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.

Online monitoring of lead-214 (214Pb) on atmospheric aerosols by low-resolution gamma-ray spectrometry.

This paper provides a new approach that simplifies the monitoring of 214Pb activity concentration on aerosols in the atmospheric surface layer. The approach allows obtaining data on 214Pb activity concentration with the discreteness of 2 h. The experimental setup described in the paper made it possible to achieve a minimum detectable activity level of 0.4 Bq m-3. Using this approach, the data on the diurnal variability of 214Pb activity concentration in the atmosphere of Sevastopol city for a period of 18 months were obtained. The 214Pb activity concentration varied from < 0.4 (less than 1% of the data series) to 8.9 Bq m-3, mean value 2.0 ± 1.0 Bq m-3. The analysis of the temporal variability of 214Pb activity concentration on different time scales (diurnal, seasonal) was carried out. Annually averaged diurnal variation curve of 214Pb activity concentration showed a peak at 6:00 local time and a minimum at 18:00. The maximum variability in the seasonal averaged diurnal cycle of 214Pb activity concentration is observed in summer (± 30% of the daily average value) and the minimum in winter (± 13%). The maximum seasonal average value of 214Pb activity concentration is observed in winter (2.5 Bq m-3) and the minimum in summer (1.4 Bq m-3). A quantitative estimate of the annual effective dose due to exposure to outdoor radon was obtained by using 214Pb data, and it was 0.03 mSv a-1.

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.

Distribution of beryllium-7 (7Be) in the Black Sea in the summer of 2016.

The spatial distribution of 7Be activity in the surface layer of the Black Sea was studied using the data of field observations made during the 87th cruise of R/V Professor Vodyanitskii. Activity of 7Be varied spatially from 4.6 to 9.5 Bq m-3 (mean 7.5 ± 1.3 Bq m-3) where about 9% was found on suspended matter. The minimum values of activity were typical for samples taken in the shelf waters and the maximum-offshore. The influence of different factors on 7Be activity was analyzed. It was revealed that variation of both 7Be wet deposition on the sea surface and concentration of suspended matter were the most significant for spatiotemporal variability of 7Be activity in seawater during the study period. The estimates of 7Be distribution coefficient between dissolved and particulate forms were obtained. This coefficient varied from 1.5·105 to 2.4·105 L kg-1, averaged (1.9 ± 0.3)·105 L kg-1.

Numerical simulation of the intra-annual evolution of beryllium-7 (7Ве) in the surface layer of the Black Sea.

A numerical model simulating the distribution of 7Ве in the Black Sea was developed and applied to study the spatial and temporal variations in the content of 7Be in the surface waters. Variations in the distribution of 7Ве were analyzed for the period from January to December of 2012. The average seasonal content of 7Ве in the surface layer ranges from 2.2 to 6.2 Bq m-3. The maximum concentration is typical for the eastern part of the sea in winter to spring, and the minimum concentration is typical for the central and western parts of the sea in summer. The seasonally averaged activity of 7Ве on suspended matter ranges from 440 to 1560 Bq kg-1. The highest values are observed in the sea in winter to spring, and the lowest values are typically observed in the central and western parts of the sea in summer. It was revealed that the adsorption of 7Ве on suspended matter is most significant for the evolution of the content of this radionuclide in shelf waters.