Chernobyl Plume Research Articles

Spatial patterns and ratios of ¹³⁷Cs, ⁹⁰Sr, and Pu isotopes in the top layer of undisturbed meadow soils as indicators for contamination origin.

Spatial distribution of activity concentrations of (137)Cs, (90)Sr, and (239,240)Pu in the top layer of undisturbed meadow soils was compared between two regional transects across Lithuania: one in the SW region, more affected by the Chernobyl radioactive fallout, and the other in the NE region. Radiochemical, γ-, α-, β-, and mass spectrometric methods were used to determine the radionuclide activity. Our results validate that higher activity concentrations in the top soil layer were present in the SW region, despite the fact that sampling was performed after 22 years of the Chernobyl Nuclear Power Plant (NPP) accident. Using the activity concentration ratio (137)Cs/(239,240)Puglobal, the contribution of the Chernobyl NPP accident to the total radiocesium activity concentrations in these meadow soils was evaluated and found to be in the range of 6.5-59.1%. Meanwhile, the activity concentration ratio (238)Pu/(239,240)Pu showed that Chernobyl-derived Pu occurred at almost half of the sampling sites. The locations with maximal values of 47% of Chernobyl-derived Pu material were close to northeastern Poland, where deposition of most of non-volatile radioisotopes from the Chernobyl plume was determined.

High spatial resolution observations of 137Cs in northern Britain and Ireland from airborne geophysical survey

This study reports the 137Cs data derived from three regional and national scale High Resolution Airborne Resource and Environmental Surveys (HiRES) in northern Britain and Ireland. The detailed spatial resolution, combined with the large areas these surveys collectively cover, gives insight into large-scale deposition patterns and possible subsequent re-distribution of 137Cs on a level that was previously not possible. The largest survey area considered covers the whole of Northern Ireland. All three data sets display some clustering of higher 137Cs activities on high ground together with regional scale NNW-SSE and NW-SE banding features. We interpret these as representing a series of rainfall interceptions of the repeated passage of the Chernobyl plume. Our observations, obtained at 200 m flight line intervals, appear to provide significant detail in relation to existing knowledge of large scale along-wind deposition of 137Cs.

Natural decrease of the intensity level of artificial radioactive isotopes in the Barents Sea

The phenomenon of artificial radioactivity has been observed for the natural environment since the first nuclear tests in 1940s and continues at present. The disposal and dumping of both solid and liquid nuclear waste were typical for the Arctic and the northern seas. Radiological hazard sites can be observed in the coastal area, which are concentrated in Kola and Motovsky bays; the city of Murmansk, as well as towns: Severomorsk, Polyarny, and Gadzhievo; and the following inlets: Saida, Olenya, Pala, Zapadnaya Litsa, Ura, and Ara. Gaseous, liquid, and solid nuclear wastes are formed there. The European radiochemical factories are the most significant producers of nuclear waste in the Arctic Ocean. The Sellafield factory (Great Britain) is the biggest one amongst them, which produced a summarized waste of 160 · 10 15 Bq. About 30% of 90 Sr and from 10 to 20% of 137 Cs produced in Sellafield is dumped in the Barents Sea. The western European plume crosses the shelf area of the Barents Sea and reaches the center of the Arctic Ocean within six years [1‐3]. The Chernobyl plume provided from 10 to 20% of the nuclear pollution in the Kara and Barents seas in the 1990s.

Down syndrome time-clustering in January 1987 in Belarus: Link with the Chernobyl accident?

The Chernobyl accident (April 26, 1986) exposed a large part of the Belarus population to ionizing radiation. We analyzed the time trends of Down syndrome (DS) in Belarus to evaluate whether either brief exposure at high dose rates during the plume passage or continuous exposure at low doses and dose rates of the residents of contaminated areas had any detectable impact on DS prevalence at birth. DS data came from the Belarus National Registry of Congenital Malformations (1981–2001). We observed a significant peak of DS in January 1987 (26 cases observed and 9.84 expected; observed/expected ratio = 2.64; 95% CI = 1.72–3.76), but found no positive long-term time trends in contaminated or control areas. The time occurrence of the January peak, high dose rates during the plume passage and experimental data showing a radiosensitive phase of oogenesis around conception time in mammals suggest that the January peak may be linked to the Chernobyl plume.

Geographical Information Systems and Geostatistics for Modelling Radioactively Contaminated Land Areas

The Chernobyl plume contaminated vast lands of Europe with radiocaesium (137Cs) in 1986 because of the deposition of radionuclides on the ground by wet and dry deposition processes. Nevertheless, in a nuclear emergency, contamination data may be very sparse and there is need to make rapid and scientifically supported decisions. Here we analyze the rainfall field, an important precursor of the wet deposition, during the passage of the plume. Thus, estimating rainfall spatial variability can help to identify possible contaminated areas and associated risks when rainfall exceeded a given threshold. In this paper, we show that the conditional probabilities of exceeding threshold rainfall values could be spatially assessed using the mutual benefits of linking geostatistical and geographical information system (GIS) to quantify the evaluation of the risk involved in decision making. In particular, the non-parametric geostatistic technique, termed Indicator Kriging (IK), enables one to efficiently estimate the probability that the true value exceeds the threshold values by means of the indicator coding transform. Afterward, GIS has been used to find the areas probably affected by wash-out (probability >0.5 that rainfall is above a certain threshold). The experimental study has been focused on a test site in Beneventan agroecosystem (Southern Italy) to model the spatial uncertainty over a continuous area from sparse rainfall data. This enabled to generate probability maps delineating area potentially affected by to contamination to be monitored after wet deposition of Chernobyl releases.

Regional distribution of Chernobyl-derived plutonium deposition in Finland

The Chernobyl nuclear power plant accident in April 1986 caused a widely spread plume of radionuclides containing, amongst other materials, plutonium isotopes. The regional deposition of these nuclides in Finland has been assessed, based on samples of lichen, peat, precipitation, surface soil and grass. Unlike the deposition of transuranium elements from the weapons tests in the 1950"s and the 1960"s, the deposition in Finland from the Chernobyl accident was very unevenly distributed. Even then, the Chernobyl-derived deposition of 239,240Pu in the most contaminated regions of Finland was only around 10% of the global fallout from weapons tests. The total amount of 239,240Pu deposited in Finland was 1.1011 Bq (»25 g), i.e., approximately half of a percent of the activity deposited in the 1950"s and the 1960"s. In addition to the alpha-emitting Pu isotopes, the Chernobyl plume also contained a significant amount of the beta-emitting 241Pu, which is the precursor of the long-lived alpha-emitter 241Am. The highest plutonium deposition values were found in a relatively narrow swath from the southwestern coast of Finland northeastwards across the country. This is related to the calculated route of the air parcel trajectory associated with the initial explosion of the Chernobyl reactor. The high deposition values found in the northeastern part of the plume route over Finland can be attributed to the simultaneous occurrence of precipitation. The relatively high plutonium deposition in the southwestern part of Finland occurred, however, without concurrent precipitation. This indicates that the plutonium was at least partly associated with relatively large particles having a substantial deposition velocity due to gravitational setting

Radionuclide behaviour and transport in a coniferous woodland ecosystem: The distribution of radionuclides in soil and leaf litter

A coniferous woodland in the vicinity of theBritish Nuclear Fuels reprocessing plant atSellafield, Cumbria, was used to examine the spatial,temporal and depth distribution of 134Cs,137Cs, 238Pu, 239+240Pu and 241Amin soil and leaf litter. All the radionuclides, withthe exception of 134Cs, showed a consistent fallin accumulated soil and litter deposits withincreasing distance from the woodland edge nearest toSellafield. 137Cs levels in soil declined from 53to 28 kBq m-2, 239+240Pu from 5.5 to 3.6 kBqm-2 and 241Am from 2.9 to 1.1 kBq m-2within 100 m of the forest edge. This decline isattributed to greater deposition occurring at theleading edge of the woodland. The uniform depositionpattern of 134Cs in soil is consistent with thehypothesis that, at the time of sampling, thesedeposits derived largely from wet deposition duringpassage of the Chernobyl plume over Cumbria in May1986. Results for the leaf litter indicate a similarspatial distribution to that observed in soil.Radionuclide concentrations were also similar but thisis not attributable to adventitious soil contaminationbecause significant differences between isotopicratios of 134Cs:137Cs and 238Pu:239+240Pu imply that the contamination on leaflitter is of more recent origin than that in soils.

The vertical distribution of the Cs-137 derived from Chernobyl fall-out in the uppermostSphagnum layer of two peatlands in the southern Alps (Italy)

The patterns of concentration of the Cs-137 derived from the Chernobyl accident were analysed in a series of vertical profiles ofSphagnum collected at two peatlands in the southern Alps. The peak concentrations of the Chernobyl radiocesium were found in segments ofSphagnum located at different distances from the growing apex, probably corresponding to the plant tissues produced in the 1986 vegetation season. This indicated that the growth rates ofSphagnum are subject to considerable variations not only between species, but also between years and even between individuals of the same species when growing in different microhabitats at the same site. However, the concentrations of the Chernobyl-derived radiocesium are high also in theSphagnum segments produced after 1986. This was due to a continuous translocation of Cs-137 towards the capitulum, probably determined by the chemical similarity between cesium and potassium. Although the two sites investigated received nearly the same amounts of rainfall in the two-week period following the arrival of the Chernobyl plume, the average concentrations of radiocesium in allSphagnum species were significantly higher at one of them, presumably because the fall-out deposition was conditioned by a number of meteorological factors besides precipitation.

Time dependent transport of Chernobyl radioactivity between atmospheric and lichen phases in Eastern Canada

The Chernobyl radioactivity plume arrived in eastern Canada by a combined Arctic and trans-Atlantic route on 7–9 May 1986, 11 days after the initial releases in the USSR. The composition of the plume over Canada underwent significant modifications on 16 May and 25 May before the concentrations of Chernobyl-labelled aerosols declined to levels below the detection level by the second week in June. The initial plume was distinguished by a comparatively large gaseous (61% of total) versus particulate 131I fraction which decreased by a factor of 2 upon the arrival of the second component of the Chernobyl plume on 16–17 May. The second component of the plume was also characterized by a higher concentration of 103Ru. Atmospheric residence times of approximately 11·1 and 11·5 days were estimated for 137Cs and 131I associated aerosols, respectively, based on the decrease with time in their concentration ratios with respect to 7Be. Measurements of Chernobyl radionuclides in lichen samples were introduced into a lichen transport model to estimate uptake rates for each radionuclide. A deposition velocity of 1·1 cm/sec provided good agreement between the model and experimental results. The deposition velocities estimated from the lichen model were combined with the atmospheric residence time data to calculate a plume height of 10 000 m for the Chernobyl cloud as it passed over eastern Canada.

Airborne radioactivity measurements from the chernobyl plume

Airborne gamma-ray measurements were made aboard the Pacific Northwest Laboratory (PNL) DC-3 and the National Oceanic and Atmospheric Administration (NOAA) King Air research aircraft before and during the first passage of the Chernobyl radioactive cloud over the west coast of the North American continent. Measurements were made from Anchorage, Alaska south to Reno, Nevada. Calculated trajectories were used to estimate the location of the Chernobyl plume. The in-situ gamma-ray analysis systems first detected the cloud on May 8, 1986. Subsequent analysis of concurrently collected air filters indicated that the leading edge of the plume was just reaching the west coast of the United States on May 6, 1986. The ratios of the observed volatile radionuclides (131I and134Cs normalized to137Cs) agreed with the reported discharge ratio.

Study of the medium- and long-range transport analysing the data of the Chernobyl accident

In the present work we analyse the meteorological factors that characterized the transport and deposition on the ground of the radionuclides from the Chernobyl nuclear power station over Northern Italy during the accident in April–May 1986. The aim of our study is to test some computational procedures and meteorological analyses specific for a comprehensive study of long-range pollution transport problem. By reconstructing the particle trajectories of the radioactive Chernobyl plume, we determined the most probable starting and arrival date of the plume and the level over the source. Moreover, analysis of the meteorological configuration up-and downwind the Alps permitted us to explain the temporal displacement between different kinds of measured fall-out.