7Be Activity Concentrations Research Articles

A cluster analysis of back trajectories to study the behaviour of radioactive aerosols in the south-east of Spain

This research is focused on the study of the influence of the air masses together with the local meteorological fluctuations on the amount of radioactive elements in aerosols at surface air of the southeastern of Iberian Peninsula. The radioactivity in aerosols has been determined by measuring the concentration activity of Gross β and 7Be from January 4th, 2011 to December 31st, 2013. The activity concentration (Bq/m3) of gross beta was measured by α/β Low-Level counter, whereas the activity concentration of 7Be (Bq/m3) was detected by gamma spectrometry (Eγ = 477.6 KeV, Yield = 10.42%). The air mass origings have been set using k-means clustering analysis of daily 72-h kinematic 3D backward trajectories at 500 m, 1500 m and 3000 m of altitude. Finally, a multiple Regression Analysis (MRA) have been carried out in order to determine the influence of the origins and trajectories of the air masses and local meteorology variations on the evolution of Gross β and 7Be activity concentration. In conclusion, the results of the current research demonstrate that the re-suspended mineral dust from Northern Africa transported by Mediterranean air masses at low altitude (500 m) and African air masses at high altitude (3000 m) increases the radioactivity concentration in aerosols at the surface atmosphere. In addition, the opposite influence of the Saharan intrusions at 1500 m of altitude on the behaviour of 7Be aerosols deserves special attention.

Mussels (Mytilus galloprovincialis) as a bio-indicator species in radioactivity monitoring of Eastern Adriatic coastal waters

Croatian Adriatic coastal waters are systematically monitored within the Mediterranean Mussel Watch Project using mussels (Mytilus galloprovincialis) as a bio-indicator species. The study includes determination of naturally occurring (7Be, 40K, 232Th, 226Ra and 238U), as well as anthropogenic 137Cs radionuclides. Activity concentrations in dry weight of mussels' soft tissue along the Croatian Adriatic coast are presented, with spatial and seasonal variations given and discussed. Samples were collected in spring and autumn for the period between 2009 and 2013. Radionuclides were determined by gamma-ray spectrometry. Activity concentrations of 7Be were the highest in spring periods, especially in the areas with significant fresh water discharges. Activity concentrations of 40K did not vary significantly with season or location. 137Cs activities were low, while 232Th, 226Ra and 238U activities were mostly below the detection limit of performed gamma-spectrometric measurement.

A climatology of 7Be in surface air in European Union

This study presents a European-wide analysis of the spatial and temporal distribution of the cosmogenic isotope 7Be in surface air. This is the first time that a long term database of 34 sampling sites that regularly provide data to the Radioactivity Environmental Monitoring (REM) network, managed by the Joint Research Centre (JRC) in Ispra, is used. While temporal coverage varies between stations, some of them have delivered data more or less continuously from 1984 to 2011. The station locations were considerably heterogeneous, both in terms of latitude and altitude, a range which should ensure a high degree of representativeness of the results.The mean values of 7Be activity concentration presented a spatial distribution value ranging from 2.0 to 5.4 mBq/m3 over the European Union. The results of the ANOVA analysis of all 7Be data available indicated that its temporal and spatial distributions were mainly explained by the location and characteristic of the sampling sites rather than its temporal distribution (yearly, seasonal and monthly). Higher 7Be concentrations were registered at the middle, compared to high-latitude, regions. However, there was no correlation with altitude, since all stations are sited within the atmospheric boundary layer. In addition, the total and yearly analyses of the data indicated a dynamic range of 7Be activity for each solar cycle and phase (maximum or minimum), different impact on stations having been observed according to their location. Finally, the results indicated a significant seasonal and monthly variation for 7Be activity concentration across the European Union, with maximum concentrations occurring in the summer and minimum in the winter, although with differences in the values reached.The knowledge of the horizontal and vertical distribution of this natural radionuclide in the atmosphere is a key parameter for modelling studies of atmospheric processes, which are important phenomena to be taken into account in the case of a nuclear accident.

The radioactivity of seasonal dust storms in the Middle East: the May 2012 case study in Jordan

Dust storms in the Middle East are common during spring. Some of these storms are massive and carry a large amount of dust from faraway regions, which pose health and pollution risks. The huge dust storm event occurred in early May, 2012 was investigated for its radioactive content using gamma ray spectroscopy. Dust samples were collected from Northern Jordan and it was found that the storm carried a large amount of both artificial and natural radioactivity. The average activity concentration of fallout 137Cs was 17.0 Bq/kg which is larger than that found in soil (2.3 Bq/kg), and this enrichment is attributed to particle size effects. 7Be which is of atmospheric origin and has a relatively short half-life, was detected in dust with relatively large activity concentrations, as it would be expected, with an average of 2860 Bq/kg, but it was not detected in soil. Despite the large activity concentration of 7Be, dose assessment showed that it does not contribute significantly to the effective dose through inhalation. The concentrations of the primodial nuclides 40K, 232Th and 238U were 547, 30.0 and 49.3 Bq/kg, respectively. With the exception of 40K, these were comparable to what was found in soil.

7Be in atmospheric deposition: determination of seasonal indices

This paper is focused on the results for activity concentrations of 7Be in depositions recorded in Vinca Institute of Nuclear Sciences, as part of radioactivity monitoring in Institute from 1994 to 2013. year. Samples were collected on a monthly basis and activities were present on sampling day (middle of the month). The activities were determined on HPGe detectors by standard gamma spectrometry, and they ranged from 0.05 to 10.4 Bq m−2. The obtained results were statistically analyzed. The 7Be activity shows a pronounced seasonal pattern, with the maximum in spring-summer and minimum in winter.

Study of the cosmogenic factors influence on temporal variation of 7Be air concentration during the 23rd solar cycle in Málaga (South Spain)

Atmospheric 7Be activity concentrations were measured in Malaga (South Spain) during the period 1997–2007. Monthly concentrations of 7Be ranged between 2.47 and 8.12 mBq m−3 showing seasonal trend with maxima in spring–summer time. Influence of solar activity, cosmic rays and aerosol optical depth on airborne 7Be was analyzed. Weak negative correlation between sunspot number and 7Be is found. Instead, both solar energetic protons >100 MeV and cosmic rays show positive weak significant correlation with this radionuclide. Meteorology may contribute to the low correlation coefficients found. Aerosol optical depth exhibits significant correlation with 7Be, confirming that this radionuclide attaches to atmospheric particles.

Epiphytic fruticose lichens as biomonitors for retrospective evaluation of the 134Cs/137Cs ratio in Fukushima fallout

In 2011–2013, sampling of epiphytic fruticose lichens of the genera Usnea, Bryoria and Alectoria was carried out on Sakhalin and Kuril Islands (the Sakhalin region, Russia) to investigate contamination of these organisms with the Fukushima-derived 134Cs and 137Cs. Activities of the radionuclides were determined in all 56 samples of lichens taken for the analysis. After correction for radioactive decay (on 15 March 2011), the activity concentrations ranged from 2.1 Bq kg−1 (d.w.) to 52 Bq kg−1 for 134Cs and from 2.3 Bq kg−1 to 52 Bq kg−1 for 137Cs. Cesium-134 and 137Cs activities for the whole set of lichens (n = 56) were strongly positively correlated; Spearman's rank correlation coefficient was calculated as 0.991 (P < 0.01). The activity concentrations of 134Cs and 137Cs in Usnea lichens from the Sakhalin and Kunashir islands declined with a factor of three in the period from 2011 to 2013. The average biological half-time for both cesium radionuclides in lichens of the genus Usnea is estimated as 1.3 y. The mean of 0.99 ± 0.10 and median of 0.99 were calculated for the decay corrected 134Cs/137Cs activities ratios in the lichens (n = 56). The radionuclides ratio in the lichens did not depend on location of sampling site, species and the time that had passed after the Fukushima accident. The regression analysis has shown the background pre-Fukushima level of 137Cs of 0.4 ± 0.3 Bq kg−1, whereas the ratio between the Fukushima-borne 134Cs and 137Cs in the lichens was estimated as 1.04. The 134Cs/137Cs activities ratio in lichens from the Sakhalin region is consistent with the ratios reported by others for the heavy contaminated areas on Honshu Island in Japan following the Fukushima accident. The activity concentrations of natural 7Be in lichens from the Sakhalin region varied between 100 Bq kg−1 and 600 Bq kg−1; the activity concentrations did not exhibit temporal variations during a 2y-period of observations. The applicability of epiphytic fruticose lichens as retrospective bio-monitors for the air-borne radiocesium contamination of the environment is discussed.

Atmospheric deposition patterns of 210Pb and 7Be in Cienfuegos, Cuba

The radiometric composition of bulk deposition samples, collected monthly for one year, February 2010 until January 2011, at a site located in Cienfuegos (22° 03′ N, 80° 29′ W) (Cuba), are analysed in this paper. Measurement of 7Be and 210Pb activity concentrations were carried out in 12 bulk deposition samples. The atmospheric deposition fluxes of 7Be and 210Pb are in the range of 13.2–132 and 1.24–8.29 Bq m−2, and their mean values are: 56.6 and 3.97 Bq m−2, respectively. The time variations of the different radionuclide have been discussed in relation with meteorological factors and the mean values have been compared to those published in recent literature from other sites located at different latitudes. The annual average flux of 210Pb and 7Be were 47 and 700 Bq m−2 y−1, respectively. Observed seasonal variations of deposition data are explained in terms of different environmental features. The atmospheric deposition fluxes of 7Be and 210Pb were moderately well correlated with precipitation and well correlated with one another. The 210Pb/7Be ratios in the monthly depositions samples varied in the range of 0.05–0.10 and showed a strong correlation with the number of rainy days.

Analysis of 7Be behaviour in the air by using a multilayer perceptron neural network

A multilayer perceptron artificial neural network (ANN) model for the prediction of the 7Be behaviour in the air as the function of meteorological parameters was developed. The model was optimized and tested using 7Be activity concentrations obtained by standard gamma-ray spectrometric analysis of air samples collected in Belgrade (Serbia) during 2009–2011 and meteorological data for the same period. Good correlation (r = 0.91) between experimental values of 7Be activity concentrations and those predicted by ANN was obtained. The good performance of the model in prediction of 7Be activity concentrations could provide basis for construction of models which would forecast behaviour of other airborne radionuclides.

Cosmogenic 22Na, 7Be and terrestrial 137Cs, 40K radionuclides in ground level air samples collected weekly in Kraków (Poland) over years 2003-2006.

A low background gamma spectrometer with an Etruscan, 2500 years old lead shield and a muon veto detector were applied to study 22Na and 7Be activity concentration in ground level air aerosol samples collected weekly over the years 2003–2006 in Kraków. Each sample was formed with ca 100 000 m3 of passed air, collected with two parallel ASS-500 high volume air samplers. The results for 40K and 137Cs are also presented for reference and comparison. Presented frequency distributions for activity concentration and correlation between the obtained results are discussed. The activity concentration results confirmed seasonal variation of activity to be different for all the investigated radionuclides. Moreover, the seasonal variation in nucleus activity ratio was also noticed for 22Na and 7Be. Cosmogenic radionuclides being mainly of stratospheric origin, are subsequently attached to fine aerosols, via which they are transported to the ground level air. The mean aerosol transport time within the troposphere was estimated as equal to 7.5 days on average, reaching even 50 days in warm seasons. Limitations of the applied model were identified.

7Be, 210Pb, and 210Po in the surface air from the Arctic to Antarctica

In the present study we have investigated the activity concentrations of 210Pb, 210Po as well as 7Be in surface air of the North and South Atlantic (1988–1989), the Arctic Ocean (1991), and along the coastline of Siberia (1994) during succeeding expeditions in the Swedish Polar Research program.During the cruises in the Arctic Ocean during 1991-07-28 to 1991-10-04 the average air concentrations of 7Be was 0.6 ± 0.4 mBq/m3, 210Pb 40 ± 4 μBq/m3 and 210Po-38 ± 10 μBq/m3. During the Swedish-Russian Tundra Ecology-94 expedition along the Siberian coastline the average air concentrations of 7Be and 210Pb measured during May–July were 11 ± 3, and 2.4 ± 0.4 mBq/m3, and during July–September they were 7.2 ± 2 and 2.7 ± 1.1 mBq/m3 respectively. The results from measurements of the activity concentration of 210Pb in the air over the Arctic Ocean vary between 75 and 176 μBq/m3. In the air close to land masses, however, the activity concentration of 210Pb in the air increases to 269–2712 μBq/m3.The activity concentration of 7Be in the South Atlantic during the cruise down to Antarctica varied between 1.3 and 1.7 with an average of 1.5 ± 0.8 mBq/m3. The activity concentration of 210Pb in the South Atlantic down to Antarctica varied between 6 and 14 μBq/m3. At the Equator the activity concentration recorded in November 1988 was 630 μBq/m3 and in April 1989 it was 260 μBq/m3. The average activity concentration of 210Pb during the route Gothenburg–Montevideo in 1988 was 290 and on the return Montevideo–Gothenburg it was 230 μBq/m3. The activity concentration of 210Po in the South Atlantic down to Antarctica varied between 15 and 58 μBq/m3. At the Equator the activity concentration in November 1988 was 170 and in April 1989 it was 70 μBq/m3. The average activity concentration of 210Po during the route Gothenburg–Montevideo in 1988 was 63 and on the return Montevideo–Gothenburg it was 60 μBq/m3. The average of the activity concentrations in the Antarctic air of 210Pb was 27 ± 10 μBq/m3 and of 210Po it was 12 ± 7 μBq/m3.All our results were compiled together with other published data, and the global latitudinal distribution of 210Pb was converted to total annual deposition (Bq/m2/a) and fitted to a 4th degree polynomial. By using the global latitudinal distribution of 210Po/210Pb-activity ratio from our own results the global latitudinal distribution of 210Po annual deposition was derived.

Meteorological Conditions for the Variability of 7Be and 210Pb Concentrations in Surface Layer Air in Poland

The aim of this study was to determine the effect of meteorological factors on the concentration of beryllium 7Be and lead 210Pb in the surface layer air on background their variability due to environmental conditions. Data analysis was carried out for 13 Polish stations for the period 2005-2009. The measurement cosmogenic and terrestrial radioactivity were collected on network station type ASS-500. The analysis includes the following meteorological elements from NWS stations: temperature, precipitation, atmospheric pressure, wind speed, humidity, solar radiation and in addition number of sunspots (SSN). It was considered that these meteorological elements mainly responsible for the transport and removal processes of 7Be and 210Pb from the atmosphere. The study method was used correlation analysis. Because of the relatively small area of Poland, it is hard to prove the dependence of 7Be activity concentration variability on the influence of such factors as geographical location or SSN. However, the activity concentration of 7Be and 210Pb are dependent on meteorological conditions. The inverse interaction of atmosphere stability conditions on 7Be and 210Pb allows one to use the 7Be/210Pb ratio as an indicator of vertical transport in the atmosphere.

Activity size distribution and residence time of 7Be aerosols in the Arctic atmosphere

The activity size distributions of the natural radionuclide tracer 7Be in different size range fractions (<0.39 μm, 0.39–0.69 μm, 0.69–1.3 μm, 1.3–2.1 μm, 2.1–4.2 μm, 4.2–10.2 μm and >10.2 μm) were determined in the boreal atmosphere in the Arctic Research Centre of the Finnish Meteorological Institute (FMI) at Sodankylä, Finland (67°22′ N, 26°38′ E, 180 m asl). The activity median aerodynamic diameter (AMAD) ranged from 0.54 μm to 1.05 μm (average 0.83 μm). A residence time of about 8 days applies to aerosols of 0.83 μm diameter, representing the residence of aerosol particles in arctic environment. The observed positive correlation between AMAD values and RH% can be explained by the fact that condensation during high relative humidity conditions becomes more intense, resulting in increased particle sizes of atmospheric aerosols. However, greater aerosol particle sizes means higher wet scavenging rate of aerosols and as a result lower activity concentration of 7Be in the atmosphere, explaining the anti-correlation between the AMAD values and activity concentrations of 7Be. But this associated with possibly higher scavenging rates of aerosols does not necessarily alone explain the anti-correlation between the AMAD and the 7Be activities. The air mass origin associated with synoptic scale weather phenomena may contribute to that too. The Flextra model was used to assess the transport pattern and to explain the deviation in radionuclide activity concentrations and AMAD values observed in the site of investigation.

A gamma–gamma coincidence/anticoincidence spectrometer for low-level cosmogenic 22Na/7Be activity ratio measurement

In this study, a digital gamma–gamma coincidence/anticoincidence spectrometer was developed and examined for low-level cosmogenic 22Na and 7Be in air-filter sample monitoring. The spectrometer consists of two bismuth germanate scintillators (BGO) and an XIA LLC Digital Gamma Finder (DGF)/Pixie-4 software and card package. The spectrometer design allows a more selective measurement of 22Na with a significant background reduction by gamma–gamma coincidence events processing. Hence, the system provides a more sensitive way to quantify trace amounts of 22Na than normal high resolution gamma spectrometry providing a critical limit of 3 mBq within a 20 h count. The use of a list-mode data acquisition technique enabled simultaneous determination of 22Na and 7Be activity concentrations using a single measurement by coincidence and anticoincidence mode respectively.

Time lag between the tropopause height and 7Be activity concentrations on surface air

A strong positive correlation between the seasonal changes of the tropopause height and the concentration of 7Be in the surface air (R = 0.94, p < 0.0001) was observed at 40°N. Moreover, a strong positive correlation was revealed between the activity concentrations of 7Be and the temperature T (°C) (R = 0.97, p < 0.001), confirming that the increased rate of vertical transport within the troposphere, especially during warmer months, has as a result the descent to the surface of air masses enriched in 7Be. The results of the present work suggest that the temperature and the tropopause height are good indicators for transport time of air masses enriched in 7Be to the surface. Higher values of temperature or tropopause height seem to result to shorter transport times. This is attributed to atmospheric convection which provides an effective mechanism for vertical transport of air masses. Increasing tropospheric temperature has generally as a result that convection penetrates more deeply which in turn leads to an increase in tropopause height. But, the atmospheric procedures do not occur immediately after the fluctuations of correlated factors. Thus, a time lag is expected between the tropopause height and 7Be activity concentrations on surface air that might be from hours to days or weeks. The result suggests that 7Be concentrations fully respond within three days after the changes in the tropopause height.

The activity concentrations of 40K, 226Ra, 232Th, 238U and 7Be in moss from spas in eastern Serbia in the period 2000-2012

In this work we present the activity concentrations of natural radionuclides 40K, 226Ra, 232Th, 238U and 7Be in mosses. One hundred and sixty-seven moss samples were collected between 2001 and 2012 from the territory of the Sokobanja, Banja Josanica and Gamzigradska Banja spas. They were classified into 23 species. The activity concentrations (Bq/kg) in moss from Sokobanja spa were: 40K 25-427; 226Ra 0.3-36; 232Th 1.0-37; 238U 0.4-28 and 7Be 29-210; from Banja Josanica spa they were: 40K 90-242; 226Ra 2.4-11.7; 232Th 2.0-12.7; 238U 1.6-11.3 and 7Be 142-212; Gamzigradska Banja spa: 40K 95-351; 226Ra 8.0-21; 232Th 5.1-19; 238U 6.7-18 and 7Be 20-144. The activity concentrations of dominant natural radionuclides (potassium, radium, thorium and uranium) in the moss samples were within the usual ranges for the territory of Serbia.

Temporal changes of beryllium-7 and lead-210 in ground level air in Serbia

7Be, 210Pb and 137Cs activity concentrations in ground level air at five monitoring stations (MS Vinca, Zeleno Brdo, Zajecar, Vranje and Zlatibor) in Serbia were determined during the period from May 2011. to September 2012., as part of the project monitoring of Serbia. Activity of the radionuclides in air was determined on an HPGe detector (Canberra, relative efficiency 20 %) by standard gamma spectrometry. Concentrations of cosmogenic 7Be, ranged from 1.5 to 8.8 mBq m-3 and exhibit maxima in the spring/summer period. The maximum concentrations for 210Pb were generally obtained in the fall for all investigated locations, and concentrations were in range 3.6 - 30 ? 10-4 Bq m-3. The activity concentrations of anthropogenic 137Cs in ground level air, during the observed period, were at level 0.3 - 8 ?Bq m-3. The variations in 7Be/210Pb activity ratio for the investigated stations are also presented.

7Be, 210Pb and 137Cs concentrations in cloud water

Cloud water was sampled during 8 months, in 2008 and 2009, at the puy de Dome high-altitude atmospheric research station (France). The concentrations of 7Be and 210Pb, both naturally occurring radionuclides, and 137Cs of anthropogenic origin, were determined. Those values are useful for a better knowledge of the aftermath cloud deposition and more generally for wet deposition assessment of radionuclides. This is of primary interest in case of a nuclear accident, especially considering 137Cs deposition, both for high-altitude locations that are regularly embedded by clouds and also for lowlands where fog can occur.The 7Be and 210Pb average activity concentrations in cloud water found were 1.9±0.11mBqm−3 air and 140±10μBqm−3 air, respectively. For 137Cs, the average concentration was 0.14±0.02μBqm−3 air. This very low-level is representative of the long term post-accidental background level. Indeed, for the studied period, the last accidental 137Cs release was that of Chernobyl accident, in April 1986. To our knowledge this is the first data about 137Cs reference level determination in cloud water. The comparison between cloud water and rain water concentrations showed a ratio cloud/rain ranging between 3.4 and 8.1, in agreement with previous studies performed on inorganic compounds. Scavenging efficiencies of aerosols by cloud droplets were also calculated with the additional aerosol concentrations routinely measured at the station and were quite low (0.13–0.40) compared to what has previously been observed for inorganic soluble ions.

Hadley cell influence on 7Be activity concentrations at Australian mainland IMS radionuclide particulate stations

Beryllium-7 (7Be) daily data from the four International Monitoring System (IMS) radionuclide particulate stations on mainland Australia are analysed over the period 2001 to 2011. The analysis indicates that levels of 7Be in surface air at the stations follow annual cycles, with yearly peak activity concentrations occurring later at stations further south. The yearly peak migrates north–south at a rate of approximately 4.4° latitude per month. The change in phase of the 7Be annual cycle between the stations corresponds with the seasonal migration of the Southern Hemisphere Hadley cell across mainland Australia. The implication is that the changing position of the downward limb of the Southern Hemisphere Hadley cell regulates the phase of the annual cycle in 7Be activity concentrations in surface air in the Australian region.

Activity size distribution of some natural radionuclides

In this study, the results concerning the activity size distribution of the long-lived ((210)Pb) radon decay product aerosols and the thoron decay product aerosols ((212)Pb) and ((7)Be) of the outdoor atmosphere are presented. Also, the mass size distribution of the aerosol particles is determined. The low-pressure Berner cascade impactor Model 20/0.015 was used as a sampling device. The activity size distribution of these radionuclides was determined by one log-normal distribution (accumulation mode) whereas the mass size distribution was by two log-normal distributions (accumulation and coarse mode). The activity median aerodynamic diameter (AMAD) of (212)Pb was found to be 305 nm with a geometric standard deviation (σg) of 2.41. The specific air activity concentration of (212)Pb was found to be 0.14 ± 0.012 Bq m(-3). An AMAD of (210)Pb of 610 nm with σg of 1.8 was determined, whereas that of 550 nm with σg of 1.97 was determined for (7)Be. The specific air activity concentration of (210)Pb and (7)Be was found to be 0.0016±2.5×10(-4) and 0.00348 ± 4×10(-4) Bq m(-3), respectively. Using a dosimetric model, the total deposition fraction as well as the total equivalent dose has been evaluated considering the observed parameters of the activity size distribution of (212)Pb. At a total deposition fraction of ∼21 %, the total equivalent dose was found to be 0.41 µSv.