Chernobyl fallout studied by Mössbauer spectroscopy V. Rusanov V. Gushterov

Chernobylfallout

studied byMössbauer

spectroscopy

V. RusanovV. Gushterov

Department of Atomic Physics, University of Sofia, Bulgaria

H. WinklerA. X. Trautwein

University of Lübeck, Germany

Computer simulation of the radioactive contamination distribution over the northern hemisphere shortly after the accident.

“Gütlich, Bill, Trautwein: M össbauer Spectroscopy and Transition Metal Chemistry@�� Springer-Verlag 2009”

“Gütlich, Bill, Trautwein: Mössbauer Spectroscopy and Transition Metal Chemistry@Springer-Verlag 2009”

Air photograph of the destroyed reactor block of the nuclear plant in Tschernobyl, Ukraine. About 600000 people were exposed to heavy irradiation. Among the rescue teams about 7000 people died. According to information from WHO 125000 people were severely falling sick. Because of danger due to radioactivity 375000 people had to be resettled. Even today inhabitants are suffering from the remainders of the accident. Children in Belarus experience the highest rate of cancer of the thyroid gland world wide. Altogether in Ukraine, Belarus and Russia an area as large as one third of the area of Germany is contaminated.

Source and Photo: DPA

V. Rusanov, V. Gushterov, H. Winkler and A. X. Trautwein, Chernobyl fallout studied by Mössbauer spectroscopy



Gross beta radioactivity of the atmospheric aerosols in SofiaYear Tests

1945 31946 1 1947 -1948 31949 11950 -1951 17 1952 111953 151954 71955 171956 271957 461958 831959 -1960 31961 311962 771963 -1964 11965 11966 81967 51968 61969 11970 91971 61972 51973 61974 81975 -1976 21977 11978 2 1979 -1980 1

(courtesy of Mrs. B. Veleva)

1959

1961

1963

1965

1967

1969

1971

1973

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

Jan

Apr

Jul

Oct

1.00

10.00

100.00

1000.00

10000.00

mBq/m3

3-4

2-3

1-2

0-1

3000 - 4000 mBq/m3

100 - 1000 mBq/m3

10 - 100 mBq/m3

1 - 10 mBq/m3- background values

Dec



3.05.1986, Sofia

8.05.1986, Sofia 1994, Sofia

Top left - mean value of the beta radioactivity of atmospheric air based on 5 different sampling regions in Bulgaria; top right and bottom left: autoradiography of air filters dated as shown, the bright spots are “hot particles” with very high specific radioactivity; bottom right - autoradiography of a tree leaf grown on 90Sr contaminated soil near Sofia.

0 5 10 15 20 25

0.01

0.1

1

10

100

Mea

n va

lue

of g

ross

bet

a ra

dioa

ctiv

ity

of th

e at

mos

pher

ic a

er, B

q/m3

Days after the "zero" day of the Chernobyl accident 26.04.1986

2.05.1986



Mössbauer spectra of an air filter collected during 30.04.-05.05.1986 taken at 293 K and 77 K. This sampling time coincides with the maximum contaminating fallout due to the Chernobyl accident detected in Bulgaria. Measurements confirmed the presence of large quantities of magnetite Fe3O4, mixtures of various oxyhydroxides mainly γ-FeOOH, a superparamagnetic component, and Fe3+ in clay and silicate minerals. The Mössbauer spectrum taken at liquid nitrogen temperature shows that a considerable part of the ultra fine particles of α-Fe2O3 (particle size less than 20 nm) had been in superparamagnetic state at room temperature. The iron concentration in air of 3.69 μg/m 3 was high and typical for

days with large air pollutions.

-8 -6 -4 -2 0 2 4 6 80.996

0.997

0.998

0.999

1.000

1.001

-8 -6 -4 -2 0 2 4 6 8 100.996

0.997

0.998

0.999

1.000

1.001

silicate minerals

B-sites

or superparamagneticFe

3+ in oxyhydroxides

Fe3+

magneticFe2+ in clay or

Tra

nsm

issi

on

Velocity, mm/s

Fe3O4

A-sites

a293 K

silicate minerals

Fe2O3

b77 K


3+ in oxyhydroxides

Fe3O4Fe2+ in clay or



Mössbauer spectra of an air filter collected during 06.05-07.05.1986 taken at 293 K and 77 K. Change in the chemical composition including the presence of α-Fe2O3 and oxyhydroxides, as well as absence of magnetite, were detected.

The iron concentration remained high – 3.61 μg/m3.

-8 -6 -4 -2 0 2 4 6 80.994

0.995

0.996

0.997

0.998

0.999

1.000

1.001

-8 -6 -4 -2 0 2 4 6 8 100.994

0.995

0.996

0.997

0.998

0.999

1.000

1.001silicate minerals

Tra

nsm

issi

on Fe2O3

a293 K


3+ in oxyhydroxides

Fe2+ in clay or

silicate mineralsFeOOH

Fe2O3

b77 K


3+ in oxyhydroxides

Fe2+ in clay or

Velocity, mm/s



Mössbauer spectra of an air filter collected during 09.05-10.05.1986 taken at 293 K and 77 K. In the Mössbauer spectra a magnetically split component was not detected at room temperature. Small quantities of α-FeOOH and γ-FeOOH were measured in the liquid nitrogen temperature spectrum. The measured iron concentration was extremely low, 0.79 μg/m3, which is typical for days of small air pollution.

-8 -6 -4 -2 0 2 4 6 80.998

0.999

1.000

1.001

-8 -6 -4 -2 0 2 4 6 8 100.998

0.999

1.000

1.001silicate minerals

Tra

nsm

issi

on

a293 K

or superparamagnetic

Fe3+

in oxyhydroxides

Fe2+ in clay or

silicate minerals

FeOOH

b77 K


Fe3+

in oxyhydroxides

Fe2+ in clay or

Velocity, mm/s


Fit results from the sum of three Mössbauer spectra of air filters collected between 30.04. and 10.05.1986. The consecutive measurements showed clearly that after the first wave of radioactive contaminations from May 1 st to May 5th the concentration of iron in the air dropped considerably. The overall pollution was not caused by a single radioactive wave. New contaminations and redistribution of the radioactive fallout had been detected.


-8 -6 -4 -2 0 2 4 6 8

0.995

0.996

0.997

0.998

0.999

1.000

1.001

-8 -6 -4 -2 0 2 4 6 8 10

0.995

0.996

0.997

0.998

0.999

1.000

1.001

Tra

nsm

issi

on


mineralsFe

3+ in oxyhydroxides

Fe2+

in clay or silicateFe3+

magnetic

Fe2O3

Fe3O4

a293 K

30.04.-05.05.1986

06.05.-07.05.1986

09.05.-10.05.1986

FeOOH


mineralsFe

2+ in clay or silicate

Fe3+

in oxyhydroxides

Fe2O3

Fe3O4

b77 K

30.04.-05.05.1986

06.05.-07.05.1986

09.05.-10.05.1986

Velocity, mm/s


The results from the first air filter of Chernobyl fallout (black) were compared to results from air filters collected long after the accident on days of high (red) pollution (windy summer days) and low (blue) pollution (winter days after snowfall). The comparison confirms the major conclusion that the aerosols collected right after the Chernobyl accident contain magnetite, Fe3O4. Magnetite is, as usual, nonstoichiometric and partially oxidized to maghemite, γ-Fe2O3. Such contamination of the air over Sofia is not unusual. In days of high air pollution we detect magnetite, which most probably originates from the steel production plant near Sofia. Nevertheless, the magnetite concentration in the filter from right after

the accident is 2-3 times higher and, therefore, is mainly a result of the polution due to the accident.


-8 -6 -4 -2 0 2 4 6 8

0.995

0.996

0.997

0.998

0.999

1.000

1.001

-8 -6 -4 -2 0 2 4 6 8 10

0.995

0.996

0.997

0.998

0.999

1.000

1.001


3+ in oxyhydroxides

mineralsFe

2+ in clay or silicateFe

3+ magnetic

Fe2O3

Fe3O4

a293 K

Velocity, mm/s

Tra

nsm

issi

on

16.02.-19.02.1992

30.04.-05.05.1986

11.07.-25.07.1990


3+ in oxyhydroxides

mineralsFe

2+ in clay or silicateFeOOH

Fe2O3

Fe3O4

b77 K

16.02.-19.02.1992

30.04.-05.05.1986

11.07.-25.07.1990


ConclusionThe increase of iron-containing material in the air pollution as a result of the Chernobyl reactor accident was expected. B. and M. Kopcewiczs were the first to use Mössbauer spectroscopy for such studies of air filters from Warsaw [1]. Our own results obtained with the filters from Sofia [2] confirm that for the initial filters, collected during the contaminating fallout (30.04-05.05.1986), the iron concentration was highest and magnetite Fe3O4 was present. This is most likely due to the fact that during the accident large amounts of iron-construction materials were destroyed, evaporated and transported together with the radioactive fallout. The presence of magnetite particles of industrial origin in air pollutions in Sofia is not exceptional and originates mostly from the steel plant situated nearby. Nevertheless, the major Chernobyl fallout in Bulgaria happened during four consecutive holidays after May 1st, and we could assume that on these days the industrial plants had worked on minimal power. During these days the magnetite concentration in the air filter was 2-3 times higher compared to that from days with high air pollution in Sofia. This finding confirms that the large part of the iron-containing contaminations was caused by release from the reactor accident. A definite conclusion about an increase of the isotope abundance of 57Fe in the Chernobyl fallout cannot be based on Mössbauer spectroscopy only. Additional mass-spectroscopic measurements are needed. [1] B. Kopcewicz and M. Kopcewicz, Hyperfine Interactions, Mössbauer study of iron-containing atmospheric aerosol collected during the Chernobyl accident, 139/140, 657-665 (2002).[2] V. Rusanov, V. Gushterov, H. Winkler and A. X. Trautwein, Iron-containing atmospheric aerosols in the Chernobyl fallout, Hyperfine Interactions, 166, 625-630 (2005).


AcknowledgementsThe authors are indebted to Mr. V. Mavrodiev for providing the filters. Thanks are due to the Alexander von Humboldt Foundation, special program Stability Pact for South Eastern Europe (V. R. and A. X. T.).

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Chernobyl fallout studied by Mössbauer spectroscopy V. Rusanov V. Gushterov