Solar and meteorological influences on seasonal atmospheric 7Be in Europe for 1975 to 2018

Short-lived natural radionuclides as tracers in hydrogeological studies - A review

Fundamental approaches to the study of groundwater rely on investigating the spatial and temporal distribution of stable and radioactive isotopes and other anthropogenic compounds in natural waterbodies. The most often used tracers for estimating groundwater flow paths and residence times, groundwater/surface water interaction as well as tracing chemical (contamination) sources include stable isotopes of water (δ 18O and δ 2H), radiocarbon (14C; t1/2 = 5730 a), tritium (3H; t1/2 = 12.43 a) as well as unreactive fluorine-containing gases (e.g., chlorofluorocarbons CCl3F or CFC-11; CCl2F3 or CFC-12; C2Cl3F3 or CFC-113; and SF6). While gas tracers are usually referred to as transient tracers and are appropriate for investigating modern flow systems, the isotopic tracers are often used to investigated paleo or regional flow systems. Stable isotopes of water can also be used to investigate groundwater/surface water interactions. Another, thus far been less frequently used group of groundwater tracers, are cosmo- and geo- genic short-lived radioisotopes. These isotopes are uniquely suited for studying a wide range of groundwater problems that have short time scales including high aquifer vulnerability to quantitative and qualitative impacts and groundwater discharge to surface waters. Here, we discuss and compare the applications of radio‑sulphur (35S; half-life t1/2 = 87 d), radio‑beryllium (7Be; t1/2 = 53 d), radio‑phosphorus (32/33P; combined t1/2 = 33 d), natural tritium (3H; t1/2 = 12.43 a), radon (222Rn; t1/2 = 3.8 d) and short-lived radium (224/223Ra; combined t1/2 = 5.2 d). The paper discusses the principles of the individual tracer methods, focusing on the isotopes' input functions or values, on sampling techniques, and on methods of analyses. Case studies that applied a combined use of the tracers are referred to for readers who wish to learn more about the application of the so far underused cosmo- and geo- genic radioisotopes as aquatic tracers.

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.

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.

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.

Analysis of Alpha Activity Levels and Dependence on Meteorological Factors over a Complex Terrain in Northern Iberian Peninsula (2014-2018)

Alpha ambient concentrations in ground-level air were measured weekly in Bilbao (northern Spain) by collecting aerosols in filters between 2014 and 2018. Over this period, the alpha activity concentrations in the aerosol's samples range from 13.9 µBq/m3 to 246.5 µBq/m3, with a mean of 66.49 ± 39.33 µBq/m3. The inter-annual and intra-annual (seasonal and monthly) variations are analyzed, with the highest activity in autumn months and the lowest one in winter months. Special attention has been paid to alpha peak concentrations (weekly concentrations above the 90th percentile) and its relationship with regional meteorological scenarios by means of air mass trajectories and local meteorological parameters. The meteorological analysis of these high alpha concentrations has revealed two airflow patterns-one from the south with land origin and one from the north with maritime origin-mainly associated with these alpha peak concentrations. Surface winds during representative periods of both airflow patterns are also analyzed in combination with 222Rn concentrations, which demonstrated the different daily evolution associated with each airflow pattern. The present results are relevant in understanding trends and meteorological factors affecting alpha activity concentrations in this area, and hence, to control potential atmospheric environmental releases and ensure the environmental and public health.