7Be, 210Pb and 40K depositions over 11 years in Málaga

Transport and deposition of radionuclides from northern Africa to the southern Iberian Peninsula and the Canary Islands during the intense dust intrusions of March 2022

The present study focuses on the two consecutive and markedly intense Saharan dust intrusion episodes that greatly affected southern Spain (Málaga) and, to a lesser extent, the Canary Islands (Tenerife), in March 2022. These two episodes were the result of atypical meteorological conditions in the region and resulted in record levels of aerosols in the air at the Málaga location. The activity levels of various natural and artificial radionuclides (7Be, 210Pb, 40K, 137Cs, 239Pu, 240Pu, 239+240Pu) and radioactive indicators (gross alpha and gross beta) were impacted by these events and the results are described herein. These episodes caused, for example, the activities of 137Cs in aerosol samples at the Málaga monitoring station to reach the highest concentrations ever recorded since high-volume aerosol monitoring started at this site in 2009. A link between the activity levels of 137Cs, 40K and gross alpha in the atmospheric aerosols and daily PM10 concentrations during the episodes is also reported. In addition, isotopic ratios are discussed in the context of the source and destination of the various anthropogenic radionuclides measured. The atmospheric residence time of aerosols during these episodes is also evaluated because it concerns how intrusions to the Canary Islands should be analysed. Finally, for the first time, the concentrations of 137Cs deposition by rainwater during a Saharan dust intrusion are reported and the deposition rate of these radionuclides during these episodes is discussed.

Atmospheric depositional fluxes of 210Pb in bulk precipitation at the Adriatic coast, Croatia

The atmospheric bulk depositional fluxes of 210Pb were measured at a station on the Adriatic coast, Croatia over 4 years period from March 2017 to December 2020. The monthly depositional fluxes followed oceanic deposition patterns with a lower flux between 0.0735 and 16.9 Bq m-2 month-1. The volume-weighted activities were 0.000514 and 1.35 Bq L-1 and decreased with increasing precipitation. A clear seasonal trend was observed with higher depositional flux in autumn and minimum value in the winter season. The average annual bulk depositional flux and volume-weighted activities of 210Pb were 73.8 Bq m-2 y-1 and 0.119 Bq L-1 respectively. The precipitation normalized enrichment factor (α) indicates higher depositional fluxes of 210Pb during summer and spring than desired value according to the amount of precipitation. We found that the 210Pb depositional fluxes in the coastal stations are lower due to 210Pb-depleted oceanic air masses and increase with the amount of precipitation.

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.

10-Years assessment of 7Be and 210Pb in atmospheric bulk depositions in Cienfuegos (Cuba)

10-years records of monthly bulk atmospheric fluxes of ⁷Be and ²¹⁰Pb (wet + dry, n = 119 samples) at a coastal station in Cienfuegos (Cuba) between 2010 and 2019 were reported and assessed in function of their temporal variability and meteorological influence. Fluxes of ⁷Be and ²¹⁰Pb ranged from 120 to 15617 and from 29 to 911 mBq m^-2 day^-1, respectively. Both radionuclides exhibited a similar seasonal trend with highest values during wet months and minimum values during dry months. The removal of ⁷Be and ²¹⁰Pb from the atmosphere was mainly controlled by wet depositions, while dry deposition was estimated to be more important for ²¹⁰Pb (29% of the total bulk deposition) than for ⁷Be (12%). The ²¹⁰Pb/⁷Be ratios (average of 0.10) showed low variability during wet months with abrupt peaks in the driest months with low temperatures and the highest wind speed and pressure, which was mainly attributed to contributions from soil resuspension. The calculated total deposition velocity of aerosols derived from ⁷Be (average of 0.48 cm s^-1) and ²¹⁰Pb (average of 0.47 cm s^-1) was in agreement with values reported in the literature. Multiple linear regression models for the monthly fluxes of ⁷Be and ²¹⁰Pb based on precipitation, temperature and pressure and explaining about 60% of their variances were derived, highlighting the preponderant role of the local and regional conditions on the variability of these radionuclides. The annual fluxes of ⁷Be (209-1901 Bq m^-2 y^-1) and ²¹⁰Pb (35-123 Bq m^-2 y^-1) were in the range of variations observed in other coastal stations worldwide, showing fluctuations affected by changes in the amount of precipitation during the wet periods. ⁷Be annual variability also evidenced a significant modulation with the solar activity.

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.

Deposition of naturally occurring 7Be and 210Pb in Northern Finland

This study presents observations of naturally occurring ⁷Be and ²¹⁰Pb in total deposition collected in three deposition sampling stations located in three towns in Northern Finland at Rovaniemi, Sodankylä and Ivalo. The deposition samples were measured in three-month intervals and the collected data covered the years from 1991 to 2017 in Rovaniemi and the years from 1999 to 2017 in Sodankylä and Ivalo. The ⁷Be deposition was observed to be dependent on the amount of precipitation where higher amount of precipitation meant higher ⁷Be deposition. The ⁷Be deposition showed a distinctive seasonal cycle where the highest ⁷Be deposition values were observed occur during July-September and the lowest values during January-March. From the annual total deposition 72-84% occurred during the months of April-September (2^nd and 3^rd quarters). The precipitation normalized enrichment factor (α) determined the excess or deficiency of ⁷Be relative to the amount of rain. The most excess of ⁷Be in the deposition was observed during April-June (2^nd quarter) while the most ⁷Be depleted precipitation occurred during January-March (1^st quarter). The large excess of ⁷Be in precipitation during April-June (2^nd quarter) was an indication of injections of ⁷Be rich stratospheric air into troposphere. By using simultaneously collected ⁷Be aerosol concentration data at Rovaniemi and Ivalo, the ⁷Be deposition velocities were determined. The deposition velocities (V_D) were also found to have a strong seasonal cycle where low velocities were observed during winter and higher ones during summer. The ⁷Be deposition time series were also compared with other time series that are known to affect ground level ⁷Be aerosol concentrations. These were precipitation, sunspot number (SSN), galactic cosmic ray flux (GCR), Arctic Oscillation (AO), North Atlantic Oscillation (NAO) and Scandinavian Pattern (SCAND) indices. The Pearson correlation and wavelet coherence (WTC) was used to analyze possible correlations between the time series. The analyses showed that the coherences were location dependent. Rovaniemi ⁷Be deposition data correlated strongly with rain and weakly with the SCAND index at the 6-8 year scale. The Sodankylä ⁷Be deposition data correlated strongly with the precipitation and SSN and GCR and weakly with AO and NAO indices. Ivalo ⁷Be deposition data correlated with strongly with ⁷Be aerosol concentration data, SSN, GCR and NAO index and weakly with the AO index. The WTC analysis revealed anti-phase coherences with the AO and NAO indices at 4-6 year scale. The ²¹⁰Pb deposition data was sparse and only available from 2011 onwards. ²¹⁰Pb deposition had a seasonal cycle where higher deposition values were observed during summer and lower ones deposition during winter. The annual ²¹⁰Pb deposition was determined at Rovaniemi and Sodankylä during 2014. The values of ⁷Be/²¹⁰Pb ratio was found to vary significantly seasonally, higher ⁷Be/²¹⁰Pb ratios were measured during summer and lower ones during winter.

Atmospheric depositional characteristics of 210Po, 210Pb and some trace elements in İzmir, Turkey

The total atmospheric deposition rates of ²¹⁰Po, ²¹⁰Pb and some trace elements (Li, Be, B, Na, Mg, Al, Si, P, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Mo, Ag, Cd, Sn, Sb, Ba, La, Ce, Tl, Pb and U) have been determined for a year (November 2014-October 2015) collecting samples monthly using bulk collectors at three sites in İzmir, Turkey (Aliağa, Bornova, and Dikili). The annual ²¹⁰Po flux was found as 34.8 Bq m^-2 y^-1 in Aliağa, 29.2 Bq m^-2 y^-1 in Bornova, 21.1 Bq m^-2 y^-1 in Dikili; the annual ²¹⁰Pb flux was found as 41.7 Bq m^-2 y^-1 in Aliağa, 43.6 Bq m^-2 y^-1 in Bornova, 28.6 Bq m^-2 y^-1 in Dikili. The annual depositional fluxes of ²¹⁰Po and ²¹⁰Pb were generally correlated with the amount of precipitation. For most trace elements the highest fluxes were observed in Aliağa, while the lowest fluxes were observed in Dikili.

Evidences of different meteorological patterns governing 7Be and 210Pb surface levels in the southern Iberian Peninsula

⁷Be, ²¹⁰Pb and PM₁₀ levels in surface air have been simultaneously measured at two sampling sites in the southern Iberian Peninsula for a period of two years. Each site covers one different meteorological area of the Guadalquivir valley, from the mouth (Huelva) to the middle point (Cordoba). The objective of the present study is to analyse the spatial variability of both natural radionuclides, and to identify and characterise the meteorological patterns associated with similar and different surface concentration levels in this complex region. Concentrations are similar in both sampling sites. ⁷Be level is in the 0.6-15.5 mBq m^-3 range in Huelva and 1.2-13.3 mBq m^-3 in Córdoba, ²¹⁰Pb activity concentrations are between 0.04 and 2.30 mBq m^-3 in Huelva, and between 0.03 and 1.2 mBq m^-3 in Cordoba, and PM₁₀ concentrations are found to be in the 5.1-81.3 μg m^-3 range in Huelva, and 8.2-76.3 μg m^-3 in Cordoba, respectively. A linear regression analysis indicates more regional variability for ²¹⁰Pb than for ⁷Be between simultaneous measurements. Principal components analysis (PCA) is applied to the datasets and the results reveal that aerosol behaviour is mainly represented by two components, which explain 82% of the total variance. The analysis of surface measurements and meteorological parameters revealed that component F1 groups sampling periods in which the influence of similar meteorological conditions over the region lead to similar ⁷Be, ²¹⁰Pb and PM₁₀ concentration levels in both sampling sites. On the other hand, component F2 detaches the ⁷Be, ²¹⁰Pb and PM₁₀ concentration levels between monitoring sites, and the meteorological analysis shows how surface concentrations within this component are associated with the development of different mesoscale circulations in each part of the valley. The identification of sampling periods characterised by differences in surface concentrations and wind patterns between stations suggests that the valley could not be considered as one single unit for certain meteorological scenarios. These results evidence how the understanding of wind characteristics within a complex terrain provide some essential knowledge in the regionalization and/or optimization of monitoring networks.

A study of temporal variations of 7Be and 210Pb concentrations and their correlations with rainfall and other parameters in the South West Coast of India

As a part of establishing a regional database on natural radioactivity, the atmospheric concentrations of ²¹⁰Pb and ⁷Be were measured over a three and half year period (2014-2017) in Mangalore and Kaiga in the South West Coast of India. A total of 99 air samples, collected in the different months of the year, were analysed in this study. The mean activity concentrations of ⁷Be and ²¹⁰Pb were found to be 5.5 ± 3.1 mBq m^-3 and 1.1 ± 0.73 mBq m^-3, respectively. Both the radionuclides exhibited strong seasonal variations, with maximum concentration of ⁷Be occurring in the summer and that of ²¹⁰Pb in the winter season. The concentration of both the radionuclides was minimum in the rainy season. Higher ²¹⁰Pb concentration during winter was attributed to the ingression of continental air masses due to the wind regime from the North East. The sunspot number index of the solar activity also plays an important role in the increase and decrease of ⁷Be concentration in the air. A clear trend of increased and lowered concentration of ⁷Be with lower and higher solar activity (low and high sunspot number), respectively, in accordance with the 11-year solar cycle, was observed in this study. The temporal variation of PM₁₀ concentration was also studied and it showed maximum value in the winter and minimum in the rainy season with an average of 56.9 μg m^-3. Statistically significant positive correlation was observed between the PM₁₀ and ²¹⁰Pb activity concentration, whereas a weak correlation was observed between PM₁₀ and ⁷Be. This is due to the fact that ⁷Be is largely associated with sub-micrometer size particles, whereas PM₁₀ is contributed by larger sizes. The dependence of the activity concentrations of ⁷Be and ²¹⁰Pb with meteorological parameters such as rainfall, temperature, and humidity was studied through linear regression analysis. A significant correlation was observed between ⁷Be and ²¹⁰Pb concentrations with rainfall intensity (with identical correlation coefficients), which suggested that the removal mechanisms of these two radionuclides were similar. ⁷Be showed a strong correlation with temperature, whereas ²¹⁰Pb with humidity. A comparison of the data obtained in the present study for the South West Coast of India with the global literature values of ⁷Be and ²¹⁰Pb in aerosols showed that the values did not reflect the well-known latitudinal dependence of the ⁷Be tropospheric fluxes. Overall, the study provides an improved understanding of the correlation and variability of ²¹⁰Pb and ⁷Be concentrations in the atmosphere in the South West Coast of India.