6G. Lujanien_e et al. / <strong>Journal</strong> <strong>of</strong> <strong>Environmental</strong> <strong>Radioactivity</strong> xxx (2012) 1e10Fig. 6. Backward trajectories <strong>of</strong> air masses transport ending on 30 March, 1 April and 4 April, 2011 in Vilnius.Please cite this article in press as: Lujanien_e, G., et al., Radionuclides from the Fukushima accident in the air over Lithuania: measurement andmodelling approaches, <strong>Journal</strong> <strong>of</strong> <strong>Environmental</strong> <strong>Radioactivity</strong> (2012), doi:10.1016/j.jenvrad.2011.12.004
G. Lujanien_e et al. / <strong>Journal</strong> <strong>of</strong> <strong>Environmental</strong> <strong>Radioactivity</strong> xxx (2012) 1e10 7Activity concentration, mBq/m 3100001000100101131 I137 Cs103Ru29 1 4 7 10 13 16 25 1 4AprilMay June 1986Fig. 7. Activity concentrations <strong>of</strong> 131 I, 137 Cs, 103 Ru in aerosol samples in Vilnius in 1986.with higher probability, due to the precipitation effect and rathershort residence time <strong>of</strong> water soluble aerosols in the boundary layer.3.3. Comparison with the Chernobyl accidentThe consequences <strong>of</strong> the Fukushima accident were estimated tobe close to the Chernobyl accident according to the given level 7 onthe INES scale (IAEA, 2011). The long-term radiological impact <strong>of</strong> theChernobyl accident on the environment and humans due to releasedradioactivity, migration, resuspension <strong>of</strong> deposited radionuclideshas been studied over 20 years. During the accident, and the postChernobyl period, many measurements <strong>of</strong> gamma, beta and alphaemittersin aerosol samples were carried out in Vilnius (Lujanaset al., 1994; Lujanien_e et al., 1997, 1999, 2009). A wide spectrum <strong>of</strong>radionuclides and “hot particles” were detected in Vilnius followingthe Chernobyl accident, when activity concentrations were therehigher by 4 orders <strong>of</strong> magnitude as compared to the Fukushimaaccident. The maximum activities in Vilnius during the first weekafter the Chernobyl accident were 45.2 Bq/m 3 for 131 I (aerosolfraction) and 27.9 Bq/m 3 for 137 Cs. The 132 Te and 103 Ru activityconcentrations in AprileMay,1986 ranged from 0.1 Bq/m 3 to 51.0 Bq/m 3 and from 0.1 Bq/m 3 to 20.3 Bq/m 3 , respectively (Fig. 7).In the Chernobyl plume Zr, Nb, Ru and Ce isotopes were detectedin the air as well. In addition, the presence <strong>of</strong> “hot particles” <strong>of</strong>0.37e22.2 mm in size carrying beta-emitters, and “hot particles” <strong>of</strong>0.7e2 mm containing alpha-emitters ( 233 U, 234 U, 235 U, 238 Pu, 239 Pu,240 Pu, 241 Am, 242 Cm, 244 Cm) in 1986 were also found in aerosolfilters collected in Vilnius. The activity ratio <strong>of</strong> 238 Pu/ 239,240 Puvaried from 0.44 to 0.5 and the atom ratio <strong>of</strong> 240 Pu/ 239 Pu rangedfrom 0.41 to 0.42. The high activities detected in Vilnius after theChernobyl accident were explained by quite close location(480 km) <strong>of</strong> the site.Furthermore, the Chernobyl accident resulted in contamination<strong>of</strong> large areas <strong>of</strong> the Earth’s surface in Europe including six millionha <strong>of</strong> forested land <strong>of</strong> the Ukraine, Belarus and Russia (De Cort et al.,1998). The 137 Cs surface deposition (Fig. 8) exceeded 1480 kBq/m 2(0.03% <strong>of</strong> the European territory). The prediction <strong>of</strong> 137 Cs surfacedeposition after the Fukushima accident was made usinga numerical atmospheric chemistry/transport model Polyphemus/Polair3D, and compared with contamination <strong>of</strong> Europe after theChernobyl accident (Winiarek et al., 2011). The results indicatedobvious differences in the consequences <strong>of</strong> the Chernobyl andFukushima accidents, especially at the level <strong>of</strong> highly contaminatedterritories. However, a contamination <strong>of</strong> the marine environmentand a deposition to the bottom sediments were not taken intoaccount in this model. It is expected that the main radiologicalproblems will arise from contaminated seafood, while the atmosphericdeposition will again trigger discussions on the impact <strong>of</strong>low-level radiation doses on the public.Areas with high Chernobyl 137 Cs ground depositions locatedclose to Lithuania have been a source <strong>of</strong> the secondary contaminationdue to the forest fires and soil resuspension for a long time(Lujanien_e et al., 2009). The transport <strong>of</strong> aerosol particles, whichderived from resuspension and/or forest fires in 1997e2001 and2005e2006 was modelled using the HYSPLIT. The backwardtrajectories were calculated for 4 selected sectors for 72 h at theheights <strong>of</strong> 20, 500 and 1000 m AGL (Fig. 8). However, not allcalculated trajectories were possible to assign to a particular sector.Very complicated trajectories that did not match any sector wereassociated with sector 0.In both studied periods a weak correlation between the 137 Csactivity concentration and height (R ¼ 0.28 (20 m), 0.32 (500 m),and 0.31 (1000 m) in 1997e2001; and for 2005e2006 R ¼ 0.41(20 m), 0.49 (500 m), and 0.49 (1000 m)) was found for the Chernobylsector, while for other sectors no correlation was observed. Adissimilar behaviour <strong>of</strong> Pu isotopes was explained by their differentvolatility as compared to Cs ones. This is again in good agreementwith results obtained in 2005e2006 (Fig. 9) where 239,240 Puactivities ranged from 2 to 49 nBq/m 3 , with maxima observed inMay (29 and 49 nBq/m 3 , respectively), and they obviously derivedfrom soil resuspension. The 241 Am activity concentrations variedfrom 1 to 25 nBq/m 3 and the highest values were also detected inMay. Variations in the 241 Am/ 239,240 Pu activity ratios from 0.27 to0.65 were found in the analyzed samples with the average value<strong>of</strong> 0.44.The 238 Pu/ 239,240 Pu activity ratios in aerosol samples collected inVilnius during the Chernobyl accident were in the range 0.44e0.50,while the 240 Pu/ 239 Pu atom ratios in the same samples ranged from0.41 to 0.42. The 240 Pu/ 239 Pu atom ratios in monthly samples inVilnius in 1995e2003 varied from 0.14 to 0.40, whereas in samplescollected during forest fires the ratio was between 0.19 and 0.23. Inaddition, an exponential decrease in the 240 Pu/ 239 Pu atom rati<strong>of</strong>rom 0.30 to 0.19 (mean values) was observed during 1995e2003.The characteristic 238 Pu/ 239,240 Pu activity ratio <strong>of</strong> global fallout is0.03, while that <strong>of</strong> the Chernobyl accident is 0.45 (Livingston andPovinec, 2002). The enhanced activity ratios <strong>of</strong> 238 Pu/ 239,240 Pu(from 1 to 3) have been measured in environmental samplesderived from industrial nuclear effluents. The highest ratio <strong>of</strong>238 Pu/ 239,240 Pu ¼ 25.3 was reported in October 1982 and wasattributed to discharges from the reprocessing plants at La Hagueand Sellafield (Martin and Thomas, 1988).In order to check the presence <strong>of</strong> Pu isotopes in samplescollected after the Fukushima accident between 23 March and 15April, 2011 (N ¼ 30, sampling air volume <strong>of</strong> w2 10 6 ) all sampleswere combined together to form one sample and Pu isotopes wereseparated and measured by means <strong>of</strong> alfa-spectrometry (Fig. 10).The activity concentration <strong>of</strong> 239,240 Pu in this integrated sample wasfound to be 44.5 2.5 nBq/m 3 , very close to the value measured inMay, 2005 (Fig. 9), and higher than the activity measured inAprileMay, 2006. The values measured in March, 2006(12.0 0.6 nBq/m 3 ) and May, 2006 (29.2 1.5 nBq/m 3 ) could servetherefore as reference data for comparison. From the spectrumshown in Fig. 10 it can be seen that the activity <strong>of</strong> 238 Pu is higherthan that <strong>of</strong> 239,240 Pu (by a factor <strong>of</strong> 1.2).The 238 Pu/ 239,240 Pu activity ratios in aerosol samples observed inMay 1986 at Tsukuba, Japan ranged from 0.04 to 0.33. The aerodynamicdiameter <strong>of</strong> particles carrying the Chernobyl derivedplutonium was estimated to be <strong>of</strong> 1.1e7 mm and the mean monthly239,240 Pu activity concentration increased only by 0.03 mBq m 3Please cite this article in press as: Lujanien_e, G., et al., Radionuclides from the Fukushima accident in the air over Lithuania: measurement andmodelling approaches, <strong>Journal</strong> <strong>of</strong> <strong>Environmental</strong> <strong>Radioactivity</strong> (2012), doi:10.1016/j.jenvrad.2011.12.004
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