Pb-210 and fly ash particles as indicators of industrial impact in peatlandsTaavi Vaasma, Helen Karu, Madis Kiisk, Margus Pensa, Alan Henry Tkaczyk

University of Tartu, Institute of Physics andInstitute of Ecology and Earth SciencesTallinn University, Institute of Ecology INCO-PoPb-201511-14.10.2015 Kusadası, Turkey

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Research at the University of Tartu

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TARTU

Institute of Physics

3

Where can we find oil shale?

The oil shale industry

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Estonian oil shale

What is oil shale?

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The oil shale-fired power plants

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~20% Pb-210Around 60 GBq Pb-210 emitted yearly

0.77 1.12 3 3.85 4.2

Pb-210 enrichment factor

Pulverized fuel technology

?% Po-210

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Emissions to the environment

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Few available research on the distribution of natural

(U-238 and Th-232 series) radioactive isotopes in

soils near thermal power plants.

Average Pb-210 and Ra-226 values around Ra-rich

soils remain between 90-95 Bq/kg.

Fly ash deposition from PP’s.

Location Kg m-2 a-1

Narva-Jõesuu 0.21

Narva 0.24

Eesti PP 0.14

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Selisoo mireLocated in the northeast of Estonia

Ombrotrophic and Sphagnum-dominated bog with sparse pine cover

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~ 50 km

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Pb-210 activity concentrations

Approximately 30 cm long peat cores were taken.

These cores were sliced into 1 cm thick samples.

Samples were packaged, sealed and measured gammaspectrometrically.

Maximum values remain between 6-8 cm.

Results indicate to an additional influx of Pb-210.

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0-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9

9-10 10-11 11-12 12-1313-1414-1515-1616-1717-1920-2121-2222-2323-2424-2525-2626-27

0 100 200 300 400 500 600

367.7282.7

310.6384.7386.3

487.3498.1

431.0405.7

399.2386.2

370.6328.1

271.7216.2193.9

186.199.695.1107.3

78.272.066.3

28.2

Pb-210 activity concentration (Bq/kg)

Dep

th (

cm)

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Ash particles

Spherical ash particles are created by oil shale combustion (PF boilers).

Temperatures in the combustion boiler are up to 1400 °C.

Dominating are particles, which consist mainly of aluminosilicate glassy material.

Samples were pretreated and homogenized.

Known amount of Lycopodium clavatum marker-spores were added.

Spores and ash particles were counted and the number of spherical ash particles

were calculated from the known concentration of the exotic spores (Alliksaar,

2000).

The concentration of the spherical particles were up to 20 000 per gramm of peat

and were predominantly of glassy type.

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Ash particles in the moss

Results follow similar trend with Pb-210

values.

Majority of ash particles remain fixed to the

moss layer where they are precipitated.

Under 1% of fly ash particles placed on the

surface of a 6–10 cm thick Sphagnum layer

were washed out with water during a 241 days

of lab experience (Punning and Alliksaar,

1997).

Low mobility of ash particles and Pb-210

within the moss is expected.

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0-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9

9-10 10-11 11-12 12-1313-1414-1515-1616-1717-1920-2121-2222-2323-2424-2525-2626-27

0 500 1000 1500 2000

186.477439695516

194.116757056936446.7328766988

92 1541.993526499141098.895669759

21143.88126982211078.432862430

051416.94190425365595.9289994647

74605.282503878439

380.741003032911423.23028996743881.00186557256

8563.7938967697762

14.3574859342811

7.30453442638719

08.081165671156

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Ash particles per cm3 of peat

Dep

th (c

m)

0-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9

9-10 10-11 11-12 12-1313-1414-1515-1616-1717-1920-2121-2222-2323-2424-2525-2626-27

0 100 200 300 400 500 600

367.7282.7

310.6384.7386.3

487.3498.1

431.0405.7

399.2386.2

370.6328.1

271.7216.2193.9

186.199.695.1107.3

78.272.066.3

28.2

Pb-210 activity concentration (Bq/kg)

Dep

th (c

m)

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Emissions from the power plants

Similar trends between oil shale consumption and fly ash

emissions.

Impact of the emissions on peatlands:

• Increased deposition of airborne nutrients and alkaline dust in

surrounding environment;

• Increase in the bog tree diameter and elevated forestation of the

bog area;

• Increase in pH values in nearby peatlands;

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1960

1965

1970

1975

1980

1988

1990

1992

1995

1999

2000

2001

2002

2003

0 10000 20000 30000 40000

6955

14721

20488

28144

30818

25853

25699

20501

15420

12662

13254

13250

13077

15474

Consumption of oil shale (thousands of tonnes/year)

Yea

r

1960

1965

1970

1975

1980

1988

1990

1992

1995

1999

2000

2001

2002

2003

0 100000 200000 300000

122150

193750

256100

263700

232180

194800

182200

132278

69600

61030

48270

46520

25410

21920

Fly ash from oil shale-fired power plants (tonnes/year)

Yea

r

18081821183418471860187318861899191219251938195119641977199020030

0.5

1

1.5

2

2.5

Incr

ease

in d

iam

eter

(m

m)

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Anthropogenic radionuclides

Measurements of anthropogenic radionuclides

(Cs-137 and Am-241) to specify the time of

radionuclide and fly ash deposition.

Maximum Cs-137 values are between 12-13 cm.

This indicates to a period around 1960’s (nuclear

weapons testing).

Due to Cs-137 migration potential, errors in

estimations can occur.

Am-241 measurements give ground to similar

assumptions.

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0-2 2-3

3-4

4-5

5-6

6-7

7-8

8-9

9-10

10-11

11-12

12-13

13-14

14-15

15-16

16-17

17-19

20-21

21-22

22-23

23-24

24-25

25-26

26-27

0

50

100

150

200

250

300

350

400

450

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Depth (cm)

Am-2

41 a

ctivi

ty co

ncen

trati

on (B

q/kg

)

Cs-

137

acti

vity

con

cent

rati

on (B

q/kg

)

1960’s

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To conclude Pb-210 activity concentration and number of spherical fly ash particles

possess similar trend with the maximum values at the depth of 7-8 cm.

This data coincides well with the consumption of oil shale and the amount of fly ash released from the power plants.

Cs-137 and Am-241 measurements help to improve the determination of the deposition period.

Combining radionuclide measurements and ash particle data we aim assess the magnitude of the radiological impact from industrial activity during different time periods.

Peatlands have the potential to be used as archives to estimate pollution from industrial installations.

The next steps:

• Additional cores have been gathered for further measurements;

• Test if a correlation between spherical particles and Pb-210 can be found

in fly ash.

• Use the collected data and parameters to try and date the peat cores.

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Acknowledgement

COST Action TU1301. www.norm4building.org

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And the work goes on…