共查询到20条相似文献,搜索用时 46 毫秒
1.
H. Muramatsu S. Yoshizawa T. Abe T. Ishii M. Wada Y. Horiuchi R. Kanekatsu 《Journal of Radioanalytical and Nuclear Chemistry》2008,275(2):299-307
The concentration of 7Be in surface air at Nagano City has been measured during the period from August 2000 to March 2005. The average monthly concentrations
of 7Be in surface air were in the range of 3.3–14 mBq/m3 with pronounced two peaks in spring and autumn. It took 30–40 hours to recover the 7Be concentrations observed before, once 7Be was washed out by wet precipitations. For a pronounced increase in the concentrations of 7Be found in winter, a low-pressure trough coming close to the Japanese Islands with high concentrations of 7Be is responsible under the characteristic distribution of atmospheric pressure around the Japanese Islands. 相似文献
2.
F. Piñero-García M. A. Ferro-García 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(3):1193-1204
The modulation of 7Be-aerosols concentration due to solar activity during the cycle 23 is studied in the present research. For that purpose, was analyzed the differences in the long-term variation of geomagnetic and solar activity to assess the physical effects over the evolution of 7Be during the period 1996–2010. Furthermore, exploratory data analysis was applied to understand better the behavior of 7Be-aerosols in the surface atmosphere. This study shows that there is an inverse relationship among 7Be measured in the near ground air and solar activity. The modulation of 7Be-aerosols during the cycle 23 was divided in two steps. In the first stage, ascending phase, 1996–2002, the solar activity played an important role in the production rate of 7Be, r = ?0.75. However, during the descending phase, 2002–2009, the role of the solar activity was secondary, r = ?0.30, allowing that 7Be-aerosols reached the maximum concentration, 9.33 mBq m?3 in August-09 when the solar activity was zero. Moreover, the remaining solar activity after the end of the ascending phase and the last important solar storm (December-06) caused the slowdown of 7Be production rate from 2001 to 2004 and the rupture of the seasonal behavior of 7Be in 2007, respectively. Finally, this research highlight the necessity to take into account the solar cycle phase, ascending or descending, to model studies of atmospheric process with 7Be as tracer since the contribution of the variables studied are so different in these stages. 相似文献
3.
Zhonglin Shi Anbang Wen Dongchun Yan Xinbao Zhang Li Ju 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(3):671-676
The deposition flux of 7Be was measured in the range from 0.4 to 5.2 Bq m?2 d?1, with a mean value of 2.6 Bq m?2 d?1, during the period of May 31, 2009?CMay 31, 2010 in the Three Gorges Reservoir region, China. The low annual deposition flux of 7Be was probably due to the adsorption of 7Be within high altitude clouds and the Qinling-Daba Mountain??s barrier and blocking effects on the cold air during winter months. There was a seasonal trend for 7Be deposition, showing a spring maximum and winter minimum, which may be attributed to the seasonal folding of tropopause in spring and little rainfall amount in winter. A strong positive correlation (R 2 = 0.67) between 7Be deposition flux and rainfall was observed. The depth distribution of 7Be in undisturbed purple soil profiles suggested that the nuclide was mainly distributed within the top 20.0 kg m?2 (~1.5 cm) of soil in depth and the maximum concentration occurred at a depth of 3.0 kg m?2 (~0.2 cm), then the concentration declined quickly and exponentially with depth. The seasonal inventories of 7Be in soils were consistent with the values calculated from the atmospheric fluxes, which shows a great potential for using 7Be as a tracer to assess soil redistribution in purple soil areas of China. 相似文献
4.
Houali Allal Azahra Mustafa El Bardouni Tarek Ferro García Maria Angeles Piňero García Francisco Chham Essaid 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(2):271-280
For the first time, atmospheric aerosols were collected in Tetouan city (Morocco), from June 2015 to February 2017, through which 7Be activity was measured. We studied data variation by time series analyses and the impact of local meteorological factors on it. 7Be concentrations, in mBq/m3, ranged from 1.65 to 7.79 with mean value of 4.69. 7Be behaviour is mainly influenced by air temperature, precipitations, relative humidity and atmospheric pressure. A prediction model was suggested and validated. This study helps understanding climatic variables impact on the environmental processes as aerosols transport and deposit, and to predict 7Be behaviour in Mediterranean regions like Tetouan.
相似文献5.
The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is supported by a global network of monitoring stations that perform high-resolution gamma-spectrometry on air filter samples for the identification of radionuclides indicative of nuclear weapons tests and reactor incidents. These daily measurements have created an invaluable resource for understanding variations in natural background radioactivity, including the contribution of 7Be. Statistical analysis has been performed on 7Be data collected by CTBT stations hosted by the United Kingdom including at British Indian Ocean Territory (RN66), St Helena (RN67) and Tristan da Cunha (RN68) during 2005–2013. The results have been found to follow a lognormal distribution which implies that the 7Be activity is the multiplicative product of many small independent factors, such as meteorology, elevation, local station conditions, sample acquisition and analysis. This has the potential to identify discrepant measurements not attributable to the intrinsic variability of the distribution and indicative of station malfunction. Variations in 7Be activity have been considered on monthly, weekly and daily timescales and characterised using the geometric mean in accordance with the properties of the lognormal probability density function. Seasonal variations have been identified, with summer maxima and winter minima that are attributable to changes in mixing within the stratosphere and troposphere. Such fluctuations have been examined using the Fast Fourier Transform which may indicate variations associated with the 27 day solar cycle. 相似文献
6.
Near-surface air concentrations of7Be and its deposition rates were measured in the atmosphere in Bratislava from 1977 to 1994. Late spring and summer maxima were observed in the near-surface air concentrations on an annual basis. Using measured deposition rates and the calculated average tropospheric content of7Be atoms, their mean tropospheric residence time (27–48 days) was determined. An anticorrelation between the measured7Be concentration and the sunspot number with correlation factor of 0.55 was observed. 相似文献
7.
C. Dueñas M. C. Fernández J. Carretero E. Liger S. Cañete 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(2):249-253
Measurements of 7Be and 210Pb in atmospheric air (1 m above the ground) have been carried out each week over one and a half year period. The method used to determine 7Be and 210Pb activities is based on the total amount of radioactive aerosols filtered from the air. The activities of 7Be and 210Pb were determined by a hyper-pure germanium detector using standard gamma-spectrometry. The average weekly concentrations of 7Be were in the range of 1.21-12.1 mBq.m-3 and for 210Pb in the range of 0.8-2.4 mBq.m-3. The weekly variations were discussed in relation to various meteorological factors. It can be said that our results showed a prevailing influence of weekly average temperature for 7Be concentration and the weight of aerosols and wind speed for 210Pb oncentrations. 相似文献
8.
Young Hyun Cho Wanno Lee Kun Ho Chung Geun Sik Choi Chang Woo Lee 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(3):531-538
The seasonal variation of the 7Be activities in air and the size distribution of the 7Be aerosols were studied by using a continuous air sampler and a five stage cascade impactor. The mean monthly activity level
of 7Be at the Korea Atomic Energy Research Institute (KAERI) site varied from 0.5 to 4.8 Bq·m−3 and revealed a seasonal variation, in which the 7Be activity levels were high in winter and low in summer. The mass size distribution showed a bi-modal distribution with a
higher peak around 0.49 μm and a smaller peak between 3 μm and 7.2 μm. The activity median aerodynamic diameter (AMAD) decreased
with increasing ambient 7Be concentrations. The mean residence times by using a mean growth rate of 0.004 μm·h−1 were estimated to be 2.5–6.4 days. The AMAD has an increasing tendency with higher relative humidity. It seemed that the
high humidity condition facilitated the growth of the aerosol, resulting in increased deposition rates of the aerosols and
the low 7Be content in the surface air. The AMAD of the 7Be aerosols increased with an increasing temperature, but the temperature dependency of AMAD should be explained with geological
and meteorological conditions. 相似文献
9.
Keyan Tan Yongliang Yang Xiaohua Zhu Yong Li Shu Chen Hanqing Yu Xingchun Jiao Nan Gai Yi Huang 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(2):883-891
A high-volume air sampler and a high-resolution gamma-ray spectrometer have been used to measure the activity of 7Be in near-surface atmospheric aerosols at sampling frequency of 3 days week for 1 year from August 2009 to July 2010 at Beijing in the mid-latitude region of East Asia monsoon. The measurements indicate that the average concentration of 7Be was 8.39 ± 0.49 mBq m?3, which was significantly higher than values reported for other cities in the East Asia monsoon region and in the world during the same period. The maximum and minimum of the weekly means of 7Be concentration were observed in September and May, respectively. The 7Be concentrations varied in accordance with the monsoon phases. Low but frequent wet precipitation may have caused lower 7Be observed in July when southeasterly was prevailing. Higher seasonal mean of 7Be concentrations in autumn could be attributed to the abnormal atmospheric circulation in autumn 2009. 相似文献
10.
Antonia Camacho Montserrat Montaña Isabel Vallés Ricard Devesa Raquel Céspedes-Sánchez Isabel Serrano 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):297-306
22 sludge samples were analyzed from three municipal wastewater treatment plants to assess both the occurrence and the temporal behavior of radioactivity during 8 sampling campaigns carried out over the period 2007–2009. As regards natural gamma emitters radionuclides from the natural 238U series (such as 234Th, 214Pb, 214Bi, 210Pb) and the 232Th series (such as 228Ac, 212Pb, 212Bi and 208Tl) and other natural gamma emitters such as 7Be, 210Pbu or 40K were measured. In the case of man-made radionuclides small amounts of 137Cs were found, while significant amounts of 131I were detected in some samples. Correlations were found between radionuclides with the same origin. No seasonal variation for the 238U and 232Th series was found in the studied period but 7Be and 210Pbu showed seasonal variation that was explained by the monthly rainfall. The internal and external hazard indices were calculated and the results indicate that the radiological characteristics of the sludge do not present a significant radiological risk and make them suitable for future applications. 相似文献
11.
S.-H. Lee M. K. Pham P. P. Povinec 《Journal of Radioanalytical and Nuclear Chemistry》2002,254(3):445-453
Radionuclides in aerosols and precipitation have been analyzed by IAEA-MEL in Monaco since 1987 and 1999, respectively, to identify their behavior in the atmosphere and delivery into the northwestern Mediterranean Sea. While the concentration of 7Be in aerosols has been affected by the stratospheric-tropospheric mixing and precipitation, the concentration of 137Cs in aerosols has been influenced by a combination of local meteorological conditions and re-suspension of 137Cs from soil. Higher concentrations of 7Be, 137Cs, 239,240Pu and 241Am in precipitation occurred during spring and summer. The highest deposition rates of these radionuclides were observed in spring and autumn during periods of high precipitation. A good correlation was found between the amount of precipitation and depositional flux for 7Be, but not for 137Cs, 239,240Pu and 241Am. This indicates that the wet process as well as the dry process seem to be important factors in determining the annual deposition for transuranic radionuclides and 137Cs. 相似文献
12.
M. Azahra J. J. López-Peñalver M. A. Camacho-García C. González-Gómez T. El Bardouni H. Boukhal 《Journal of Radioanalytical and Nuclear Chemistry》2004,261(2):401-405
Aerosols samples in near-surface air of Granada (Spain) were collected on a weekly basis. The seasonal 210Pb and 7Be concentrations were determined during the five-year period, from October 1993 to September 1997. The elements, despite their different origin and their different distribution throughout the atmosphere, present the same seasonal variation. There was a tendency for a maximum during the summer season and a minimum during fall and/or winter. In this work, the concentration of 7Be and 210Pb and meteorological data have been used in order to determine the periods of the potential radioactive pollution. This study, also, shows that the deposition of 7Be occurs primarily by precipitation except during the investigation periods where precipitation was scarce and irregular.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
13.
Fengbao Zhang Mingyi Yang Bo Zhang 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(1):75-79
Beryllium-7 (7Be) activity in maize was measured in Yangling County, Shaanxi Province, on the Loess Plateau Region of China in 2007. The
7Be mass activity concentration in maize leaf samples was significantly greater than in maize stem, maize root and maize grain
samples. The 7Be activity in maize leaves accounted for 78% of the total maize 7Be activity. The 7Be mass activity concentration in maize varied from 25.4 to 122.4 Bq kg−1 and areal activity concentration held by maize from 1.2 to 111.5 Bq m−2 during the growth period. The percentage of 7Be areal activity concentration held by maize relative to the 7Be areal activity concentration measured in reference soils ranged from 0.4 to 24.2% with a mean of 13.7%. 相似文献
14.
A. Ioannidou E. Kotsopoulou C. Papastefanou 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):395-400
7Be activity concentrations were measured in the lower atmosphere at Thessaloniki, Northern Greece (40°38′N, 22°58′E) over
the year 2009, a year of a particular minimum of solar activity. The mean annual activity concentration of 7Be at that year was 6.01 mBq m−3. The variability of 7Be surface concentrations related to the solar cycle appeared to be deviated about 40% between the maximum and the minimum
values. A positive correlation (R = 0.97) was revealed between the activity concentrations of 7Be and the temperature, confirming that the increased rates of vertical transport within the troposphere, especially during
the warmer months, resulted in carrying down to the surface layer air masses enriched in 7Be. Relatively high values of 7Be activity concentrations were observed by increasing of the tropopause height. A negative correlation (R = −0.65) between the 7Be activity concentrations and the relative humidity was due to the condensation process in the lower atmosphere which resulted
in increased aerosol particle sizes with higher scavenging rates of aerosols and low activity concentrations of 7Be in the atmosphere. Influence of precipitation on the changes of 7Be activity concentrations was also observed. 相似文献
15.
S. Sato Y. Koike T. Saito J. Sato 《Journal of Radioanalytical and Nuclear Chemistry》2003,255(2):351-353
The atmospheric concentration of 210Pb and 7Be was observed at Sarufutsu on the coast of the Sea of Okhotsuk in Hokkaido, Japan. Measurements were carried out during the period from February to August, 2001. The atmospheric concentrations of 210Pb and 7Be ranged from 0.2 to 2.5 mBq/m3 and from 0.0 to 4.2 mBq/m3, respectively. The seasonal variation pattern of the atmospheric concentration of 210Pb indicated that the air mass from Chinese Continent reached the coast of the Sea of Okhotsuk. 相似文献
16.
Andra-Rada Iurian Arsenio Toloza Joseph Adu-Gyamfi Constantin Cosma 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(3):1857-1863
The 7Be approach in estimating the erosion rates is based on the assumption that the deposition of 7Be fallout associated with the erosive event is spatially uniform. The objective of the present work was to verify this assumption by assessing the influence of heavy rainfalls on the 7Be spatial distribution in Seibersdorf soils, Austria. Incremental and bulk soil depth profiles were collected from a flat site, undisturbed for the last 9 months prior sampling and with no evidence of erosion or deposition after the occurrence of heavy rains (>30 mm day?1). The mean value of the 7Be areal activities (Bq m?2) measured at 10 different points from the selected area was 312 Bq m?2. This value corresponded to a total rainfall of 295 mm within the last 5 months prior sampling, considering that the highest mass activity of 7Be at soil surface will decay below the minimum detectable activity after 5 months’ time. The resulted coefficient of variation had a value of 19 % showing acceptable spatial variability of 7Be fallout connected with individual storm events on a local scale. 相似文献
17.
Y. Narazaki K. Fujitaka S. Igarashi Y. Ishikawa N. Fujinami 《Journal of Radioanalytical and Nuclear Chemistry》2003,256(3):489-496
Seasonal variations of 7Be deposition in regions throughout Japan (26°18'N-43°05'N, 127°54'E-141°27'E) were observed during the period of 1989-1995. The observation indicated that 7Be deposition peaked in spring all over Japan except in the inland central basin. However, spring peak was not always the annual maximum. Along the coastal side of the Japan Sea, especially around Hokuriku region, 7Be deposition was at its maximum in winter. In addition, September peak also was observed in some regions, which was presumably caused by high precipitation or blowing in of northern air stream. Variations were classified into 4 types according to meteorological factors and local geographical conditions: winter peak, double peaks (spring and September peaks), spring peak and non-peak. A correlation between 7Be deposition and precipitation was observed in winter. 相似文献
18.
Sylwia Błażej Jerzy W. Mietelski 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(2):747-756
A low background gamma spectrometer with an Etruscan, 2500 years old lead shield and a muon veto detector were applied to study 22Na and 7Be activity concentration in ground level air aerosol samples collected weekly over the years 2003–2006 in Kraków. Each sample was formed with ca 100 000 m3 of passed air, collected with two parallel ASS-500 high volume air samplers. The results for 40K and 137Cs are also presented for reference and comparison. Presented frequency distributions for activity concentration and correlation between the obtained results are discussed. The activity concentration results confirmed seasonal variation of activity to be different for all the investigated radionuclides. Moreover, the seasonal variation in nucleus activity ratio was also noticed for 22Na and 7Be. Cosmogenic radionuclides being mainly of stratospheric origin, are subsequently attached to fine aerosols, via which they are transported to the ground level air. The mean aerosol transport time within the troposphere was estimated as equal to 7.5 days on average, reaching even 50 days in warm seasons. Limitations of the applied model were identified. 相似文献
19.
Moumita Maiti Santosh R. Tiwari Nilesh B. Dubey Hemlata Bagla Susanta Lahiri 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(2):1443-1446
We have measured 7Be activity in moss samples collected from in and around Mumbai, India. The use of heavily shielded Compton suppressor system is more efficient than the conventional gamma spectroscopic system for detection of 7Be. The 7Be accumulation capacities of mosses are more than other plant samples. Therefore monitoring of young moss samples by Compton suppressor system is an excellent tool for determination of atmospheric fallout of 7Be. A positive bias in the high altitude samples has been observed which might be due to any of the two reasons (i) higher cosmic ray flux in the high altitude or (ii) high pollution in the lower altitude area ultimately inhibits uptake of 7Be. 相似文献
20.
Michael E. Kitto Traci A. Menia Douglas K. Haines Shaun E. Beach Clayton J. Bradt Eileen M. Fielman Umme-Farzana Syed Thomas M. Semkow Abdul Bari A. J. Khan 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(1):49-56
An air-sampling network that operates continuously as part of New York State’s environmental surveillance program collected radionuclides emitted as a result of the Fukushima nuclear accident. Samples were collected, typically for 7 days each, by drawing ~600 m3 of air through a particulate-collecting filter followed in series by a canister containing activated charcoal. Additional air sampling was implemented at ~3-day intervals at two locations. Gamma-ray spectroscopy was used to confirm the detection of 131I, 137Cs, 134Cs, and 7Be in the particulate phase at all sites, with maximum concentrations near 1,260, 160, 160, and 5,200 μBq/m3, respectively. Gas-phase 131I, collected on activated charcoal, exhibited a maximum concentration of 3,400 μBq/m3 at the sites. Assessment of radionuclide levels in the air samples suggests that there were minimal health impacts from the airborne radionuclides as the activities contributed an insignificant amount to the annual human dose. 相似文献