タグ「Chernobyl fallout」
Title: Seasonal 7Be and 137Cs activities in surface air before and after the Chernobyl event
Author: A. Kulan
Reference: Journal of Environmental Radioactivity, Volume 90, Issue 2, 2006, Pages 140-150
DOI: http://dx.doi.org/10.1016/j.jenvrad.2006.06.010
Keywords: 7Be; 137Cs; Atmosphere; Aerosols; Chernobyl fallout; Nuclear weapons fallout; Sweden; Europe
Abstract: Seasonal fluctuations of cosmogenic 7Be (T1/2 = 53.4 days) and anthropogenic 137Cs (T1/2 = 30 years) activities in surface air (aerosols) have been extracted from a long data record (1972–2000) at high latitude (56°N–68°N, Sweden). Normalization to weekly average values was used to control long-term trends so that cyclical trends could be investigated. Enhanced 7Be activity was observed in spring and summer seasons and likely relates to the seasonal thinning of the tropopause. Variations in the 137Cs activity record seem to reflect how the isotope was injected in the atmosphere (stratospheric from bomb tests and tropospheric from the Chernobyl accident) and subsequent transport mechanisms. Accordingly, until 1986, the surface air 137Cs activity was strongly related to nuclear weapons test fallout and exhibits temporal fluctuations resembling the 7Be. Conversely, since 1986 the Chernobyl-produced 137Cs dominates the long-term record that shows annual cycles that are strongly controlled by atmospheric boundary layer conditions. Additionally, short-term data within the post-Chernobyl period suggest subtle intrusion of air masses rich in 137Cs that may occur throughout the year, and differences resulting from spatial occurrence at these latitudes. This is an important observation that may have to do with year-to-year variation and calls for caution when interpreting short-term data records.
URL: http://www.sciencedirect.com/science/article/pii/S0265931X06001032
Title: Geographical mapping and associated fractal analysis of the long-lived Chernobyl fallout radionuclides in Greece
Author: N.P Petropoulos, M.J Anagnostakis, E.P Hinis, S.E Simopoulos
Reference: Journal of Environmental Radioactivity, Volume 53, Issue 1, 2001, Pages 59-66
DOI: http://dx.doi.org/10.1016/S0265-931X(00)00111-9
Keywords: Chernobyl fallout; Mapping; Fractal analysis; Deposition pattern
Abstract: Immediately after the Chernobyl accident, a soil sampling programme was undertaken in order to detect and quantitatively analyse the long-lived radionuclides in the Chernobyl fallout. Soil samples (1242 in number) of 1 cm thick surface soil were collected in Greece during the period from May–November 1986. The samples were counted and analysed using Ge detector set-ups. The fallout data have already been analysed, mapped and published. In an attempt to improve this analysis and also to extend it to other fallout radionuclides, an in-house unix-based data base/geographical information system (DBGIS) was developed. Multifractal analyses of the deposition patterns have also been performed. In the present work, an analysis of the results of the deposition of [, , , , , , , , ]and are presented together with relevant fractal analysis and three characteristic contour maps. The maximum detected values of the above-mentioned radionuclides were 149.5±0.1, 76.1±0.1, 32.9±0.2, 46±2, 4.56±0.02, 7.98±0.02, 79.1±0.4, 337±2, 20.1±0.2 and 3.02±0.02 kBq m−2, respectively. Furthermore, a statistical technique to compare contour maps was introduced and applied to explain the differences which appeared in the maps of the above-mentioned radionuclides.
URL: http://www.sciencedirect.com/science/article/pii/S0265931X00001119
Title: Accumulation of Chernobyl-derived 137Cs in bottom sediments of some Finnish lakes
Author: Erkki Ilus, Ritva Saxén
Reference: Journal of Environmental Radioactivity, Volume 82, Issue 2, 2005, Pages 199-221
DOI: http://dx.doi.org/10.1016/j.jenvrad.2005.01.008
Keywords: Lake sediments; Chernobyl fallout; Caesium-137; Sedimentation rate
Abstract: The amount and vertical distribution of Chernobyl-derived 137Cs in the bottom sediments of some Finnish lakes were studied. Sediment and surface water samples were taken in 2000 and 2003 from 12 stations in nine lakes and the results were compared with those obtained in corresponding surveys carried out in 1969, 1978, 1988 and 1990. Each of the five deposition categories of Chernobyl fallout in Finland were represented. The depth profiles of 137Cs in the sediments showed considerable variety in the lakes studied. The peak values varied between 1.5 and 46 kBq kg−1 dry wt. The size and shape of the peak did not always correlate with the amount of deposition in the area, but on the other hand, reflected differences in sedimentation processes in different lakes. In some of the lakes the peak still occurred in the uppermost (0–2 cm) sediment layer, but in an extreme case the peak occurred at a depth of 22–23 cm corresponding to a sedimentation rate of 16 mm year−1 during the 14 years after the Chernobyl accident. The total amounts of 137Cs in sediments varied from 15 to 170 kBq m−2 at the sampling stations studied. Since 1990, the amounts have continued to increase slightly in two lakes, but started to decrease in the other lakes. In most of the lakes, the total amounts of 137Cs in sediments were about 1.5–2 times higher than in local deposition. In two lakes, the ratio was below 1, but in one case 3.2. Compared with the total amounts of 137Cs at the same stations in the late 1960s and 1970s, the values were now at their highest, at about 60-fold. The most important factors affecting 137Cs values in sediments were the local amount of deposition and the type of the lake and the sediment, but in addition, there were a number of other factors to be considered.
URL: http://www.sciencedirect.com/science/article/pii/S0265931X0500041X
Title: Separation of Tc-99 in soil and plant samples collected around the Chernobyl reactor using a Tc-selective chromatographic resin and determination of the nuclide by ICP-MS
Author: Uchida, S.; Tagami, K.; Ruhm, W.; Steiner, M.; Wirth, E.
Reference: Applied Radiation and Isotopes, July-Aug. 2000, vol.53, no.1-2, pp. 69-73
DOI: http://dx.doi.org/10.1016/S0969-8043(00)00112-3
Keywords: Technetium-99; Chernobyl fallout; Organic soil; Plants of the understorey vegetation
Abstract: Technetium (Tc) is known to have high mobility in a soil–water system and also high bioavailability for plants, because the most stable form of Tc in natural surface environment is thought to be TcO−4 which is highly soluble. The chemical form of Tc, however, changes with environmental conditions. Thus, it is necessary, for realistic assessment, to obtain transfer parameters, such as transfer factors, under natural conditions. However, it is difficult to obtain these parameters using global fallout in actual fields due to its low concentration. In this study, concentrations in surface soil and plant leaf samples collected from forest sites within the 30-km zone around the Chernobyl reactor were measured for the first time. In the case of soil samples, a simple and rapid analytical method for determination of is used which consists of volatilizing and trapping Tc in a combustion apparatus, purifying the Tc with an extraction chromatographic resin, and measuring it by inductively coupled plasma mass spectrometry (ICP-MS). For plant samples, a wet digestion method in combination with the resin is applied and the is measured by ICP-MS. Concentrations of in organic soil samples and leaves of strawberry (Fragaria vesca) range from 1.1–14.8 Bq kg−1 dry weight and 0.2–6.0 Bq kg−1 dry weight, respectively. Our results indicate that soil-to-plant transfer factors for Tc are similar to those for Cs.
URL: http://www.sciencedirect.com/science/article/pii/S0969804300001123
Title: Lichen (sp. Cladonia ) as a deposition indicator for transuranium elements investigated with the Chernobyl fallout
Author: Paatero, Jussi / Jaakkola, Timo / Kulmala, Seija
Reference: Journal of Environmental Radioactivity, 38 (2), p.223-247, Jan 1998
doi: 10.1016/S0265-931X(97)00024-6
Kewords: Plutonium, Lichen (Cladonia), Chernobyl fallout
Abstract: The feasibility of employing carpet-forming lichens (sp. Cladonia) as a measure for the deposition of transuranium elements was investigated with the Chernobyl fallout. In Finland, the deposition of these elements after the accident was very uneven. The highest deposition values for 238Pu, 239,240Pu, 241Am, 242Cm and 243,244Cm were 5.7, 3.0, 1.3, 98 and 0.025 Bq m−2, respectively. The amount of deposited 239,240Pu was, however, only some percent of the fallout of the nuclear test explosions of the 1950s and the 1960s. Instead, practically no 242Cm was released into the environment during the weapons’ testing.
URL: http://www.sciencedirect.com/science/article/pii/S0265931X97000246
Title: Resuspension of coarse fuel hot particles in the Chernobyl area
Author: Wagenpfeil, Florian / Tschiersch, Jochen
Reference: Journal of Environmental Radioactivity, 52 (1), p.5-16, Jan 2001
doi: 10.1016/S0265-931X(00)00081-3
Keywords: Resuspension; Chernobyl fallout; Hot particles; Aerosol sampler; Digital autoradiography
Abstract: Measurements of resuspended aerosol in the Chernobyl 30-km exclusion zone have shown coarse fuel hot particles in the activity range 1–12 Bq per particle. The particles were sampled with newly designed rotating arm impactors which simultaneously collect during the same experiment three samples with fuel particles in the size ranges larger than 3 μm, larger than 6 μm and larger than 9 μm in geometric diameter. The radionuclide ratios, determined after γ-spectrometry, were in good agreement with the theoretical calculations for the radionuclide-composition of the Chernobyl Nuclear Power Plant at the moment of the accident and the measured hot particles in soil in the early years after the accident. The number concentrations of airborne hot particles were derived from digital autoradiography. For wind resuspension, maximal concentrations of 2.6 coarse hot particles per 1000 m3 and during agricultural activities 36 coarse hot particles per 1000 m3 were measured. The geometric diameter of single hot particles was estimated to be between 6 and 12 μm.
URL: http://www.sciencedirect.com/science/article/pii/S0265931X00000813
Title: Seasonal 7 Be and 137 Cs activities in surface air before and after the Chernobyl event
Author: Kulan, A.
Reference: Journal of Environmental Radioactivity, 90 (2), p.140-150, Jan 2006
DOI: 10.1016/j.jenvrad.2006.06.010
Keywords: 7Be; 137Cs; Atmosphere; Aerosols; Chernobyl fallout; Nuclear weapons fallout; Sweden; Europe
Abstract: Seasonal fluctuations of cosmogenic 7Be (T1/2 = 53.4 days) and anthropogenic 137Cs (T1/2 = 30 years) activities in surface air (aerosols) have been extracted from a long data record (1972–2000) at high latitude (56°N–68°N, Sweden). Normalization to weekly average values was used to control long-term trends so that cyclical trends could be investigated. Enhanced 7Be activity was observed in spring and summer seasons and likely relates to the seasonal thinning of the tropopause. Variations in the 137Cs activity record seem to reflect how the isotope was injected in the atmosphere (stratospheric from bomb tests and tropospheric from the Chernobyl accident) and subsequent transport mechanisms. Accordingly, until 1986, the surface air 137Cs activity was strongly related to nuclear weapons test fallout and exhibits temporal fluctuations resembling the 7Be. Conversely, since 1986 the Chernobyl-produced 137Cs dominates the long-term record that shows annual cycles that are strongly controlled by atmospheric boundary layer conditions. Additionally, short-term data within the post-Chernobyl period suggest subtle intrusion of air masses rich in 137Cs that may occur throughout the year, and differences resulting from spatial occurrence at these latitudes. This is an important observation that may have to do with year-to-year variation and calls for caution when interpreting short-term data records.
URL: http://www.sciencedirect.com/science/article/pii/S0265931X06001032
