Total deposition velocities and scavenging ratios of 7Be and 210Pb at Rokkasho, Japan

The atmospheric concentrations and deposition fluxes of ⁷Be and ²¹⁰Pb were observed biweekly in Rokkasho, Japan on the Pacific Ocean coast at the northern end of Honshu Island, from March 2000 to March 2006, to clarify their regional features. Seasonal variation pattern of atmospheric ⁷Be concentrations had double peaks, and that of ²¹⁰Pb had a single peak. Deposition fluxes of ⁷Be and ²¹⁰Pb showed the same patterns. The total deposition pattern of ⁷Be was similar to that commonly seen on the Pacific Ocean side of northern Honshu Island, while the pattern of ²¹⁰Pb was similar to that commonly seen on the Japan Sea side. The lack of high spine mountains windward in Rokkasho may be the cause of this ambiguity in the winter monsoon season. Total deposition velocities and scavenging ratios of ²¹⁰Pb were similar to those of ⁷Be from spring to fall, and showed that both nuclides had a similar removal process from the atmosphere. However, the scavenging ratios of ²¹⁰Pb were slightly larger than those of ⁷Be in winter, indicating different behaviors for both nuclides in the scavenging process. The scavenging ratios of both nuclides inversely correlated with precipitation rate, and the ratios in winter were larger than in the other seasons.     

Mechanism of 7Be scavenging from the atmosphere through precipitation in relation to seasonal variations in Rokkasho Village, Aomori Prefecture, Japan

⁷Be deposition fluxes and atmospheric concentrations were measured at Rokkasho Village, Aomori Prefecture, Japan, from 2000 to 2005. It was confirmed that the ⁷Be deposition fluxes were minimum in summer, and the fallout maximizes in winter. The atmospheric concentration of ⁷Be was especially low in summer, and high in the other three seasons. A positive correlation was observed between the amount of precipitation and ⁷Be deposition. Clear seasonal differences were evident among the ratios of ⁷Be deposition flux to precipitation amounts in the four seasons. The ratios were especially high in winter, higher than those in the other three seasons. ⁷Be deposition flux was estimated by a simple simulation model using atmospheric ⁷Be concentrations and local meteorological data. As a result, the estimated deposition value was relatively lower than the measured value in winter.     

Temporal variation of 7Be fallout and its inventory in purple soil in the Three Gorges Reservoir region, China

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.     

Atmospheric concentrations of 7Be and 210Pb in Granada, Spain

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.     

Variation of 7Be concentration in surface air at Nagano, Japan

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.     

Radionuclide variations in the air over Monaco

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.     

Investigation of7Be in the Bratislava atmosphere

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.     

Atmospheric deposition of 7Be, 40K, 137Cs and 210Pb during 1993-2001 at Tokai-mura, Japan

To evaluate the radionuclide migration from the atmosphere to the ground surface, atmospheric deposition samples were collected from 1993 to 2001 with a basin set up at Tokai-mura, Japan. Monthly samples were evaporated to dryness to obtain residual samples and measured with a Ge detector for ⁷Be, ⁴⁰K, ¹³⁷Cs and ²¹⁰Pb. According to the analysis, clear seasonal variations with spring peaks of deposition weight and deposition amounts of all the radionuclides were found. The analysis also showed that these radinuclides can be divided into two groups, each having different carrier particle sizes and, hence, different deposition processes.     

Seasonal variation of natural radionuclides and some elements in plant leaves

Leaf and aerosol samples were monthly collected in Mt. Sefuri (Fukuoka Prefecture). Radioactivities of ⁷Be, ²¹⁰Pb and ⁴⁰K were determined with gamma-ray spectrometry. The concentrations of some elements in the leaf samples were determined by neutron activation analysis. Similar seasonal variation of ⁷Be and ²¹⁰Pb was observed between leaf and aerosol samples, high in spring and winter and low in summer. Correlation factors for trace elements contained in the leaf show large variations. This indicates that the contribution of two sources (atmospheric deposition and uptake from soil) is very variable.     

Beryllium-7 in near-surface atmospheric aerosols in mid-latitude (40°N) city Beijing, China

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.     

Seasonal variation and activity size distribution of <Superscript>7</Superscript>Be in ambient air

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.     

<Superscript>7</Superscript>Be in the lower atmosphere at a mid-latitude (40°N) during the year 2009 of a particular minimum of solar activity

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.     

Direct determination of selenium in whole blood by anodic stripping voltammetry

Trace quantities of selenium can be determined in the presence of iron, copper and lead using anodic stripping voltammetry, depositing at –0.60 V in 0.1M HClO₄ and stripping in the anodic direction. Two separate peaks are observed at –0.25 V and –0.10 V belonging to copper and selenium, respectively. Sometimes one peak may be observed for both copper and selenium. In this case one more stripping (without deposition) must be done to obtain separate peaks. After standard addition, two strippings have to be done also. With this proposed method, 10^–7 M selenium could be determined as (1.09±0.03) × 10^–7 M with a 90% confidence interval in blood samples without any separation.Presented at Xth National Chemistry Congress, Bursa, Turkey, September 19–21, 1994     

Comparison of <Superscript>14</Superscript>C levels in urban area with background levels in the atmospheric CO<Subscript>2</Subscript> in Kanazawa,Ishikawa prefecture,Japan

The temporal variation of ¹⁴C concentrations in atmospheric CO₂ samples collected every 10 days was measured in the Takao area of Kanazawa, Ishikawa prefecture, Japan (36.52°N, 136.64°E), from April 1991 to December 1995. The monthly mean levels of ¹⁴C concentration in the Takao area demonstrated 10–50‰ lower concentrations than the background levels only in the winter season. This decrease seemed to be caused by the local fossil fuel contribution by heating in the winter season in the Takao area, which is located in an urban region near the center of Kanazawa. It is noteworthy that a remarkable peak was observed from late April to mid-May each year from 1991 to 1995 in the variation of ¹⁴C concentrations in atmospheric CO₂. This phenomenon is similar to that of the so-called “spring peak” observed in Japan for other radionuclides.     

An attempt to evaluate dry deposition velocity of airborne210Pb in a forest ecosystem

Atmospheric concentration and total (wet plus dry) and dry deposition of²¹⁰Pb and⁷Be have been measured at our laboratory in Ishikawa Prefecture in Japan which faced the Sea of Japan during 1993–1994. At the same time inventories of excess²¹⁰Pb in soil samples were measured from a mixed pine forest. On the basis of the data obtained, an attempt was made to evaluate the dry deposition velocity as a result of the interception by the canopies of airborne²¹⁰Pb in a pine stand The dry deposition velocity of²¹⁰Pb in the pine stand was roughly estimated to be 0.9–0.8 cm/s, higher by a factor of about 10 than the value (mean: 0.12±0.09 cm/s; range: 0.06–0.28 cm/s) in the open area measured on the roof of our laboratory.     

Preliminary application of low-background gamma-spectrometry to volcanic ground water

To enrich cosmogenic ⁷Be and ²²Na, artificial ¹³⁷Cs and natural radium isotopes, three chemical methods were applied to large volumes (100–300 l) of ground water from Daisen Volcano, Japan. The co-precipitation method using BaSO₄, Fe(OH)₃ and AMP, yielded ⁷Be, ¹³⁷Cs and radium isotope levels of nearly 100%. An ordinary ion-exchange column method, selectively recovered ²²Na (77%) through two continuous column operations. ⁴⁰K was satisfactorily removed in both, the co-precipitation and column methods. In addition, the simple batch method was suitable for rapid treatment even on the slope of a volcano without sacrificing yields. Low-background γ-spectrometry combined with these chemical treatments enabled the determination of extremely low-levels of ⁷Be, ²²Na, ¹³⁷Cs and radium isotopes (0.01–4 mBq/l) in ground water samples. The measurement of these nuclides of Daisen ground water provide new information on the flow system of volcanic water, including residence time, the mixing of precipitation, and the aquifer’s environment.     

Atmospheric deposition fluxes of <Superscript>7</Superscript>Be, <Superscript>210</Superscript>Pb and <Superscript>210</Superscript>Po at Xiamen,China

The atmospheric deposition fluxes of ⁷Be, ²¹⁰Pb and ²¹⁰Po at Xiamen were measured. The samples were collected from March 2004 to April 2005 and the sampling period was one month. The ⁷Be and ²¹⁰Pb activity were measured using HPGe γ-spectrometer after concentration using Fe(OH)₃ co-precipitation method. The ²¹⁰Po was counted with an α-spectrometer after the sample was digested and spontaneous plated onto a silver planchet. At Xiamen, the atmospheric deposition fluxes of ⁷Be varied between 0.11 and 2.93 Bq·m⁻²·d⁻¹ and the average was 1.64 Bq·m⁻²·d⁻¹; ²¹⁰Pb fluxes varied between 0.04 and 0.85 Bq·m⁻²·d⁻¹, and the average was 0.51 Bq·m⁻²·d⁻¹; ²¹⁰Po fluxes varied between 0.002 and 0.133 Bq·m⁻²·d⁻¹, and the average was 0.061 Bq·m⁻²·d⁻¹. There were positive correlations between the deposition fluxes of ⁷Be, ²¹⁰Pb or ²¹⁰Po and the amount of precipitation. The residence time of aerosols varied between 6.0 and 54.0 days with a mean of 27.1 days, which were calculated by ²¹⁰Po/²¹⁰Pb fluxes ratios.     

Temporal variation of tritium concentration in tree-ring cellulose over the past 50 years

Concentration of organically-bound tritium in the tree-ring cellulose of a pine tree grown in Shika-machi, Ishikawa prefecture, Japan (37.1°N, 136.5°E), was measured during the ring-years from 1949 to 1999. The results were compared with those of a pine tree grown in Tatsunokuchi-machi, Ishikawa prefecture, Japan (36.4°N, 136.5° E). The annual variation of tritium in tree rings demonstrated two differences between the Shika-machi tree and the Tatsunokuchi-machi tree. No secondary peak appeared in the period after the maximum peak of 1963 for the Shika-machi tree, while two peaks appeared in 1966 and 1970 for the Tatsunokuchi-machi tree. In addition, the height of the 1963 peak was 30% higher for the Shika-machi tree than for the Tatsunokuchi-machi tree. These differences are considered to be caused by the influence that the underground water in the root zone of the Tatsunokuchi-machi tree was strongly affected by water which was transported to the tree site from mountain regions as compared to the Shika-machi tree.This study was supported in part by a Grant from the Ishikawa Prefectural Institute of Public Health and Environmental Science.     

Temporal variation of tritium concentration in tree-ring cellulose over the past 50 years

Concentration of organically-bound tritium in the tree-ring cellulose of a pine tree grown in Shika-machi, Ishikawa prefecture, Japan (37.1°N, 136.5°E), was measured during the ring-years from 1949 to 1999. The results were compared with those of a pine tree grown in Tatsunokuchi-machi, Ishikawa prefecture, Japan (36.4°N, 136.5° E). The annual variation of tritium in tree rings demonstrated two differences between the Shika-machi tree and the Tatsunokuchi-machi tree. No secondary peak appeared in the period after the maximum peak of 1963 for the Shika-machi tree, while two peaks appeared in 1966 and 1970 for the Tatsunokuchi-machi tree. In addition, the height of the 1963 peak was 30% higher for the Shika-machi tree than for the Tatsunokuchi-machi tree. These differences are considered to be caused by the influence that the underground water in the root zone of the Tatsunokuchi-machi tree was strongly affected by water which was transported to the tree site from mountain regions as compared to the Shika-machi tree.This study was supported in part by a Grant from the Ishikawa Prefectural Institute of Public Health and Environmental Science.     

Fallout of7Be in Damascus City

Atmospheric fallout of⁷Be was measured over a 2 year period (January 1995–January 1997) at Damascus city (33 N^o, 727 m above sea level). The annual total deposition of⁷Be was found to be 420 and 634 Bq·m⁻² for 1995 and 1996, respectively, reflecting a Mediterranean climate where two well recognized periods are dominant (wet and dry). The depositions in the wet periods were 303 Bq·m⁻² and 517 Bq·m⁻² for 1995 and 1996, respectively, while unexpected equal deposition rates in the two dry periods were found to be about 117 Bq·m⁻². In addition, monthly deposition rate of⁷Be showed a maxima in February in 1995 and January for 1996. Moreover, a comparison has been set for our measurements and other data obtained at different locations in the world.