National survey of indoor thoron concentration in FYR of Macedonia (continental Europe – Balkan region)

As a part of the national survey of natural radioactivity in The Former Yugoslav Republic of Macedonia, indoor thoron gas concentration was measured in 300 dwellings during one year, from December 2008 till December 2009 using passive discriminative radon–thoron detectors. Detectors were deployed at a distance of >50 cm from walls in order to be less sensitive to distance from walls. Altogether 532 measurements were performed: 53 in winter, 57 in spring, 122 in summer and 300 in autumn. The frequency distribution is well described by a log-normal function. The geometric means of indoor thoron concentration (with geometric standard deviations in brackets) in winter, spring, summer and autumn were obtained to be: 39 Bq m⁻³ (3.4), 32 Bq m⁻³ (2.8), 18 Bq m⁻³ (2.8), 31 Bq m⁻³ (2.9), respectively. Seasonal variations of thoron appear lower than those of radon. The seasonal corrected annual mean concentration ranges between 3 and 272 Bq m⁻³ with a geometric mean of 28 Bq m⁻³ (2.12). A detailed statistical analysis of the geogenic and building factors which influence the indoor thoron concentration is also reported. This survey represents the first national survey on indoor thoron in continental Europe.     

Radon exhalation and gamma radioactivity levels in soil and radiation hazard assessment in the surrounding area of National Thermal Power Corporation,Dadri (U.P.), India

In the present study soil samples were collected from the region around a National Thermal Power Corporation (NTPC) at Dadri (U.P.), India. Radon activity and radon exhalation rates were measured by using “sealed can technique” using LR 115-type II nuclear track detectors. Radon activities are found to vary from 177.5 ± 23.1 to 583.4 ± 4.9 Bq m⁻³ with an average value of 330.5 ± 30.4 Bq m⁻³. Surface exhalation rates in these samples vary from 63.9 ± 8.3 to 210.2 ± 15.1 mBq m⁻² h⁻¹ with an average value of 119.1 ± 11.1 mBq m⁻² h⁻¹, whereas mass exhalation rates vary from 2.5 ± 0.3 to 8.1 ± 0.6 mBq kg⁻¹ h⁻¹ with an average of 4.6 ± 0.4 mBq kg⁻¹ h⁻¹.Activity concentrations of naturally occurring radionuclides (²²⁶Ra, ²³²Th and ⁴⁰K) were also measured in these soil samples using high resolution γ–ray spectroscopic system. Activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K vary from 32.2 ± 6.0 to120.9 ± 4.5 Bq kg⁻¹, 19.3 ± 0.9 to 44.6 ± 1.5 Bq kg⁻¹ and 195.4 ± 2.8 to 505.4 ± 6.3 Bq kg⁻¹ with overall mean values of 70.0 ± 8.9 Bq kg⁻¹, 34.8 ± 1.2 Bq kg⁻¹ and 436.1 ± 5.6 Bq kg⁻¹ respectively. From the activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K, radium equivalent activity (Ra_eq) and the external hazard index (H_ex) were calculated and found to vary from 73.4 to 214.7 Bq kg⁻¹ and from 0.2 to 0.6 respectively.     

Seasonal and location dependence of indoor and soil radon concentrations in two villages,Najran region,Saudi Arabia

Seasonal (winter-summer) indoor and soil radon comparison is made in two villages in Najran region, south west of Saudi Arabia, using CR-39 Dosimeter. Summer indoor radon concentrations were measured in the villages of Fara Al-Jabal and Hadadah. The respective winter-summer average values of 42 ± 4 Bq m⁻³ and 74 ± 5 Bq m⁻³ are measured in Fara Al-Jable village and the average values of 47 ± 4 Bq m⁻³ and 76 ± 5 Bq m⁻³ are measured in Hadadah village. The respective winter-summer soil values are 1.40 ± 0.21 kBq m⁻³ and 0.99 ± 0.04 kBq m⁻³ in Fara Al-Jabal village while those measured in Hadadah village are 2.90 ± 0.17 kBq m⁻³ and 1.40 ± 0.66 kBq m⁻³. Indoor radon levels are found to be seasonal dependent while that of soil are found seasonal and location dependent. Meteorological and geological factors are expected to have caused the measured significant differences in radon levels in dwellings and soil in the two villages.     

Radon concentrations in schools of the Neapolitan area

A radon survey was carried out in 30 schools located in the metropolitan area around Naples, Italy. Radon concentration was measured using the SSNTD (Solid State Nuclear Track Detectors) method with LR115 detectors. Time integrated measurements covered two consecutive 6-month periods at different locations inside the school buildings: classrooms, laboratories and offices. Data distribution is well fitted by a log-normal curve. The arithmetic mean annual radon concentration is 144 Bq m⁻³, the geometric mean is 86 Bq m⁻³; the standard deviations are respectively 7 Bq m⁻³ and 3. The fractions of rooms where radon concentrations exceed the reference levels of 200, 400 and 500 Bq m⁻³ are 21.3%, 7.6% and 4.5% respectively.The results show that radon concentration in scientific laboratories and in offices is higher than in classrooms.     

Observation of fallout deposition in an outdoor swimming pool 50 km away from the Fukushima Daiichi nuclear power plant

After the accident at the Fukushima Daiichi nuclear power plant (NPP), outdoor school swimming pools at Fukushima were decontaminated to curb the redistribution of radioactivity into downstream farmlands. In the process, the radioactivity concentrations of the pool water and sediment substances (residue) were measured to estimate the deposition density of the fallout. At a pool situated 50 km away from the NPP, the average concentrations of radiocesium (^134+137Cs) for the water and residue were quantified as 170 Bq L⁻¹ and 3.6 × 10⁵ Bq kg⁻¹, respectively. Taking account of the radioactivity concentrations and of the water balance in and around the pool, the deposition density of radiocesium, as of August 2011, was precisely determined to be 0.32 ± 0.03 MBq m⁻² (k = 1). The density corroborated the previous results obtained by other methods, i.e., airborne surveys, in-situ Ge surveys and soil samplings at neighboring locations. Other than radiocesium, the only gamma-emitting nuclide detected was ^110mAg, with a concentration of 560 Bq kg⁻¹ in the residue. The radioactivity concentrations of ⁸⁹Sr, ⁹⁰Sr, ²³⁸Pu and ^239+240Pu in the water were all less than the minimum detectable activities – 2, 0.1, 0.002 and 0.002 Bq L⁻¹, respectively.     

Seasonal variations of radon and the radiation exposure levels in Nerja cave, Spain

²²²Rn concentrations in the air in Nerja cave (Spain) (3° 52′35′′W 36° 43′50′′N) were measured by continuous monitoring using Alpha-Guard, Genitron instrument equipment. The ²²²Rn measurements were carried out for a complete annual cycle in the different halls: Vestibule hall from July 2003 to June 2004, Ballet hall from July 2004 to June 2005 and Mirador hall from July 2005 to June 2006. Starting from the entrance of the cave we successively find the Vestibule hall, the Ballet hall and the Mirador hall. The range of ²²²Rn levels were of 8–627 Bq m⁻³ for the Vestibule hall, 28–575 Bq m⁻³ for the Ballet hall and 38–578 Bq m⁻³ for the Mirador. The aim of this study was to detect seasonal variation patterns of ²²²Rn concentrations. The seasonal variations of ²²²Rn concentrations are discussed in relation to various meteorological factors measured inside and outside the cave. The radiation exposure levels for workers and tourists with different equilibrium factors have been evaluated. The radiation exposure levels for workers and tourists only represent a low percentage of the exposure guides for the general population.     

Indoor radon measurement via Nuclear Track Methodology: A comparative study

Indoor radon concentration represents an important public health challenge, for simple and inexpensive measurement devices and methods, suitable for large-scale indoors radon measurements, are required. Nuclear Track Methodology, by using a closed-end cup device as a radon chamber is an attractive option for such large-scale indoor radon measurements. A comparative analysis of the detection efficiency of four different (one commercial and 3 specially designed) passive closed-end cup devices for the measurement of indoor radon concentrations is presented. CR-39 (Lantrack®) polycarbonate was the detector material. The four devices were simultaneously exposed to a mean radon concentration of 860 ± 60 Bq m⁻³ inside a closed room for periods of one, two and three months. An AlphaGUARD^® radon monitoring system was used to continuously monitor the radon concentration within the room. The chemical etching and reading procedures were carried out following a well-established protocol for indoor radon surveys. The detection efficiency and the exposure-time-response relationship of each of the devices were determined.     

Correlations between radon in soil gas and the activity of seismogenic faults in the Tangshan area,North China

The spatial variation of soil gas radon values were correlated with the seismogenic faults and earthquakes in the Tangshan area (north China). Radon concentrations were measured at 756 sites in an area about 2500 km² from April to May 2010. The background and anomaly threshold values calculated were 4730.4 Bq/m³ and 8294.1 Bq/m³, respectively. Radon concentrations highlight a decreasing gradient from NE to SW in the area. Higher values mostly distributed in the NE sector of the Tangshan fault and the Luanxian fault where the Tangshan (Ms 7.8), and Luanxian (MS 7.1) earthquakes occurred in 1976 and 17 earthquakes with MS = 3.0 occurred in this area since 2005. Radon values illustrated a close relation with the shallow fault trace and earthquake activity in the area. The active fault zones and the associated fractures formed by the larger earthquakes, act as paths for radon migration.     

Atmospheric 222Rn concentration and source term at El Arenosillo 100 m meteorological tower in southwest Spain

²²²Rn concentration time series at 10 m and at 100 m have been measured hourly for one year at the meteorological station, El Arenosillo, on the Spanish southwest coast. A ²²²Rn flux characterization was also done.A seasonal analysis of atmospheric ²²²Rn concentration was performed and results for each season present evidence associated with the origin of air masses reaching the El Arenosillo station. An increase in ²²²Rn concentration was observed when the wind came from Morocco, the Sierra Morena and the Guadalquivir valley areas. On the other hand, a net ²²²Rn concentration decrease was found when the wind came from the Atlantic Ocean and the South of Portugal.Low ²²²Rn flux of 4 Bq m^?2 h^?1 was measured. This result makes this station a useful site for studies related to remote ²²²Rn source contributions because of low local ²²²Rn background. The measured annual average concentration of ²²²Rn gas at the El Arenosillo station is 3.51 ± 0.05 Bq m^?3 at 10 m and 2.61 ± 0.05 Bq m^?3 at 100 m.     

Natural radiation background in the ancient city of Palmyra

Natural radiation background has been determined for the Ancient City of Palmyra and its surrounding areas. Car-borne gamma spectrometry, indoor radon gas concentration and natural radionuclides levels in environmental samples (soil, water and plants) have been determined. Two types of dwelling were involved in this study, one with cancer cases, and the others without. The results showed that indoor radon gas concentrations and radiation exposure rates are within reported mean background levels in Syria (45 Bq m^?3 and less than 0.1 μSv h^?1, respectively); no differences were noticed between the dwelling groups. In addition, the results did not indicate any relation between recorded cancers and measured natural radioactivity.     

Efficiency of ionizers in removing airborne particles in indoor environments

Air ionizers are increasingly being used to clean indoor environments of particle pollution. We tested the efficiency of a small negative ion generator (Aironic AH-202) in removing ultrafine particles from indoor environments. A high-flow air filter fitted with a HEPA filter was used to compare the removal efficiencies. We estimated the percentage of particles removed when the ionizer was operated within a closed chamber of volume 1 m³, in a closed unventilated room of volume 20 m³ and in three force-ventilated rooms of volume 32, 45 and 132 m³. The closed chamber studies were conducted with ambient particles and with smoke at particle number concentrations of 5 × 10³ and 7 × 10⁴ cm⁻³, respectively. In both cases, 70% of the particles were removed by the ionizer in 15 min. In general, the particle removal efficiency of both the ionizer and the air filter decreased as the room size increased. Both devices were also more effective in unventilated rooms than in ventilated rooms. The most important finding in this study was that, while the air filter was more effective than the ionizer in the two small rooms, the ionizer was clearly more effective than the air filter in the three largest rooms. We conclude that air ionizers are more suited than high-flow air filters in removing ultrafine particles from rooms larger than about 25 m³. The investigation also showed that small ions produced by the ionizer, placed in one room, were carried through the air conditioning system into other rooms, effectively removing particles from the air in these rooms in the process.     

An intercomparison of indoor radon data using NTD and different dynamic recording systems

Indoor radon data monitored with several different recording systems in a controlled cellar were analyzed. The one-room cellar is carved into volcanic rock and presents an almost constant radon emanation throughout the year. Measurements were performed using the AlphaGUARD^®, Sun Nuclear^® 1027, DOSEman^® and RAD7^® radon monitors, and CR-39 Lantrack^® in a passive integrating detector. The radon concentrations measured by the active detection systems and averaged over the three-month measurement period ranged from 533 to 805 Bq m⁻³. The response of the passive detector system was a linear function for exposure times of one, two and three months. The data are discussed as a function of changes in the distribution of radon within the cellar and the response characteristics of the detection devices.     

Seasonal indoor radon concentration in FYR of Macedonia

This paper presents the results of the seasonal indoor radon concentration measurements in dwellings in all regions of the Former Yugoslav Republic (FYR) of Macedonia. The measurements were made in 437 dwellings using CR-39 track detectors over four successive three-month periods (winter, spring, summer and autumn) throughout 2009. The results of analysis of variance showed statistically significant differences between indoor radon concentrations in different seasons. The geometric mean values and geometric standard deviations of indoor radon concentrations in winter, spring, summer and autumn were obtained to be: 115 Bq m^?3 (2.02), 72 Bq m^?3 (1.97), 46 Bq m^?3 (1.95), 92 Bq m^?3 (2.02), respectively. The geometric mean values of spring, summer and autumn to winter ratios were found to be: 0.63 (1.50), 0.40 (1.81), and 0.80 (1.58), respectively. The results of the analysis of the variance showed statistically significant differences among the indoor radon measurements for the regions in different seasons. The influence of the factors linked to building characteristics in relation to radon measurements in different seasons was examined. The factors which enable a differentiation into subgroups (significance level p < 0.05) are the floor level, basement and building materials.     

Natural radionuclides and hazards of rock samples collected from Southeastern Nigeria

Gamma radiation from natural radionuclides in thirty eight rock samples collected from Southeastern Nigeria was measured using gamma-ray spectrometry method. The activity concentrations varied from 13.1 ± 1.6 Bq kg⁻¹ (ferrogeneisis shale) to 129 ± 38 Bq kg⁻¹ (granite) for ²²⁶Ra, 42.4 ± 4.5 Bq kg⁻¹ (siltstone) to 150 ± 23 Bq kg⁻¹ (pegmatite) for ²³²Th and 64.5 ± 6.3 Bq kg⁻¹ (ferrogeneisis shale) to 882 ± 298 Bq kg⁻¹ (granite) for ⁴⁰K. Hazard indices were used to determine the suitability of the rock samples for building in the context of radiological hazard. The results obtained for the radium equivalent activity and the external hazard index show that two of the samples, granite and pegmatite exceeded the recommended limits of 370 Bq kg⁻¹ and 1, respectively. However the results of the gamma index were below the recommended limit. The dose rates and the annual effective dose calculated ranged from 0.012 to 0.042 μGy h⁻¹ and 0.06–0.21 mSv, respectively.     

Application of recurrent radon precursors for forecasting large earthquakes (Mw > 6.0) near Antung,Taiwan

Radon anomalies in groundwater were recorded prior to three major earthquakes – (1) 2003 M_w = 6.8 Chengkung, (2) 2006 M_w = 6.1 Taitung, and (3) 2008 M_w = 5.4 Antung. The epicenters were located 24 km, 52 km, and 13 km, respectively, from the Antung radon-monitoring station. Prior to the three major earthquakes, radon decreased from background levels of 29.3 ± 1.7, 28.2 ± 2.1, and 27.2 ± 1.8 Bq dm^?3 to minima of 12.1 ± 0.3, 13.7 ± 0.3, and 17.8 ± 1.6 Bq dm^?3, respectively. Based on the radon precursory data, this paper correlates the observed radon minima with earthquake magnitude and precursory time. The correlations provide a possible means for forecasting local disastrous earthquakes in the southern segment of coastal range and longitudinal valley of eastern Taiwan.     

Radioactivity levels in surface water of lakes around Izmir/Turkey

The aim of this study is to determine the radioactivity levels as a baseline for further studies and to obtain the distribution patterns of radioactivity in lake surface water around Izmir/Turkey. In this study, surface water samples were collected from three lakes around Izmir–Turkey. Surface water samples were analyzed for pH, mV conductivity and alkalinity content. The gross alpha/beta and uranium concentrations were investigated in the collected lake water samples. Mean gross alpha and gross beta activity concentrations in the surface water were found to be between (0.03 and 2.62) Bq l⁻¹ for Karagol Lake, (0.75 and 2.35) Bq l⁻¹ for Golcuk Lake, (0.03 and 1.77) Bq l⁻¹ for Cakalbogaz Lake, respectively. Uranium concentration varied between (0.05 and 900) μg l⁻¹ for Karagol Lake, (0.05 and 0.95) μg l⁻¹ for Golcuk Lake and (3.33 and 10) μg l⁻¹ for Cakalbogaz Lake. Radioactivity contour maps were produced and their data were evaluated statistically.     

Radon in soil and its concentration in the atmosphere around Mysore city, India

Radon concentration in soil-gas and in the atmospheric air has been studied around Mysore city (12°N and 76°E) using Solid State Nuclear Track Detectors. The radon in soil-gas is found to be higher at a depth of 1 m than at a depth of 0.5 m from the ground surface. The higher radon concentration in soil was observed near Chamundi Hills and Karigatta village with average values of 5.94 kBq.m⁻³ and 5.32 kBq.m⁻³ at 1 m depth from the ground surface. Seasonal variations in radon in soil gas shows that, the concentration is lower in summer with an average value of 0.60 kBq.m⁻³ and higher in monsoon season with an average value of 4.70 kBq.m⁻³. Estimation of ²²⁶Ra in soil at these locations is also made using HPGe detector. The activity of ²²⁶Ra, varies from 4.82 to 74.23 Bq.kg⁻¹ with an average value of 32.11 Bq.kg⁻¹. Radon concentrations in soil-gas shows good correlation with the activity of ²²⁶Ra in soil with a correlation coefficient of 0.76     

Exposure to indoor radon and natural gamma radiation in public workplaces in north-western Greece

Measurements of indoor radon levels and gamma dose rates were performed in 42 workplaces in Ioannina, north-western Greece. Radon concentrations followed a log-normal distribution with an arithmetic mean of 95 ± 51 Bq m^?3. In all cases, radon levels were below 400 Bq m^?3, which is the action level implemented by the Greek Regulation for Radiation Protection, in accordance with the European Commission recommendation. Comparing summer and winter measurements, no statistically significant seasonal variation was established. However, radon concentrations measured in basement and ground floor workplaces were significantly higher (p < 0.01) than those measured in the first and upper floors. Annual effective dose rates from inhalation of radon and its decay products were estimated to be in the range from 0.13 to 1.36 mSv y^?1 with a mean value of 0.62 mSv y^?1. Indoor exposure to natural gamma radiation entailed an average effective dose rate of 0.13 mSv y^?1, of which approximately 62% was due to terrestrial and the rest due to cosmic sources. The reported data contribute to the assessment of radon distribution and dose estimate at the national level.     

Enhancement of Anammox performances in an ABR at normal temperature by the low-intensity ultrasonic irradiation

A lab-scale ultrasound enhancing Anammox reactor (ABR_U) was established and irradiated once a week by ultrasound with the optimal parameter (frequency of 25.0 kHz, intensity of 1.00 W cm⁻² and exposure time of 36.0 s) obtained by response surface methodology (RSM). ABR_U and the controlled Anammox reactor (ABR_C) without ultrasonic treatment were operated in parallel. The start-up time of Anammox process in ABR_U (59 d) was shorter than that in ABR_C (69 d). At the end of the nitrogen load-enhancing period, NLR (0.500 kg N m⁻³ d⁻¹) and NRR (0.430 kg N m⁻³ d⁻¹) in ABR_U were both higher than NLR (0.400 kg N m⁻³ d⁻¹) and NRR (0.333 kg N m⁻³ d⁻¹) in ABR_C. The results of RTQ-PCR demonstrated that the specific low-intensity ultrasound irradiation improved the enrichment levels of AnAOB in mature sludge. SEM images and the observation of the macroscopic morphology of mature sludge showed that the ultrasound irradiation strengthened the formation of Anammox granular sludge, thereby improved the interception capacity and impact load resistance of the reactor, and enhanced the nitrogen removal performance in ABR_U. The ultrasonic enhanced Anammox reactor based on an ABR with the optimal parameters can promote the rapid start-up and efficient and stable operation of the Anammox process at normal temperature (around 25.0 °C).     

Radium equivalent and annual effective dose from geological samples from Pedra – Pernambuco – Brazil

The natural radioactivity of an uranium-anomalous area utilized for agricultural activities in Pedra, Brazil, was monitored. For this, samples from the granite and calcium-silicate amphibole rocks underlying this area and also from samples of the soil derived from these rocks were collected and analyzed by high-resolution gamma spectrometry. The equivalent radium (Ra_eq) was used as a reference for estimating the rate of the effective equivalent dose. The average, minimum and maximum values for the samples were of 319.2 Bq kg^?1 (91.1–758.5 Bq kg^?1) for soil; 327.5 Bq kg^?1 (36.3–1624.0 Bq kg^?1) for granitic rocks and 70,124.5 Bq kg^?1 (16,979.6–147,159.0 Bq kg^?1) for the calcium-silicate amphibole rocks. An estimation of the external exposition was carried out based on the calculation of the parameters obtained.