Pb-210 and fly ash particles as indicators of industrial impact in peatlands Taavi Vaasma, Helen Karu, Madis Kiisk, Margus Pensa, Alan Henry Tkaczyk University of Tartu, Institute of Physics and Institute of Ecology and Earth Sciences Tallinn University, Institute of Ecology INCO-PoPb Kusadası, Turkey

Research at the University of Tartu 2 INCO-PoPb-2015 TARTU Institute of Physics

Where can we find oil shale? The oil shale industry 3 INCO-PoPb-2015 Estonian oil shale What is oil shale?

The oil shale-fired power plants INCO-PoPb ~20% Pb-210 Around 60 GBq Pb-210 emitted yearly Pb-210 enrichment factor Pulverized fuel technology ?% Po-210

Emissions to the environment INCO-PoPb  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 Bq/kg.  Fly ash deposition from PP’s. LocationKg m-2 a-1 Narva-Jõesuu0.21 Narva0.24 Eesti PP0.14

Selisoo mire  Located in the northeast of Estonia  Ombrotrophic and Sphagnum-dominated bog with sparse pine cover INCO-PoPb ~ 50 km

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. INCO-PoPb

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 per gramm of peat and were predominantly of glassy type. INCO-PoPb

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. INCO-PoPb

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; INCO-PoPb

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 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. INCO-PoPb ’s

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. INCO-PoPb

Acknowledgement COST Action TU INCO-PoPb

INCO-PoPb And the work goes on…