Content of cosmogenic 7Be in the air layer at the ground at temperate latitudes

Abstract

The 7 Be content was measured in aerosols (once per week) and precipitation (once per month) was monitored as part of the monitoring of the radioactivity of the atmospheric layer near the ground in Rostovon-Don in 2001-2005. Data were obtained on the correlations between the 7 Be volume activity in aerosols and the Wolf number, temperature, and amount of precipitation. The highest correlation coefficients were observed during the spring (k = 1). It was determined that the volume activity of 7 Be changes in the second half of the 23rd cycle of solar activity, i.e., the yearly average 7 Be concentration increases toward the end of the cycle. Data were obtained on the seasonal dependence of the precipitation density and the volume activity of 7 Be on the meteorological parameters (temperature, amount of precipitation).Cosmogenic 7 Be (T 1/2 = 52.3 days) forms in nuclear spallation reactions when high-energy protons (∼1 GeV) when cosmic rays interact with nitrogen nuclei in the stratosphere 14 N + p → 7 Be (up to 70-80%) and secondary neutrons with nitrogen nuclei and oxygen in the troposphere 14 N + n → 7 Be and 16 O + n → 7 Be (up to 20-30%) [1,2]. During changes in the solar activity (number of sun spots -the Wolf number W) within the 11-year solar cycle and aperiodic bursts of solar activity, the geomagnetic field changes, cosmic rays are deflected and, correspondingly, the 7 Be production rate changes [3]. A decrease of the 7 Be production rate corresponds to an increase of solar activity (increase of the Wolf number) and vice versa, i.e., there is an anticorrelation between the 7 Be content in the atmospheric air and the Wolf number with coefficient k = −0.81 according to [4] and k = −0.83 ± 0.03 according to the data in [5]. Over the 11-year solar cycle, the yearly average content at the maximum and minimum differs by approximately 45%. The 7 Be production rate also depends on the geographical coordinates of the observations station because of the effect of the Earth's magnetic field on the cosmic ray distribution.Long (more than two cycles of solar activity) systematic measurements on the global network of stations must be performed in order to determine reliably the relation between the 7 Be volume activity in the air layer at the ground and the solar activity against the background of variations of a different origin. The results of the determination of 7 Be in the atmosphere in 1974-1999 at 26 stations were analyzed in [3]. The existence of the anticorrelation indicated above, which explains about 54% of all temporal variations of the 7 Be for stations in Australia, New Zealand, and North America and only 18% of the variations for the stations in South America and Antarctica, has been proven. Long-time measurements (1987Long-time measurements ( -2003 were performed recently at temperate latitudes (40°38′) [6]. Under especially favorable conditions (regularity of measurements of the meteorological parameters, absence of any effect due to some of them, and so forth), a correlation between the 7 Be content an...

Turnover of 137 Cs in ‘soil–tree’ system: An experience of measuring the isotope flows in a Siberian conifer forest

“…As it has been said above, the most probable source of 7 Be is the atmospheric fallout that have two well expressed maxima, in spring and in autumn (Buraeva et al, 2007). Over the area of study, young needles appear from end of May to first days of June and they have small leaf area at the beginning.…”

Seasonal and inter-annual variation of Beryllium-7 deposition in birch-tree leaves and grass in the northeast upland area of the Czech Republic

“…Activity concentrations of 7 Be in the atmospheric layer near the ground reached values between 1 and 10 mBq m À3 (Azahra et al, 2003;Cannizzaro et al, 2004;Ioannidou et al, 2005). In similar studies of 7 Be concentration in near-surface air in Rostov-on-Don (Russia) and in Brisbane (Australia), Buraeva et al (2007) and Doering and Akber (2008) reported that the 7 Be content in atmospheric aerosols near the ground and the 7 Be deposition measurements indicated a seasonal variation of the 7 Be volume activity; i.e. a springesummer maximum and an autumnewinter minimum.…”

“…The 7 Be deposition, the 7 Be content in air (atmosphere) near the ground and the content as related to the scavenging mechanism and to removal processes were studied by many authors (e.g. Azahra et al, 2003;Buraeva et al, 2007;Doering and Akber, 2008;Hasegawa et al, 2007;Karunakara et al, 2003;Momoshima et al, 2006;Zhu and Olsen, 2009). They suggested that the seasonal variation of the 7 Be volume activity exhibiting a springesummer maximum and an autumnewinter minimum may be significantly dependent on the precipitation mode.…”

Photonuclear channel of 7Be production in the Earth’s atmosphere

“…The change in the content of 7 Be in air stems from the solar activity and have characteristic seasonal variations and a latitude dependence [1,2]. Because of the fast decay of 7 Be, its activity changes in plants versus synoptic conditions.…”

“…It is commonly believed that basic reactions leading to the production of beryllium isotopes in the Earth's atmosphere are induced by the interaction 1 of cosmic rays with nuclei of nitrogen and and oxygen [4], which are dominant constituents of atmospheric air. These are the so-called spallation reactions 14 N(p, X) 7 Be, 16 O(p, X) 7 Be, 14 N(n, X) 7 Be, and 16 O(n, X) 7 Be.…”