducted in this area.

Estimation of groundwater discharge and associated chemical fluxes into Poyang Lake, China: approaches using stable isotopes (δD and δ18O) and radon

Poyang Lake is the largest freshwater lake in China and is well known for its ecological and economic importance. Understanding the contribution of groundwater to Poyang Lake is important for the lake’s protection and management. In this study, stable isotopes (δD and δ18O), 222Rn measurements, and corresponding models (222Rn and 18O mass balance models) were employed to evaluate the groundwater discharge and associated chemical inputs to Poyang Lake. The results showed that the distribution of δ18O in the lake water reflects the groundwater discharge into the lake. The groundwater discharge estimated using the 222Rn mass balance model was in reasonable agreement with the groundwater discharge derived from the 18O mass balance model. The 222Rn mass balance model showed that the groundwater discharge rate was 24.18 ± 6.85 mm/d with a groundwater discharge flux of (2.24 ± 0.63) × 107 m3/d, which accounts for 6.52–11.14% of river-water input in the Poyang Lake area. The groundwater discharge flux estimated using the 18O mass balance model was 3.17 × 107 m3/d, and the average groundwater discharge rate was 26.62 mm/d. The estimated groundwater discharge was used to estimate the associated chemical fluxes. It was found that groundwater-derived heavy metals such as iron and manganese are potential threats to the lake ecological system because of their large inputs from groundwater discharge.

Investigating the Effect of Bioirrigation on In Situ Porewater Concentrations and Fluxes of Polychlorinated Biphenyls Using Passive Samplers.

Polychlorinated biphenyl (PCB) fluxes from contaminated sediments can be caused by mechanisms including diffusion, bioirrigation, and resuspension, but it is often unclear which mechanisms are important. In the Lower Duwamish Waterway (Seattle, Washington), the presence of abundant benthic macrofauna suggests that porewater bioirrigation may be an important mechanism for PCB transport from the bed into the overlying water column. In this field study, the fluxes of PCBs due to bioirrigation were quantified by using (a) polyethylene (PE) samplers to quantify in situ and ex situ (i.e., equilibrium) PCB porewater concentration profiles and (b) measurements of the geochemical tracer 222Rn to quantify the rate of porewater exchange with overlying water. The results showed that bioirrigation caused sorptive disequilibrium with the surrounding sediment, which led to lower in situ porewater concentrations than expected from sediment concentrations. The combined fluxes of seven PCB congeners (Σ7PCBs) were 1.6-26 ng/m2/day for the three field sites, similar in magnitude to the upper limit estimates of diffusive fluxes calculated assuming water-side boundary layer control (Σ7PCBs = 1.3-47 ng/m2/day). Moreover, the depleted in situ porewater concentrations imply lower diffusive flux estimates than if the ex situ porewater concentrations had been used to estimate fluxes (Σ7PCBs = 89-670 ng/m2/day). These results suggest that nondiffusive PCB fluxes from the sediment bed are occurring and that quantifying in situ porewater concentrations is crucial for accurately quantifying both diffusive and nondiffusive PCB fluxes.

Measurement of 222Rn and 220Rn exhalation rate from soil samples of Kumaun Hills, India

The source terms, i.e., exhalation and emanation from soil and building materials are the primary contributors to the radon (222Rn)/thoron (220Rn) concentration levels in the dwellings, while the ecological constraints like ventilation rate, temperature, pressure, humidity, etc., are the influencing factors. The present study is focused on Almora District of Kumaun, located in Himalayan belt of Uttarakhand, India. For the measurement of 222Rn and 220Rn exhalation rates, 24 soil samples were collected from different locations. Gamma radiation level was measured at each of these locations. Chamber technique associated with Smart Rn Duo portable monitor was employed for the estimation of 222Rn and 220Rn exhalation rates. Radionuclides (226Ra, 232Th and 40K) concentrations were also measured in soil samples using NaI(Tl) scintillation based gamma ray spectrometry. The mass exhalation rate for 222Rn was varying between 16 and 54 mBq/kg/h, while the 220Rn surface exhalation rate was in the range of 0.65–6.43 Bq/m2/s. Measured gamma dose rate for the same region varied from 0.10 to 0.31 µSv/h. Inter-correlation of exhalation rates and intra-correlation with background gamma levels were studied.

Unperturbed, high spatial resolution measurement of Radon-222 in soil-gas depth profile

This work presents a method for measuring the depth distribution of 222Rn activity in soil gas. The method is based on the capacity of polycarbonates to absorb 222Rn and on the possibility of performing sensitive measurements of 222Rn absorbed by the polycarbonates via liquid scintillation counting (LSC). The method is the following: cylindrical holes are drilled along a metal rod and Makrofol® N polycarbonate foils enclosed in polyethylene envelopes are placed in each hole. The rod is driven into the soil and kept for a certain time. As long as the rod is in the soil, the polycarbonate foils are exposed to the 222Rn concentration at their depth. At the end of the exposure the rod is pulled out and the foils are transferred to liquid scintillation (LS) vials filled with liquid scintillator. The 222Rn absorbed in the foils is then measured with a LS analyzer. The rod with the polycarbonate foils acts as a passive probe which senses the 222Rn concentration at different depths beneath the ground surface. The achievable minimum detectable 222Rn activity concentration with the equipment and conditions used in this study is around 12.5 kBq/m3. It can easily be lowered below 1 kBq/m3 if larger foils and low-background LS analyzers are used. Since the method does not require air sampling the depth distribution of 222Rn in the soil is unperturbed by the sampling. The spatial distribution and the maximum measurement depth are set by the distance between the holes and the depth to which the rod can be fixed into the ground. Results from in situ applications of the method in terrains with high 222Rn in soil-gas are reported, which demonstrate the feasibility and the usefulness of the proposed approach.

Ra and Rn isotopes as natural tracers of submarine groundwater discharge in the patagonian coastal zone (Argentina): an initial assessment

Submarine groundwater discharge (SGD) is herein recognized as a significant pathway of material transport from land to the coastal SW Atlantic Ocean and thus, it can be a relevant factor affecting the marine biogeochemical cycles in the region. This paper focuses on the initial measurements of 226Ra, 228Ra and 222Rn made in Patagonia’s coastal zone of Chubut and Santa Cruz provinces (42°S–48°S, Argentina). 226Ra activity ranged from 2.9 to 73.5 dpm 100 L−1, and 228Ra activity ranged from 11.9 to 311.0 dpm 100 L−1 in groundwater wells. The radium activities found in Patagonia’s marine coastal regions and adjacent shelf indicate significant enrichment throughout the coastal waters. Groundwater samples presented the largest 222Rn activity and ranged from 2.66 to 1083 dpm L−1. Conversely, in the coastal marine environment, the 222Rn activity ranged from 1.03 to 6.23 dpm L−1. The Patagonian coastal aquifer showed a larger enrichment in 228Ra than in 226Ra, which is a typical feature for sites where SGD is dominant, probably playing a significant role in the biogeochemistry of these coastal waters.

Studies on ambient gamma dose rate and enrichment of radon, thoron, and progeny concentration in various types of dwellings and outdoor environments of Kalliasseri, Kannur district, Kerala

The major contribution of natural background radiation exposure comes from radon, thoron, and their progeny. The activity concentration of these radionuclides depends on various factors, and the concentration level varies from place to place. The indoor concentration in dwellings depends mainly on the materials used for building construction and ventilation patterns. In the present study, an attempt is made to estimate the indoor and outdoor radon, thoron, and their progeny concentration in various types of dwellings and outdoor environments of Kalliasseri Panchayat, Kannur district, Kerala. 222Rn and 220Rn measurements were carried out using LR-115 type II-based pinhole cup dosimeters. Indoor and outdoor gamma exposure rate measurements were also carried out in all the dwellings using scintillation-based microradiation survey meter. The average concentrations of radon and thoron were estimated in about 40 dwellings categorized according to the construction type. The seasonal variation in the enrichment of radionuclides concentration has also been studied. The respective radon and thoron progeny levels were also estimated. The average radon concentration from the present study was well within the action level (200 Bq/m3) recommended by the International Commission of Radiological Protection (ICRP). The annual effective doses due to indoor radon and thoron were within the action level 3–10 mSv/y as suggested by the ICRP.

Submarine groundwater discharge drives biogeochemistry in two Hawaiian reefs

AbstractGroundwater inputs are typically overlooked as drivers of environmental change in coastal reef studies. To assess the impact of groundwater discharge on reef biogeochemistry, we examined two fringing reef environments, located in Maunalua Bay on the south shore of O‘ahu, Hawai‘i, that receive large inputs of submarine groundwater discharge. We supplemented 25‐ and 30‐d time series measurements of salinity, water temperature, pH, dissolved oxygen, and 222Rn with high‐resolution 24‐h nutrient, dissolved inorganic carbon (DIC), total alkalinity (TA), and δ13C–DIC measurements to evaluate both groundwater‐induced and biologically‐driven changes in coastal carbonate chemistry across salinity gradients. Submarine groundwater discharge at these two locations was characterized by low pHT (7.36–7.62), and variable DIC (1734–3046 μM) and TA (1716–2958 μM) content relative to ambient seawater. Groundwater‐driven variability in coastal carbonate system parameters was generally on the same order of magnitude as biologically‐driven variability in carbonate system parameters at our study locations. Further, our data revealed a shift in reef metabolism from net dissolution to net calcification across this groundwater‐driven physicochemical gradient. At sites with high levels of groundwater exposure, net community production and calcification rates were reduced. Our findings shed light on the importance of considering groundwater inputs when examining coastal carbonate chemistry.

Synthesis and characterisation of scintillating microspheres made of polystyrene/polycarbonate for 222Rn measurements

Several studies have demonstrated that polycarbonate-based polymers have good capacities for the absorption of 222Rn. Meanwhile, polystyrene polymers are reported to be the most appropriate for developing plastic scintillator materials for the detection of radioactivity. The objective of this work was to develop plastic scintillators in the form of microspheres (PSm) composed of polystyrene and polycarbonate that could be used to measure 222Rn and improve this performance thanks to the combination of characteristics of both polymers. Our results show that PSm of polystyrene and polycarbonate can be made via the evaporation/extraction method, despite the two polymers not being miscible. From the point of view of the radioactive measurements, we observed that the addition of polycarbonate causes quenching, although it does not significantly affect the detection efficiency for alpha and high-energy beta emitters. From the point of view of 222Rn absorption, we observed that synthesis of the PSm through the evaporation/extraction method changes the 222Rn absorption of the raw material. This result demonstrates that the method of production of the polymer and the resulting physical characteristics are a key parameter for its final 222Rn absorption properties.

Spatial distribution correlation of soil-gas radon (222Rn) and mercury with leveling deformation in northern margin fault zone of West Qinling, China

This study concerns measurement of 222Rn and mercury concentrations in soil-gas in the northern margin fault zone of West Qinling, Tibet (China). Based on profiles crossing perpendicularly the different segments of the fault at six different locations, the relations between the gas measurements, fault deformation, and seismic activity in each segment of the studied fault were analyzed, determining seismic risks in the fault zone. Soil-gas data are heterogeneous, but appear relatively organized along the three segments of the fault. The detailed multidisciplinary analysis reveals complex interactions between the structural setting, uprising fluids, leveling and seismic activity in different fault segments. The results for both fault soil gas and deformation indicated relatively stronger fault activity in the Wushan segment in the middle-eastern segment of the northern margin fault zone of West Qinling and lower activity in the Zhangxian segment, whereas the fault in the Tianshui segment was relatively locked. Additionally, in the Wushan strike-slip pull-apart area, the active influence of fluid activities facilitated the occurrence of small to medium-sized seismic events, which prevented the occurrence of larger events; in contrast, in the Tianshui segment, the west Zhangxian segment, the weak fluid activities and the corresponding strain rate will probably lead to strong earthquake buildup.

INDOOR RADON, THORON AND THEIR PROGENY CONCENTRATIONS IN HIGH THORON RURAL SERBIA ENVIRONMENTS.

This article deals with the variation of radon (Rn), thoron (Tn) and their progeny concentrations expressed in terms of equilibrium equivalent concentrations (EERC and EETC), in 40 houses, in four villages of Sokobanja municipality, Southern Serbia. Two types of passive detectors were used: (1) discriminative radon-thoron detector for simultaneous Rn and Tn gases measurements and (2) direct Tn and Rn progeny sensors (DRPS/DTPS) for measuring Rn and Tn progeny concentrations. Detectors were exposed simultaneously for a single period of 12 months. Variations of Tn and EETC appear higher than those of Rn and EERC. Analysis of the spatial variation of the measured concentrations is also reported. This work is part of a wider survey of Rn, Tn and their progeny concentrations in indoor environments throughout the Balkan region started in 2011 year.