Long term 7Be deposition in Romania

This study is based on monthly ⁷Be deposition data at 29 of the stations of Romania's National Environmental Radioactivity Surveillance Network (NERSN), with different geographical and climatological conditions, extending over periods up to 17 years (1979-1995). The ⁷Be activity in each monthly sample from each station was determined using high-resolution gamma-ray spectrometry performed at the Environmental Radioactivity Laboratory, Bucharest-Afumati. The annual dynamics of atmospheric deposition of ⁷Be at each NERSN station showed a strong seasonal trend, very similar to the precipitation regime, with the highest values being observed in spring/summer and the lowest in winter. But the annual ⁷Be deposition fluxes varied broadly from station to station and year to year, from a minimum of 164 Bq/m²/y (Bechet, 1989) to a maximum of 1388 Bq/m²/y (Baia Mare, 1988). This large space-time variability of deposition was mainly due to the variability of the precipitation regime. The analysis of experimental data confirms the strong correlation of ⁷Be deposition data with precipitation, air temperature and the number of sunspots. Wet and dry deposition data are presented and discussed for four stations where separate dry and wet ⁷Be deposition measurements were performed.

Distribution of 7Be, 210Pb and 137Cs in watersheds of different scales in the Seine River basin: inventories and residence times

The activity of environmental radionuclides ((7)Be, (210)Pb and (137)Cs) was monitored in nested catchments, inside the Seine River basin. Suspended matter data was collected at 8 different watersheds, ranging from order 1 to order 7, and ranging in size over 4 orders of magnitude. Suspended matter was analyzed for (210)Pb, (137)Cs and (7)Be, and used to calculate the flux of sediments out of each watershed. Monthly atmospheric flux data of (210)Pb and (7)Be was analyzed to assess the input flux of each into the watersheds, taking into account the rainfall during sampling periods. Taking advantage of the different half-lives of (7)Be (53 days) and (210)Pb (22 years), a two-box model was built for each of the catchments following a methodology previously developed by Dominik et al. [Dominik J, Burrus D, Vernet JP. Transport of the environmental radionuclides in alpine watershed. Earth Planet Sci Letters 1987; 84: 165-180.]. The model divides the watershed into a soil box and a rapid reservoir and provides insight into the removal rate of suspended matter from the surrounding watershed. The model enables the assessment of the surface area and the residence time of slow and rapid reservoirs to describe the fate of contaminants of atmospheric origin inside the river basin. The model was improved by considering the dissolved fraction in the total flux and adding the (137)Cs inventory as an additional constraint. The effects of these changes are discussed. Residence times in the soil box, characterized by low transport velocity, range between 4800 years at Melarchez (order 1) to about 30000 years at Andresy and Poses (order 7). They remain constant in each watershed over a large range of variation of atmospheric fluxes of (7)Be and (210)Pb during the whole study, but are sensitive to SM variations. The residence time in the rapid box, which includes the surface of the river and immediate surroundings, is less than one year, while its surface area is in the range 0.6% to 2.2% of the total catchment area. They are sensitive to (7)Be atmospheric flux variations. The two-box model was used to estimate the amount of the radionuclides in each reservoir. Inventories appear to be constant from one watershed to the next. The (7)Be inventory ratio in the rapid and slow boxes expresses the rate of particle-reactive atmospheric pollutants that will be rapidly delivered to the river.

Reconstruction of 137Cs signal in Cuba using 7Be as tracer of vertical transport processes in the atmosphere

Levels of 137Cs and 7Be in aerosols have been measured in the region of Cienfuegos (Cuba) during the period 1994-1998. 137Cs showed the same seasonal trend as 7Be and the monthly regimes of precipitation seemed to be responsible for the observed pattern. The 137Cs/7Be ratio obtained in Cienfuegos and Miami (FL) in this period was used to calibrate the long-term database of 137Cs concentrations recorded in Miami (250 km from Cienfuegos). The database was then employed to reconstruct the 137Cs monthly concentrations in Cienfuegos since 1957.

Variations in 7Be concentrations in the atmosphere of Kuwait during the period 1994 to 1998

The Beryllium-7 (7Be) concentrations in the atmosphere of Kuwait, as found by gamma-ray measurements for 243 air filters collected over a five-year period, produced variable values ranging from 0.2 to 14.9 mBq/m3 with a behavior pattern which has oscillatory characteristics, with increased activities occurring in the summer months of each year. The annual levels of occurrence of 7Be were found to be correlate with the cyclic pattern resulting from the eleven-year temporal variations associated with the solar activity.