Monitoring of 7Be in surface air of varying PM10 concentrations

7Be, 210Pb, airborne particulate matter and PM10 concentrations in relation to meteorological conditions in southern Poland in 1998-2016

An analysis of the concentration of ⁷Be in aerosol samples collected in one of the most polluted areas in Europe (Katowice and Krakow in southern Poland) indicated seasonal variability, with a maximum in the summer months. The average concentrations of ⁷Be were 4616.1 μBq m^-3 in Katowice and 3259.4 μBq m^-3 in Krakow, respectively, and they are among the highest values recorded in Poland in the studied period (1998-2016). These cities are also characterised by Poland's highest concentrations of ²¹⁰Pb (547.8 μBq m^-3 and 513.2 μBq m^-3). The highest radioactive concentrations of ²¹⁰Pb were observed in the winter and autumn, since in the case of these industrial areas, the combustion processes related to heating in the cold season of the year are an additional source of this isotope, next to its natural origin. The airborne particulate matter concentrations at both locations correlate with the concentrations of ²¹⁰Pb. The average values of PM10 concentrations (71.1 μg m^-3 in Krakow to 45.0 μg m^-3 in Katowice), were 2-3 times higher than the average ones recorded in northern Poland. It has been proven that air temperature is the key parameter affecting the transport of isotopes, especially in the warm season of the year, when its increase causes increased thermal convection, leading to intense vertical mixing and exchange in the troposphere. Analyses using the machine learning method allowed for an indication of the correlation between relative humidity and atmospheric precipitation, as well as higher wind speed and concentrations of ⁷Be which is inversely proportional. Geographical factors (the latitude of the station and the land elevation) have no impact on near-surface concentrations of ⁷Be in Poland.

Study of the naturally occurring radionuclide Beryllium-7 (Be-7) in Hong Kong

Beryllium-7 (Be-7) is one of the naturally occurring radionuclides being monitored under the Global Atmosphere Watch Programme of the World Meteorological Organization. Be-7 mainly originates from cosmic rays. It can be used as a tracer to facilitate understanding of the atmospheric vertical transport by observing its spatial and temporal distribution characteristics. The Hong Kong Observatory has been operating an environmental radiation monitoring programme for decades, and long record of Be-7 activity concentration data in airborne particulate samples are available to characterize the behaviour of Be-7 in the lower atmosphere in Hong Kong. In this study, Be-7 activity concentration data of airborne particulates collected at three locations in Hong Kong from 1993 to 2020 are examined. Temporal variations are analyzed. In particular, the long-term monthly average Be-7 activity concentrations are found to be most sensitive to precipitation. The relevant data analysis, as well as key factors affecting the Be-7 activity concentrations in the lower atmosphere in Hong Kong, will be described.

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.

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.

7Be behaviour and meteorological conditions associated with 7Be peak events in Spain

This work regards a comprehensive analysis of the overall distribution of ⁷Be activity concentrations in Spain and the synoptic meteorological conditions associated with the highest ⁷Be peaks (>8 mBq/m³). The use of four sampling stations (Barcelona, Bilbao, Madrid, and Sevilla) included in REMdb, with different latitudinal location, as well as the relatively long time period used in this study (2001-2010), allowed to improve the understanding of ⁷Be spatio-temporal distribution in Spain. The comparison of the ⁷Be activity concentrations mean values indicated a north-south gradient (from 3.1 ± 1.1 mBq/m³ in Bilbao to 4.0 ± 1.8 mBq/m³ in Sevilla), even though not statistically significant (as indicated by the t-test). However, the analysis of frequency distributions and temporal evolutions of ⁷Be activity concentrations have suggested the presence of two main areas, namely northern (Bilbao and Barcelona) and southern (Sevilla) Spain. The identification and analysis of periods associated with the highest values of ⁷Be have allowed studying the different synoptic patterns associated with stratospheric-tropospheric transport (STT). In particular, three episodes (one in the north and two in the south) potentially associated with vigorous STT have been identified and analysed in detail. The results displayed that the omega block configuration, extending either over western Russia and Scandinavia or into the Atlantic Ocean, forced the prevailing jet stream to the northeast and south of Spain respectively with subsequent subsidence. In summer, this blocking configuration at high latitudes was combined with the presence of the Azores high pressure system to the west of Spain, affecting the ⁷Be activity concentration recorded in the south.

Monitoring of (7)Be and gross beta in particulate matter of surface air from Mallorca Island, Spain

Measurements of airbone radionuclides (7)Be and gross beta (Aβ) jointly with atmospheric aerosols, i.e. particulate matter (PM) were routinely carried out for 10 years (2004-2014) at the University of the Balearic Islands, Spain. A total of 728 filter (0.8 μm pore size) samples were collected, and in all of them (7)Be and Aβ specific activities were detected. The maximum and minimum specific activities monitored were 0.73 ± 0.41 - 15.8 ± 1.26 mBq m(-3) of (7)Be and 0.14 ± 0.02 - 2.55 ± 0.04 mBq m(-3) of Aβ. PM concentrations were also determined, showing seasonal behavior with the highest concentration in summer and the lowest one in winter. Several meteorological parameters have been considered to explain this intra-annual variation. Principal component analysis (PCA) was applied to the dataset indicating that it is well represented by two principal components that explain 76.6% of total variance. Additionally, a second study with preliminary results of the specific activities of two natural radiotracers ((7)Be and (210)Pb) in PM10 samples was carried out. They were monitored for two years (2013-2015) in air of Mallorca Island. (7)Be and (210)Pb were detected in most of the PM10 filters, in 100% and 93% of them, respectively. The relationship between activities of both radionuclides and several relevant meteorological parameters was established at 95% confidence level. As a common result to PM and PM10 samples, a strong positive correlation between the evaluated radionuclides and temperature was found.