At the end of 1990’s I started studying environmental radioactivity problems and from 2001, after retirement of our earlier professor Timo Jaakkola, these have been my major research field.
Physicochemical forms of natural radionuclides in drilled well waters and their removal by ion exchange
A large proportion of the Finnish population consumes drinking water from drilled wells that often contain unusually high concentrations of natural radionuclides. In the doctoral thesis of Kaisa Vaaramaa, which I supervised, we studied the presence of 210Po, 210Pb, 226Ra and uranium in particles of various sizes in waters taken from drilled wells. We found that most of the 210Po and 210Pb are bound in particles but that 226Ra and uranium are more or less soluble. We also tested a wide range of organic and inorganic ion exchange materials for the removal of these nuclides from waters. Since uranium is mainly present as an anionic carbonate complex UO2(CO3)34- in ground waters a strongly basic resin was the most effective ion exchanger for uranium. The strong cation exchange resin, zeolite A and an aminophosphonate resin performed well with the removal of radium. However, polonium and lead could not be removed by ion exchange due to their particle-bound nature.
Plutonium in the air in Kurchatov, Kazakhstan
In 2000-2001 Laboratory of Radiochemistry was a partner in Finnish team testing two air samplers in Kurchatov, Kazakhstan. Weekly air samples were taken over a one-year period in Kurchatov and another three month period in Astana, the capital of Kazakhstan. The purpose of this field trial was to test the samplers for the detection of undeclared nuclear activities. Kurchatov was chosen as a trial site since it is located at the edge of the Semipalatinsk nuclear test site which contains huge amounts of radioactivity in the ground. The role of the Laboratory of Radiochemistry in this study was to carry out the radiochemical separations of uranium and plutonium and to determine the plutonium isotopes. It was found that the plutonium concentrations in the air in Kurchatov were elevated and varied in a 100-fold range. The radiation doses to the local population caused by inhalation were, however, found to be rather low: 13 nSv/a.
Radiological characterization of the Semipalatinsk nuclear test site in Kazakhstan
In 2002-2006 I was a member in the International Atomic Energy Agency’s (IAEA) coordination group responsible for the comprehensive radiological characterization of the Semipalatinsk nuclear test site. The Semipalatinsk test site is a large area of almost 20,000 km2 and some parts of it are highly contaminated from the 460 nuclear weapons test carried out between 1949 and 1989. The purpose of the characterization programme was to provide the Kazakhstan government with recommendations as to which areas can be released for habitation and industrial use and which areas have to be decontaminated or sealed off.
Long-term behaviour of radionuclides from nuclear weapons test fallout in the boreal forest environment in Finnish Lapland
From the beginning of 1960’s the Laboratory of Radiochemistry has studied the behaviour of fallout radionuclides from atmospheric nuclear weapons tests in the environment and in food chains in Finnish Lapland. From 2001 onwards I have been in charge of these studies. The latest phase of these studies began in 1997 and ever since a large number of environmental samples have been collected from the Muddusjärvi area. These samples include sediment, water, fish, soil and vegetation from which 137Cs activity has been measured by gamma spectrometry, and from some soil and vegetation samples the 239,240Pu and 241Am activities have been determined as well. The purpose of the studies is to predict the long-term behaviour of these nuclides in northern boreal ecosystems.
241Am fallout from Chernobyl accident in Finland
Spatial distribution of 241Am in Finland was determined in 2003-2004 by measuring 241Am concentrations in peat samples from sixty peat bogs in Southern and Middle Finland collected immediately after the Chernobyl accident in May 1986. The 241Am fallout from the Chernobyl fallout was seen to be only 1.3% of the total 241Am inventory in Finland, the rest originating from nuclear weapons test fallout. The fallout pattern of americium fallout followed that of plutonium and the heaviest fallout was found in a sector from the south-western coast towards northeast.
210Po and 210Pb in forest environment
Since 2005 I have been involved with Dr. Kaisa Vaaramaa’s postdoctoral research project in which 210Po and 210Pb in forest environment have been studied. Distribution of polonium and lead in various layers of podzolic soil and their transfer from soil into forest plant have been explored.
137Cs, 239,240Pu and 241Am in Lake Päijänne, Finland
In 2007 sediment profiles and surface water samples were collected from the Asikkalanselkä, a southern basin of Lake Päijänne, where the drinking water is taken to the Helsinki metropolitan area. 137Cs activity in water was 19 Bq/m3 and in sediment 100 kBq/m2. Only 0.3% on the total cesium inventory was in the water phase. About 99% of the cesium activity originates from the Chernobyl accident. The situation in case of americium and plutonium was different: they originate by 98% from the nuclear weapons test fallout. Their activities in water were four to five thousand times lower than that of cesium: 4.9 mBq/m3 for plutonium and 4.1 mBq/m3 for americium. The deposition of plutonium and americium in the sediment were 20 Bq/m2 and 45 Bq/m2. The 241Am/239,240Pu ratio was higher in the water phase and in the upper sediment layers compared to the ratio in the deeper sediment layers indicating higher solubility on americium.
Cleanup of large areas contaminated by nuclear accidents
In 1990-1993 I worked as coordinator of the project in the Nordic Nuclear Safety Programme (NKS). The project dealt with the cleanup of large areas contaminated by nuclear accidents. In the project we studied various cleanup methods for urban, forest and agricultural environments, estimated the amounts of radioactive wastes obtained in the cleanup and planned options to dispose of these wastes.