7Be Activity Concentrations Research Articles

Atmospheric concentrations of 7Be and 210Pb in weekly aerosols at Hirosaki, a heavy snowfall area in Japan.

To understand the regional properties of atmospheric 7Be and 210Pb concentrations at Hirosaki, aerosol samples were collected weekly for the investigation. Total suspended particles (TSP) concentration ranged from 0.14 to 1.19mgm-3 with a mean value of 0.29±0.08mgm-3. The activity concentrations during the observation period have shown a similar trend between 7Be and 210Pb, comparable to reported studies. The activity concentrations of 7Be and 210Pb ranged from 0.46 to 4.94 mBq m-3 with an average of 2.22 mBq m-3 and from 0.26 to 1.29 mBq m-3 with an average of 0.64 mBq m-3, respectively. The relation between precipitation and radionuclide concentrations indicated that precipitation is an essential factor in the radionuclide removal process. The rainfall/snowfall had a significant impact on the deposition, and the process was greatly affected by the changes in the features of raindrops and snowflakes, such as intensity, shape, surface area, and falling speed.

Variation analysis of atmospheric 7Be activity concentrations with respect to precipitation

Beryllium-7 activity concentrations in the atmosphere and precipitation were continuously measured every day between April 2011 and December 2015 in Dazaifu, western Japan. The measured data were quantitatively analyzed to determine the precipitation-induced variation in 7Be activity concentrations. The average concentrations on nonprecipitation and precipitation days were 5.5 and 3.8 mBq/m3, respectively. This difference of 31% (1.7 mBq/m3) on average, was attributable to the washout effect, which was more significant in the summer. Regarding the association between 7Be activity concentration and precipitation, the concentration remained at a similar level for the small precipitation amount of <5.0 mm/day and showed a decreasing trend (but was insignificant) for the precipitation of 5.0–10.0 mm/day. A significant decrease in the concentration was observed for ≥10 mm/day. Furthermore, when precipitation occurred on two successive days, the 7Be activity concentrations on the second day significantly decreased regardless of precipitation.

Assessment of Be-7, Pb-210 and Po-210 Activities in Airborne Particulate Matter Over Istanbul, Türkiye.

Airborne particulate matter is one of the air pollutants which can have detrimental health effects in the human body. Radionuclides adsorb onto air particles and make their way to humans primarily through inhalation. Naturally-occurring radionuclides, 210Pb and 210Po, are of notable health concern due to their relatively elevated ingestion and inhalation doses. In the current study, activity concentrations of 7Be, 210Pb and 210Po were determined in air particulate matter (PM). PM2.5 was collected on the European side, while PM10 was collected on the Anatolian side of Istanbul. Be-7, 210Pb and 210Po activities were found to be 5.17 ± 2.35, 0.96 ± 0.42; 0.25 ± 0.14 mBq m- 3 in Anatolian side, respectively. Be-7, 210Pb and 210Po activities were found to be 3.81 ± 2.27, 0.62 ± 0.29, 0.29 ± 0.26, mBq m- 3 in European side, respectively. The ratio of 210Po/210Pb was found to be higher (0.47 ± 0.31 for PM2.5 and 0.34 ± 0.27 for PM10) than the global average of 0.1. This result can be explained by the fact that Po is more volatile than Pb and enhanced in the air by the combustion process. Inhalation dose rates of 210Pb and 210Po due to PM10 exposure were calculated to be 7.70 ± 3.30 and 4.05 ± 2.31 µSv year- 1, respectively. Pb-210 bioaccessibility was assessed by the extraction of the particles in simulated lung fluids. Approximately 24.8% of inhaled 210Pb was estimated to be bioaccessible. This study suggests that 210Po and 210Pb activities are partially enhanced in the air particles in Istanbul and should be regularly monitored.

Temporal variations of 7Be and 210Pb activity concentrations in the atmospheric aerosols during 2018–2019 in Beijing, China and their correlations with meteorological parameters

In order to establish a regional database on natural radioactivity, a series of measurements of 713 atmospheric aerosol samples collected on filters over a two-year period (2018–2019) in center of Beijing, northeastern China have been performed to analyze 7Be and 210Pb activity concentrations. The mean activity concentrations of 7Be and 210Pb were found to be 7.10 ± 2.44 mBq m−3 and 2.93 ± 1.52 mBq m−3, respectively. Both the radionuclides exhibited strong seasonal variations, with maximum concentration of 7Be occurring in the spring and that of 210Pb in the winter. The concentration of both the radionuclides was minimum in the rainy summer. Higher 7Be concentration in the spring was mainly caused by the stratosphere to troposphere exchange. Higher 210Pb concentration during winter was maybe attributed to the combustion processes in heating systems and the ingression of continental air masses resulted from winds originating from northwest. The dependence of the activity concentrations of 7Be and 210Pb with meteorological parameters such as rainfall, temperature, and humidity was studied through linear correlation analysis. Statistically significant negative correlations were observed between 7Be and 210Pb activity concentrations with rainfall, respectively, which suggested that the removal mechanisms of these two radionuclides were similar. Lead-210 showed statistically significant correlations with temperature, humidity and PM10. A comparison of the data obtained in the present study for Beijing with the northern hemisphere literature values of 7Be and 210Pb in the atmospheric aerosols showed that the values were smaller than the ones observed in the present study. Overall, the study provides an improved understanding of the temporal variability and correlation of 7Be and 210Pb concentrations in the atmosphere in center of Beijing, northeastern China.

Influence of Precipitation on the Spatial Distribution of 210Pb, 7Be, 40K and 137Cs in Moss

Mosses have been widely used as biomonitors of a variety of atmospheric pollutants, including radionuclides. Here we determine the radionuclide activity concentration of 210Pb, 137Cs, 7Be, and 40K in moss tissue (Hylocomium splendens) collected from 24 sites across Ireland and assess the influence of precipitation on radionuclide spatial distribution. Lead-210 was the most abundant radionuclide (range: 226–968 Bq kg–1), followed by 7Be (range: &lt;DL—604 Bq kg–1), 40K (range: &lt;DL—155 Bq kg–1), and 137Cs (range: &lt;DL—41 Bq kg–1). Albeit nearly thirty years since the Chernobyl disaster, 137Cs activity concentration was detected at 67% of the study sites; however, the spatial distribution was not fully consistent with the 1986 Chernobyl deposition pattern. Rather, 137Cs was weakly correlated with rainfall, with higher concentrations along the west coast, suggesting that the 2011 Fukushima Dai-ichi nuclear accident was also a potential source. Average annual rainfall was a significant predictor of 210Pb activity (linear regression, R2 = 0.63, p &lt; 0.001). As such, the highest radionuclide activity was observed for 210Pb (average: 541 Bq kg–1), owing to the high levels of precipitation across the study sites (average: 1585 mm). In contrast, 7Be or 40K were not correlated with precipitation; rather, 40K and 7Be were significantly correlated to each other (rs = 0.7), suggesting that both radionuclides were transferred from the substrate or through soil re-suspension. Precipitation is widely reported as an important factor in the spatial distribution of radionuclides; however, only 210Pb activity concentrations in moss were strongly influenced by precipitation in the current study.

PSCF and CWT methods as a tool to identify potential sources of 7Be and 210Pb aerosols in Granada, Spain

This research is focused on studying the preferred source regions and the pathways of the air masses with high particulate concentrations impacting on the activity concentrations of 7Be and 210Pb aerosols in Granada atmosphere. For this purpose, three different source-receptor methods have been used: Cluster Analysis, Potential Source Contribution Function (PSCF), and Concentration Weighted Trajectory (CWT). Air filter samples were weekly collected and analysed in Granada university (Spain 37.177N, 3.598 W, 687m a.s.l.) during 12 years (2006–2017) for the activity concentration of 7Be, and during 5 years (2010–2014) for the one of 210Pb. The time series of the collected data indicate that the concentration of both radiotracers present a cyclical and seasonal pattern, in association with their origins and atmospheric conditions. Clustering analysis showed that the air masses arriving to Granada can be classified as: (1) tropical continental air masses coming from the Mediterranean Sea, (2) tropical and warm polar maritime air masses produced over the Atlantic Ocean, and (3) continental air masses originated over Europe and Northern Africa. The PSCF and CWT methods confirmed that the main source areas of 7Be are located in the Atlantic coast of southern Morocco, and Northern Africa. On the other hand, southern France and the Algerian desert were found to be the main region sources of 210Pb. In addition, the Mediterranean Basin has been postulated as a strong source region for 7Be and 210Pb. Furthermore, the PSCF and CWT models show that the regions with larger 7Be/210Pb ratios are located in the Atlantic Ocean, due to frequent stratospheric intrusions specially during the winter months.

Analysis of Factors Contributing to the Increase in 7Be Activity Concentrations in the Atmosphere.

In March 2013, increased 7Be activity concentrations in the atmosphere were observed for successive days in Dazaifu, western Japan. The daily 7Be activity concentration ranged from 0.93 to 14 mBq/m3, with a monthly average of 8.3 mBq/m3. This average was the highest among the monthly averages observed between 1999 and 2015, and higher than the monthly average over this period (4.7 mBq/m3) plus twice the standard deviation. Also, this exceeded the monthly average (6.0 mBq/m3) only for March 1999–2015 (excluding 2013, when the cosmic-ray intensity, a component producing 7Be, decreased). Based on the backward trajectory analysis etc. results, the inflow of air from the stratosphere and upper troposphere at high latitudes that frequently occurred in March 2013 was considered the reason for the 7Be activity concentration increase.

Precipitation scavenging of beryllium-7 (7Be): Observation results and parameterization

This study aims to develop a 1D model that makes it possible to calculate the daily total 7Be wet deposition flux. For this purpose, long-term (2015–2021), high-frequency (daily) and time-synchronized series of observations of 7Be wet deposition flux and its atmospheric activity concentration are analyzed in this paper. Daily mean 7Be activity concentration in the atmosphere, daily total 7Be wet deposition flux and mean 7Be activity concentration, washout ratio, deposition velocity and scavenging coefficient with individual precipitation events lie in the range of 0.1–17 mBq m−3, 0.8–117.2 Bq m−2 d−1, 0.4–11.3 Bq L−1, 331–3799, 0.2–24.7 cm s−1 and (0.8–35.6) × 10−5 s−1, respectively. Quantitative estimates of the influence of precipitation parameters (amount, intensity and duration) on the daily total 7Be wet deposition flux, mean 7Be activity concentration in precipitation, washout ratio, deposition velocity and scavenging coefficient with individual precipitation events have been obtained using correlation analysis. It has been found that precipitation amount has the greatest influence on 7Be deposition flux and deposition velocity, precipitation intensity has the greatest influence on washout ratio and scavenging coefficient, and precipitation duration has the greatest influence on 7Be activity concentration in precipitation. The relationships between these parameters have been parameterized. Based on these parameterizations, five 1D models that calculate the daily total 7Be wet deposition flux have been introduced and validated against the observation data. It has been revealed that the model, which is based on deposition velocity parameterization and uses the data on 7Be activity concentration in the atmosphere and the daily amount of precipitation as predictors, reproduces the highest fraction of the observational data (88%) with the lowest average calculation error (32%) compared to the other four models.

Airflow and teleconnection patterns driving the spatial and temporal variability of high 7Be air concentrations in Europe

The long-term monitoring of the cosmogenic 7Be activity concentrations has been used to better understand the influence of large-scale atmospheric circulation dynamics in the troposphere. With an aim, this study analyzes weekly 7Be data from 15 sampling stations in Europe over 2005–2014. We first define peak (or extremely high) events in each station as those activity concentrations above the 90th percentile, and then investigate their temporal and spatial variability. These events are most frequent in the spring and summer seasons, with a notable latitudinal variability in their number. Next, we use back-trajectory cluster analysis to identify the main advection pathways associated with these high concentrations. To achieve this, persistent periods, i.e., sampling periods over which at least 60% of the calculated backward trajectories arriving at a given site correspond to the same airflow pattern, are taken as reference. This method reveals large differences in the association between the airflow patterns observed at different stations in connection with the 7Be peaks. A comparison between stations shows no clear spatial pattern, which suggests a further influence of mesoscale/local physical processes on the surface 7Be activity concentrations. Finally, the main airflow pattern at each sampling site and the associated 7Be peaks, are related to the main teleconnection patterns of large scale and regional climate variability in Europe: North Atlantic Oscillation, Arctic Oscillation, East Atlantic, East Atlantic/Western Russia, Scandinavian pattern and Western Mediterranean Oscillation. The results point out the connection between the negative phases of NAO and We-MO, and the positive phase of EA with the spatial and temporal variability and occurrence of the 7Be peak activity concentrations. These results show a latitudinal division between northern and southern sites, with similar influence of teleconnection patterns, while those located in the central part of Europe present larger variability in the impact of teleconnection patterns.

Induced Radionuclides and Their Activity Concentration in Gel Dosimeters Irradiated by Carbon Ion Beam.

Radioactivity was measured in a micellar gel dosimeter, a polymer gel dosimeter, and water was irradiated by carbon ion beams at various beam energy conditions. Monte Carlo simulation was also performed to estimate the radioactivity. Short-lived positron-emitting nuclides were observed immediately after irradiation, but they decayed rapidly into the background. At 24 h post-irradiation, the dominant measured radioactivity was of 7Be. The simulation also showed minor activity of 24Na and 3H; however, they were not experimentally observed. The measured radioactivity was independent of the type of gel dosimeter under all irradiation conditions, suggesting that the radioactivity was induced by the interaction of carbon ions with water (the main component of the gel dosimeters). The ratio between the simulated and measured radioactivity was within 0.9–1.5. The activity concentration of 7Be was found to be less than 1/10 of the value derived using the exemption concept proposed by the International Atomic Energy Agency. This result should be applicable to irradiated gel dosimeters containing mainly water and 0–4 wt.% C and 0–1.7 wt.% N.

Comparison of dimension reduction techniques applied to the analysis of airborne radionuclide activity concentration

Temporal variation of airborne radionuclide activity concentration is highly influenced by several meteorological parameters. A traditional key tool to perform a combined analysis on these data is Principal Component Analysis (PCA), a linear dimensionality reduction technique that prioritizes the conservation of the data set global structure. While it reveals important information regarding the correlation among the considered variables, the obtained visual representations do not usually allow to clearly discern different clusters of states with common properties. The main goal of this study is applying two recently introduced non linear dimensionality reduction techniques, t-distributed Stochastic Neighbor Embedding (t-SNE) and Uniform Manifold Approximation and Projection (UMAP) to a data set composed by 7Be and gross beta (Aβ) activity concentration and other meteorological data gathered in Mallorca (Spain) between 2004 and 2014. Compared to PCA, both algorithms reveal more details on the local structure of the data set. UMAP allows to clearly identify data clusters with different characteristics that are not clearly identified with the alternative techniques.

Influence of precipitation on the daily beryllium-7 (7Be) activity concentration in the atmospheric surface layer

The paper presents the monitoring results of the temporal variability of daily 7Be activity concentration in the atmospheric surface layer at Sevastopol in 2011–2020. The 7Be activity concentration in individual samples of atmospheric aerosols varies from 0.1 to 13.3 mBq m−3 and averages 4.0 ± 2.0 Bq m−3. Higher 7Be activity concentrations have been observed during the period from May to August while lower concentrations have been measured from December to January. Quantitative estimates of the influence of precipitation (amount, duration, intensity) on the temporal variability of 7Be activity concentration have been obtained. It has been found that daily 7Be activity concentration decrease by 2–82% on the first day with precipitation. It has been shown that an increase in precipitation duration and a decrease in its intensity lead to a more significant decrease in the daily 7Be activity concentration. The estimates of the scavenging coefficient have been obtained; the average value is 0.6 ± 1.0 h−1. An increase in the precipitation intensity or amount is accompanied by a decrease in the 7Be scavenging coefficient. Mean 0.5-folding and residence times of 7Be activity concentration in the atmosphere during a moderate rain event are 2.9 ± 2.2 and 15.4 ± 13.6 h, respectively. The recovery of 7Be activity concentration in the atmosphere after precipitation has been investigated. It has been found that this process takes 1–2 days. The mean value of the reload coefficient is 0.94 ± 0.34 d−1. The relationship between the value of the reload coefficient and local meteorological parameters (air temperature, relative humidity, atmospheric pressure, wind speed, surface net solar radiation flux) has been investigated. No statistically significant correlations at a 95% confidence level between the reload coefficient and the considered meteorological parameters have been revealed. Parameterization describing a decrease in the daily 7Be activity concentration in the atmosphere due to precipitation and its recovery during the precipitation-free period has been introduced.

Cosmogenic 7Be: Particle size distribution and chemical composition of 7Be-carrying aerosols in the atmosphere in Japan

The particle size distributions of airborne aerosols with 7Be were measured using cascade impactors at Dazaifu, a city in western Japan, in 2018 to observe their seasonal variation. Beryllium-7 was found to be adsorbed to aerosols with a particle size of less than 2.1 μm; in general, particles sized 0.43–0.65 μm had the highest 7Be activity concentrations. The activity median aerodynamic diameter (AMAD) of 7Be fluctuated less over the year within the range of 0.40–0.52 μm, which is the size range of particles that can reach human alveoli, and had an annual mean of 0.43 ± 0.034 μm. The activity concentrations of 7Be were significantly lower in summer, which affected 7Be activity concentration for each particle size fraction. The particle size distribution of 7Be-carrying aerosols was also affected by that of the aerosol particles in the atmosphere. Finally, findings suggest that 7Be was mainly adsorbed to sulfate aerosols (particularly ammonium sulfate aerosols).

Investigation of the 2018 Shiraz dust event: Potential sources of metals, rare earth elements, and radionuclides; health assessment

In the middle of May 2018, an unprecedented dust storm occurred in the Shiraz metropolis. After the storm, several samples were collected from dust that settled around the city. These dust samples were analysed for potentially toxic elements (PTEs), rare earth elements (REEs), and radionuclides. This work is the first study that considered rare earth elements (REEs) for source identification and radionuclide contamination of Shiraz dust event. Hysplit model analysis and NASA and NOAA satellite maps illustrated that the air mass affecting Shiraz was moving mainly through the Saudi Arabian deserts. In addition, REE results of the dust that settled in Shiraz showed a trend similar to shale, sandstone, and especially Saudi Arabian soils. Ti/Al (0.01), Fe/Al (0.92), and Mg/Al (0.55) ratios and the values of LaN/SmN (0.91–0.98), GdN/YbN (1.8–2), LaN/YbN (1.7–1.9), HREE/LREE (0.52–0.6), Ce/Ce∗ (1.09–1.13), Eu/Eu∗ (1.03–1.18), Pr/Pr∗ (0.85–0.87), Gd/Gd∗ (1.1–1.15), and MREEs/MREE∗ (4.3–4.5) ratios provided insights into dust sources. These values indicated that Shiraz dust was affected by Asaluyeh and Iraq soils during transport and the main source of the dust that settled in Shiraz on the May 13, 2018 was Saudi Arabian soil. The concentrations of Mo, Cu, Pb, Zn, Ni, Co, Mn, As, Cd, Ti, Al, Sc, and Fe in the settled dust were 0.24, 47.67, 67.33, 244, 70.27, 19.33, 664, 8.39, 0.65, 537.33, 40933.33, 11.54, and 37800 mg/kg, respectively. According to the enrichment factor (EF), coefficient variation, and Positive Matrix Factorization (PMF) model the Mo, Cu, Pb, Zn, and Cd mainly originated from exhaust emissions and industrial activities. The activity concentrations of the radionuclides 7Be, 4 K, 137Cs, and 235U in the Shiraz-settled dust were 814, 421, 14, and 5.4 Bq kg−1, respectively and the activity concentration of 4 K was higher than the crustal average. Health risk assessment indices for the elements considering all three pathways revealed the following trend: dermal contact (HQderm)< inhalation (HQinh)< ingestion (HQing). The values of HQinh and HQing for children were higher than adults, while the values for the skin adsorption pathway for adults were higher than for children.

Correlations between 7Be, 210Pb, dust and PM10 concentrations in relation to meteorological conditions in northern Poland in 1998–2018

Analysis of a twenty-year (1998–2018) data series on 7Be concentrations in weekly collected aerosol samples in northern Poland showed a clear pattern of seasonal changes in 7Be with a maximum in the summer period associated with the most intensive thermal convection and vertical mixing. Activity concentrations of 7Be ranged from 480 μBq m−3 to 9370 μBq m−3. A strong relationship has been shown between 7Be concentrations observed in years and the activity of the Sun related to the sunspot number. Activity concentrations of 210Pb in aerosol ranged from 17 μBq m−3 to 1490 μBq m-3 with maximum occurring in the winter. The difference in the seasonal pattern in 7Be and 210Pb concentrations were directly related to the different sources of both isotopes, as an additional source of 210Pb was the products of combustion during the heating season. Similar pattern with maximum concentrations in winter was observed for PM10, as the main source is the same as in the case 210Pb. A content of PM10 was in the range from 6.5 to 81.7 μg m−3. A statistically significant correlation between both isotopes occurs. At the same time, 7Be, 210Pb and PM10 are visibly related to the dust concentrations ranged from 7.3 μg m−3 in winter to 134.8 μg m−3 in spring. Statistical analysis carried out with simple regression model, stepwise multiple regression, and Random Forest models showed that the sunspots number, air temperature and sunshine duration have the most substantial impact on transport, and hence the concentration of 7Be in the surface layer of the atmosphere. The increase in relative humidity and precipitation and higher wind speed have a statistically significant effect on the reduction of 7Be concentrations in surface air.

Meteorological Factors Controlling 7Be Activity Concentrations in the Atmospheric Surface Layer in Northern Spain

This work presents the analysis of weekly 7Be activity concentrations in the air measured in Bilbao (northern Spain) by collecting aerosols in filters over a ten years period (2009–2018). 7Be level is in the 0.35–7.3 mBq/m3 range, with a mean of 3.20 ± 1.12 mBq/m3. The trend, cycle, seasonal and monthly variability are evaluated using time series analysis techniques. The results indicate the impact of sunspots (24th solar cycle) on interannual 7Be activity concentrations, and a significant seasonal and monthly variation, with maximum concentrations occurring in spring-summer and minimum in the winter. The correlation of different 7Be ranges with local meteorological parameters, such as precipitation, temperature, relative humidity, and pressure, is also addressed, with precipitation having the greatest impact on 7Be activity values. The analysis of synoptic airflows, by calculating the back-trajectory clusters, and local winds at surface level reveals the important influence of the arrival of slow northwest Atlantic flows and the development of breezes on reaching high 7Be activity concentrations in this area.

Influence of Meteorological Parameters on the Variations of Atmospheric Radionuclides Concentration in Dar es Salaam, Tanzania

Atmospheric concentrations of 7Be and 212Pb were measured for 11 years (2008 – 2018) in Dar es Salaam, Tanzania. The mean activity concentrations of 7Be and 212Pb were found to be within the range of 1.29 – 5.71 mBq/m3 and 10.85 – 50.06 mBq/m3, respectively. The annual mean activity concentrations of 7Be and 212Pb were 4.72 ± 1.18 mBq/m3 and 29.76 ± 13.63 mBq/m3, respectively. Distinct annual trends were depicted on 7Be and 212Pb, suggesting that the two radionuclides were affected differently with atmospheric conditions. Monthly atmospheric concentrations of 7Be showed a strong seasonal variation trend with the highest in January and February and lowest in April. 212Pb depicted the highest concentration during June and July and lowest in January and December. The regression analysis for 7Be and 212Pb activity concentrations together with number of meteorological parameters revealed that the relative humidity, rainfall, air temperature, absolute humidity and wind speed are the most significant parameters affecting radionuclides activity concentrations in the atmosphere. The sunspot numbers show 66.7% of its variability with 7Be activity concentration which further suggesting that other parameters may influence its variation. 212Pb, on the other hand, shows only 27.3% of its variability which clearly indicates that the existence of cosmic rays does not affect its activity concentration in the atmosphere.

Impact of a massive dust storm on the gross alpha, gross beta, 40K, 137Cs, 210Pb, 7Be activities measured in atmospheric aerosols collected in Tenerife, Canary Islands

Abstract From February 22 to 24, 2020, an intense dust storm affected the Spanish archipelago of the Canary Islands. Here we assess the radiological impact on the Canary Islands population of several natural and artificial radionuclides (40K, 137Cs, 210Pb, 7Be), and other radiological parameters (gross alpha and gross beta activity concentrations) measured in atmospheric aerosols before, during and after the dust storm. Total Suspended Matter highly correlated with PM10 (Pearson's correlation coefficient, ro = 0.98), showed increments ranging from 849% to 1778% against the background average levels, reaching levels of >3000 μg m−3. 40K and 137Cs radionuclides showed activity values over the minimum detection activity from January to March 2020, coupled with dust intrusion episodes during the study. This finding supports the use of these radionuclides as radiotracers for African low altitude dust intrusions occurring particularly during winter months over the Canary Islands. A high correlation between gross beta and 210Pb activities suggests that the latter is the main source for gross beta emitters in aerosol samples collected in the study region. 210Pb and 7Be showed a moderate positive correlation and did not show any significant change during the storm, suggesting a similar dynamics of alpha and beta emitters in the low atmosphere. A Principal Component Analysis of these observations showed two components representing a Saharan component (based on 40K, 137Cs, gross alpha, and PM10) and a heterogeneous component representing North Atlantic and Europe air masses (based on 7Be, 210Pb, and gross beta). In addition, a K-means cluster analysis helped to disentangle the origin of air masses arriving at the archipelago. Three different clusters were identified: a continental cluster (based on gross beta, 210Pb, and 7Be activity concentrations); an oceanic cluster (with low values of PM10 air concentrations, gross beta, gross alpha, and 210Pb, and 7Be and 40K activity concentrations), reflecting the Atlantic air contributions with lower radionuclide activity and microparticulate matter; and a dust intrusion cluster (with high PM10 values and 137Cs, 40K and gross alpha activity concentrations) representing dust intrusion episodes observed in Tenerife Island. These studies allow the detection and monitoring of radioactive elements, estimating the potential radiological risk to the population associated with mineral dust intrusions.

7Be atmospheric activity concentration and meteorological data: Statistical analysis and two-layer atmospheric model

Atmospheric activity concentration of 7Be in the air was monitored during the period of one year from September 2015 to September 2016 at Ostrava, Czech Republic, with a two-day frequency that is shorter compared to a standard 7-day frequency of routine 7Be measurements. Simultaneously, relevant meteorological data (temperature, rainfall amount, precipitation particle size and speed, tropopause height, and PM10 concentrations) and the sunspot number were accumulated. Weighted linear regression analysis applied to the 7Be atmospheric activity concentration, the measured meteorological explanatory variables and the sunspot number revealed temperature as the most statistically significant explanatory variable. The tree model proved temperature as the most important explanatory variable and predicted the threshold value separating low and high temperature behavior of 7Be at about 13 °C (2-day average). A simple local two-layer (stratosphere and troposphere) atmospheric model was then applied to the data analysis. The model is able to fit the data for a larger accumulation period (6 days).

Temporal Variations of 7Be and 210Pb Activity Concentrations in the Atmosphere and Aerosol Deposition Velocity in Shenzhen, South China

Naturally occurring beryllium-7 (7Be) and lead-210 (210Pb) serve as powerful tracers in atmospheric studies. In this study, 7Be and 210Pb were simultaneously measured in atmospheric aerosols and deposition samples for an entire year (from January to December 2017) in Shenzhen, South China. The activity concentrations of the airborne 7Be and 210Pb ranged from 0.33 to 9.42 mBq m–3 (averaging 3.23 mBq m–3) and from 0.59 to 4.72 mBq m–3 (averaging 1.58 mBq m–3), respectively, and were observed to be high during the winter but low during the summer. Moreover, the relatively high 210Pb concentration was probably due to the elevated level of radon in this region’s soil. The deposition fluxes of the 7Be and 210Pb were found to range from 0.25 to 3.04 Bq m–2 day–1 (averaging 1.57 Bq m–2 day–1) and from 0.34 to 1.31 Bq m–2 day–1 (averaging 0.73 Bq m–2 day–1), respectively. The temporal trends of these fluxes were largely influenced by rainfall and the origin and pathway of air masses, as well as by atmospheric circulation. Based on their concentrations in the aerosols and their deposition fluxes, the average deposition velocities of 7Be and 210Pb were calculated to be 0.83 and 0.62 cm s–1, respectively. The deposition velocities of both radionuclides correlated well with the amount of rainfall, indicating that precipitation plays a crucial role in removing 7Be and 210Pb from the air. The activity size distributions of these nuclides combined with the characteristic meteorological conditions in this region resulted in high deposition velocities during summer and low ones during winter.