ARKHANGELSK, November 30. /TASS/. Experts of the Federal Research Center for Integrated Arctic Research (the Russian Academy of Sciences’ Urals Branch) for the first time analyzed radionuclides accumulated in the Arkhangelsk Region’s peatlands. The Center’s representative Evgeny Yakovlev told TASS that the studies also involved specialists from the Belarus’ Academy of Sciences’ Institute of Radiobiology.
"We have focused on spread of radioactivity inside peatlands," he said. "The thing is that this area was exposed to radioactivity as a result of nuclear tests in the atmosphere and as a result of technological accidents."
"The Arctic has suffered a lot, since here used to be a test range on Novaya Zemlya, and many other factors, including even a Chernobyl trace," the scientist said. "Studies of the kind have not been conducted in Russia’s European part."
According to him, specialists from Norway and Sweden have been studying the issue actively. Most peatlands are in Russia’s sub-Arctic districts: in the Murmansk, Arkhangelsk and Nenets Regions with a very damp and cold climate, where the amount of water evaporating is less than that of precipitation. "This part of the country accounts for about a third part of Russia’s peat resources," the expert continued. "About 50% of the world’s peats are in Russia, which is a lot."
The European part of Russia is known for the so-called upper peats. "They are fed from the atmosphere: dust, aerosols, snow, rain and whatever comes from the atmosphere, thus making the peats a mighty information base of atmospheric pollutants," he added.
In the Arkhangelsk Region’s two districts (Mezensky and Primorsky), the scientists took peat samples at the depth of up to 70cm. It is the lowest level of man-made radionuclides fallout. In the Mezensky District, major operational enterprises are very few, and thus the sample from there was less contaminated. The other sample comes from an area not far from Severodvinsk - "a more contaminated place," the expert said. Specialists have tested concentrations of main atmospheric radionuclides: caesium-137, isotopes of plutonium, uranium, americium-241 and lead-210.
Radionuclide activity varied depending on the sampling depth. The experts used the excessive lead determination method to see the age of peat in young sediments. Lead-210, unlike other radionuclides, practically remains where it is. "It migrates very badly with water or any humidity: it falls out, gets fixed and remains there," the scientist said. "Other radionuclides may move upwards or downwards depending on changing parameters, on changing flora and moss." This way the specialists could date different layers of peat.
Scientists have found two peaks in the samples when the amount of radionuclides is maximum high. The first corresponds to about 1962. "We can see clearly the peak of 1962 has emerged due to man-made radioactivity. It is at similar levels in both sections - about 40 cm. 40 cm have accumulated since 1962," he said, explaining the fallout origin by mass nuclear tests in the atmosphere, which were outlawed in 1963. "Plus, the accident of the Transit B-5 satellite, a nuclear-powered American satellite fueled with plutonium."
The satellite’s launch failure occured on April 21, 1964. It burned down above the Indian Ocean, when 950 grams of plutonium-238 fell out, boosting the planet’s radioactive background by more than ten times.
Chernobyl’s trace in the Arctic
Another activity peak was registered at the depth of about 10-15cm, corresponding to 1986-88. "Apparently, that was a trace from the Chernobyl accident. But here the activity of radionuclides varies, sometimes not fitting into the time limit," he added.
In order to establish that global nuclear weapons tests and the Chernobyl accident were the source of those radionuclides, the experts studied the ratio of plutonium-239 isotope to plutonium-240 isotope. In case of the Chernobyl accident, it is different from that during global tests. "We calculated their atomic ratio, and saw that the lead peak of 1962 corresponds to the global fallouts. The numerical value is 0.18. As for the peak between 1986 and 1988, the average ratio is 0.3, which is typical of Chernobyl according to all reference data. Thus, the Chernobyl fallout made it here, although there have been different opinions, mainly claiming that none had reached the Arctic. And yet, the Chernobyl background is apparent in the Arkhangelsk Region. This was an important result," the researcher said.
To clarify the data on composition of the Chernobyl radionuclides, the scientists took samples in Belarus. The radio-ecological studies were conducted in the 30-kilometer exclusion zone of the Chernobyl nuclear power plant in the Polessky State Radiation Ecological Reserve. It was established in 1988 on the territory of the most affected areas in Belarus’ Gomel Region. There are 96 abandoned settlements, where more than 22,000 thousand people used to live before the accident. "We took peat samples there to see the spectrum of radionuclides that fell out of the atmosphere during the Chernobyl accident," he added.
The scientists explained the shift of some radionuclides from exact time intervals by changing physical and chemical structures of peats and by the impact of plants. Unlike lead, other radionuclides have a higher degree of migration. For example, caesium-137 has a peak near the surface, and the only source of this element was the Chernobyl accident’s fallout. "In fact, isotope caesium-137 is a chemical analog of potassium. It is an alkaline earth metal too, while potassium and cesium are absorbed easily by plants. Plants, sphagnum and moss constantly pull it upwards, this is why its concentration in the upper centimeters is the highest," the scientist continued.
According to Yakovlev, the amount of caesium-137 is quite small, and its half-life is about 30 years, so it is not hazardous. But due to the global climate change and the warming in the Arctic, other radionuclides, that are now located inside peatlands, may also begin to move. "Take for example americium or plutonium isotopes - they will start moving upwards. They will also affect plants and animals. Caesium-137 has mostly decayed. But plutonium and americium have a much longer half-life, and their contribution to the radiation dose will only increase," he added. "Thus it is important to monitor these radioactive elements now."
There is data on Spitsbergen, where radionuclides from global fallouts have been found in peatlands. Since it is cold there, isotopes practically do not move. "They get fixed inside a certain layer, and the activity levels there are also quite high. With the climate changes they will all start to move upwards. So far, they do not affect plants or animals in any way," the scientist said. "In the future, this problem will increase, and we will see higher radioactivity on the surface due to release of radionuclides, which was fixed inside the peat layers."
The study also established the rate of peat accumulation over the recent 150 years. It differed from year to year. "When it is warm, peat builds up faster, by slightly more than one millimeter, and in cold years, the rates are low. Thus, we have received important data that boost our understanding regarding climate characteristics," he concluded.
The studies were conducted as part of an international project of the Russian Foundation for Basic Research.