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1. Full name: Jukka Kalevi Lehto
2. Date and place of birth: 1st of October 1953, Nokia, Finland
3. Current position:
4. Education and training:
5. Previous professional appointments:
6. Research awards, research honours and major stipendiary support for research
Research honours:
Major research funding:
7. Editorial board memberships
8. Memberships in scientific societies
9. Other academic and professional activities
Further academic and professional activities:
Refereeing a docentship:
Supervising of doctor’s theses:
Supervising of licentiate thesis:
Acting as an opponent for doctor’s theses:
Refereeing doctor’s theses:
Refereeing licentiate theses:
1. ENVIRONMENTAL RADIOACTIVITY STUDIES
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.
1.1.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.
1.2.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.
1.3.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.
1.4.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.
1.5.241Am 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.
1.6.210Po and 210Pb in forest environment
In 2005-2010 I was involved with Dr. Kaisa Vaaramaa’s postdoctoral research project in which 210Po and 210Pb in forest environment ere studied. Distribution of polonium and lead in various layers of podzolic soil and their transfer from soil into forest plants, mushrooms and wild berries, were explored.
1.7.137Cs, 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.
1.8.Immobilization of radionuclides and heavy metals from mining mill tailings
In 2010 I started supervising the doctoral thesis work of Hanna Tuovinen. The work will deal with the immobilization of radionuclides and heavy metals from mining mill tailings from Sokli phosphate ore (mine not in operation) in the Northern Finland and from Paukkajanvaara uranium mine (operated in 1958-19661) and possibly Talvivaara nickel mine. The four years’ project is financed by the Academy of Finland.
1.9.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.
2. STUDIES ON THE MIGRATION OF WASTE RADIONUCLIDES IN GEOSPHERE
2.1. Sorption of trivalent actinides on clay mineral surfaces
In 2007 I started supervision of Nina Huittinen’s doctoral work on the sorption of trivalent actinides on clay mineral surfaces. The objective of the study is to identify the actinide species taken by the various types of hydroxyl groups on clay surfaces. The clay minerals under study are gibbsite and kaolinite. In addition silica and γ-alumina have been studied. The actinide studied has been curium but also actinide analogues europium and gadolinium have been studied. Actinide/lanthanide speciation in solution and in the solid phase has been studied by Laser Induced Fluorescence, IR and NMR spectrometries. In addition batch sorption studies on lanthanides by the minerals have been carried out.
2.2. Migration of long-lived radionuclides in soil
From 2008 on I have been supervising two doctoral thesis work with Posiva Companys funding on the migration of long-lived radionuclides 135Cs, 129I, 99Tc, 94Nb, 93Mo and 79Se in soil of Olkiluoto where the final disposal repository will be constructed for the spent nuclear fuel from Finnish nuclear reactors. All these radionuclides, except 135Cs, may exist as anionic forms which make them very mobile in soil. Both sorption of radionuclides on various soil layers and sequential leaching of soils have been studied.
3. ION EXCHANGE RESEARCH
3.1. Development of selective inorganic ion exchangers for the removal of radionuclides from nuclear waste effluents
I started my research career in 1980 by studying the ion exchange behaviour of sodium titanates for the selective removal of radionuclides from nuclear waste effluents. This was also the topic of my doctoral thesis in 1987. Since this was a novel topic in the Laboratory of Radiochemistry, University of Helsinki, I had to initiate and construct the research methodology. First by myself and later together with Dr. Risto Harjula we have established a research group around this topic. In the last twenty-five years we have synthesised a wide range of inorganic ion exchangers, especially transition metal hexacyanoferrates, titanates and mixed metal oxides, such as titanium antimony oxides. The main purpose for the development of these radionuclide-selective ion exchangers has been to reduce nuclear waste volumes for final disposal and to reduce discharges to the environment from nuclear plants.
A Finnish company, Fortum, is presently manufacturing three exchangers developed by the group:
These unique exchangers have been utilised in industrial-scale separation processes in many countries (e.g. USA, UK, Japan, Finland, Hungary and Russia).
Recently a new family of mixed oxides has been developed by our laboratory. These exchangers include pyroclore and rutile structured oxides of antimony, titanium and manganese. The primary aim of this development has been to obtain exchangers which are resistant to high concentrations of calcium in solution and which are suitable for use in acidic solutions.
In the last few years I have focussed my main efforts into the field of environmental radioactivity and Dr. Harjula has taken over the leadership of the ion exchange research group.
3.2. Characterization of inorganic ion exchange materials
In addition to testing the inorganic ion exchangers with respect to their ability to remove radionuclides from nuclear waste effluents their physicochemical properties have been characterised in many ways:
In the early 1980’s I also developed a solidification method for the final disposal of inorganic ion exchangers. In this method the ion exchangers were mixed with clay and ceramised into solid blocks by heating.
3.3. Removal of heavy metals from metallurgical waste effluents
In 1996-1999 I worked as a coordinator in the EU funded research project “Removal of heavy metals from metallurgical waste effluents by ion exchange”. In addition to Finland we had partners from UK and Germany. In the Laboratory of Radiochemistry we studied the use of chelating ion exchanger resins, activated carbons and inorganic ion exchangers for the removal Cd, Co, Ni, Cr, Zn and Cu from the waste effluents from metal plating plants. Based on this study the Finnair metal plating plant took into use an ion exchange facility to remove Cd and Ni as an end-polishing step following their existing waste treatment plant.
3.4. Ion exchange properties of chelating ion exchange resins
In the 1990’s I studied the basic ion exchange properties of chelating ion exchange resins, especially iminodiacetate and aminophosphonate resins. Special focus was paid to Zn and Ni ion exchange equilibria and to hydrolysis of the exchangers.
4.1. Study of cesium in blood plasma
I have been a supervisor of the doctoral thesis of Matti Kaikkonen from the Faculty of Veterinary Sciences, University of Helsinki. This work deals with the determination of cesium (stable and radioactive) in blood plasma. We have developed a novel method to determine added stable cesium in plasma. The method is based on binding cesium in ammonium-iron(II)-hexacyanoferrate (AFCF) and precipitating AFCF with plasma proteins. The method can bE utilised, for example, in studying the plasma kinetics of cesium.
4.2. Behaviour of heavy metals in lakes in the northwestern Russia
In 2005 water and sediment samples were taken from Lake Umbozero, the second largest lake in the Kola Peninsula. The purpose of the study was to see if the lake would have been affected by the atmospheric emissions from the metal smelters in the Kola region, especially by the Monchegorsk smelter 60 kilometres west of the lake. Clearly increasing trend of metals was seen in the sediment profiles but in general the lake was seen to be rather clean, especially compared to the Lake Imandra close to the Monchegorsk smelter.
Similar study was done in 2007 in Kostamus region where there is a large iron mine and ore dressing mill only 30 kilometres east of the Finnish-Russian border. Water and sediment samples were taken from four lakes in a water stream leading from the waste pond of the plant to Lake Keskikuittijärvi 60 kilometres northeast of the plant. In this water system clearly increasing trend on most metals was seen to towards the plant. In another studied direction, 70 kilometres west of the plant, water and sediment samples were taken from two lakes in the Russian side and from another two lakes in the Finnish side. In this direction, where only atmospheric releases are possible, no effects of the plant were seen.
Courses lectured
Principles of radiochemistry, years 2000-2018, 2008, 5 credit units
Chemistry and analysis of radionuclides, 2001-2017, 5 credit units
Environmental radioactivity, 2001-2016, 3 credit units
Radioactive tracer techniques, 1997-2000, 3 credit units
Ion exchange and its use in the treatment of industrial waste effluents, together with Dr. Risto Harjula, 1999-2002, 2 credit units
Chemistry of the final disposal of spent nuclear fuel, 2013-2017, 3 credit units
1. Radioactivity, radionuclides, and radiation
2. Special characteristics of the chemistry and analysis of radionuclides
3. Need for radiochemical separations
4. Radiochemical separation methods
5. Yield determinations and source preparations in radiochemical analyses
6. Radiochemistry of alkali metals
7. Radiochemistry of alkaline earth metals
8. Radiochemistry of 3d transition metals
9. Radiochemistry 4d transition metals
10. Radiochemistry of lanthanides
11. Radiochemistry of halogens
12. Radiochemistry of noble gases
13. Radiochemistry of tritium and 14C
14. Radiochemistry of lead and polonium
15. Radiochemistry of actinides
16. Speciation – physical and chemical forms of radionuclides
17. Measurement of radionuclides with mass spectrometry
18. Sampling and pre-treatment of environmental samples
19. Chemical changes in the matter induced by the radioactive decay process
J.Lehto, Basics of nuclear physics and of detection and measurement of radiation, 2016, 200 pages, available at http://nucwik.com/textbooks/index.html
Contents:
1. What is radiochemistry
2. What is radioactivity
3. History of radiochemistry
4. Structure of atom and nucleus
5. Nuclides, isotopes, isobars – nuclide chart
6. Stability of nuclides
7. Radionuclides
8. Modes of radioactive decay
9. Rate of radioactive decay – equilibria in successive decays processes
10. Interaction of radiation with matter
11. Detection and measurement of radiation
12. Measurement of radiation with gas chambers
13. Liquid scintillation counting
14. Statistical treatment of results
15. Nuclear reactions
16. Preparation of radionuclides
17. Isotope separations
Forskningsoutput: Tidskriftsbidrag › Artikel › Vetenskaplig › Peer review
Forskningsoutput: Tidskriftsbidrag › Artikel › Vetenskaplig › Peer review
Forskningsoutput: Tidskriftsbidrag › Artikel › Vetenskaplig › Peer review
Forskningsoutput: Tidskriftsbidrag › Artikel › Vetenskaplig › Peer review
Forskningsoutput: Tidskriftsbidrag › Översiktsartikel › Peer review
01/06/2013 → …
Projekt: Forskningsprojekt
Lusa, M., Lehto, J., Kasko, J. J. & Kaipainen, M.
01/01/2016 → 31/12/2016
Projekt: Forskningsprojekt
19/03/2010 → 30/04/2015
Projekt: Forskningsprojekt
01/02/2010 → 31/01/2013
Projekt: Forskningsprojekt
Lehto, Jukka (!!Recipient), 2013
Pris: Pris och hedersbetygelser
Lehto, Jukka (!!Recipient), 1993
Pris: Pris och hedersbetygelser
Lehto, Jukka (!!Recipient), 2017
Pris: Pris och hedersbetygelser
Jukka Lehto (Deltagare)
Aktivitet: Andra aktivitetstyper › Typer av övriga aktiviteter - Övrigt
Jukka Lehto (Deltagare)
Aktivitet: Andra aktivitetstyper › Typer av övriga aktiviteter - Övrigt
Jukka Lehto (Deltagare)
Aktivitet: Andra aktivitetstyper › Typer av övriga aktiviteter - Övrigt
Jukka Lehto (Deltagare)
Aktivitet: Andra aktivitetstyper › Typer av övriga aktiviteter - Övrigt
Jukka Lehto (Handledare)
Aktivitet: Examinationstyper › Opponent i doktorsavhandling