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

Abstract

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.