7Be activity variation in atmospheric fallout and weather factors in 2004–2005 in Samarkand

Abstract

7 Be (T 1/2 = 54 days, E γ = 478 keV) is formed in the upper layers of the atmosphere in reactions where cosmic rays split nitrogen and oxygen atoms. The 7 Be ions formed attach to dust and aerosol particles and fall together with them onto the Earth's surface [1]. We present below the results of γ-spectrometric studies of the activity of 7 Be (N) in monthly (m) atmospheric fallout in the period 2004-2005 in Samarkand and compare these data with the amount of precipitation, average humidity, and average air temperature (data from the Samarkand regional hydrometeorological office).The atmospheric fallout samples were obtained as follows. A 100 × 100 cm and 10 cm high Duralumin vessel, whose bottom was smeared with 100 g of glycerin and covered with a layer of gauze, was exposed monthly on the roof of an 8 m high building. After the exposure was completed, the gauze we removed from the vessel. Any rain water or snow present in the vessel was evaporated to volume ≤100 ml, and the vessel was carefully wiped clean with fresh gauze.Two types of samples were prepared successively from the atmospheric fallout:• the gauze was allowed to dry (samples G with mass 180-230 g) and then folded into strips and neatly packed into one-liter Marinelli vessels; • after the samples G were measured, the gauze was removed from the Marinelli vessels, placed in a porcelain cup, and calcined in a muffle furnace (≤400 °C); the ash was packed into a 40 × 40 mm polyethylene packet (samples A with mass ∼8-25 g). Inert samples, prepared by the methods indicated above from 1 m 2 clean (unexposed) gauze, were used to determine the background component in the spectra of the experimental samples.The γ-ray spectra of the samples were measured with a 63 × 63 mm NaI(Tl) scintillation crystal and a 100 cm 3 Ge(Li) detector with resolution ∆E γ /E γ ≈ 10% and ∆E γ = 6.7 keV, respectively, on the 1332 keV 60 Co line, which were placed inside lead shielding with 10 cm thick walls. The MARS (JINR, Dubna) computer program was used for acquisition and processing of the spectra. The duration of individual measurements was 2-6 h.The γ-ray spectrometers were calibrated with respect to detection efficiency using 226 Ra, 232 Th, 40 K, and 137 Cs from the OMASN system (for the G samples) and 241 Am, 22 Na, and 137 Cs from the OSGI system (for the A samples).A dominant contribution from the background radiation to the intensity was observed, together with contributions from 7 Be and 226 Ra, 232 Th, and 40 K of natural origin, in the instrumental spectra of the samples. In the semiconductor spectra of the samples which were (Fig. 1) and were not (Fig. 2) calcined, the 478 keV 7 Be total absorption peak is well resolved

7Be variation in monthly atmospheric precipitation in 2002–2005 in Samarkand

“…In addition,7 Be nuclei formed as a result of the fragmentation of heavy nuclei and in thermonuclear fusion reactions 3 He + 4 He = 7 Be + γ on the surface of the Sun and in other parts of the Universe penetrate into enter the Earth's atmosphere. In addition,7 Be nuclei formed as a result of the fragmentation of heavy nuclei and in thermonuclear fusion reactions 3 He + 4 He = 7 Be + γ on the surface of the Sun and in other parts of the Universe penetrate into enter the Earth's atmosphere.…”

“…In addition,7 Be nuclei formed as a result of the fragmentation of heavy nuclei and in thermonuclear fusion reactions 3 He + 4 He = 7 Be + γ on the surface of the Sun and in other parts of the Universe penetrate into enter the Earth's atmosphere. Systematic studies of monthly atmospheric precipitation of 7 Be in Samarkand began in 2002 [5][6][7].The present work compares the regularities observed in variations of 7 Be activity in atmospheric precipitation in 2002-2005 in Samarkand with those found in other regions of the Earth.Methodology. Studies performed over many years in different regions of the Earth have established that the 7 Be concentration in the air layer at the ground is correlated with solar activity and the local physical-geographic characteristics while for atmospheric precipitation there is a correlation with the amount of the wet precipitation [1][2][3][4].…”